Syntheses, Structures, and Theoretical Insights of Homobimetallic Ruthenium Complexes Comprising Mercaptobenzothiazolyl Ligands

This article presents the synthesis, structural characterization, and variable coordination modes of the 1,3- N,S -mercaptobenzothiazolyl ligand at the ruthenium center. Room-temperature reaction of [(η 6 - p -cymene)Ru(μ 2 -Cl 3 )Ru(Cl)(CO)(PPh 3 )] ( 1 ) with the potassium salt of Mbz (Mbz = 2-mercaptobenzothiazolyl) led to the formation of complexes [(η 6 - p -cymene)Ru{(μ 2 - k 2 - N,S -(NS 2 C 7 H 4 ))(μ 2 - k 2 - S- (NS 2 C 7 H 4 ))(μ 2 - k 1 - S, k 2 - N,S -(NS 2 C 7 H 4 ))}Ru{ k 1 - S -(NS 2 C 7 H 4 )}(CO)] ( 2 ) and [(η 6 - p -cymene)Ru{(μ 2 - k 2 - N,S -(NS 2 C 7 H 4 ))(μ 2 - k 2 - S -(NS 2 C 7 H 4 ))(μ 2 - k 1 - S, k 2 - N,S -(NS 2 C 7 H 4 ))}Ru{ k 1 - S -(NS 2 C 7 H 4 )}(PPh 3 )] ( 3 ). The solid-state X-ray structure of 2 shows unusual coordination modes of the three bridging mercaptobenzothiazolyl units at the ruthenium(II) center. Two of the bridging mercaptobenzothiazolyl ligands adopted μ 2 - k 2 - S -(NS 2 C 7 H 4 ) and μ 2 - k 2 - N,S -(NS 2 C 7 H 4 ) coordination modes, while the third bridging ligand binds through both nitrogen and sulfur atoms in a μ 2 - k 1 -S,k 2 - N,S -(NS 2 C 7 H 4 ) fashion, forming a four-membered chelate ring with a metal center. Further, the reaction of 3 with the sodium salt of the [H 2 B(Mbz) 2 ] ligand led to the formation of bimetallic ruthenium(II) borate complex, [(η 6 - p -cymene)Ru{μ 2 - k 2 - N,S -(NS 2 C 7 H 4 )(μ 2 - k 2 - S- (NS 2 C 7 H 4 ) 2 )}Ru( k 3 - H,S,S′ -H 2 B(NS 2 C 7 H 4 ) 2 )] ( 4 ). The solid-state X-ray structure of 4 shows μ 2 - k 2 - S -(NS 2 C 7 H 4 ) and μ 2 - k 2 -N,S -(NS 2 C 7 H 4 ) coordination modes of the bridging mercaptobenzothiazolyl units, which are similar to those observed in 3 . Comparative cyclic voltammetry was conducted to compare the electronic behavior of these bimetallic complexes. To understand the electronic structures of these complexes, DFT has been carried out.