The chemistry of κ2-N,S-chelated Ru(II) complexes with 1,4-diethynylbenzene

Abstract

The chemistry of κ2-N,S-chelated Ru(II) complexes, [Cp*RuPPh3(κ2-N,S-(NC7H4S2)] (Cp*=ƞ5-C5Me5), 1a and [PPh3{κ2-N,S-(NS2C7H4)}Ru{κ3-H,S,S-H2B(NC7H4S2)2}], 1b has been explored with a terminal alkyne 1,4-diethynylbenzene. For example, the room-temperature reaction of Cp* based κ2-N,S-chelated Ru(II) species 1a with 1,4-diethynyl-benzene yielded [RuCp*(κ1-N,S-C7H4NS2)C7H4NS2-(E)-N−C=CHC8H5], 2. On the other hand, although treatment of 1b with 1,4-diethynylbenzene at room temperature showed no reactivity, thermolysis led to the formation of two borate complexes, [PPh3{C7H4NS2-(E)-N−C=CHC8H5}Ru{κ3-H,S,Sʹ-H2B(C7H4NS2)2}], 3 and [PPh3(κ2-N,S-C7H4NS2) Ru{κ3-S,Sʹ,Sʹʹ-HB(C7H4NS2)3}], 4, albeit in poor yields. Both the Ru(II) species 2 and 3 contain a five-membered ruthenacycle with an exocyclic C=C moiety attached to carbon atom. In complex 4, the ruthenium center is stabilized by hydrotrisborate, phosphine, and hemilabile one N,S-chelating ligand. The key feature of 4 is the coordination of the boron atom to the metal center through a common sulphur atom of the 2-mercaptobenzothiazole ligand. Characterization of these Ru(II) species has been carried out by various spectroscopic techniques and single-crystal X-ray diffraction analysis for 4. In addition, Density Functional Theory (DFT) calculations were further performed to provide insight into the bonding and electronic structures of these complexes.