The reaction of the group-13 alkyls ER3 (E = Al, Ga, In; R=CH2t-Bu, CH2SiMe3) with the platinum-complex [(dcpe)Pt(H)(CH2t-Bu)]

The reactions of the sterically demanding group-13 alkyls ER3 (E=Al, Ga, In; R=CH2 t-Bu, CH2SiMe3) with the platinum-complex [(dcpe)Pt(H)(CH(2)t-Bu)] were re-investigated. The bimetallic compounds [(dcpe)Pt(ER2)(R)] (3: E=Ga, R=CH2SiMe3; 5: E=In, R=CH(2)t-Bu; dcpe = bis(dicyclohexylphosphino)ethane) with direct sigma(Pt-E) bonds were obtained by oxidative addition of an E-C bond to the coordinatively unsaturated fragment [(dcpe)Pt] produced in situ by thermolysis of the starting complex [(dcpe)Pt(CH(2)t-Bu)(H)]. The single crystal structure determination reveals a Pt-Ga bond length of 2.376(2) Angstrom and a Pt-In bond length of 2.608(1) Angstrom. All new compounds were characterised by elemental analysis, P-31 and Pt-195 NMR spectroscopy. Interestingly, the Pt-Ga compound 3 slowly transforms into the platinum alkyl/hydride isomer {(dcpe)Pt(mu(2)-H)[CH2Si(CH3)(2) CH2Ga(CH2-SiMe3)(2)]} (4) during crystallization from solution at room temperature. The X-ray single crystal structure analysis revealed both complexes 3 and 4 coexisting in the unit cell in a 1:1 relation. The inaccessibility of analytically pure samples of the Pt-Al complex {(dcpe)Pt[Al(CH(2)t-BU)(2)](CH(2)t-Bu)} (6), postulated as intermediate of the reaction of [(dcpe)Pt(H)(CH(2)t-Bu)] with Al(CH(2)t-Bu) on the basis of P-31 and Pt-195 NMR data, is attributed to an enhanced tendency to isomerisation into the alkyl/hydride Pt/Al congener of 4. A brief DFT analysis of the bonding situation of the model complex [(dhpe)Pt(GaMe2)(Me)] (1M) revealed, that the contribution of pi(Pt-Ga) back-bonding is negligible. (C) 2004 Published by Elsevier B.V.