Highly Reduced Organometallics. 14. Six- and Seven-Coordinate Organotin Derivatives of the Tetrasodium Tetracarbonylmetalates(4-) of Chromium, Molybdenum, and Tungsten

Treatment of Na₄[M(CO)₄ with 2 equiv of Ph₃SnCl provides approximately 50% yields of [Et₄N]₂-[(Ph₃Sn)₂M(CO)₄] for M = Cr and W and very low yields for M = Mo. The reaction of L₂M(CO)₄) where L₂ = norbornadiene, cyclooctadiene, tetramethylethylenediamine, or ethylenediamine (M = Cr, Mo, W), with 2 equiv of Ph₃SnLi is a more facile and often higher yield route (60-70% for M = Cr, Mo; 35% for M = W) to the same dianions. These materials react with Ph₃SnCl to provide 30-40% yields of [Et₄N][(Ph₃Sn)₃M(CO)₄], in which Cr, Mo, and W are seven-coordinate. Reactions of [Et₄N]₂-[(Ph₃Sn)₂M(CO)₄] (M = Cr, Mo) with acetic acid, [Me₂NCCl₂]Cl, and methyl iodide in acetonitrile provide 30-40% yields of [Et₄N][H(Ph₃Sn)₂M(CO)₄], containing seven-coordinate metals, trans-Ph₃Sn(CO)₄M蠁 CNMe₂, and [Et₄N][(Ph₃Sn)M(CO)₄(CH₃CN)], respectively. The coordinated acetonitrile in the latter compounds is slowly displaced by PPh₃ in acetonitrile at 25 C to give 35-50% yields of [Et₄N]-[Ph₃SnM(CO)₄(PPh₃)]. All of these new materials are characterized by elemental analyses and IR and ¹H NMR spectra.