Homoleptic Tetrakis(silyl) Complexes of Pd0 and Pt0 Featuring Metal-Centred Heterocubane Structures: Evidence for the Existence of the Corresponding Mononuclear PdI and PtI Complexes

We report on the first homoleptic tetrakis(silyl) complexes of zerovalent Group10 metals. The compounds [MLi4{Si(3,5-Me(2)pz)(3)}(4)] (M=Pd and Pt; 3,5-Me(2)pz=3,5-dimethylpyrazolyl) exhibit very appealing metal-centred heterocubane structures with the central d(10) metal atoms surrounded by four silicon and four lithium atoms. Both compounds were characterised in detail, including X-ray crystal-structure analysis and 2D NMR spectroscopic methods such as Li-7,Si-29 and Li-7,(195)PtHMQC. Cyclic voltammetry studies, in combination with density functional theory (DFT) calculations, revealed that the corresponding mononuclear cationic d(9)-M-I and dicationic d(8)-M-II complexes are accessible by stepwise one-electron oxidation of the title compounds. Electron paramagnetic resonance (EPR) investigations provided evidence for the existence of the corresponding paramagnetic palladium(I) and platinum(I) complexes.