Chemistry of dihydrogen complexes containing only phosphorus co-ligands

A series of new dicationic dihydrogen complexes of ruthenium of the type cis-[(dppm)2Ru(eta2-H2)(L)][BF4]2 (dppm = Ph2PCH2PPh2; L = phosphite) have been prepared by protonating the precursor hydride complexes cis- [(dppm)2Ru(H)(L)][BF4] using HBF4•Et2O. The precursor hydride complexes have been obtained from trans-[(dppm)2Ru(H)(L)][BF4] (L = phosphite) via a rare acidcatalysed isomerization reaction in six coordinate species. The trans- [(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.