Reaction of Fe2(CO)9with Lithium: Preparation and Structures of Compounds with Strong Ion Pairing

Abstract

The reduction of Fe2(CO)9 with elemental lithium in THF solution at room temperature generates the dinuclear complex [Li2(THF)6Fe2(CO)8] (1), in which the Li atoms are bonded to the oxygen atoms of bridging CO groups. Dissolution of 1 in toluene leads to loss of two THF molecules to give the polymeric complex [Li2(THF)4Fe2(CO)8]n (2); dimeric units (n = 2) are formed with the help of a planar Li2O2 ring, and these units are further linked by Li−O contacts to terminal carbonyl groups. Alkylation of 1 with MeSO3CF3 yields the known dinuclear compound [(CO)3Fe(μ-C(Me)O)2Fe(CO)3] (4). Treatment of 1 with Me3SnCl leads to splitting of the Fe−Fe bond, resulting in cis-[CO)4Fe(SnMe3)2] (6) as the main product. The X-ray structures of 1, 2, and 4 are presented along with the structure of the sodium salt [Na2(THF)4Fe2(CO)8]n (5), which has only terminal CO groups.