Postprint of: Journal of Organometallic Chemistry Volume 696, Issue 3, 1 February 2011, Pages 748–757

Reactivity of TpMe2Ir(C2H4)(DMAD) with carboxylic acids. A DFT study on geometrical isomers and structural characterization

Verónica Salazar (a), Gloria Sánchez-Cabrera (a), Francisco J. Zuno-Cruz (a), Oscar R. Suárez-Castillo (a), Julián Cruz (a), Rosa Padilla (a), Martín Hernández (a), Arián E. Roa (a), Celia Maya (b), Marco A. Leyva (c), María J. Rosales-Hoz (c), Pandiyan Thangarasu (d)

a Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Hidalgo, Ciudad Universitaria, Km 4.5 Carretera Pachuca-Tulancingo, 42184 Pachuca, Hidalgo, México

b Instituto de Investigaciones Químicas, Departamento de Química Inorgánica, Consejo Superior de Investigaciones Científicas (CSIC) and Universidad de Sevilla, Avenida Américo Vespucio 49, Isla de la Cartuja, 41092 Sevilla, Spain

c Departamento de Química, Centro de Investigación y de Estudios Avanzados del I.P.N., Avenida Instituto Politécnico Nacional 2508, Col San Pedro Zacatenco, 07360 México D. F., México

d Facultad de Química, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, Coyoacán, 04510, México D.F., México

Abstract

The thermally unstable adduct TpMe2Ir(C2H4)(DMAD), which was generated “in situ” by the reaction of DMAD with TpMe2Ir(C2H4)2 (1) at low temperature, reacted with different carboxylic acids to produce the following compounds: TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H4R), (R = H, 2a; o-OH, 2b; o-Cl, 2c; m-Cl, 2d; o-NO2, 2e; m-NO2, 2f;o-Me, 2g;p-Me, 2h) and TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)Me) 3. In the reaction of derivative 2a with Lewis bases, TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(L)(OC(O)C6H5), (L = Py, 4a; m-Br–Py, 4b; m-Cl–Py, 4c; NCMe, 5) were obtained, of which 4b and 4c were isolated as a mixture of two isomers in which the substituted pyridine ring was present at different rotational orientations. All new compounds prepared were characterized by 1H and 13C{1H} NMR spectroscopy, the structure of compounds 2d, 2h and 4a being determined by X-ray diffraction analysis. DFT was used to analyze the relative stability and the structural orientation of the isomers.

Keywords

Alkyne insertion; TpMe2 iridium complexes; Dimethylacetylene dicarboxylate; C–H activation; DFT calculations

1. Introduction

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The insertion of unsaturated molecules into M–H or M–C bonds is an important reaction in organometallic chemistry [1]; in particular, alkynes constitute interesting building blocks in metal-mediated organic synthesis of compounds that possess many industrial applications [2]. In previous studies, it has been clearly shown that the presence of a Tp ligand in a metal′ compound (Tp stands for any type of hydrotris(pyrazolyl)borate ligand) favors octahedral′ coordination [3], [4], [5] and [6], thus, for TpMe2Ir derivatives, the +3 oxidation state is favorable [7] and [8]. The reaction of the Ir(I) olefin derivative TpMe2Ir(C2H4)2 with dimethylacetylene dicarboxylate (DMAD) forms the mixed adduct TpMe2Ir(C2H4)(DMAD) at low temperature and it is stable below 10 °C [9]; above this temperature, in the absence of other reagents, it evolves by C–H activation of the ethylene, as observed for other related derivatives of composition TpMe2Ir(C2H4)(L) (L = C2H4, PR3, …) [8], [9] and [10]. This is in contrast with TpMe2Ir(C2H4)(DMAD), where it forms an iridacyclopentene by the oxidative coupling of the two unsaturated ligands [11]. The ethylene ligand in the TpMe2Ir derivative is weakly bonded, and can be easily replaced by other Lewis bases [9].

An early example of the insertion of DMAD into an Ir–H bond reported the formation of an E-alkenyl derivative by the reaction of Ir(H)(CO)(PPh3)3 with DMAD [12]; similarly, the insertion of this alkyne into M–acyl or M–aryl bonds is also known [13] and [14], as well as for other insertions, that finally yield alkenyl derivatives [15] and [16]. In this paper, we report the reaction of the above mentioned Ir(I) derivative TpMe2Ir(C2H4)(DMAD) with aliphatic and aromatic carboxylic acids to produce the E-alkenyl iridium complexes TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H4R), (R = H, 2a; o-OH, 2b; o -Cl, 2c; m-Cl, 2d; o-NO2, 2e; m-NO2, 2f;o-Me, 2g;p-Me, 2h) and TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)Me) (3) as the result of the insertion of the alkyne into the hypothetical Ir–H bond formed upon protonation of the metal compound by the corresponding acid. Furthermore, the adducts TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(L)(OC(O)C6H5), (L = Py, 4a; m-Br–Py, 4b; m-Cl–Py, 4c; NCMe, 5) were synthesized by the reaction of the convenient precursor with the appropriate Lewis base. The existence of two isomers of compounds 4b and 4c was found in solution by NMR, and DFT calculations were used to analyze their structural orientation.

2. Results and discussion

2.1. Synthesis and characterization of irida-E-alkenyl compounds

In the reaction of TpMe2Ir(C2H4)2 (1) dissolved in CH2Cl2 with DMAD (1.0 equiv amount) and then with 1.0 equiv amount of a substituted benzoic acid at low temperature (−10 °C), E-alkenyl derivatives 2a–2h were obtained (Scheme 1). These derivatives exhibit a high thermal stability since they experience no structural transformation when heated in cyclohexane at 150 °C.

The above scheme shows that the two C2H4 molecules in the starting material have been replaced by alkenyl and carboxylate ligands and the final compounds satisfy the 18 e− count by the coordination of a molecule of adventitious water. Once the presence of water in the final products was realized, the reactions were carried out by adding a slight excess of this reagent. The use of those different carboxylic acids has revealed that there is no significant change in the chemical reactivity varying the electron-donors OR withdrawing substituent.

The NMR data confirm the structure proposed for compounds 2. For 2a, in the 1H NMR spectrum, a signal at low field (9.12 ppm) accounts for the coordinated water molecule, while the alkenyl hydrogen (4-H) resonates at 4.62 ppm. In the 13C{1H} NMR, the carboxylate ester

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carbons give rise to singlets at 180.8 and 163.4 ppm, while the signal at 181.9 ppm is assigned to the carboxylate carbon of the former acid. The resonances for two alkenyl carbons are found at 152.1 (Ir–C(R)) and 126.7 ppm (Ir–C(R)double bond; length as m-dashC(H)(R)).

When the reaction (Scheme 1) was performed with acetic acid instead of a benzoic one, a new derivative TpMe2Ir(MeCO2Cdouble bond; length as m-dashCHCO2Me)(H2O)(OCOMe) (3, Scheme 2) was obtained. A deuterium labeled isotopic experimental using D2O and MeCO2D was performed to show that the source of the proton of the E-alkenyl ligand was from the acid.

The formation of complexes 2 and 3 can then be proposed as shown in Scheme 3. The known TpMe2Ir(C2H4)(DMAD) [9] and [17] is initially formed (it is in fact observed in monitoring the reaction by NMR, CD2Cl2, −40 °C), to be protonated by the acid. Subsequent migratory insertion of the alkyne into the Ir–H bond, replacement of the ethylene by the corresponding carboxylate, and coordination of water, would yield the final products.

2.2. Reactivity of the irida-E-alkenyl 2a towards Lewis bases

The reactions of 2a with pyridine (Py) and its monosubstituted derivatives (m-Br–Py, m-Cl–Py) or with acetonitrile (MeCN) were carried out in order to determine its chemical behavior in the presence of Lewis bases. These reactions provide the adducts TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(NC5H4R)(OC(O)C6H5) (R = H, 4a; m-Br, 4b; m-Cl, 4c) and TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(NCMe)(OC(O)C6H5) (5) in high yields (≥90%, Scheme 4).

The structure proposed for compounds 4 and 5 is assigned on the bases of NMR and X-ray analyses (see below). The pyridine derived compound 4a exhibits five different signals for the pyridine protons in the 1H NMR spectrum, thus indicating a restricted rotation around the Ir–N(Py) bond. The signal for the alkenyl proton appears at 4.52 ppm, in the same region as the parent compounds 2. In the reactions of 2a with the halogenated pyridines (m-Br–Py or m-Cl–Py), compounds 4b and 4c are formed, respectively. The 1H NMR spectra recorded for the compounds show that there are two different sets of signals (see Experimental section) in each case, corresponding to two different products, possibly two isomers having different pyridine ring orientations, due to restricted rotation around the Ir–N.

A variable temperature NMR study (from 25 to 70 °C) shows no exchange between the two sets of signals in each case. Although we were unable to separate both isomers, 2D-NOESY NMR spectra indicate for the major isomer in each case, a correlation between the pyridine 14-H (the H atom in the ortho position close to the halide substituent) and the carboxylate 9-H and H-13 atoms, indicating that the major isomer in both cases is the one with the halide substituent in the pyridine being close to the carboxylate ligand phenyl ring.

3. DFT geometrical analysis of compound 4b

In order to analyze the pyridine ring orientations in compound 4b, DFT was used to analyze its structural parameters. First a partial optimization for 4b was performed by DFT; then the rotational barrier over the equatorial plane (O–Ir–NPy–CPy) was obtained to generate the different rotamers. In the rotation process, at every 20° change, the geometry was optimized and the resulting structures are presented in Fig. 1. In the potential energy surface (PES) analysis, it was found that there are two low energy rotamers that have an energy difference of 0.5 kcal mol−1. The stable conformer 4b (structure IV) (Fig. 1) was found at a rotational′ angle of 340°, and another isomer 4b″ (structure II) (Fig. 1) at 160° was detected. In conformer

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4b , the bromine atom attached to the pyridine ring is nearest to benzoate group, while for the′ other isomer 4b″, the bromine atom is placed on the opposite side of the benzoate group. Furthermore, other higher energy conformers (structures I at 60° and III at 240°) are shown (Fig. 1). For the structures II and IV, a full optimization was performed by using different functionals (LDA, PW91 and PBE) with base sets TZP and the results show that structure IV (4b) is more stable than that of II (4b″) having an energy difference about 0.33–0.6 kcal/mol; this′

observation is in agreements with the NMR results that the stable isomer is IV (4b ).′

The stable conformers [II (4b″) and IV (4b )] exhibit a distorted octahedral geometry (Fig. 2).′ The bond distances obtained for conformer II were: Ir–NTp = 1.97, 2.03 and 2.09 Å and Ir–NPy = 2.09 Å, and for conformer IV, Ir–NTp = 2.05, 2.06 and 2.13 Å and Ir–NPy = 2.08 Å. In both structures, the existence of non-conventional hydrogen bonds, i.e., C–H–O = 2.03 Å and C–H–N = 2.04 Å for II and C–H–O = 2.00 Å and C–H–N = 2.44 Å for IV, is established. The theoretical geometrical data are in good agreement with that observed in the X-ray structure of compound 4a.

Since the energy barrier between the stable conformers [II (4b″) and IV (4b )] is high (13.8 kcal′ mol−1), (Fig. 2) the inter-conversion between one isomer and another turns out to be a difficult process, and there is also a steric hindered congestion between the substituted pyridine ring and other neighboring groups; as seen in Fig. 3. Therefore; compounds 4b and 4b′″ are produced separately with different pyridine ring orientations. This observation is in agreement with the variable temperature NMR results in that no inter-conversion of isomer 4b to 4b″ is observed. From the above studies, we propose that the major isomer 4b is assigned′ ′

to the conformer IV while other isomer 4b″ corresponds to conformer II (Scheme 5). Similarly, for compounds 4c and 4c″, the same calculation method was employed, the results were′ almost same as those observed for 4b; this suggests that the existence of the same type of geometrical rotamers for 4c is manifested. Furthermore, since the non-conventional hydrogen bonds that are present in the structure can also contribute to the prevention of the rotation of the pyridine ring, the presence of two conformers in the NMR solution is confirmed.

4. X-ray diffraction studies

Suitable crystals for compounds 2d, 2h and 4a were obtained and their solid-state structures were determined by X-ray diffraction analysis.

4.1. Complexes 2d and 2h

ORTEP views of 2d and 2h are shown in Fig. 4 and Fig. 5, respectively while Table 1 shows selected bond lengths [Å] and angles [°] for compounds 2 and 4a. Both compounds 2 exhibit a distorted octahedral coordination, as expected for these Ir(III) derivatives [7] and [18]. The alkenyl bonds C(18)–C(19) have typical values for Cdouble bond; length as m-dashC double bonds [19] (1.349(7) for 2d and 1.350(8) for 2h). The three distances to iridium Ir(1)–C(18), Ir(1)–O(6) and Ir(1)–O(1), with values of 2.031(5) 2.089(3) and 2.099(3) Å for 2d and 2.019(6), 2.069(4) and 2.094(4) Å for 2h, fall in the range of a single bond. Because of the higher trans influence of alkenyl ligand in comparison with the two o-donor ligands water and carboxylate, the Ir–N(pyrazolyl) bonds trans to the oxygen atoms (2.0225 av 2d and 2h) are shorter than the distance trans to the carbon atom C(18) (2.148 av 2d and 2h) and 2h[9].

In both structures, the presence of a hydrogen bond between oxygen (benzoic acid) and hydrogen atoms (water molecule) was observed. The H-bond distance O(7)–H(1B) = 1.811 Å for 2d and O(7)–H(1A) = 1.712(5) Å for 2h was seen to be smaller than the sum of their Van der

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Waals radii (ΣVwRO–H = 2.72 Å) [20] and greater than the sum of covalent radii (ΣCRO–H = 0.97 Å) [21].

4.2. Complex 4a

For the case of 4a, two molecules are present in the asymmetric unit cell. Fig. 6 shows an ORTEP view for one of these molecules. The distortion of the octahedral geometry, characteristic of TpMe2Ir(III) derivatives, is shown by the deviation of the bond angles: N(2)–Ir(1)–N(4) = 89.16(18)°, N(2)–Ir(1)–N(6) = 88.30(18)°, N(4)–Ir(1)–N(6) = 87.80(17)°. Furthermore, the angle for C(18)–Ir(1)–N(7) = 96.1(2)° is greater than that observed for C(18)–Ir(1)–O(1),91.65(17)° and 90.7(2)° for 2d and 2h, respectively. The shortest angle obtained for O(6)–Ir(1)–N(7) 83(16)° is due to the bulky ligand (Py vs. H2O) in 4a, implying that the pyridine ring is arranged in such a way that it interacts with hydrogen atoms of methyl pyrazolyl fragment (H-4a and H-14c): (H’s(Pz)⋅Py: 3.413 (15) and 3.030(21) Å). Once more, the bond length of Ir(1)–N(6), of 2.130(4) Å, is larger to the other two distance from Ir to the N atoms of the pyrazolyl rings, due to the larger trans influence of the alkenyl ligand coordinated trans to N(6).

The bond distance C(18)–C(19) (1.349(8) Å) observed in 4a is similar to that found in compounds 2d and 2h, thus indicating that the coordination nature of E-alkenyl fragment is not affected by coordinating the Lewis base to the metal ion. Furthermore, other bond lengths Ir(1)–C(18) 2.057(6), Ir(1)–O(6) 2.048(4) and Ir(1)–N(7) 2.068(5) Å are characteristic of single bonds. It is noticed that the carboxylate carbonyl group is symmetrically located between two pyrazolyl rings, having a short contact with the CH2Cl2 molecule [H s(CH2Cl2)′ ⋯O(7): 2.3726(1) and 2.7037(1) Å].

5. Conclusions

The Ir(1) adduct TpMe2Ir(C2H4)2(DMAD) reacts with a variety of carboxylic acids to yield alkenyl derivatives of the DMAD ligand, with displacement of the olefin. The products formed, which contain the alkenyl moiety, the carboxylate ligand and a coordinated molecule of water, have been shown to react with Lewis bases, this reagent substituting for the labile water. For the case of two derivatives containing benzoate and m-substituted pyridines, two sets of isomers are formed, which are derived from restricted rotation of the coordinated Lewis base. DFT studies were performed to analyze the nature of the mentioned isomers.

6. Experimental section

6.1. General procedures

All experiments were performed under a nitrogen or an argon atmosphere using conventional Schlenk techniques. Solvents were dried, degassed and then used for the experimental studies. The prepared compounds were purified by flash column chromatography using silica gel (Merck 60, 230–400 mesh). Mass spectra were recorded at Mass Service unit, university of Sevilla, Spain (FAB/High Resolution) and at CINVESTAV-México (HR-LC 1100/MSD TOF Agilent Technology equipment). Elemental analyses were obtained in a Perkin–Elmer series II Analyzer 2400. Infrared spectra were recorded for the complexes in the solid state as KBr pellets on a PERKIN Elmer 2000 FT-IR instrument. NMR spectra are measured on JEOL Eclipse 400, Bruker DRX-500, DRX-400, DPX-300 and VARIAN 400 spectrometers in CDCl3. The 1H or 13C residual resonance signal of the solvent was used as an internal standard, but chemical shifts are reported with respect to TMS. Most of the NMR assignments are based on the extensive 1H–1H decoupling experiments, and homo and heteronuclear two-dimensional spectra. The

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complexes TpMe2Ir(C2H4)2 (1) and TpMe2Ir(C2H4)(DMAD) were prepared according to published procedure [8] and [9].

6.2 General procedure for the synthesis of the iridium complexes TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H4R), (R = H, 2a; o-OH, 2b; o-Cl, 2c; m-Cl, 2d; o-NO2, 2e; m-NO2, 2f, o-Me, 2gp–Me, 2h) and TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)Me) (3)

To the compound TpMe2Ir(C2H4)2 (1) dissolved in CH2Cl2 (5 ml), at −10 °C, DMAD (1 equiv) was added. The respective mixture was stirred for 10 min and then 1.0 equiv amount of aromatic or aliphatic carboxylic acid was added. The mixture was allowed to reach the room temperature (25 °C) and then it was stirred for 14 h. The solvent was removed under low pressure. The product obtained was washed with pentane (10 ml), and dried under vacuum.

6.3. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H5) (2a)

The above procedure was employed for the preparation of 2a. The following compounds were used: TpMe2Ir(C2H4)2 (1) (50 mg; 0.091 mmol), DMAD (11.2 μL; 0.091 mmol), benzoic acid (11.1 mg; 0.091 mmol) and CH2Cl2 (3.0 mL). Yield: (solid, 62.9 mg, 89%). 1H NMR (CDCl3): δ = 9.12 (br s, 2H, H2O), 7.93 (d, 2H, 3JH–H = 7.7 Hz, 9-H, 13-H), 7.43 (t, 1H, 3JH–H = 7.4 Hz, 11-H), 7.33 (t, 2H, 3JH–H = 7.7 Hz, 10-H, 12-H), 5.86, 5.83, 5.75 (3s, 1H each, 3CHPz), 4.62 (s, 1H, 4-H), 3.72 (s, 3H, 1-CH3), 3.59 (s, 3H, 6-CH3), 2.48, 2.45, 2.40, 2.27, 2.24, 2.19 (6s, 3H each, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 181.9 (C-7), 180.8 (C-2), 163.4 (C-5), 152.1 (C-3), 152.1, 151.3, 151.2, 144.3, 144.1, 144.0 (6CqPz), 134.1 (C-8), 131.5 (1JC–H = 159.8 Hz, C-11), 129.3 (1JC–H = 161.5 Hz, C-9, C-13), 127.8 (1JC–H = 152.6 Hz, C-10, C-12), 126.7 (1JC–H = 166.1 Hz, C-4), 108.4, 108.2, 107.7, (1JC–H = 174.4 Hz, 3CHPz), 52.1 (1JC–H = 146.8 Hz, CH3-1), 50.9 (1JC–H = 146.1 Hz, CH3-6), 14.6, 13.5, 12.7, 12.3 (in a 1:1:3:1 ratio respectively) (1JC–H = 128.4 Hz, 6CH3Pz). IR (KBr): ν = 3388 (H2O), 2948 (CH3), 2533 (BH), 1714 (CO) cm−1. HR-MS (ESI-TOF) calcd for MH+ (C28H37BN6O7Ir) 773.2440, MH+ found 773.2458.

6.4. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H4o–OH) (2b)

According to the above mentioned procedure, compound 1 (50 mg; 0.091 mmol), DMAD (11.2 μL; 0.091 mmol), salicylic acid (11.1 mg; 0.091 mmol) and CH2Cl2 (3 mL) were used to prepare the complex 2b. Yield: (solid, 33.1 mg, 46%). 1H NMR (CDCl3): δ = 11.40 (br s, 1H, OH), 8.40 (br s, 2H, H2O), 7.69 (dd, 1H, 3JH–H = 7.9, 4JH–H = 1.8 Hz, 13-H), 7.31 (td, 1H, 3JH–H = 7.3, 4JH–H = 1.8 Hz, 11-H), 6.87 (dd, 1H, 3JH–H = 8.0, 4JH–H = 1.2 Hz, 10-H), 6.73 (td, 1H, 3JH–H = 7.3, 4JH–H = 1.2 Hz, 12-H), 5.87, 5.84, 5.76 (3s, 1H each, 3CHPz), 4.60 (s, 1H, 4-H), 3.75 (s, 3H, 1-CH3), 3.58 (s, 3H, 6-CH3), 2.49, 2.45, 2.41, 2.24, 2.16, (6s, 1:1:1:2:1, 3H each, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 183.0 (C-7), 181.2 (C-2), 163.5 (C-5), 160.4 (C-9), 152.1, 151.4, 151.3, (3CqPz), 151.1 (C-3), 144.6, 144.5, 144.3 (3CqPz), 134.3 (1JC–H = 158.4 Hz, C-11), 131.3 (1JC–H = 164.4 Hz, C-13), 127.1 (1JC–H = 166.1 Hz, C-4), 118.7 (1JC–H = 162.2 Hz, C-12), 117.1 (1JC–H = 163.7 Hz, C-10), 116.4 (C-8), 108.6, 108.4, 107.9, (1JC–H = 176.1 Hz, 3CHPz), 52.1 (1JC–H = 147.60 Hz, CH3-1), 51.1 (1JC–H = 146.0 Hz, CH3-6), 14.7, 13.6, 12.8, 12.7, 12.4 (in a 1:1:2:1:1 ratio respectively) (1JC–H = 128.3 Hz, 6CH3Pz). IR (KBr): ν = 3439 (H2O), 2949 (CH3), 2534 (BH), 1696 (CO) cm−1. HR-MS (ESI-TOF) calcd for MH+ (C28H37BN6O8Ir) 789.2389, found 789.2369.

6.5. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H4o–Cl) (2c)

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According to the above procedure, compound 2c was obtained by using compound 1 (50 mg; 0.091 mmol), DMAD (11.2 μL; 0.091 mmol), o-chlorobenzoic acid (14.3 mg; 0.091 mmol) and CH2Cl2 (3.0 mL). Yield: (solid, 36.1 mg, 49.0%). 1H NMR (CDCl3): δ = 8.70 (br, s, 2H, H2O), 7.71 (dd, 1H, 3JH–H = 7.7, 4JH–H = 1.5 Hz, 13-H), 7.24 (dd, 1H, 3JH–H = 8.0, 4JH–H = 1.1 Hz, 10-H), 7.19 (td, 1H, 3JH–H = 7.3, 4JH–H = 1.8 Hz, 11-H), 7.10 (td, 1 H, 3JH–H = 7.40, 4JH–H = 1.1 Hz, 12-H), 5.78, 5.72, 5.67 (3s, 1H each, 3CHPz), 4.53 (s, 1H, 4-H), 3.79 (s, 3H, 1-CH3), 3.52 (s, 3H, 6-CH3), 2.37, 2.36, 2.32, 2.27, 2.17, 2.14 (6s, 3H each, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 179.8 (C-7), 179.7 (C-2), 162.4 (C-5), 151.0, 150.5, 150.3 (3CqPz), 150.3 (C-3), 143.3, 143.1, 143.0 (3CqPz), 133.3 (C-8), 131.3 (C-9), 130.1 (1JC–H = 164.0 Hz, C-13), 129.9 (1JC–H = 162.9 Hz, C-11), 129.6 (1JC–H = 166.9 Hz, C-10), 126.1 (1JC–H = 166.1 Hz, C-4), 125.1 (1JC–H = 163.0 Hz, C-12), 107.3, 107.1, 106.6 (1JC–H = 175.2 Hz, 3CHPz), 51.5 (1JC–H = 147.6 Hz, CH3-1), 49.9 (1JC–H = 146.8 Hz, CH3-6), 13.9, 12.4, 12.3, 11.6, 11.3 (in a 1:1:1:2:1 ratio respectively) (1JC–H = 129.2 Hz, 6CH3Pz). IR (KBr): ν = 3426 (H2O), 2925 (CH3), 2532 (BH), 1719 (CO) cm−1. HR-MS (FAB) calcd for MH+ (C28H35BClN6O7Ir) 807.2056, found 807.2097.

6.6. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H4m-Cl) (2d)

Similarly, compound 1 (50 mg; 0.091 mmol), DMAD (11.2 μL; 0.091 mmol), m-chlorobenzoic acid (14.4 mg; 0.091 mmol) and CH2Cl2 (3.0 mL) were used to prepare the complex 2d. Yield: (solid, 50.2 mg, 68%). 1H NMR (CDCl3): δ = 8.83 (br s, 2H, H2O), 7.82 (t, 1H, 4JH–H = 1.7 Hz, 9-H), 7.73 (td, 1H, 3JH–H = 8.1, 4JH–H = 1.5 Hz, 13-H), 7.32 (ddd, 1H, 3JH–H = 8.1, 4JH–H = 2.2, 1.1 Hz, 11-H), 7.18 (t, 1H, 3JH–H = 8.1 Hz, 12-H), 5.79, 5.76, 5.67 (3s, 1H each, 3CHpz), 4.53 (s, 1H, 4-H), 3.64 (s, 3H, 1-CH3), 3.51 (s, 3H, 6-CH3), 2.41, 2.37, 2.33, 2.19, 2.15, 2.09 (6s, 3H each, 6CH3pz). 13C{1H} NMR (CDCl3): δ = 179.7 (C-2), 179.3 (C-7), 162.4 (C-5), 150.5 (C-3), 151.0, 150.3, 150.2, 144.3, 143.2, 143.1 (6CqPz), 134.9 (C-8), 132.9 (C-10), 130.5 (1JC–H = 166.10 Hz, C-11), 128.3 (1JC–H = 167.6 Hz, C-9), 128.1 (1JC–H = 163.0 Hz, C-12), 126.3 (1JC–H = 168 Hz, C-13), 125.8 (1JC–H = 165.30 Hz, C-4), 107.4, 107.2, 106.7, (1JC–H = 174.5 Hz, 3CHPz), 51.1 (1JC–H = 146.8 Hz, CH3-1), 49.8 (1JC–H = 146.0 Hz, CH3-6), 13.6, 12.4, 11.7, 11.3 (in a 1:1:3:1 ratio respectively) (1JC–H = 129.0 Hz, 6CH3Pz). IR (KBr): ν = 3426 (H2O); 2925 (CH3), 2533 (BH), 1715 (CO) cm−1. HR-MS (FAB) calcd for MH+ (C28H36BClN6O7Ir) 807.2056, found 807.2087.

6.7. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H4o–NO2) (2e)

For complex 2e, compound 1 (50 mg; 0.091 mmol), DMAD (11.2 μL; 0.091 mmol), o-nitrobenzoic acid (15.3 mg; 0.091 mmol) and CH2Cl2 (3 mL) were employed. Yield: (solid, 66.0 mg, 88.2%). 1H NMR (CDCl3): δ = 8.42 (br, s, 2H, H2O), 7.93, 7.50 (m, 4-H, 10-H–13-H), 5.88, 5.82, 5.74 (3s, 1H each, CHPz), 4.57 (s, 1H, 4-H), 3.80 (s, 3H, 1-CH3), 3.59 (s, 3H, 6-CH3), 2.46, 2.44, 2.40, 2.32, 2.20, 2.19 (6s, 3H each, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 180.8 (C-2), 177.9 (C-7), 163.6 (C-5), 152.2, 152.0, 151.4 (3CqPz), 151.0 (C-3), 150.3 (C-9), 144.6, 144.4, 144.3 (3CqPz), 131.5, 131.2, 131.0, 123.0 (1JC–H = 166.0 Hz, C-10–C-13), 128.7 (C-8), 127.5 (1JC–H = 166.0 Hz, C-4), 108.6, 108.3, 107.9 (1JC–H = 176.1 Hz, 3CHPz), 52.7 (1JC–H = 146.3), 51.2 (1JC–H = 147.6 Hz, CH3-6), 15.0, 13.6, 13.2, 13.0, 12.9, 12.6 (1JC–H = 128.4 Hz, 6CH3Pz). IR (KBr): ν = 3427 (H2O), 2925 (CH3), 2534 (BH), 1714 (CO) cm−1. HR-MS (ESI-TOF) calcd for MH+ (C28H36BN7O9Ir) 818.2291, found 818.2290.

6.8. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H4m-NO2) (2f)

7

In the same procedure mentioned above, compound 1 (50 mg; 0.091 mmol), DMAD (11.2 μL; 0.091 mmol), m-nitrobenzoic acid (15.2 mg; 0.091 mmol) and CH2Cl2 (3 mL) were used to prepare complex 2f. Yield: (solid, 56.1 mg, 75.0%). 1H NMR (CDCl3): δ = 8.76 (t, 1H, 4JH–H = 1.9 Hz, 9-H), 8.73 (br, s, 2H, H2O), 8.30 (ddd, 1H, 3JH–H = 8.0, 4JH–H = 2.2, 1.1 Hz, 11-H), 8.27 (dd, 1H, 3JH–H = 8.1, 4JH–H = 1.5 Hz, 13-H), 7.54 (t, 1 H, 3JH–H = 8.1 Hz, 12-H), 5.90, 5.86, 5.77 (3s, 1H each, 3CHpz), 4.62 (s, 1H, 4-H), 3.70 (s, 3H, 1-CH3), 3.58 (s, 3H, 6-CH3), 2.50, 2.46, 2.42, 2.30, 2.24, 2.17 (6s, 3H each, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 180.8 (C-2), 179.2 (C-7), 163.6 (C-5), 152.2, 151.5, 151.3 (3CqPz), 151.3 (C-3), 148.3 (C-10), 144.7, 144.6, 144.5 (3CqPz), 136.1 (C-8), 135.0 (1JC–H = 165.2 Hz, C-13), 129.2 (1JC–H = 165.2 Hz, C-12), 127.2 (1JC–H = 166.3 Hz, C-4), 126.3 (1JC–H = 177.1 Hz, C-11), 124.6 (1JC–H = 170.6 Hz, C-9), 108.7, 108.6, 108.0 (1JC–H = 175.20 Hz, 3CHPz), 52.4 (1JC–H = 146.8 Hz, CH3-1), 51.2 (CH3-6), 14.8, 13.7, 13.0, 12.9, 12.5 (in a 1:1:1.2:1 ratio respectively) (1JC–H = 129.2 Hz, 6CH3Pz). IR (KBr): ν = 3420 (H2O), 2926 (CH3), 2531 (BH), 1715 (CO) cm−1. HR-MS (ESI-TOF) calcd for MH+ (C28H36BN7O9Ir) 818.2291, found 818.2291.

6.9. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H4o–CH3) (2g)

With the same general procedure, the complex 2g was prepared by using compound 1 (50 mg; 0.091 mmol), DMAD (11.2 μL; 0.091 mmol), o-methylbenzoic acid (22.0 mg; 0.091 mmol) and CH2Cl2 (3.0 mL). Yield: (solid, 70.0 mg, 97%). 1H NMR (CDCl3): δ = 9.13 (br, s, 2H, H2O); 7.82 (d, 1H, 3JH–H = 7.4 Hz, 13-H); 7.29 (t, 1H, 3JH–H = 7.3 Hz, 12-H); 7.13 (d, H, 3JH–H = 7.3 Hz, 10-H), 7.12 (t, 1H, 3JH–H = 7.3 Hz, 11-H); 5.84, 5.80, 5.75 (3s, 1H each, 3CHPz); 4.60 (s, 1H, 4-H); 3.83 (s, 3H, 1-CH3); 3.59 (s, 3H, 6-CH3); 2.49 (s, 3H, CH3o–CH3); 2.44, 2.41, 2.25, 2.23, 2.21 (5s, in a 6:3:3:3:3 H ratio respectively, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 183.6 (C-7); 180.7 (C-2); 163.4 (C-5); 152.0 (C-3); 151.8, 151.2, 150.4, 144.2, 144.0, 143.9 (6CqPz); 138.6 (C-8); 133.8 (C-9); 131.2 (1JC–H = 158.4 Hz, C-10); 130.5 (1JC–H = 160.3 Hz, C-13); 125.2 (1JC–H = 163.8 Hz, C-11,C-12); 126.8 (1JC–H = 166.2 Hz, C-4); 108.3, 108.0, 107.6 (1JC–H = 171.0 Hz, 3CHPz); 52.2 (1JC–H = 146.9 Hz, CH3-1); 50.9 (1JC–H = 146.2 Hz, CH3-6); 21.4 (1JC–H = 127.7 Hz, CH3o–CH3); 14.7, 13.5, 13.0, 12.6, 12.4 (in a 1:1:1:2:1 ratio respectively) (1JC–H = 130.0 Hz, 6CH3Pz). IR (KBr): ν = 3439 (H2O), 2922 (CH3), 2533 (BH), 1692 (CO) cm−1. HR-MS (ESI-TOF) calcd for MH+ (C29H39BN6O7Ir) 787.2597, found.787.2600.

6.10. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)C6H4p–CH3) (2h)

Compound 1 (50 mg; 0.091 mmol), DMAD (11.2 μL; 0.091 mmol), p-methylbenzoic acid (22.0 mg; 0.091 mmol) and CH2Cl2 (3.0 mL) were used to prepared complex 2h by employing the above described general method. Yield: (solid, 65.0 mg, 90.3%). 1H NMR (CDCl3): δ = 9.17 (br, s, 2H, H2O); 7.81(d, 2H, 3JH–H = 8.4 Hz, 9-H, 13-H); 7.13 (d, 2H, 3JH–H = 8.4 Hz, 10-H, 12-H); 5.85, 5.82, 5.74 (3s, 1H each, 3CHPz); 4.60 (s, 1H, 4-H); 3.71 (s, 3H, 1-CH3); 3.58 (s, 3H, 6-CH3); 2.35 (s, 3H, 14-CH3); 2.47, 2.44, 2.40, 2.25, 2.23, 2.17 (6s, 3H each, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 182.3 (C-7); 181.0 (C-2); 163.7 (C-5); 152.6 (C-3); 152.3, 151.5, 144.4, 144.3, 144.2 (in a 1:2:1:1:1 ratio respectively) (6CqPz); 142.1 (C-11); 131.6 (C-8); 129.5 (1JC–H = 161.4 Hz, C-9, C-13); 128.7 (1JC–H = 158.4 Hz, C-10, C-12); 126.7 (1JC–H = 166.1 Hz, C-4); 108.5, 108.4, 107.9 (1JC–H = 175.3 Hz, 3CHPz); 52.4 (1JC–H = 146.1 Hz, CH3-1); 51.1 (1JC–H = 146.1 Hz, CH3-6); 21.7 (1JC–H = 126.0 Hz, CH3p–CH3); 14.7, 13.7, 13.0, 12.9, 12.8, 12.5 (1JC–H = 129.1 Hz, 6CH3Pz). IR (KBr): ν = 3407 (H2O), 2950 (CH3), 2533 (BH), 1698 (CO) cm−1. HR-MS (ESI-TOF) calcd for MH+ (C29H39BN6O7Ir) 787.2597, found 787.2597.

6.11. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(H2O)(OC(O)Me) (3a)

8

Similarly, the product was obtained with using compound 1 (50 mg; 0.091 mmol), DMAD (11.2 μL; 0.091 mmol), acetic acid (5.24 μL; 0.091 mmol) and CH2Cl2 (3.0 mL). Yield: 49.6 mg, 76.3% of beige solid. 1H NMR (CDCl3): δ = 8.78 (br, s, 2H, H2O), 5.87, 5.80, 5.73 (3s, 1H each, 3CHPz), 4.58 (s, 1H, 4-H), 3.93 (s, 3H, 1-CH3), 3.60 (s, 3H, 6-CH3), 1.99 (s, 3H, 8-CH3), 2.43, 2.42, 2.38, 2.25, 2.22, 2.18 (6s, 3H each, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 187.7 (C-7), 180.7 (C-2), 163.7 (C-5), 152.4, 152.2, 151.3 (3CqPz), 151.3 (C-3), 144.4, 144.3, 144.26 (3CqPz), 126.9 (1JC–H = 166.1 Hz, C-4), 108.6, 108.4, 107.9 (1JC–H = 175.3 Hz, 3CHPz), 52.3 (1JC–H = 146.9 Hz, CH3-1), 51.1 (1JC–H = 146.0 Hz, CH3-6), 24.2 (1JC–H = 127.6 Hz, CH3-8), 14.4, 12.9, 12.8, 12.78, 12.5 (in a 1:1:2:1:1 ratio respectively) (1JC–H = 124,6 Hz, 6CH3Pz). IR (KBr): ν = 3419 (H2O), 2926 (CH3), 2529 (BH), 1713 (CO) cm−1. HR-MS (ESI-TOF) calcd for MH+ (C23H35BN6O7Ir) 711.2284, found 711.2286.

6.12. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(NC6H5)(OC(O)C6H5) (4a)

The solution of compound 2a (50 mg; 0.065 mmol) dissolved in pyridine (1.0 mL; 12.4 mmol) was stirred at 60 °C for 12 h. The volatiles were removed in vacuum, and the quantitative conversion into 4a was verified by 1H NMR spectroscopy. The obtained compound was crystallized from hexane at −20 °C, Yield: (solid, 48.0 mg, 89%). 1H NMR (CDCl3): δ = 9.20 (d, 1H, 3JH–H = 5.5 Hz, 14-H), 8.02 (d, 2H, 3JH–H = 7.7 Hz, 9-H, 13-H), 7.65 (t, 1H, 3JH–H = 7.3 Hz, 16-H), 7.50 (d, 1H, 3JH–H = 5.4 Hz, 18-H), 7.36 (t, 1H, 3JH–H = 6.2 Hz, 17-H), 7.27 (m, 3H, 10-H–12-H), 6.91 (t, 1H, 3JH–H = 6.6 Hz, 15-H), 5.76, 5.63, 5.56 (3s, 1H each, CHPz), 4.52 (s, 1H, 4-H), 3.88 (s, 3H, 1-CH3), 3.46 (s, 3H, 6-CH3), 2.44, 2.38, 2.36, 1.93, 1.54, 0.83 (6s, 3H each, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 177.9 (C-2), 171.7 (C-7), 164.0 (C-5), 155.8 (C-3), 154.0 (1JC–H = 178.4 Hz, C-18), 153.5 (1JC–H = 182.20 Hz, C-14), 152.7, 151.2, 151.1, 144.6, 143.2 (in a 1:1:1:1:2 ratio respectively) (6CqPz), 137.7 (1JC–H = 159.1 Hz, C-16), 135.8 (C-8), 130.0 (1JC–H = 159.1 Hz, C-10), 129.7 (1JC–H = 162.20 Hz, C-9, C-13), 127.6 (1JC–H = 158.4 Hz, C-11,C-12), 127.2 (1JC–H = 166.3 Hz, C-4), 124.5 (1JC–H = 166.8 Hz, C-15), 123.9 (1JC–H = 169.9 Hz, C-17), 108.3, 107.5, 107.2 (1JC–H = 173.8 Hz, 3CHPz), 51.0 (1JC–H = 146.1 Hz, CH3-6), 50.9 (1JC–H = 146.1 Hz, CH3-1), 15.3, 14.7, 13.0, 12.7, 10.9 (in a 1:1:2:1:1 ratio respectively) (1JC–H = 128.4 Hz, 6CH3Pz). IR (KBr): ν = 3447 (H2O), 2927 (CH3), 2532 (BH), 1703 (CO) cm−1. The compound shows decomposition during mass spectrometric experiments.

6.13. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(NC5H4m-Br)(OC(O)C6H5) (4b)

A solution of compound 2a (25 mg; 0.033 mmol) in CH2Cl2 (3.0 mL) and m-Br–pyridine (10.0 μl; 0.098 mmol) was stirred at 60 °C for 5 h. After the reaction was completed, volatiles were removed in vacuum and the quantitative conversion into 4b was verified by 1H NMR spectroscopy. 4b :4b″ in a 80:20 ratio. Major isomer 4b : 1H NMR (CDCl3): δ = 9.47 (d, 1H, 4JH–′ ′H = 2.0 Hz, 14-H), 9.29 (d, 1H, 3JH–H = 5.6 Hz, 18-H), 8.10 (m, 2H, 9-H, 13-H), 7.88 (dm, 1H, 3JH–H = 8.4 Hz, 16-H), 7.57 (d, 1H, 3JH–H = 5.6 Hz, 11-H), 7.35 (m, 2H, 10-H, 12-H), 6.88 (dd, 1H, 3JH–H = 8.0, 5.6 Hz, 17-H), 5.83, 5.72, 5.63 (3s, 1H each, CHPz), 4.57 (s, 1H, 4-H), 4.06 (s, 3H, 1-CH3), 3.54 (s, 3H, 6-CH3), 2.51, 2.45, 2.42, 2.00, 1.63, 0.95 (6s, 3H each, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 177.2 (C-2), 171.2 (C-7), 163.7 (C-5), 154.8 (C-3), 154.7 (1JC–H = 193.9 Hz, C-14), 152.0 (1JC–H = 162.0 Hz, C-18), 152.5, 150.7, 150.6, 144.4, 143.1, 143.0 (6CqPz), 140.0 (1JC–H = 171.0 Hz, C-16), 135.1 (C-8), 129.9 (1JC–H = 158.1 Hz, C-11), 129.3 (1JC–H = 160.9 Hz, C-9, C-13), 127.4 (1JC–H = 158.7 Hz, C-10, C-12), 126.9 (1JC–H = 165.7 Hz, C-4), 124.7 (1JC–H = 169.0 Hz, C-17), 119.1 (C-15), 108.1, 107.3, 107.1 (1JC–H = 174.7 Hz, 3CHPz), 51.1 (1JC–H = 145.5 Hz, CH3-6), 50.7 (1JC–H = 145.3 Hz, CH3-1), 15.0, 14.5, 12.7, 12.4, 10.7 (in a 1:1:2:1:1 ratio respectively) (1JC–H = 128.7 Hz, 6CH3Pz). Minor isomer 4b″: 1H NMR (CDCl3):

9

δ = 8.68 (s, 1H, 4JH–H = 1.6 Hz, 14-H), 8.53 (d, 1H, 3JH–H = 3.6 Hz, 18-H), 8.09 (m, 2H, 9-H, 13-H), 7.82 (dm, 1H, 3JH–H = 8.4 Hz, 16-H), 7.35 (m, 3H, 11-H, 12-H), 7.20 (dd, 1H, 3JH–H = 8.0, 4.8 Hz, 17-H), 5.87, 5.70, 5.66 (3s, 1H each, CHPz), 4.56 (s, 1H, 4-H), 3.95 (s, 3H, 1-CH3), 3.54 (s, 3H, 6-CH3), 2.53, 2.45, 1.99, 1.65, 0.98 (5s, in a 3:6:3:3:3 H ratio respectively, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 177.5 (C-2), 171.3 (C-7), 163.7 (C-5), 154.7 (C-3), 154.3 (1JC–H = 190.0 Hz, C-14), 151.8 (1JC–H = 164.5 Hz, C-18), 152.4, 150.5, 150.6, 144.7, 143.2, 143.0 (6CqPz), 140.2 (1JC–H = 170.9 Hz, C-16), 135.4 (C-8), 128.1 (1JC–H = 160.4 Hz, C-11), 129.3 (1JC–H = 160.9 Hz, C-9, C-13), 126.9 (1JC–H = 165.0 Hz, C-10, C-12), 127.0 (1JC–H = 165.6 Hz, C-4), 124.2 (1JC–H = 168.5 Hz, C-17), 119.4 (C-15), 108.2, 107.3, 107.2 (1JC–H = 173.4 Hz, 3CHPz), 50.8 (1JC–H = 145.4 Hz, CH3-6), 50.7 (1JC–H = 145.3 Hz, CH3-1), 14.8, 14.4, 12.8, 12.7, 12.5, 10.9 (1JC–H = 128.4 Hz, 6CH3Pz). Anal. for C33H38N7BO6BrIr·0.1CH2Cl2 (Mw = 920.13448): calcd: C, 43.21; H, 4.18; N, 10.66 Expt.: C, 42.33; H, 4.16; N, 9.89.

6.14. TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(NC5H4m-Cl)(OC(O)C6H5) (4c)

A solution of compound 2a (25 mg, 0.033 mmol) in CH2Cl2 (3.0 mL) and m-Cl–pyridine (9 μl, 0.096 mmol) was stirred at 60 °C for 5.0 h and then volatiles were removed under reduced pressure. The quantitative conversion into 6c was confirmed by 1H NMR spectroscopy. 4c :4c″′ in a 76:24 ratio. Major Isomer 4c : 1H NMR (CDCl3): δ = 9.36 (d, 1H, 4JH–H = 2.4 Hz, 14-H), 9.25′ (d, 1H, 3JH–H = 5.6 Hz, 18-H), 8.12 (m, 2H, 9-H, 13-H), 7.75 (dm, 1H, 3JH–H = 8.8 Hz, 16-H), 7.54 (d, 1H, 3JH–H = 6.0 Hz, 11-H), 7.41 (dd, 1H, 3JH–H = 13.6, 8.0 Hz, 10-H), 7.37 (m, 1H, 12-H), 6.94 (dd, 1H, 3JH–H = 8.4, 6.0, 17-H), 5.84, 5.73, 5.64 (3s, 1H each, CHPz), 4.59 (s, 1H, 4-H), 4.05 (s, 3H, 1-CH3), 3.55 (s, 3H, 6-CH3), 2.52, 2.46, 2.44, 2.02, 1.63, 0.96 (6s, 3H each, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 174.6 (C-2), 168.8 (C-7), 161.5 (C-5), 152.8 (C-3), 150.7 (1JC–H = 186.6 Hz, C-14), 149.7 (1JC–H = 184.0 Hz, C-18), 150.5, 148.8, 148.7, 142.7, 141.4, 141.3 (6CqPz), 135.7 (1JC–H = 166.3 Hz, C-16), 133.6 (C-8), 129.9 (C-15), 128.5 (1JC–H = 154.4 Hz, C-11), 127.9 (1JC–H = 156.9 Hz, C-9, C-13), 126.1 (1JC–H = 155.4 Hz, C-10, C-12), 125.6 (1JC–H = 160.7 Hz, C-4), 123.2 (1JC–H = 164.3 Hz, C-17), 107.2, 106.5, 106.3 (1JC–H = 173.4 Hz, 3CHPz), 51.6 (1JC–H = 146.4 Hz, CH3-6), 51.3 (1JC–H = 145.9 Hz, CH3-1), 16.5, 16.1, 14.4, 14.0, 12.4 (in a 1:1:2:1:1 ratio respectively) (1JC–H = 128.3 Hz, 6CH3Pz). Minor isomer 4c″: 1H NMR (CDCl3): δ = 8.58 (d, 1H, 4JH–H = 2.0 Hz, 14-H), 8.49 (dd, 1H, 3JH–H = 4.8, 4JH–H = 1.2 Hz, 18-H), 8.10 (m, 2H, 9-H, 13-H), 7.67 (dm, 1H, 3JH–H = 8.4 Hz, 16-H), 7.37 (m, 3H, 10-H, 11-H, 12-H), 7.27 (dd, 1H, 3JH–H = 13.2, 5.6 Hz, 17-H), 5.88, 5.71, 5.67 (3s, 1H each, CHPz), 4.58 (s, 1H, 4-H), 3.96 (s, 3H, 1-CH3), 3.55 (s, 3H, 6-CH3), 2.54, 2.46, 2.01, 1.66, 0.99 (5s, in a 3:6:3:3:3 H, 6CH3Pz). 13C{1H} NMR (CDCl3): δ = 174.9 (C-2), 168.9 (C-7), 161.5 (C-5), 152.8 (C-3), 150.5 (1JC–H = 183.2.0 Hz, C-14), 149.5 (1JC–H = 184.0 Hz, C-18), 150.3, 148.8, 148.6, 142.9, 141.5, 141.3 (6CqPz), 135.8 (1JC–H = 166.2 Hz, C-16), 133.9 (C-8), 130.3 (C-15), 126.7 (1JC–H = 156.1 Hz, C-11), 127.9 (1JC–H = 156.9 Hz, C-9, C-13), 125.1 (1JC–H = 155.4 Hz, C-10, C-12), 125.7 (1JC–H = 160.7 Hz, C-4), 122.7 (1JC–H = 164.2 Hz, C-17), 107.4, 106.5, 106.4 (1JC–H = 174.8 Hz, 3CHPz), 51.4 (1JC–H = 146.3 Hz, CH3-6), 51.3 (1JC–H = 145.9 Hz, CH3-1), 16.4, 16.0, 14.5, 14.1, 12.6 (in a 1:1:2:1:1 ratio respectively) (1JC–H = 127.2 Hz, 6CH3Pz). Anal. for C33H38N7BO6ClIr·0.5CH2Cl2 (Mw = 909.6566): calcd: C, 44.23; H, 4.32; N, 10.78 Expt.: C, 44.09; H, 4.28; N, 9.94.

6.15 TpMe2Ir(E-C(CO2Me)double bond; length as m-dashCH(CO2Me))(OC(O)C6H5)(NCMe) (5)

A solution of compound 2a (50 mg, 0.065 mmol) in acetonitrile (3.0 mL, 54 mmol) was stirred at 60 °C for 12 h. After the reaction was completed, volatiles were removed in vacuum. The quantitative conversion into 5 was established by 1H NMR spectroscopy. The compound

10

obtained was crystallized from hexane at −20 °C, Yield (solid, 50.5 mg, 98%). 1H NMR (CDCl3): δ = 7.87 (d, 2H, 3JH–H = 7.30 Hz, 9-H, 13-H); 7.33 (t, 1H, 3JH–H = 7.40 Hz, 11-H); 7.26 (t, 2H, 3JH–H = 6.60 Hz, 10-H, 12-H); 5.82, 5.80, 5.78 (3s, 1H each, 3CHPz); 4.64 (s, 1H, 4-H); 3.80 (s, 3H, 1-CH3); 3.57 (s, 3H, 6-CH3); 2.74 (s, 3H, 14-CH3); 2.44, 2.41, 2.29, 2.20, 2.12 (5s, in a 6:3:3:3:3 H ratio respectively, 6CH3Pz).13C{1H} NMR (CDCl3): δ = 177.8 (C-2); 173.2 (C-7); 163.7 (C-5); 152.3 (C-3); 152.0, 151.7, 151.0, 144.2, 143.8, 143.5 (6CqPz); 135.6 (C-8); 129.8 (C-11); 129.3 (C-9, C-13); 127.3 (C-10, C-12); 125.8 (C-4); 117.7 (C-15); 108.0, 106.9 (in a 2:1 ratio respectively) (3CHPz); 51.7 (CH3-1); 50.8 (CH3-6); 14.8, 14.5, 12.9, 12.8, 12.7, 12.3 (6CH3Pz); 3.8 (CH3-14). IR (KBr): ν = 2924 (CH3); 2519 (BH); 2237 (CN); 1710 (CO) cm−1. HR-MS (ESI-TOF) calcd for MH+ (C30H38BN7O6Ir) 796.2600, found 796.2604.

7. Computational procedure

Calculations were carried out by using Amsterdam Density Functional (ADF) code [22]. The geometry optimization was worked out using the LDA [23], PW91 [24] and PBE [25] exchange-correlation (XC) functional. The triple ζ + polarization (TZP) basis of Slater-type orbitals provided with the ADF package was used for all atoms. Full optimization geometry was performed for compound 4b using the X-ray structure data of compound 4a and then a rotational barrier analysis for the optimized geometry by rotating the pyridine ring in the counterclockwise up to 360° through a step 20° around the Ir–N bond and the dihedral angle (O–Ir–NPy–CPy) was used as starting point to generate the rotamers; in each step, all structures being fully optimized and they were checked by vibrational frequency analysis.

8. X-ray structure determination

Details for data collection structure refinement for 2d, 2h and 4a are presented in Table 2. The crystals (2d, and 4a) were mounted on glass fibers and the crystal 2h was mounted in MicroMounts (MitGen company, www.mitegen.com). For 2h (as solvated 2h·C5H12), data were collected using a Enraf–Nonius Kappa CCD Reflections and data for 2d (as solvated 2d·C5H12) and 4a (as solvated 4a·CH2Cl2) were collected on a Bruker SMART 5000 CCD-based diffractometer. For all compounds, all non-hydrogen atoms were refined anisotropically. Hydrogen atoms were fixed at idealized refined positions. Data collection and the determination of cell dimensions for all compounds were carried out using the collect software [26] and HKL Scalepack [27] The frames were integrated with the SAINT software package [28] using a narrow-frame algorithm. A semi-empirical absorption correction method (SADABS) [29] was applied in all cases. All structures were resolved by direct methods, completed by subsequent difference Fourier synthesis, and refined by full-matrix least-squares procedures using the SHELX-97 package [29].

Acknowledgments

Authors acknowledge the projects Consejo Nacional de Ciencia y Tecnología (CONACYT, Mexico, Grant No.: 025424, J110.380, I32816 and 84453), “Ricardo J. Zevada” Foundation, and the bilateral assistance CSIC (Sevilla, Spain)-CONACYT-UAEH (México) for the financial support. Additionally, Universidad Autónoma del Estado de Hidalgo (UAEH) Project No. DIP-ICBI-AAQ-056 is gratefully acknowledged. J. Cruz appreciates to Programa de Mejoramiento del Profesorado (PROMEP)-UAEH for the additional financial support (Grant No 103.5/08/5390). RMP, MH and AE thank CONACYT for their scholarships.

11

References

[1] D. Austruc

Organometallic Chemistry and Catalysis

Springer-Verlag, Berlin Heidelberg New York (2007) (Chapter 6). pp. 140–142

[2] Ch. S. Chin, G. Won, D. Chong, M. Kim, H. Lee

Acc. Chem. Res., 35 (2002), p. 218

[3] S. Trofimenko

Scorpionates-The Coordination Chemistry of Polypyrazolylborate Ligands

Imperial College Press, London (1999) p. 282

[4] S. Trofimenko

Chem. Rev., 93 (1993), p. 943

[5] G. Parkin

Adv. Inorg. Chem., 42 (1995), p. 291

[6] P.K. Byers, A.J. Canty, R.T. Honeyman

Adv. Organomet. Chem., 34 (1992), p. 1

[7] C. Slugovc, I. Padilla-Martinez, S. Sirol, E. Carmona

Coord. Chem. Rev., 213 (2001), p. 129

[8] Y. Alvarado, O. Boutry, E. Gutierrez, A. Monge, M.C. Nicasio, M.L. Poveda, P.J. Pérez, C. Ruiz, C. Bianchini, E. Carmona

Chem. Eur. J., 3 (1997), p. 860

[9] M. Paneque, C.M. Posadas, M.L. Poveda, Nuria Rendón, K. Mereiter

Organometallics, 26 (2007), p. 3120

[10] E. Gutiérrez-Puebla, A. Monge, M.C. Nicasio, P.J. Pérez, M.L. Poveda, L. Rey, C. Ruíz, E. Carmona

Inorg. Chem., 37 (1998), p. 4538

[11] J.M. O Connor, A. Closson, P. Gantzel′

J. Am. Chem. Soc., 124 (2002), p. 2434

[12] W.H. Baddley, M.A. Fraser

J. Am. Chem. Soc., 91 (1969), p. 3661

[13] K.R. Reddy, K. Surekha, G.-H. Lee, S.-M. Peng, S.-T. Liu

Organometallics, 20 (2001), p. 5557

12

[14] T. Yagyu, K. Osakada, M. Brookhart

Organometallics, 19 (2000), p. 2125

[15] E. Hevia, J. Pérez, L. Riera, V. Riera, D. Miguel

Organometallics, 21 (2002), p. 1750

[16] L. Cuesta, E. Hevia, D. Morales, J. Pérez, V. Riera, M. Seitz, D. Miguel

Organometallics, 24 (2005), p. 1772

[17] M. Paneque, C.M. Posadas, M.L. Poveda, N. Rendón, E. Alvarez, K. Mereiter

Chem. Eur. J., 13 (2007), p. 5160

[18] D.M. Tellers, S.J. Skoog, R.G. Bergman, T.B. Gunnoe, W.D. Harman

Organometallics, 19 (2000), p. 2428

[19] M. Paneque, M.L. Poveda, V. Salazar, E. Gutierrez-Puebla, A. Monge

Organometallics, 19 (2000), p. 3120

[20] A. Bondi

J. Phys. Chem., 68 (1964), p. 441

[21] B. Cordero, V. Gómez, A.E. Platero-Prats, M. Revés, J. Echeverría, E. Cremades, F. Barragán, S. Alvarez

Dalton Trans. (2008), p. 2832

[22] ADF: Amsterdam density functional, scientific computing and modelling (SCM), Theoretical Chemistry, Vrije Universiteit, Amsterdam. The Netherlands.

[23] S.H. Vosko, L. Wilk, M. Nusair

Can. J. Phys., 58 (1980), p. 1200

[24] J.P. Perdew, J.A. Chevary, S.H. Vosko, K.A. Jackson, M.R. Pederson, D.J. Sing, C. Fiolhais

Phys. Rev. B., 46 (1992), p. 6671

[25] J.P. Perdew, K. Burke, M. Ernzerhof

Phys. Rev. Lett., 77 (1996), p. 3865

[26] Nonius

COLLECT

Nonius BV, Delft, The Netherlands (2001)

[27] Z. Otwinowski, W. Minor

Methods in Enzymology

Academic Press, New York (1997) p. 307

13

[28] Bruker programs: SMART. Version 5.629. SAINT+.

[29] G.M. Sheldrick

Acta. Crystallogr., A64 (2008), p. 112

Figure captions

Figure 1. Energetic profile of rotamers I–IV.

Figure 2. Structures of the two most stable conformers II and IV.

Figure 3. Space filling diagram of the two most stable conformers IV (4b ) and II (4b″).′

Figure 4. ORTEP view of compound 2d (30% probability, H atoms except for water are omitted for clarity).

Figure 5. ORTEP view of compound 2h (30% probability level, H atoms except for water are omitted for clarity).

14

Table 1. Selected bond lengths [Å] and angles [°] for compounds 2d, 2h and 4a.

2d 2h 4a

Bond lengthsMolecule 1 Molecule 2

Ir(1)–N(6) 2.154(4) 2.142(5) 2.130(4) 2.134(4)Ir(1)–N(2) 2.025(4) 2.012(4) 2.031(5) 2.036(5)Ir(1)–N(4) 2.026(4) 2.027(4) 2.040(4) 2.038(4)Ir(1)–O(1) 2.099(3) 2.094(4) – –Ir(1)–O(6) 2.089(3) 2.069(4) 2.047(4) 2.050(4)Ir(1)–C(18) 2.031(5) 2.019(6) 2.056(6) 2.039(6)C(18)–C(19) 1.349(7) 1.350(8) 1.349(8) 1.328(8)C(22)–C(23) 1.514(8) 1.514(7) 1.501(8) 1.507(8)C(25)–Cl(1) 1.730(9) – – –Ir(1)–N(7) – – 2.068(4) 2.071(4)Bond angles

Molecule 1 Molecule 2O(7)–C(22)–O(6) 126.4(5) 126.2(6) 127.0(5) 125.8(5)C(18)–C(17)–O(2) 111.3(5) 124.9(6) 112.7(5) 111.5(5)C(18)–C(17)–O(3) 124.2(5) 111.8(6) 124.9(5) 124.5(5)C(19)–C(20)–O(5) 110.5(5) 111.7(6) 110.1(5) 110.2(5)C(19)–C(18)–C(17) 118.6(4) 119.4(6) 117.5(5) 118.5(5)N(2)–Ir(1)–N(4) 90.29(16) 90.47(17) 89.16(18) 88.15(17)N(2)–Ir(1)–N(6) 88.68(16) 86.44(18) 88.30(18) 88.34(17)N(4)–Ir(1)–N(6) 86.24(15) 88.14(19) 87.80(17) 88.22(17)N(2)–Ir(1)–O(1) 88.49(15) 178.91(16) – –N(4)–Ir(1)–O(1) 177.39(14) 90.47(17) – –N(2)–Ir(1)–O(6) 176.98(14) 86.44(18) 177.66(16) 178.23(17)N(4)–Ir(1)–O(6) 89.26(14) 175.83(18) 93.16(16) 92.82(16)N(6)–Ir(1)–C(18) 176.15(17) 175.40(2) 175.8(2) 177.0(2)N(6)–Ir(1)–O(6) 88.31(15) 88.07(18) 91.46(16) 93.17(16)N(4)–Ir(1)–C(18) 90.63(17) 89.1(2) 89.2(2) 90.2(2)N(2)–Ir(1)–C(18) 89.11(18) 89.9(2) 88.6(2) 89.0(2)N(4)–Ir(1)–N(7) 174.62(18) 174.20(18)C(18)–Ir(1)–O(6) 93.89(17) 94.5(2) 91.66(19) 89.53(19)O(6)–Ir(1)–O(1) 91.84(14) 91.47(16) – –C(18)–Ir(1)–O(1) 91.65(17) 90.7(2) – –O(6)–Ir(1)–N(7) – – 83.0(16) 86.11(16)C(18)–Ir(1)–N(7) – – 96.1(2) 95.4(2)

Table 2. Crystal data for complexes 2d, 2h and 4a.15

Compound 2d 2h 4a

Empirical formula C33 H47 B Cl Ir N6 O7

C34 H50 B Ir N6 O7C34 H41 B Cl2 Ir N7

O6

Formula weight 878.23 857.81 917.65Crystal colour and shape Yellow prism Yellow plate Brown prism

Crystal size (mm3) 0.3 × 0.2 × 0.1 0.25 × 0.10 × 0.03 0.31 × 0.26 × 0.17Crystal system Monoclinic Monoclinic MonoclinicSpace group P2(1)/c P2(1)/c P2(1)/nUnit cell dimensionsa, Å 12.6199(10) 19.1007(7) 16.8898(4)b, Å 19.0261(15) 11.4057(5) 20.4438(6)c, Å 16.7046(13) 19.8527(9) 22.0843(7)α, deg 90 90 90β, deg 100.142(2) 116.907(2) 103.1530(1)γ, deg 90 90 90V, Å3 3765.6(5) 3856.8(3) 7425.5(4)Z 4 4 8Dcalcd, Mg m−3 1.549 1.477 1.642μ, mm−1 3.669 3.513 3.794

Diffractometer Bruker SMART 5000 CCD

Enraf–Nonius Kappa CCD

Bruker SMART 5000 CCD

Radiation and wavelength

λ(Mo Kα), 0.71073 Å

λ(Mo Kα), 0.71073 Å

λ(Mo Kα), 0.71073 Å

monochromator Graphite graphite GraphiteScan type ω ω − ϕ Ω2θ range for collection, (°) 4.04 to 52.04 5.36 to 55.02 2.74–46.52°

T (K) 293(2) 293(2) 293(2) K

Index ranges−15 ≤ h ≤ 13; −23 ≤ k ≤ 23; −20 ≤ l ≤ 20

−24 ≤ h ≤ 18; −14 ≤ k ≤ 13; −23 ≤ l ≤ 25

−13 ≤ h ≤ 18, −22 ≤ k ≤ 22, −24 ≤ l ≤ 24

Reflections collected 24420 18038 71182Independent reflections

7395 (Rint = 0.0320) 7808 (Rint = 0.0435) 10489

(Rint = 0.0677)Observed reflections 5787 (F > 4σ(F)) 4942 (F > 4σ(F)) 8423 (F > 4σ(F))Parameters/restraints 450/0 509/89 975/0R final; R all data 0.0334, 0.0498 0.0489, 0.1005 0.0324, 0.0472Rw final, Rw all dataa 0.0851, 0.0929 0.0769, 0.0897 0.0730, 0.0781GOF (all data) 1.092 1.037 1.039Max, min peaks (e Å−3) 1.267, −0.812 1.392, −0.654 1.696, −0.964

a where .

16

Figure 1

17

Figure 2

18

Figure 3

19

Figure 4

20

Figure 5

21

Figure 6

22

Scheme 1

Scheme 1. Synthesis of Irida-E-alkenyl compounds 2a–h.

23

Scheme 2

Scheme 2. Irida E-alkenyl aqua complexes 3 and 3-d3.

24

Scheme 3

Scheme 3. Proposed stepwise formation of compounds 2 and 3.

25

Scheme 4

Scheme 4. The reaction of the Ir-derivative 2a with Lewis bases.

26

Scheme 5

Structure proposed of 4b and 4b″ complexes.′

27