Multinuclear palladium compounds containing palladium centers ligated by five silicon atoms.

Palladium (Pd) generally prefers low oxidation states. So far, no stable Pd compound with a +5 oxidation state is known. Here, we report two multinuclear Pd compounds containing Pd centers ligated by five silicon (Si) atoms. A thermal condensation reaction of [{1,2-C(6)H(4)(SiMe(2))(SiH(2))}Pd(II)(Me(2)PCH(2)CH(2)PMe(2))] (Me = methyl) afforded two stereoisomers of dinuclear Pd(II) compounds and a trinuclear Pd compound as major products and a tetranuclear Pd compound as a minor product. The structures of the four Pd compounds were confirmed by single-crystal x-ray structure analysis. The dinuclear Pd compounds have a dimeric structure of [{1,2-C(6)H(4)(SiMe(2))(SiH)}Pd(II)(Me(2)PCH(2)CH(2)PMe(2))] connected through a Si-Si single bond formed by dehydrogenation of two molecules of the starting compound. The trinuclear and tetranuclear Pd compounds proved to have Pd centers bonded to five Si atoms with normal Pd-Si single-bond distances. Theoretical calculations of the trinuclear and tetranuclear Pd compounds accurately reproduced their x-ray structures and suggested that all of the Pd-Si bonds of the central Pd atoms have a relatively high single-bond character.