Construction of a Planar Tetrapalladium Cluster by the Reaction of Palladium(0) Bis(isocyanide) with Cyclic Tetrasilane

Abstract

The planar tetrapalladium cluster Pd4{Si(iPr)2}3(CNtBu)4 (4) was synthesised in 86% isolated yield by the reaction of palladium(0) bis(isocyanide) Pd(CNtBu)2 with octaisopropylcyclotetrasilane (3). In the course of this reaction, the palladium atoms are clustered via insertion into the Si–Si bonds of 3, followed by extrusion of one SiiPr2 moiety and reorganisation to afford 4 with a 54-electron configuration. The CNtBu ligand in 4 was found to be easily replaced by N-heterocyclic carbene (iPr2IMMe) to afford the more coordinatively unsaturated cluster Pd4{Si(iPr)2}3(iPr2IMMe)3 (5) having the planar Pd4Si3 core. On the other hand, the replacement of CNtBu with a sterically compact ligand trimethylolpropane phosphite {P(OCH2)3CEt} led to a planar tripalladium cluster Pd3{Si(iPr)2}3{P(OCH2)3CEt}3 (6) and Pd{P(OCH2)3CEt}4 in 1:1 molar ratio as products.

Keywords

• palladium
• cluster
• cyclic organopolysilane
• template
• bridging silylene ligand
• isocyanide