280 Main Group and Transition Metal Cluster Compounds

References

1. C. C. Nagel, J. C. Bricker, D. G. Alway, and S. G. Shore, 3. Organornet. Chem., 219, C9 (1981). 2. A. A. Bhattacharya, C. C. Nagel, and S . G. Shore, Organometallics, 2, 1187 (1983). 3. T. J. Coffy, D. A. McCarthy, and S . G. Shore, Inorg. Synth., 32 (1998). 4. M. J. Sailor, C. P. Brock, and D. F. Shriver, J. Am. Chem. SOC., 109, 6015 (1987). 5. S. -H. Han, G. L. Geoffroy, B. D. Dombek, and A. L. Rheingold, Inorg. Chem., 27, 4355

6. G. Lavigne and H. D. Kaesz, J. Am. Chem. SOC., 106,4647 (1984). 7. D. F. Shriver and M. A. Drezdzon, The Manipulation of Air-Sensitive Compounds, 2nd ed.,

8. A. J. Gordon and R. A. Ford, The Chemist's Companion, Wiley, New York, 1972. 9. M. I. Bruce, C. M. Jensen, and N. L. Jones, Inorg. Synth., 28, 216 (1987).

(1988).

Wiley, New York, 1986.

10. S. R. Drake and P. A. Loveday, Inorg. Synth., 28, 230 (1987). 11. M. J. Went, M. J. Sailor, P. L. Bogdan, C. P. Brock, and D. F. Shriver, J. Am. Chem. SOC., 109,

6023 (1987).

44. PLATINUM-RUTHENIUM CARBONYL CLUSTER COMPLEXES

Submitted by R. D. ADAMS,* T. S. BARNARD,* J. E. CORTOPASSI,* W. WU,* and Z. LI*

Checked by J. R. SHAPLEY' and KWANGYEAL LEE'

Mixed-metal cluster complexes can exhibit modified and enhanced reacti- vities due to the effects of cooperativity or synergism between the metal atoms.'-4 It has recently been shown that the pentacarbonyl complexes of the iron subgroup readily react with P t ( c~d)~ , ' cod = 1,5-cyclooctadiene, under mild conditions to yield the hexanuclear cluster complexes Pt3Fe3(CO)1 5,6

Pt2R~4(C0)18,7 and PtzOs4(CO)18.8 The latter two complexes can be viewed as dimers of the unit PtM,(CO), and can be split upon reaction with 1,2-ethandiyldiphenylphosphine (dppe) and CO to yield two equivalents of the trinuclear species PtR~~(CO)~(dppe)' and P ~ O S ~ ( C O ) ~ ~ , respectively.'

The PtzRu4(CO)18 cluster reacts with H2 to form Pt3R~6(CO)Z1(p3-H)- (P-H)~ in which the platinum and ruthenium atoms are arranged in trian- gular layers of the pure elements." This complex can be converted to Pt3R~6(CO)zo(p3-CzPhzXl(l-H)z by reaction with diphenylacetylene." The latter complex was found to be an active catalyst for the hydrogenation

* Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208. 'Department of Chemistry, University of Illinois, Urbana, IL 61801.

Inorganic Syntheses, Volume 32 Edited by Marcetta York Darensbourg

Copyright © 1998 by John Wiely & Sons, Inc.

44. Platinum-Ruthenium Carbonyl Cluster Complaes 28 1

of diphenylacetylene to Z-~tilbene.~ The syntheses of the complexes Pt,Ru,(CO), and Pt3R~6(CO)21(p3-H)(p-H)3 are described below.

General Procedure

Caution. Due to the high toxicity of carbon monoxide and the high Jlammability of hydrogen, the reactions must be carried out in a well-ventilated hood.

Reactions are performed under an atmosphere of dry nitrogen unless speci- fied otherwise. Reagent-grade solvents are dried over 4 8, molecular sieves and deoxygenated by purging with nitrogen prior to use. The compound Pt(cod),' is prepared by the published procedure. Ru(CO), is prepared by an adaptation of a previously reported procedure as described below.''

A. IN SITU RUTHENIUM PENTACARBONYL AND OCTADECACARBONYLDIPLATINUMTETRARUTHENIUM, Pf2RUq(C0)18

4Ru(CO), + 2Pt(cod)Z -+ Pt2RU4(C0)18 + 2CO + 4COd

Caution. Photolysis by a 1000- W mercury UV lamb emits potentially blinding radiation. The apparatus should be placed in a hood whose shield is completely covered in rejective aluminum foil.

A 1-L, three-necked, round-bottomed flask with ground glass joints is equip- ped with a Teflon-covered magnetic stirring bar, a nitrogen-inlet adapter, a condenser (in the center joint), and a rubber septum. Hexane (600 mL) is added to the flask. Then Ru3(C0)',* (250 mg, 0.391 mmol) is added to the flask and the solution is stirred until all of the solid is dissolved. The solution is then irradiated using a medium-pressure mercury UV lamp (lo00 W, Cooper Industries, Vicksburg, MS, Model HC) in the presence of a slow purge of carbon monoxide at 25°C. The lamp source is placed ca. 10 in. from the flask and should be cooled by a slow stream of air from a compressed air line. Note: The use of a lamp with less power (e.g., a 250-W high-pressure mercury lamp) lengthens the time for the formation of Ru(C0)' considerably. Reaction is complete when the color of the solution has changed from orange to colorless (ca. 1.5 h) and the characteristic IR absorptions of RU~(CO)~ , [vcco, 2061 (vs), 2031 (s), and 2012 (m)] disappear and the absorptions of

* Purchased from Strem Chemicals, Inc., Newburyport, MA.

282 Main Group and Transition Metal Cluster cbmpounds

Ru(CO), appear [vccO) 2038 (s), 2003 (vs)]. The yield of Ru(CO)S is assumed to be quantitative.

The flask of the Ru(CO), solution is cooled to 0"C, evacuated, and refilled with nitrogen 10 times to remove excess CO. Under nitrogen, Pt(cod)z (145.3 mg, 0.353 mmol) is dissolved in CH2Cl2 (25 mL). Pt(cod)z is not stable in CHzClz for long periods. This solution should be prepared just prior to use. Add this solution quickly (in a few seconds) to the Ru(CO), solution, and stir the mixture at 0°C for 30 min*. During this 30-min period the reaction flask is evacuated and refilled with nitrogen every 5min to remove the liberated CO. After 30 min, an additional quantity of P t ( ~ o d ) ~ (97.0 mg, 0.236 mmol) is dissolved in CHzClz (25 mL) and added to the reaction mixture. The mixture is stirred at 0°C for an additional 30 min.* Once again, the flask is evacuated and refilled with nitrogen periodically to remove the liberated CO. The reaction mixture is stirred for an additional 9 h at 25°C with no further CO removal during this period. The resulting purple solution is reduced in volume to ca. 100 mL by using a rotary evaporator, and the components are then separated by silica-gel column chromatography (25 x 500 mm). The first yellow band eluting with hexane is Ru3(C0)12, 101.9 mg, 41% [based on Ru(CO),]. The second band is purple and elutes with a CH2C12/hexane (1/4) solvent mixture. This is the product PtzRu4(CO)ls, 174.4 mg, 46% based on platinum.

The periodic removal of CO is used to obtain the best yields of the product. The authors routinely perform this reaction with one-half the required amount of Pt(cod), to increase the yield based on platinum added. The amount of Ru3(C0)12 is increased by this method, but it is easily recovered and can be reused to synthesize RU(CO)~ in subsequent preparations.

Anal. Calcd. for C18018PtzRu4: C, 16.64. Found C, 16.90.

Properties

The complex forms purple air-stable crystals and has good solubility in both polar and nonpolar solvents (e.g., acetone, dichloromethane, tetrahydro- furan, benzene, and hexane). It has been characterized crystallographically.7 The structure is an open, but folded, ladder-like array of six metal atoms with the two platinum atoms in the center. The IR spectrum (hexane) exhibits qc0) bands at 2085 (m), 2062 (vs), 2035 (vs), 2016 (w). PtZRu4(C0)1s has been found to be very useful for the synthesis of new platinum-ruthenium cluster c o r n p l e ~ e s . ' ~ ~ ' ~ * ' ~

*Note: The checkers found that the yield of Pt,Ru4(CO),B is increased to 61% when the reaction flask is wrapped in foil and the hood light is turned off.

44. Platinum-Ruthenium Carbonyl Cluster Complexes 283

B. HENEICOSACARBONYLTETRAHYDRIDOTRIPLATINUM- HEXARUTHENIUM, Pt3Rb(CO)z,( ~3-H)(r-H)3

A dry, 300-mL, three-necked flask with ground glass joints is equipped with a Teflon-covered magnetic stirring bar, a nitrogen-inlet adapter, a condenser (in the center joint) connected to an oil bubbler, and a rubber septum. A Variac-controlled heating mantle is placed under the flask. Heptane, 140 mL, is added to the flask, followed by PtzRu4(CO)18 (25.0 mg, 0.019 mmol) which is dissolved by stirring. The solution is purged with hydrogen for 5 min and then heated to a slow reflux. Note: Vigorous refluxing or purging of the solution decreases the yield of Pt3R~6(C0)z1(p3-HXp-H)3 dramatically, and results in an increased yield of Pt3R~7(C0)zz(p3-H)z. The heating and a slow hydrogen purge (ca. 3-4 bubbles per second) are continued for 15 min. The hydrogen purge is stopped and the solution is cooled to ca. 50°C by using a water bath. The solution is then filtered into a 250-mL round-bottomed flask. The solvent is removed by using a rotary evaporator and the solid is scraped from the sides of the flask with a spatula. This solid is then washed with 5-mL portions of cold pentane until the washings are colorless. The washings are collected in a separate round-bottomed flask. After washing, the remaining solid is the pure product P~,Ru~(C~),,(~,-H)(~-H)~, 15.8 mg. If desired, the compounds in the washings can be separated by TLC in air (silica gel, 7/3 hexane/CHzClz as the eluent) to yield 1.4 mg of a combination of RU, (CO)~~ and R U ~ ( C O ) ~ ~ ( ~ - H ) ~ in the first band (yellow), 0.6 mg of unreac- ted Pt2R~4(C0)18 in the second band (purple), 1.4mg of the product P ~ , R U ~ ( C O ) ~ ~ ( ~ ~ - H M ~ - H ) ~ in the third band (brown), and 0.9 mg of Pt3R~7(C0)z2(p3-H)212 in the fourth band (green). The combined amounts of Pt,Ru6(CO)z 1(/~3-H)(p-H)3 gives 17.2 mg (76% yield).

Anal. Calcd. for CZ1H4Oz1Pt3Ru6: C, 14.14; H, 0.23. Found: C, 14.49; H, 0.26.

Properties

The product is a black microcrystalline solid at 25°C. It is readily soluble in dichloromethane, sparingly soluble in hexane and benzene, and decomposes in coordinating solvents such as tetrahydrofuran, acetonitrile, and acetone. It is stable in air at -20°C as a solid for periods of several weeks. Its structure has been determined crystallographically.'O The metal atoms are arranged into a face-shared bioctahedral cluster. The central triangular layer contains the three platinum atoms. The outer triangles contain the ruthenium atoms. Three of the hydride ligands bridge the edges of one of the ruthenium

284 Main Group and Transition Metal Cluster Compounds

triangles, while the fourth hydride is a triply bridging ligand on the face of the other ruthenium triangle. In CHzClz solvent, the IR spectrum shows absorp- tions at 2081 (w, sh), 2066 (vs), 2052 (m, sh), 2026 (w) cm-'. The 'H NMR spectrum at -88°C shows resonances at 6 = -15.84 (s, 3H) and -19.26 (s, 1H) in acetone-& Due to a dynamical averaging process, the hydride resonances are broadened at higher temperatures and are not observed at 25°C. Pt3Ru6(C0)2 1(,u3-H)(,u-H)3 has been used for the synthesis of new higher nuclearity platinum-ruthenium mixed-metal cluster complexes.14v'

References

1. R. D. Adams, Ed. in Comprehensive Organometallic Chemistry I I , E. W. Abel, F. G. A. Stone, and G. Wilkinson, Ed.-in-Chief, Pergamon, Oxford, 1995, Vol. 10.

2. R. D. Adams, Polyhedron, 7, 2251 (1988). 3. R. Giordano and E. Sappa, J. Organomet. Chem., 448, 157 (1993). 4. R. D. Adams, T. S. Barnard, Z. Li, W. Wu, and J. Yamamoto. J . Am. Chem. Soc., 116,9103

5. J, L. Spencer, Inorg. Synth., 19, 213 (1979). 6. R. D. Adams, I. Arafa, G. Chen, J.-C. Lii, and J.-G. Wang. Organometallics, 9, 2350 (1990). 7. R. D. Adams, G. Chen, and W. Wu, J . Cluster Sci., 4 , 119 (1993). 8. R. D. Adams, M. Pompeo, and W. Wu, Inorg. Chem., 30, 2425 (1991). 9. P. Sundberg, J . Chem. SOC., Chem. Commun., 1987, 1307.

(1994).

10. R. D. Adams, T. S. Barnard, Z. Li, W. Wu, and J. Yamamoto, Organometallics, 13, 2357

11. R. Huq, A. J. Poe, and S. Chavala, Inorg. Chim. Acta, 38, 121 (1980). 12. R. D. Adams, Z. Li, J.-C. Lii, and W. Wu, Organometallics 11, 4001 (1992). 13. R. D. Adams and W. Wu, Organornetallics, 12, 1248 (1993). 14. R. D. Adams T. S. Barnard, and J. E. Cortopassi, Organometallics, 14, 2232 (1995). 15. R. D. Adams, T. S. Barnard, J. E. Cortopassi, and L. Zhang, Organometallics, 15,2664 (1996).

(1994).

45. TRI(c(-CARBONYL)NONACARBONYLTETRARHODIUM, Rh4(C(-CO)3(C0)9

Submitted by Ph. SERP, Ph. KALCK*, R. FEURER*, and R. MORANCHO* Checked by KWANG YEOL LEE' and JOHN R. SHAPLEY'

RhC13 * 3H20 + 3CO CH30HIN2~

H [RhClZ(CO)J + HCl + (CH30)ZCO

* Ecole Nationale Suphieure de Chimie de Toulouse 118, rue de Narbonne, 31077 Toulouse cedex, France.

Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.