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 phosphorus atom of the ligand tri(1-cyclohepta-2,4,6-trienyl)phosphane P(C7H7)(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 equatorial 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) under irradiation. Stepwise photo-elimination of two equatorial CO ligands can be used to convert 4a,b through the intermediate M(CO)(3)[P(C7H7)(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 seven-membered rings is coordinated to the metal in the form of a norcaradienyl substituent. The new complexes were characterized by a consistent set of H-1-, C-13- and P-31-NMR spectra, and the molecular geometry of 6a has been determined by a single-crystal structure analysis.