MONONUCLEAR AND BINUCLEAR COMPLEXES OF RUTHENIUM(II) WITH THE LIGAND 1-(DIPHENYLPHOSPHINO)-2-(2-PYRIDYL)ETHANE

The ligand 1-(diphenylphosphino)-2-(2-pyridyl)ethane (ppye) forms six-co-ordinate species [RuX2(ppye-P,N)2] (X = Cl, Br or I), the solution behaviour of which has been investigated by P-31-{H-1} and C-13-{H-1} NMR, UV/VIS spectroscopy, and conductivity measurements. Halide dissociation from the neutral species yields the five-co-ordinate cations [RuX(ppye-P,N)2]+ which can dimerize to [Ru2X2(ppye-P,N)4]2+ depending on the size of the halide. The chloro derivative [Ru2Cl2(ppye)4]-[PF6]2 has been characterized crystallographically. Both the five-co-ordinate cations and the dimeric species react with carbon monoxide forming cationic monocarbonyls, while the octahedral species undergo rupture of the Ru-N bond and neutral carbonyl derivatives are formed containing a dangling, P-bound ppye ligand. All these carbonyl derivatives are formed as the kinetically preferred species with a P atom trans to CO, and are converted in solution at room temperature into the thermodynamically preferred isomers in which the P and CO groups are mutually cis.