Mono- and bi-nuclear complexes of ruthenium(II) with the ligand 1-(diphenylphosphino)-2-(2-pyridyl)ethane

Abstract

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 ³¹P-{¹H} and ¹³C-{¹H} 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.