Synthesis and structural characterisation of the palladium cluster compounds [Pd3(µ-SO2)2(µ-PPh2py)2(PBz3)2] and [Pd4(µ-SO2)2(µ3S)(CNR)(PBz3)4] (R =tBu, 2,6-dimethylphenyl and cyclohexyl)

We have reported previously that the reaction of [Pd2(dba)3](dba = dibenzylideneacetone) with PBz3 in the presence of SO2 yields [Pd2((mu)-SO2)((mu)-dba)(PBz3)2](1) and [Pd3((mu)-SO2)3(PBz3)3](2)(which can be prepared selectively by varying the concentration of SO2). Here the reactions of 1 and 2 with PPh2py (diphenylpyridine phosphine) to yield [Pd2((mu)-SO2)((mu)-PPh2py)(PBz3)2](4) and [Pd3((mu)-PPh2py)2((mu)-SO2)2(PBz3)2](5), respectively, are reported. Structural characterisation of 5 shows it to be an unusual trimetallic compound. The reaction between the tetrahedral cluster [Pd4((mu)3-S)((mu)-SO2)2(CO)(PBz3)4](3)(which is prepared by reacting dimer 1 with COS) and CNR has also been studied. The isostructural clusters [Pd4((mu)3-S)((mu)-SO2)2(CNR)(PBz3)4](R =tBu, 6; CNCy, 7; CNXyl, 8; CNMe, 9) have been prepared and the structures of three of them are described here.