Reactivity of the palladium dimer [Pd2(µ-SO2)(µ-dba)(PBz3)2]. Syntheses and structural characterisation of [Pd3(µ-SO2)3(PBz3)3], [Pd2(µ-SO2)(µ-dppm)(PBz3)2], [Pd(SO2)(PBz3)2], [Pd3(µ-CO)2(µ-SO2)(PBz3)3] and [Pd3(µ-SO2)2(CNBut
)2(PBz3)3] (Bz = benzyl)†
Abstract
The reaction between [Pd2(dba)3]·solvent (dba = dibenzylideneacetone, solvent = CHCl3 or C6H6) and PBz3 (Bz = benzyl) in the presence of SO2 led to either [Pd2(µ-SO2)(µ-dba)(PBz3)2] 1 or [Pd3(µ-SO2)3(PBz3)3] 2 depending on the absence or presence of an excess of SO2 in solution or in the recrystallisation. The crystal structure of 2 shows it to be a regular triangulo-cluster with Pd–Pd bond distances 2.7225(9) Å. Complex 1 reacted with dppm with displacement of dba to give [Pd2(µ-SO2)(µ-dppm)(PBz3)2] 3. The crystal structure of 3 shows it to have a much shorter Pd–Pd bond length than 1 [2.670(2) Å for 3 cf. 2.885(2) Å for 1], which can be rationalised on the basis of the palladium atoms having been formally oxidised to PdI and the SO2 reduced to SO22–. Complex 1 reacted with PBz3 to give two mononuclear complexes, the previously characterised [Pd(dba)(PBz3)2] and the new complex [Pd(SO2)(PBz3)2] 4 which was characterised by a single crystal X-ray analysis. Complex 4 forms a distorted T-shaped structure with the P–Pd–P angle 163.67(14)°. It contains a η1-pyramidal SO2 ligand, and is the first mononuclear palladium SO2 complex to be crystallographically characterised. Complex 1 reacts with CO to give a mixture of the triangulo-clusters [Pd3(µ-CO)2(µ-SO2)(PBz3)3] 5 and [Pd3(µ-CO)(µ-SO2)2(PBz3)3] 6. Reaction with an excess of CO converted 6 into 5, and the crystal structure of 5 reveals relatively short Pd–Pd bond lengths consistent with a 42-electron cluster. Complex 1 reacted with CNBut to give [Pd3(µ-SO2)2(CNBut)2(PBz3)3] which has also been crystallographically characterised.
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)2(PBz3)3] (Bz = benzyl)