Organometallics of diphosphazanes: V. The different coordination behaviour of cis- and trans-cyclodiphosphazanes towards Group 6 metal carbonyl moieties

Abstract

The reactions of cyclodiphosphazanes [PhNP(OR)] 2 (R = CH 2CF 3 ( 1) and C 6H 4Me- p ( 2) with Group 6 metal carbonyl derivatives have been investigated. The stereochemistry of the ligand appears to play a significant role in determining its coordination behaviour. The cyclodiphosphazane 1 (isolated as the trans-isomer) affords the dinuclear complexes 9– 11 in which the two metal centres are bridged by the diphosphazane ligand. In contrast the cyclodiphosphazane 2 (isolated as a 3/1 mixture of cis-and trans-isomers) yields the mononuclear complexes 3– 7 in which the cyclodiphosphazane is coordinated in the η 1-fashion. The structures of [W(CO 4(NHC 5H 10) (PhNP(OC 6H 4Me- p)) 2] ( 6) and [Mo(CO) 4(NHC 5H 10) 2μ-[PhNP(OCH 2 CF 3)]2] ( 9a) have been determined by X-ray crystallography.