Pyridine-based SNS-iridium and -rhodium sulfide complexes, including d8–d8 metal–metal interactions in the solid state

Abstract

The cationic, pincer-type complexes [(SNS)Ir(COE)][BF₄] (1) and [(SNS)Rh(COE)][BF₄] (2) (SNS = 2,6-bis(t-butylthiomethy1)pyridine; COE = cyclooctene) complexes were prepared, and their structure and reactivity were studied. They are fluxional at room temperature as a result of “arm” hemilability, which can be frozen at low temperatures. Reaction of complex 1 with H₂ resulted in a dimeric dihydride complex [(SNS)Ir(H₂)]₂[BF₄]₂ (3) in which the sulfur atoms bridge between two metal centers. The Rh complex 2 did not react with H₂. Both the carbonyl complexes [(SNS)Ir(CO)][BF₄] (5) and [(SNS)Rh(CO)][BF₄] (6) show differences in the IR stretching frequencies in solution vs. solid states, which are a result of uncommon metal–metal interactions between square planar d⁸ systems in the solid state. Complexes 1, 3, 5 and 6 were structurally characterized by X-ray crystallography. A network of hydrogen bonds involving the BF₄⁻ counter anion and hydrogen atoms of complex 5 was observed.