The reaction of the group-13 alkyls ER3 (E = Al, Ga, In; R = CH2t-Bu, CH2 SiMe3) with the platinum-complex [(dcpe)Pt(H)(CH2t-Bu)]

The reactions of the sterically demanding group-13 alkyls ER3 (E = Al, Ga, In; R = CH2t-Bu, CH2SiMe3) with the platinum-complex [(dcpe)Pt(H)(CH2t-Bu)] were re-investigated. The bimetallic compounds [(dcpe)Pt(ER2)(R)] (3: E = Ga, R = CH2SiMe3; 5: E = In, R = CH2t-Bu; dcpe = bis(dicyclohexylphosphino)ethane) with direct σ(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(CH2t-Bu)(H)]. The single crystal structure determination reveals a Pt–Ga bond length of 2.376(2) Å and a Pt–In bond length of 2.608(1) Å. All new compounds were characterised by elemental analysis, 31P and 195Pt NMR spectroscopy. Interestingly, the Pt–Ga compound 3 slowly transforms into the platinum alkyl/hydride isomer {(dcpe)Pt(μ2-H)[CH2Si(CH3)2 CH2Ga(CH2SiMe3)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(CH2t-Bu)2](CH2t-Bu)} (6), postulated as intermediate of the reaction of [(dcpe)Pt(H)(CH2t-Bu)] with Al(CH2t-Bu) on the basis of 31P and 195Pt 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 π(Pt–Ga) back-bonding is negligible.