Main group derivatives of a cyclometallated iron carbonyl anion. Crystal structures of Fe(CO) 2{P(OPh) 3}{(PhO) 2POC 6H 4}(SnPh 3) and two isomers of Fe(CO) 2{P(OPh) 3}{(PhO) 2POC 6H 4}(I)

Abstract

The iron hydrido complex HFe(CO) 2{P(OPh) 3}{(PhO) 2POC 6H 4} ( 1), was rapidly deprotonated by DBU or [BzMe 3N][OH] in THF to afford the new carbonyl iron anion [Fe(CO) 2{P(OPh) 3}{(PhO) 2POC 6H 4}] − ([ 2] −), containing an ortho-metallated triphenyl phosphite ligand. Complex [ 2] − reacted with triorganostannyl and plumbyl salts and with halogens to give the octahedral Fe II compounds Fe(CO) 2{P(OPh) 3}{(PhO) 2POC 6H 4}(X) (X=SnPh 3, 3; SnMe 3, 4; PbPh 3, 5; PbMe 3, 6; Cl, 7; Br, 8; I, 9). The Group 14 complexes 3– 6 were obtained in one isomeric form in which the P III-donor atoms are mutually cis, the carbonyl ligands are cis and the P(OPh) 3 and MR 3 (M=Sn, Pb; R=Ph, Me) groups are trans as determined by solution-state IR, 31P and 13C NMR spectroscopic data. This geometry was confirmed for 3 by a single crystal X-ray diffraction study. The halide complexes, however, were obtained as a mixture of isomers. The major isomer ( 7, X=Cl; 8a, X=Br; 9a, X=I) has cis P atoms, trans CO groups and the halide located trans to the phosphorus atom of the ortho-metallated phosphite ligand. The structure of 9a was confirmed by an X-ray diffraction study. Two other isomers, designated 8b (X=Br) and 9b (X=I), with cis P atoms and cis CO groups were isolated from the reactions of [ 2] − with Br 2 and I 2, respectively. The structure of the latter was established by X-ray crystallography and is related to 9a by exchange of the P(OPh) 3 ligand and a carbonyl group such that the metal-bound C atom of the five-membered metallacycle is trans to CO. The stereo-geometry of 8b could not be unambiguously assigned from the spectroscopic data; however, two of the seven possible geometric isomers were suggested as plausible structures.