Indian Journal of ChemistryVol. 20A. November 1981. pp. 1054-1056

j-Buten-r-oxy Derivatives of Boron, Aluminium, Germanium,Titanium, Niobium, Tantalum & Tin

S. C. GOEL & R. C. MEHROTRA *tChemistry Department, University of Delhi, Delhi 110 007

Received 4 February 1981; revised and accepted 18 March 1981

3-Buten-l-oxy derivatives of boron, aluminium. germanium, titanium, niobium, tantalum and mono-, di-, andtrl-butyltins have been synthesized by alcohol interchange technique. The germanium derivative has also been syn-thesized by the direct reaction of germanium tetrachloride and 3-buten-l-ol in the presence of dry ammonia gas and thetitanium derivative by the addition of pyridine to the alkenol before adding titanium tetrachloride to it, followed bytreatment with ammonia. The boron derivative has been prepared by heating boric oxide and alkenol in benzene.These derivatives are volatile under reduced pressure and have been characterized by elemental analyses, molecularweight determinations and IR and PMR spectral studies.

COMPARED to extensive studies with metalalkoxides!' 2, metal alkenoxides have receivedmuch less attention. In continuation of our

work in this field>", the present communicationdeals with the synthesis of 3-buten-l-oxy derivativesof boron, aluminium, germanium, titanium, nio-bium, tantalum and tin. The preparation of tri-3-buten-l-yl borate has already been reported? by theinteraction of boron trichloride and 3-buten-l-01.

Materials and MethodsStringent precautions were taken to exclude mois-

ture. Isopropoxides of aluminium, germanium,titanium, niobium, tantalum and butyltin wereprepared by reported methods'. Ethyl borate(Fluka) was used as such. 3-Buten-l-ol (Fluka)was dried over anhydrous potassium carbonate anddistilled (b.p. 113-14°). Azeotropically liberatedalcohol (ethanol or isopropanol) was estimated byoxidimetric method", Boron, aluminium, germa-nium, titanium, niobium, tantalum and tin wereestimated as described earlier+".

Infrared spectra were recorded as neat liquid filmson a Perkin-Elmer spectrophotometer 621 and PMRspectra on a Perkin-Elmer 90MHz instrument (R-32)in COCl3 solution using TMS as internal standard.Molecular weights were determined in benzene solu-tion in a semimicro ebulliometer (Gallenkamp) usingthermistor sensing, and refractive indices using anAbbe refractometer (Toshniwal).

Reac tion of 's-buten-t-ot with alkoxides - To aweighed amount of alkoxide (ethoxide or isopro-poxide) in benzene was added a calculated amountof 3-buten-l-ol. The reaction mixture was heatedunder reflux under a fractionating column and theliberated ethanol or isopropanol fractionated outazeotropically till completion. Finally excess solventwas removed under reduced pressure and the residue

+Present address: Department of Chemistry, University ofRajasthan, Jaipur 302 004.

:j:JR Vmax in em= and PMR chemical shifts in II-scale.

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distilled to give the pure product. The relevantexperimental details and analytical data aresummarized in Table 1.

Reaction of germanium tetrachloride and 3-buten-1-01 - To a solution of germanium tetrachloride(2.53 g) in benzene was added 3-buten-l-ol (,......4.0g).A current of dry ammonia was passed through thereaction mixture for ,......45min. Resulting reactionmixture was refluxed for 1 hr, filtered through asintered glass funnel to remove ammonium chlorideand excess solvent from the filtrate stripped offunder reduced pressure. The residue was distilledunder reduced pressure to get pure germanium tetra-3-buten-1-oxide; b.p. 126°/2.5 mm; yield 90 %.

Reaction of titanium tetrachloride and 3-buten-l-01-Benzene solution of titanium tetrachloride (2.03 g)was added to a mixture of 3-buten-I-ol (,......4g) andpyridine (,......8 g) followed by the passage of dryammonia into the reaction mixture till the reactionmixture cooled down to the room temperature.The contents were again refluxed for ,......1hr andammonium chloride and pyridinium hydrochlorideformed during the reaction filtered off. Excess sol-vent from the filtrate was removed under reducedpressure. Pure product titanium tetra-3-buten-l-oxide was isolated by distillation under reducedpressure; b.p. 131%.6 mm; yield 70%.

Reaction of boric oxide with 's-buten-i-ot=: Toboric oxide (1.01 g) was added 3-buten-l-ol (,....7.0 g)and benzene (,......70 ml). The reaction mixture washeated under reflux and the water formed during thereaction fractionated out simultaneously. Whenall the boric oxide dissolved, excess of solvent wasremoved and residue distilled under reduced pressureto give pure 3-buten-l-yl borate as a colourlessliquid; b.p. 134°/18 mm; yield 80%.

Results and DiscussionThe compounds reported in this paper have been

synthesized by the alcohol interchange technique>",as depicted by Eqs (1) and (2) ;

GOEL & MEHROTRA : 3-BUTEN-1-0XY DERIVATIVES OF SOME ELEMENTS

Alkoxide Product isolated"

TABLE 1 - 3-BuTEN-l-oxy DERIVATIVES OF BORON, ALUMINIUM, GERMANIUM, TITANIUM, NIOBIUM, TANTALUM & TINt

Mol wt obs nD(calc.) (room temp.)

b.p.°C/mm

Alcohol in Metal (%)azeotrope(g) obs (calc.)obs. (calc.)

Molar ratio(alkoxide :

3-buten-l-o 1)

B(OEt). 1 :3 B[OCH,CH.CH =CH,]. 134/18 2.97 4.67 239 1.419(32)(3.08) (4.82) (224)

Al(OPri). 1 :3 AI[OCH,CH,CH =CH21. 215/0.4 2.80 11.08 1004

Ge(OPri)4(2.91) (11.23) (240)

1:4 Ge[OCHzCHzCH=CH04 105/0.4 1.69 20.20 359 1.439(32)

Ti(OPri){(1.80) (20.32) (357)

1:4 Ti[OCH,CH,CH=CH2]4 131/0.6 1.82 14.35 653 1.525(20)

Nb(OPri).(1.90) (14.42) (332)

1:5 Nb[OCHzCH2CH =CH2J. 186-88/0.5 2.35 21.28 848 1.516(34)

Ta(OPri).(2.44) (20.71) (448)

1 :5 Ta[OCH2CHzCH = CHzJs 192/0.5 1.75 33.91 1022 1.494(32)

Bu.Sn(OPri)(1.82) (33.72) (536)

1 :1 Bu3Sn[OCH,CH2CH =CHz] 104/0.5 0.31 32.66 382 1.465(32)

BuzSn(OPri),(0.33) (32.86) (361)

1:2 BuzSn[OCH2CHzCH = CHz]. 126/0.5 0.62 31.29 386 1.479(39)

BuSn(OPri).(0.64) (31.60) (375)

1 :3 BuSn[OCH,CH,CH = CHz], 116/0.2 1.15 30.25 806 1.503(39)

*Yield 75-90%(1.20) (30.50) (389)

M(OR)n + n CH2= CHCH2CH20H --7

M(OCH2CH2CH=CH2)" + nROH ... (1)(where, R=Et or Pr' and M=B and AI, n=3;

M=Ge and Ti, n=4; M=Nb and Ta,n = 5).

benzeneBUnSn(OPr')4_n+4-nCH2=CHCH2CH20H ---+

BUnSn(OCH2CH2CH=CH2)4_n+4-nPr'OH.. . (2)

(where, n = 1, 2 and 3)Germanium tetrachloride did not appear to react

with 3-buten-l-01 at all, but the germanium tetra-3-buten-J-oxide could be prepared by passing ammo-nia in the above reaction mixture, the stoichiometrybeing represented by Eq. (3).GeCI4+4CH2=CHCH2CH20H+4NH3 ---+

Ge(OCH2CH2 CH=CH2)4 + 4NH4CI... (3)

However, the same technique could not be utilizedfor the synthesis of titanium, niobium and tantalumderivatives as hydrogen chloride produced initiallyin the reaction appeared to react with 3-buten-I-blresulting into the formation of 3-butenyl chlorideand water, which complicated the reaction. Thiscomplication could be avoided (cf. reaction ofsilicon tetrachloride with tertiary butenol") usingpyridine in the reaction followed by passage of ammo-nia; hydrogen chloride produced in the reactionwas consumed by pyridine (stronger base than 3-buten-l-ol) and the reaction was completed by ex-cess ammonia (Eq. 4)TiCI4+4CH2=CHCH2CH20H+4NH3 --+

Ti(OCH2CH2CH=CH2)4 + 4NH4CI " .(4)The tri-3-buten-I-yl borate could also be pre-

pared by the reaction of boric oxide and alkenol inbenzene (Eq. 5). Water liberated during the reac-tion was fractionated out azeotropicallyB20a+6CH2=CHCH2CH20H --+

2B(OCH2CH2CH=CH2)3 + 3H20 ... (5)

All these newly synthesized derivatives could bedistilled under reduced pressure. They are colourlessliquids, soluble in common organic solvents andsensitive to moisture. An olefinic double bond inthe 3-position in 3-buten-l-oxy group does notappear to have any marked effect on the propertiesof the alkenoxides but it appears that the electronreleasing tendency of 3-buten-I-oxy group is inter-mediate between n-butoxy and s-butoxy groups .This is reflected in the boiling points of 3-buten-l-oxides lying between those of the latter two-"',

Molecular weights of these derivatives (Table 1)show close similarity in molecular association ton-butoxides1o'b2. The aluminium derivative is tetra-meric while titanium, niobium, tantalum and mono-butyltin are dimeric. Derivatives of boron, germa-nium and tri- and di-butyltin are monomeric.

The vOH of 3-buten-1-01 at 3350 disappears inthe IR spectra'[ of the alkenoxides. However thereis no change in vC = C(1650±5) of the parentalkenol and the alkenoxides, A few bands at 1835±5 of weak intensity, 995 ± 5 and 915 ± 5 of strongintensity may be attributed to different modes ofvibrations of vinylic group-". The v(C-O) in thealkenoxides appear at 1110 ± 10 (at 1150 cnr+in alkyltin derivatives) and 1055 ± 5. In theboron derivative the vB-O appears at 1495, 1430and 1355. In other derivatives, vM-O appearsbetween 500 and 700 cm-1 and are in conformitywith the published data on metal alkoxides1o,12,13.

PMR spectrum of alkenyl group contains a largenumber of closely spaced lines and thus it is rela-tively difficult to interpret-s, The PMR data onthese 3-buten-1-oxide derivatives are summarizedin Table 2. The PMR spectra of the parent alkenoland the aiken oxides do not differ much, except inthe region where OCH2 signals appear. The -OCH2signal shows the largest shift upon changing theelement to which the alkenyl group is attached.This is in accordance with the fact that -OCH2protons are closer to the bonding end of the alkenoxy

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INDIAN J. CHEM., VOL. 20A, NOVEMBER 19~1

TABLE 2 - PMR DATA (8 VALUES) OF SOME 3-BuTEN-I-oXYDElUVATIVES

Compound

IRbHOCH~CH~CHc = C,

<, HaB[OCR~CH.CR = CH')3AI[OCH.CH.CR = CH')3Ge[OCH2CH2CH = CH214Ti[OCH.CH.CH = CH')4Nb[OCH.CH2CH = CH.).Ta[OCH2CH.CH = CH.).BU3Sn[OCH.CH2CH = CR,)Bu,Sn[OCH.CH,CH = CH.).BuSn[OCH.CH,CH = CH.).

b c d ea

5.80

5.725.785.815.815.835.845.785.805.76

5.15

5.085.145.125.085.08).165.105.165.12

5.05

4.984.975.024.974.984.994.925.055.04

2.30 3.64

2.32 3.802.35 3.882.35 4.902.40 4.302.36 4.402.35 4.332.29 3.702.32 3.722.33 3.78

group than are the vinylic protons and will be in-fluenced most by the nature of the element. Theroom temperature -OCH2 proton signal could notbe distinguished into terminal and bridging alkenoxygroups in aluminium, titanium, niobium, tantalumand monobutyltin derivatives (these derivatives showmolecular association of 4, 2, 2, 2 and 2 respectively)which must have both types of alkenoxy groups.In the corresponding alkoxide derivatives", thesignal due to -OCH2 protons could not be distin-guished even upon cooling up to -60°C. The inabi-lity to observe more than one -OCH2 signal maybe either due to fluxional properties of these alkeno-xides, involving rapid interchange of the terminaland bridging alkenoxy groups or due to insufficientchemical shift difference between the -OCH2 pro-tons of terminal and bridging alkenoxy groups.The chemical shifts of -OCH2 protons follow atrend parallel to the electronphilicity of elementsreflected by their electro negativity values : B 2.01,Ge 2.02, Ti 1.32, Ta 1.33 and Nb 1.23. However,-OCH2 proton signal of the aluminium derivative

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appearing at 3.88, does not appear to follow theabove trend (AI has electro negativity value 1.47).The observed downfield shift in this case may bedue lessening of the natural electronphilicity ofaluminium due to higher association. The down-field shift of -OCH2 signal in butyltin derivativesfollows the increasing order of Lewis acid character:BuSn> Bu2Sn > Bu3Sn.

AcknowledgementFinancial assistance from the CSIR, New Delhi

is gratefully acknowledged.

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