RETARDATION EFFECT OF TRIMETHYL PHOSPHITE ON CHELATE RING-CLOSURE OF 2,2'-BIPYRIDINE (BIPY) IN CIS-[W(CO)4(P(OME)3)-(BIPY)]

1994-08-07
KAYRAN, C
Özkar, Saim
SULTAN, WIM
In order to study the effect of a donor ligand on the chelate ring-closure reaction of a diimine ligand co-ordinated in monodentate fashion, cis-[W(CO)4{P(OMe)3}(bipy)] was synthesised from [W(CO)5{P(OMe)5}] and 2,2'-bipyridine (bipy) by using a newly developed method and characterized by means of IR and NMR spectroscopies. The complex was found to undergo neither cis-->trans isomerization nor chelation thermally up to 150-degrees-C. However the ring-closure reaction occurs photochemically. Thus irradiation of the complex yielded fac-[W(CO)3{P(OMe)3}(bipy)] which was also isolated and characterized. The extraordinary retardation effect of trimethyl phosphite on the ring-closure reaction of the 2,2'-bipyridine ligand is attributed to the reduction in substitution lability of the CO groups in the complex upon introduction of the phosphite donor ligand.