Transition Metal Polypnictides from Zintl Ions

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Date
1995Author
Charles, Scott
Advisor
Eichhorn, Bryan W.
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The chemistry of the soluble E7 3- ions (E = P, As, Sb) with various transition
metal complexes has been investigated. Alloys of K3E7 react with (arene)M(CO)3 (M
= Cr, Mo, W) complexes in the presence of three equivalents of 2,2,2-crypt in
ethylenediamine to give [K(2,2,2-crypt)]3[E7M(CO)3] complexes. Nine
[E7M(CO)3] 3- compounds (E = P, As, Sb; M = Cr, Mo, W) have been prepared. The
compounds have norbomadiene-like E7 fragments, with a formal negative charge
associated with the unique two-coordinate pnictogen furthest from the transition
metal. The bonding is described as E7 π-type interactions with the metal center. 31p
NMR studies show that these compounds undergo an intramolecular wagging process
in solution. The [E7M(C0)3] 3- ions are modestly basic and highly nucleophilic. The
complexes react with weak acids, tetraalkylammonium salts and
(arene)M'(CO)3 complexes to form the [K(2,2,2-crypt)]2[HE7M(CO)3], [K(2,2,2-
crypt)]2[RE7M(CO)3] and [K(2,2,2-crypt)]3[(L2)(CO)3M'E7M(CO)3] compounds,
respectively. Each of the structures contains a norbornadiene-like E7 fragment bound
η4 to the M(CO)3 fragment and η1 to the appended moiety [H+, R+, M(CO)3(en)] that is attached to the pnictogen atom furthest from the M(CO)3 center. The [K(2,2,2-crypt)]3 [η4-E7M(CO)3] complexes also react with carbon monoxide at the M(CO)3 center and reversible binds CO to form [K(2,2,2-crypt)]3[η4-E7M(CO)4] complexes.
These complexes are more easily protonated and undergo faster alkylations of the E7
cages than the parent [K(2,2,2-crypt)]3[η4-E7M(CO)3] compounds. Each of these
structures contains an E7 fragment bound η2 to the M(C0)4 center. Products were
characterized by various physical and spectroscopic techniques including UV-vis, IR,
1H, 13C, and 31P NMR spectroscopies, mass spectrometry, elemental analyses, and
single crystal X-ray diffraction studies.