Synthesis and reactivity of a Ru(I) dimer devoid of pi-acid ligands.

Zinc reduction of [(Cym)RuCl(2)](2) gives [(Cym)RuCl](2), (Cym = 1,4-Me(i)PrC(6)H(4)), whose reactivity is evaluated. This Ru(I) dimer with two bridging chlorides shows no reactivity towards H(2), N(2), N(2)O or methyl triflate, but does add HCl to form (Cym)(2)Ru(2)HCl(3). Attempts to form a monomeric monovalent ruthenium complex with dppm, Ph(2)PCH(2)PPh(2), gives disproportionation to (Cym)RuCl(2)(eta(1)-dppm) and (Cym)Ru(eta(2)-dppm). With terpyridyl, the analogous disproportionation behavior is observed, to form Ru(terpy)(2)(2+) and a zero valent product, which decomposed before it could be isolated. The molecular orbitals, from a DFT calculation, of [(Cym)RuCl](2) show the LUMO to be in a sterically crowded region of the molecule, and thus helps to account for the reactivity targeted for small and more nucleophilic reagents, while the HOMO is accessible to reaction with HCl.