Reactivity of amidinatosilylenes and amidinatogermylenes with [PtMe2(η4-cod)]: cis- versus trans-[PtMe2L2] complexes and cyclometalation reactions

Abstract

The reactions of [PtMe2(η4-cod)] (cod = 1,5-cyclooctadiene) with 2 equiv of the amidinatotetrylenes E(tBu2bzam)X (tBu2bzam = N,N′-bis(tertbutyl)benzamidinate. E = Si; X = Mes (1Si-Mes) and CH2SiMe3 (1Si-Tmsm); E = Ge; X = Mes (1Ge-Mes) and CH2SiMe3 (1Ge-Tmsm)] led to disubstituted derivatives of generic formula [PtMe2{E(tBu2bzam)X}2] (2E-X) in which the ligand arrangement is trans for the silylenes (trans-2Si-Mes and trans-2Si-Tmsm) but cis for the germylenes (cis-2Ge-Mes and cis-2Ge-Tmsm). DFT calculations indicated that the different stereochemistry observed for complexes 2E-X, E = Si (trans) and Ge (cis), has a kinetic origin. Both mesityl derivatives trans-2Si-Mes and cis-2Ge-Mes reacted with 1 equiv of [H(OEt2)2][BARF] (BARF = B{3,5-(CF3)2C6H3}4) to give isostructural ionic complexes, [Pt{E(tBu2bzam)C6H2(CH2)Me2}{E(tBu2bzam)Mes}][BARF] (E = Si (3Si-Mes), Ge (3Ge-Mes)), in which a cationic 14-electron platinum(II) complex is stabilized by both a cyclometalated tetrylene and a noncyclometalated tetrylene that has a mesityl methyl group agostically interacting with the platinum atom.