MONONUCLEAR CARBONYL METAL-COMPLEXES OF IRON AND RUTHENIUM M(CO)(N)[P(C7H7)(3)] (M = FE, RU, N = 4,3,2), WITH THE MULTIDENTATE LIGAND TRI-(1-CYCLOHEPTA-2,4,6-TRIENYL)PHOSPHANE

A series of trigonal-bipyramidal complexes of the type M(CO)(n)(P(C7H7 )(3)] (M = Fe, Ru; n = 4,3,2) has been investigated in which the phosp horus atom of the ligand tri(1-cyclohepta-2,4,6-trienyl)phosphane P(C7 H7)(3) (1), is coordinated in an axial position and up to two olefinic side-arms may be used for additional coordination to the metal in equ atorial positions. The reaction of either Fe-2(CO)(9) or Fe-3(CO)(12) with 1 in THF solution leads to the phosphane complex Fe(CO)(4)[P(C7H7 )(3)] (4a); the ruthenium analogue 4b is obtained from Ru-3(CO)(12) un der irradiation. Stepwise photo-elimination of two equatorial CO ligan ds can be used to convert 4a,b through the intermediate M(CO)(3)[P(C7H 7)(2)(eta(2)-C7H7)] (M = Fe (5a), Ru (5b)) into M(CO)(2)[P(C7H7)(eta(2 )-C7H7)(2)] (M = Fe (6a), Ru (6b)). In C6D6 solution, the bis(olefinic ) complexes 6a,b slowly isomerize to give the orange end-products M(CO )(2)[P(C7H7)(2)(eta(4)-C7H7)] (7a,b) in which only one of the three se ven-membered rings is coordinated to the metal in the form of a norcar adienyl substituent. The new complexes were characterized by a consist ent set of H-1-, C-13- and P-31-NMR spectra, and the molecular geometr y of 6a has been determined by a single-crystal structure analysis.