Chemistry of dihydrogen complexes containing only phosphorus co-ligands

A series of new dicationic dihydrogen complexes of ruthenium of the typecis-(dppm)₂Ru(η₂-H₂)(L)]BF₄]₂ (dppm = Ph₂PCH₂PPh₂; L = phosphite) have been prepared by protonating the precursor hydride complexescis-(dppm)₂Ru(H)(L)]BF₄] using HBF₄•Et₂O. The precursor hydride complexes have been obtained fromtrans-(dppm)₂Ru(H)(L)]BF₄] (L = phosphite) via a rare acid-catalysed isomerization reaction in six coordinate species. Thetrans-(dppm)₂Ru(H)(L)]BF₄] complexes (L = phosphine) upon protonation gave the isomerized derivatives, however, further addition of acid resulted in a five-coordinate species, (dppm)₂RuCl]⁺ presumably via an intermediate phosphine dihydrogen complex. The electronic as well as the steric properties of the co-ligands seem to strongly influence the structure-reactivity behaviour of this series of complexes.