The use of spectroelectrochemistry to probe the redox-activated ligand-exchange reactions of the complexes trans-[NBu_4][RuX_4-(CNXyl)_2] (X = Cl or Br, Xyl = 2,6-dimethylphenyl)

摘要

The previously unreported complexes trans-[NBu_4][RuX_4(CNXyl)_2] (X = Cl or Br, Xyl = 2,6-dimethylphenyl) have been prepared by treating [NBu_4]_2[RuX_6] with the isocyanide ligand CNXyl in dichloromethane-ethanol and characterised by IR and UV-Vis spectroscopy, fast-atom-bombardment mass spectrometry, and elemental analysis (C,H,N and X). Their solution redox chemistry has been investigated using electrochemical and in situ spectroelectrochemical techniques. At low temperatures each complex undergoes a one-electron reduction to trans-[RuX_4(CNXyl)_2]~92-) (X = Cl or Br). At ambient temperature the same complexes undergo reduction in the presence of acetontrile to afford mer, trans-[RuX_3(CNXyl)_2(NCMe)]~-, which can be oxidised reversibly to mer, trans-[RuX_3(CNR)_2(NCMe)]~- to be evluated. The rate constants were found to vary in the order X =Cl, R = Xyl < X = Br, R = Xyl < X = Cl, R = Bu~t < X =Br, R = Bu~t. The oxidation of trans-[RuX_4(CNXyl)_2]~- (X = Cl or Br) in aceontrile is accompanied by the reductive elimination of X~*. The number of product(s) formed in dependent upon the identity of the halide. For X = Cl oxidation ultimately leads to the formation of several species, which include mer, trans-[RuCl_3(CNXyl)_2(NCMe)] and trans,trans,trans-[RuCl_2(CNXyl)_2(NCMe)_2]~+, whereas for X = Br oxidation only producers mer, trans-[RuBr_3(CNXyl)_2(NCMe)]. All of the redox products have been characterised in situ by IR and UV-Vis spectroscopy in as many oxidation states as possible.