The reactions of cis-[Fe 2(η-C 5H 5) 2(CO) 2(μ-CNMe 2) 2][SO 3CF 3] 2 and related compounds with nucleophiles

Abstract

The terminal CO ligands in the cis-[Fe 2(η-C 5H 5) 2(CO) 2(μ-CNMe 2) 2] 2+ cation are both labile and susceptible to nucleophilic attack at carbon depending on the nucleophile and the reaction conditions. The CO substitution is effected by nucleophiles L such as organonitriles, acetone or tertiary phosphines to give [Fe 2(η-C 5H 5) 2(CO)(L)(μ-CNMe 2) 2][SO 3CF 3] 2 and [Fe 2(η-C 5H 5) 2(L) 2(μ-CNMe 2) 2][SO 3CF 3] 2 salts. Coordinated acetone is replaced by organonitriles and these in turn are displaced by phosphines. These reactions may be brought about thermally or more reliably by photolysis. The consequences of varying the UV lamp power and the nature of the phosphine are reported. Similar reactions take place with cis-[Fe 2(η-C 5H 5) 2(CO) 2{μ-CN(H)Me}(μ-CNMe 2)][SO 3CF 3] 2 and cis-[Fe 2(η-C 5H 5) 2(CO) 2(μ-CNH 2)(μ-CNMe 2)][SO 3CF 3] 2 salts, but phosphines deprotonate the μ-CNH 2 ligand and lead to decomposition. Harder nucleophiles Nu − such as OH −, OR − (from NaCN–ROH) or NHR − (from RNH 2) deprotonate the μ-CN(H)Me and μ-CNH 2 ligands but do not de-methylate the μ-CNMe 2 ligand to any great extent. Instead they attack one terminal CO ligand of cis-[Fe 2(η-C 5H 5) 2(CO) 2(μ-CNMe 2) 2][SO 3CF 3] 2 to give cis-[Fe 2(η-C 5H 5) 2(CO){C(O)Nu}(μ-CNMe 2) 2][SO 3CF 3] with no evidence for attack elsewhere in the molecule. When RNH 2C 6H 11NH 2, the reaction work-up may be modified so that [Fe 2(η-C 5H 5) 2(CO)(CNC 6H 11)(μ-CNMe 2) 2][SO 3CF 3] 2 and [Fe 2(η-C 5H 5) 2(CNC 6H 11) 2(μ-CNMe 2) 2][SO 3CF 3] 2 are the products. They result from the dehydration of the first-formed carbamoyl complexes; a reaction which does not take place with the more volatile i PrNH 2. The mechanism of the reactions and the spectra of the products are discussed.