In the presence of a Lewis base solvent (THF) the Group IIB tetracarbonyl ferrates, {MFe(CO)(,4)}(,x) (M = Zn, Cd, and Hg) undergo stepwise reduction to give the mixed-metal dianion clusters, M(Fe(CO)(,4))(,2)('2-), first, and subsequently Fe(,2)(CO)(,8)('2-). The mechanism for the base reduction is considered in terms of competing base reactions. The solid state structures of {Na(THF)(,2)('+)}(,2){M(Fe(CO)(,4))(,2)('2-)} (M = Zn and Hg) have been determined and are directly related to their solution state infrared and NMR spectra with structural distortions retained in both the solution and solid states. The results of the structural determination on {Na(THF)(,2)('+)}(,2) {Zn(Fe(CO)(,4))(,2)('2-)} showed the zinc to crystallize in the space group 12/m with approximate C(,2h) site symmetry. The cell dimensions are a = 10.654(3) (ANGSTROM), b = 9.848(3) (ANGSTROM), c = 15.333(3) (ANGSTROM), (beta) = 100.79(2)(DEGREES), and V = 1580 (ANGSTROM)('3). The geometry about the iron atoms is that of a Fe(CO)(,4) tetrahedron with the zinc atom approximately bridging an edge. Crystals of the mercury analogue form in the space group C 2/m with D(,3d) symmetry site symmetry. The cell dimensions for the mercury complex are a = 12.39(3) (ANGSTROM), b = 8.54(1) (ANGSTROM), c = 16.01(1) (ANGSTROM), (beta) = 105.5(2) , and V = 1636 (ANGSTROM)('3). The mercury is capping one face of the Fe(CO)(,4) tetrahedron. Bonds between carbonyl oxygen atoms of the dianions and the Na(THF)(,2)('+) cations results in an extended structure in the solid state. ('57)Fe Mossbauer recorded on the zinc and cadmium dianion complexes gave the following parameters: Zn: (delta) = 0.156 mm s('-1) and (DELTA) = 0.910 mm s('-1); Cd: (delta) = 0.232 mm s('-1) and (DELTA) = 1.112 mm s('-1) (relative to iron foil).
The dimeric dialkyltin tetracarbonyl ferrates, {Sn(R)(,2)Fe(CO)(,4)}(,2), establish an equilibrium in Lewis base solvents forming a monomer base adduct, Sn(R)(,2){B}Fe(CO)(,4). For B = THF or C(,5)H(,4)N, the monomer adduct undergoes reduction to form a radical anion, Sn(R)(,2)Fe(CO)(,4)('-), where the reduction process is seen as populating a nonbonding sp('3) orbital on tin with possible (pi) back-bonding to the iron. The ('57)Fe Mossbauer spectrum exhibits a doublet ((delta) = 0.06 mm s('-1) and (DELTA) = 1.50 mm s('-1)) in the region of Fe(CO)(,4)('2-). The ('119)Sn Mossbauer spectrum exhibits a doublet ((delta) = 1.54 mm s('-1) and (DELTA) = 1.19 mm s('-1)) in the region normally associated with tin (IV).
| Identifer | oai:union.ndltd.org:RICE/oai:scholarship.rice.edu:1911/15788 |
| Date | January 1982 |
| Creators | SHONG, ROBERT GEORGE |
| Source Sets | Rice University |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | application/pdf |
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