Halide Ion Addition to Bismuth-Containing Iron Carbonyl Compounds: Synthesis and Characterization of the Two Bridged-Butterfly Cluster Compounds [Et(4)N][(&mgr;-H)Fe(2)(CO)(6)Bi(2){&mgr;-Fe(CO)(4)}] and [{PhCH(2)NMe(3)}{(&mgr;-H)Fe(2)(CO)(6)Bi(2)(&mgr;-Cl)(2)}](infinity) and Stabilization of Reduced-Hypervalent Bismuth Centers by Coordination to a Metal Center in [PhCH(2)NMe(3)](3)[Bi(3)Cl(4)(&mgr;-Cl)(4){Fe(CO)(3)}

Abstract

The reaction of [Q](2)[Bi(4)Fe(4)(CO)(13)] ([Q](2)[1]; [Q] = [Et(4)N](+), [PhCH(2)NMe(3)](+)) with MePCl(2) in MeCN is a complicated reaction which gives different results depending upon the stoichiometry of the reaction. At a ratio of 1:1.33 (cluster:phosphine), the reaction yields a mixture of the new bismuth-iron carbonyl compounds [Q][(&mgr;-H)Fe(2)(CO)(6)Bi(2){Fe(CO)(4)}] ([Q][2]), which has a tetrahedral Fe(2)Bi(2) core edge-bridged across the bismuth centers by an [Fe(CO)(4)](2)(-) fragment, and [Q](3)[Bi(3)Cl(4)(&mgr;-Cl)(4){Fe(CO)(3)}] ([Q](3)[3]), containing a reduced complex ion [Bi(3)Cl(8)](-) stabilized by coordination to an iron tricarbonyl fragment. Extended Hückel molecular orbital calculations on this unusual anion are consistent with each bismuth atom possessing the same reduced oxidation state of +2.33. The compound [Et(4)N][2] crystallizes in the triclinic space group P&onemacr; (No. 2) with a = 10.246(2) Å, b = 11.859(2) Å, c = 12.474(2) Å, alpha = 71.11(3) degrees, beta = 79.60(3) degrees, gamma = 76.37(3) degrees, V = 1384.7(4) Å(3), and Z = 2, while [PhCH(2)NMe(3)](3)[3].0.87Et(2)O was characterized in the orthorhombic space group Pbca (No. 61) with a = 20.801(4) Å, b = 19.937(4) Å, c = 25.480(5) Å, V = 10566.8(36) Å(3), and Z = 8. When the reaction is carried out at a ratio of 1:2, the novel hydride [{Q}{(&mgr;-H)Fe(2)(CO)(6)Bi(2){&mgr;-Cl}(2)}](infinity) ([{Q}{4}](infinity)) is isolated. This cluster also has a "tetrahedral" core, with the Bi-Bi vector bridged by a chloride ligand and the molecules joined into infinite polymeric chains in the solid state by the second intermolecularly-bridging chloride ligand. [{PhCH(2)NMe(3)}{4}](infinity) crystallizes in the monoclinic space group P2(1)/n (No. 14) with a = 7.864(2) Å, b = 22.465(4) Å, c = 13.797(3) Å, beta = 105.96(3) degrees, V = 2343.5(9) Å(3), and Z = 4. The metal framework of [4](-) is similar to that of [2](-) with the notable exception that the Bi-Bi bond present in [2](-) is missing in [4](-) because of the additional electrons provided by the chloride ions. At stoichiometries greater than 2:1, the previously reported [Fe(CO)(4)Bi(2)Cl(6)](2)(-) ion is formed.