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    THE SYNTHESIS, CHARACTERIZATION, AND REACTIVITY OF IRON CARBONYL CLUSTERS INCORPORATING MAIN GROUP HETEROATOMS

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    The reaction of Pb(OAc)\sb2 or PbCl\sb2 with K (HFe(CO)\sb4) results in formation of (Et\sb4N) \sb2 (Pb{\{Fe\sb2(CO)\sb8\}\{Fe(CO)\sb4\}\sb2) in high yield based on iron. This complex has been structurally characterized and contains a central Pb\sp{4+} atom bound to two (Fe(CO)\sb4) \sp{2-} ligands and one (Fe\sb2(CO)\sb8) \sp{2-} group (Fe-Fe = 2.617(5)A). (Et\sb4N) \sb2 (M{\{Fe\sb2(CO)\sb8\}\{Fe(CO)\sb4\}\sb2) reacts with CO and MCl\sb2 with excess K (HFe(CO)\sb4) to yield products which are formulated as (Et\sb4N) \sb2 (M{\{Fe(CO)\sb4\}\sb2) on the basis of analytical and spectroscopic data. GeI\sb2 is unreactive towards K (HFe(CO)\sb4), but when mixed with (Et\sb4N) \sb2 (Fe\sb2(CO)\sb8) formation of the novel complex (Et\sb4N) \sb2 (Fe\sb3(CO)\sb9(\mu\sb3-CO)\{\mu\sb3 - GeFe(CO)\sb4\}) occurs. When GeCl\sb4 is treated with (Et\sb4N) \sb2 (Fe\sb2(CO)\sb8) formation of (Et\sb4N) \sb2 (Fe\sb3(CO)\sb{11}) is observed with no evidence of a germanium-containing cluster. These mixed metal anions are oxidized by (Cu(CH\sb3CN)\sb4) (BF\sb4) to form the corresponding neutral spirocyclic M (Fe\sb2(CO)\sb8) \sb2 (M = Sn, Ge, Pb) species. A single crystal X-ray diffraction structure was obtained for the complex Pb (Fe\sb2(CO)\sb8\rbrack\sb2 (Fe-Fe = 2.90(2)A). Reduction of Ge (Fe\sb2(CO)\sb8\rbrack\sb2 in benzene or CH\sb2Cl\sb2 led to the recovery of (Et\sb4N) \sb2 (Fe\sb3(CO)\sb9(\mu\sb3-CO)\{\mu\sb3-GeFe(CO)\sb4). (Et\sb4N) \sb2 (Pb{\{Fe\sb2(CO)\sb8\}\{Fe(CO)\sb4\}\sb2) or (Et\sb4N) \sb2 (Pb{\{Fe(CO)\sb4\}\sb2) are recovered from reduction of Pb (Fe\sb2(CO)\sb8) \sb2, depending on the solvent used. Periodic trends were examined by utilizing bismuth as the main group element. The reaction of NaBiO\sb3 with K (HFe(CO)\sb4) resulted in isolation of (Et\sb4N) \sb3 (Bi{\{Fe(CO)\sb4\}\sb4) in which a central Bi\sp{5+} atom is tetrahedrally surrounded by four (Fe(CO)\sb4) \sp{2-} ligands. This complex decomposes in the presence of gaseous HCl to produce up to 1 mole of H\sb2 per mole of cluster via intermediate formation of H\sb2Fe(CO)\sb4. Refluxing NaBiO\sb3 with Fe(CO)\sb5 led to the isolation of (Et\sb4N) (BiFe\sb3(CO)\sb9(\mu\sb3-CO)) which is isoelectronic with (Et\sb4N) \sb2 (Fe\sb3(CO)\sb9(\mu\sb3-CO)\{\mu\sb3-GeFe(CO)\sb4\}) and contains a triangle of iron atoms capped by a bismuth atom on one face and a CO group on the other (Fe-Fe = 2.642(7)A). When (Et\sb4N) (BiFe\sb3(CO)\sb9(\mu\sb3-CO)) is treated with CO, an extensive rearrangement occurs leading to formation of (Et\sb4N) \sb2 (Bi\sb4Fe\sb4(CO)\sb{13}) in which there is a central tetrahedron of bismuth atoms attached to iron carbonyl fragments. This complex is the first "Zintl-metal carbonylate" to be reported. (Abstract shortened with permission of author.
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