Syntheses, Dynamic Behaviour and Theoretical Studies of [(Piperidinomethyl)silyl]methyl‐Cyclopalladated Dimetallic Complexes

Abstract

AbstractThe cationic complex [Pd{CH2SiPh2(CH2NC5H10)‐κ2C,N}(NCMe)2]BF4 (CH2NC5H10 = piperidinomethyl) is obtained from the reaction of [Pd{CH2SiPh2(CH2NC5H10)‐κ2C,N}(μ‐Cl)]2 with TlBF4 in the presence of NCMe. It reacts with KO2CCH3 leading to the dimetallic complex [Pd{CH2SiPh2(CH2NC5H10)‐κ2C,N}(μ‐O2CCH3‐κO:κ′O)]2, which exists only as the transoid isomer in solution. A dynamic process due to inversion of the acetato bridges is detected by variable‐temperature 1H NMR spectroscopy. The reaction of the same parent complex with Kdmpz (dmpz = dimethylpyrazolate) leads to the dinuclear complex [Pd{CH2SiPh2(CH2NC5H10)‐κ2C,N}(μ‐dmpz‐κN:κ′N)]2, which in solution exists as a mixture of cisoid and transoid isomers, but no inversion of the bridging pyrazolato groups has been observed. The reaction between equimolar amounts of these two complexes in CH2Cl2 affords low yields of the expected mixed acetato/pyrazolato‐bridged complex [Pd2{CH2SiPh2(CH2NC5H10)‐κ2C,N}2(μ‐O2CCH3‐κO:κ′O)(μ‐dmpz‐κN:κ′N)]. The mixed chlorido‐pyrazolato‐bridged complex [Pd2{CH2SiPh2(CH2NC5H10)‐κ2C,N}2(μ‐Cl)(μ‐dmpz‐κN:κ′N)] is obtained by mixing equimolar amounts of the parent dichlorido‐ and bis(dimethylpyrazolato)‐bridged dinuclear complexes, and exhibits a dynamic process in solution corresponding to the inversion of the bridges. Only the cisoid isomers are detected for both dimetallic complexes with mixed bridging ligands. The experimental findings of the preferred transoid or cisoid structure in these dinuclear Pd complexes were supported by quantum chemical calculations.