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.