Syntheses, structures and redox properties of tris(pyrazolyl)borate-capped ruthenium vinyl complexes

Reaction of RuHCl(CO)(PPh3)3 with aryl alkynes HCtriple bond; length of mdashCC6H4R-4 [1: R = N(C6H4Me-4)2 (a), OMe (b), Me (c), CO2Me (d), NO2 (e)] gives the five-coordinate vinyl complexes Ru(CHdouble bond; length as m-dashCHC6H4R-4)Cl(CO)(PPh3)2 (2a–e). Reaction of 2a with excess PMe3 gives crystallographically characterised Ru{CHdouble bond; length as m-dashCHC6H4N(C6H4Me-4)2-4}Cl(CO)(PMe3)3 (3a), whilst reaction of 2a–e with KTp affords Ru(CHdouble bond; length as m-dashCHC6H4R-4)(CO)(PPh3)Tp (4a–e) bearing the facially capping Tp− ligand. Electrochemical and spectroelectochemical properties of 4a–e are consistent with substantial redox activity associated with the vinyl ligand, and these properties have been satisfactorily modelled by DFT based calculations of electronic structure.