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

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)]2BF4]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.