Preparation of the triiron phosphinidene-imido clusters Fe3(.mu.3-PBu-tert)(.mu.3-NR)(CO)9 (R = Et, Ph) and their reactions with alkynes

Abstract

The compounds Fe[sub 3]([mu][sub 3]-PBu[sup t])([mu][sub 3]-NR)(CO)[sub 9] (R = Ph (2a), Et (2b)), which are the first examples of clusters possessing both capping imido and phosphinidene ligands, have been prepared in good yield by the photochemical reaction of the corresponding H[sub 2]Fe[sub 3]([mu][sub 3]-NR)(CO)[sub 9] cluster with Bu[sup t]PCl[sub 2]. Cluster 2a has been crystallographically characterized: C[sub 19]H[sub 14]NO[sub 9]PFe[sub 3], orthorhombic,. Like Fe[sub 3]([mu][sub 3]-NPh)[sub 2](CO)[sub 9], the cluster consists of an isosceles triangle of iron atoms with two Fe-Fe bonds and with capping phosphinidene and imido ligands above and below the metal triangle. Both clusters have been observed to react with alkynes to give a variety of products, the most interesting of which is the binuclear compound Fe[sub 2]([mu][sub 2],[eta][sup 3]-PhNC(Ph) [double bond] C(Ph)PBu[sup t])([mu][sub 2],[eta][sup 4]PhC [double bond] C(Ph)C(Ph) [double bond] CPh)(CO)[sub 4] (3) which results from the reaction of PhC [triple bond] C(Ph)PBu[sup t] ligand formed by insertion of the alkyne between the phosphinidene and imido ligands and also has a ferracyclopentadiene ligand formed by coupling of two additional alkynes: C[sub 56]H[sub 44]NO[sub 4]PFe[sub 2], triclinic.