Dinuclear Derivatives of Mn2(CO)10 with the Ligand Tri(1-Cyclohepta- 2,4,6-Trienyl)Phosphane, P(C7H7)3, and their Oxidative Cleavage

Abstract

Abstract The photo-induced reaction of Mn2(CO)10 with the olefinic phosphane P(C7H7)3 (1; [P] if coordinated to a metal) leads stepwise to the axially substituted derivatives ax-{Mn2(CO)9[P]} (2) and ax,ax-{Mn2(CO)8[P]2} (3). Oxidative cleavage of 3 by halogens gives cis-{Mn(X)(CO)4[P]} (X = Cl (4a), Br (4b), I (4c)), whereas oxidation of 3 with NOBF4 provides a route to the salt {Mn(CO)4[P]}BF4 (5) which is also accessible by halide abstraction from 4b by AgBF4. The reactivity of the bromo complex 4b has been studied, and analogues such as cis-{Mn(R)(CO)4[P]} (R = Me (4d), Fc (4e) and N(iPr)2 (4f)) have been prepared. The displacement of a carbonyl ligand from 4b by iodide leads to mer-{Mn(I)(CO)3[P]} (6c) and by 1 to mer,trans-{Mn(Br)(CO)3[P]2} (7b). The complexes mer-{Mn(X)(CO)3[P]} (6a-c) are obtained by splitting the dimers, Mn2(CO)6(CH3CN)2- (μ −X)2 (X = Cl, Br, I), with P(C7H7)3 (1). The cation in 5 and the halogeno compounds 6a-c contain [P] (1) as a chelating four-electron ligand which uses one cyclohepta-2,4,6-trienyl substituent for π-complexation. The coordinated double bond in 6c can be displaced by phosphites P(OR)3 (R = Me, Et) to give fac-{Mn(I)(CO)3[P(C7H7)3][P(OR)3]} (8c). The structures of the new complexes 2-8 have been assigned on the basis of their carbonyl stretching absorption patterns in the IR spectra and by their NMR spectra (1H, 13C, 31P). Single-crystal X-ray structure analyses have been carried out for 3 and 6c.