Transition metal complexes of a novel tetradentate phosphine and of a new diphosphine ether

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1991
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Mason, Mark
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John G. Verkade
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Chemistry

The Department of Chemistry seeks to provide students with a foundation in the fundamentals and application of chemical theories and processes of the lab. Thus prepared they me pursue careers as teachers, industry supervisors, or research chemists in a variety of domains (governmental, academic, etc).

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The Department of Chemistry was founded in 1880.

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Abstract

This dissertation describes the synthesis and coordination chemistry of two new phosphine ligands and a novel fluoride-induced redox reaction. The tetratertiary phosphine 2,3-bis(diphenylphosphinomethyl)-1,4-bis(diphenylphosphino)butane (1) coordinates to a variety of transition metal fragments (ML[subscript] n) to yield bimetallic complexes of the type L[subscript] nM(PPh[subscript]2CH[subscript]2)[subscript]2CHCH(CH[subscript]2Ph[subscript]2P)[subscript]2ML[subscript] n, and monometallic complexes of Mo(CO)[subscript]3 wherein 1 coordinates in a tridentate fashion. The structures of the homobimetallic complexes where ML[subscript] n = NiCl[subscript]2, PdCl[subscript]2, and PdI[subscript]2 have been confirmed by X-ray crystallography. Reaction of (Cl[subscript]2Pd(Ph[subscript]2PCH[subscript]2)[subscript]2CH) [subscript]2 with 1 in air gives Cl[subscript]2Pd(PPh[subscript]2Ch[subscript]2)[subscript]2CHCH(CH[subscript]2P(O)Ph[subscript]2)[subscript]2 via metal-catalyzed air oxidation. The structure of this complex is also reported. Unsuccessful attempts to prepare monometallic complexes of Rh(I), Ni(II), and Pd(II) wherein 1 would coordinate as a tetradentate ligand are also examined;The new ditertiary phosphine ether cis-1,5-bis(diphenylphosphinomethyl)-3-oxabicyclo(3.3.0) octane (2) coordinates to transition metals in either a bidentate (P, P[superscript]') manner through the two phosphorus donors, or in a tridentate (P,P[superscript]',O) manner in which the ether oxygen is also coordinated. Single-crystal X-ray diffraction studies on (2-P,P[superscript]')Mo(CO)[subscript]4 and fac-(2-P,P[superscript]',O)W(CO)[subscript]3 verify the bidentate and tridentate coordination modes of 2, respectively. The metal-ether interaction in the complexes fac-(2-P,P[superscript]',O)M(CO)[subscript]3 are liable to stereospecific substitution by additional ligands (L) to yield two diastereomers of fac-(2-P,P[superscript]')M(L)(CO)[subscript]3 (M = Mo, W; L = CO, [superscript]13CO, (P(OCH[subscript]2)[subscript]3CCH[subscript]3), CH[subscript]3CN, py, pip) in each case. Complexes of the N-donor ligands equilibrate in solution with (2-P,P[superscript]',O)M(CO)[subscript]3 and uncoordinated N-donor ligand. This equilibrium was verified by monitoring the exchange reaction between fac-(2-P,P[superscript]')W(NCCH[subscript]3)(CO)[subscript]3 and CD[subscript]3CN by [superscript]2H NMR spectroscopy;In the course of this work, it was discovered that addition of fluoride to palladium(II) phosphine complexes results in a redox reaction yielding a difluorophosphorane and a phosphine complex of palladium(0). This reaction has been explored utilizing PPh[subscript]3, Ph[subscript]2P(CH[subscript]2)[subscript] nPPh[subscript]2(n = 1-4), Ph[subscript]2PCH[subscript]2C(CH[subscript]3)[subscript]2CH[subscript]2PPh[subscript]2, MePh[subscript]2P, and P(CH[subscript]2CH[subscript]2CN)[subscript]3; several solvent systems and temperatures; and both hydrated and anhydrous fluoride sources. The rapid reduction of ((Ph[subscript]3P)[subscript]3PdCl) BF[subscript]4 to yield Pd(PPh[subscript]3)[subscript]2 in the presence of fluoride and its relevance to the previously reported synthesis of (Pd[subscript]3Cl([mu][subscript]2-PPh[subscript]2)[subscript]2(PPh[subscript]3)[subscript]3) BF[subscript]4 is also discussed. Complexes of platinum were also found to undergo this fluoride-induced redox reaction, but Ni complexes yield only NiF[subscript]2.

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Tue Jan 01 00:00:00 UTC 1991