Structural Studies of [(py)2CdFe(CO)4]3 and {(THF)5[CdFe(CO)4]3}

The structures of [(py)2CdFe(CO)4]3 and {(THF)5[CdFe(CO)4]3} have been determined (py = pyridine; THF = tetrahydrofuran). Each is composed of a six-membered ring having alternating cadmium and iron centers. The presence of the more strongly basic amine ligands in the former led to a greater contribution of an ionic resonance form, which resulted in overall longer Cd–Fe bonds and a greater contribution of a bicapped tetrahedral coordination geometry about iron. Thus, the Cd–Fe distances range from 2.5679(4) to 2.6501(1) Å for the THF complex versus 2.6445(8) to 2.6833(7) Å for the py complex. Similarly, the Fe–Cd–Fe and Cd–Fe–Cd angles for the THF complex fell in respective ranges of 139.03(2)–157.27(2)° and 84.41(1)–99.79(1)°, as compared to 135.31(3)–139.51(4)° and 102.52(3)–104.62(4)° for the py complex. The space group for the former compound is Pbcn, with a = 12.2678(2), b = 22.4601(5), and c = 17.0039(4) Å, while for the THF complex, the space group is P21/c, with a = 10.7297(2), b = 20.4961(2), c = 18.7464(3) Å, and β = 94.2715(6)°.