NUCLEOPHILIC SUBSTITUTION OF ETA(5)-PYRROLYL LIGANDS IN RUTHENIUM(II)COMPLEXES

The reaction of RuCl2(PPh3)(3) with pyrrolyllithium results in the for mation of the pyrrolyl complex (NC4H4)RuCl(PPh3)(2), 1, which has been characterized by an X-ray diffraction study. The structure confirms t he eta(5)-bonding mode for the pyrrolyl ligand. Ligand substitution re actions with 1 have led to the facile synthesis of related eta(5)-pyrr olyl ruthenium complexes with other supporting ligands. Reactions of t he PEt3 derivatives (NC4H4)RuX(PEt3)(2), X = Cl and I, with aryl- and alkyllithium reagents resulted in nucleophilic substitution of the pyr rolyl ligand accompanied by hydrogen transfer to the metal ion, formin g (2-RNC4H3)RuH(PEt3)(2). The hydride products could be converted to t he corresponding chloride derivatives in chlorinated solvents, and the complex (2-PhNC4H3)RuCl(PEt3)(2) has been structurally characterized. A second nucleophilic substitution reaction on the coordinated pyrrol yl Ligand has been characterized in some cases, and protonation of the substituted pyrrole complex led to isolation of the free substituted pyrrole with recycling of the ruthenium complex. The nucleophilic subs titutions are sensitive to the electronic features of the supporting l igands in the complex and to the strength of the nucleophiles.