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 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, leading to the bimetallic compounds [(dcpe)Pt(ER₂)(R)] with direct σ(Pt-E) bonds by oxidative addition an E-C bond to the coordinatively unsaturated fragment [(dcpe)Pt]. The reactions of the sterically demanding group-13 alkyls ER₃ (E = Al, Ga, In; R = CH₂ t-Bu, CH ₂SiMe₃) with the platinum-complex [(dcpe)Pt(H)(CH ₂t-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)[CH ₂Si(CH₃)₂ CH₂Ga(CH ₂SiMe₃)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.