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Synthesis and Structural Characterization of Lithium and Iron Complexes Containing a Chelating Phenolate Phosphane Ligand

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  • Dedicated to Professor John D. Corbett on the occasion of his 85th birthday

Abstract

The preparation and characterization of lithium and iron(II) complexes containing a potentially tridentate biphenolate phosphane ligand are reported. Deprotonation of 2,2′-phenylphosphanyl-bis(4,6-di-tert-butylphenol) (H2LPh) with one or two equivalents of nBuLi in diethyl ether solutions at –35 °C produces binuclear {Li(HLPh)(OEt2)}2 or tetranuclear Li4(LPh)2(OEt2)3, respectively. An X-ray study of {Li(HLPh)(OEt2)}2 showed it to be a Ci-symmetric dimer composed of two Li(HLPh)(OEt2) units linked with dative O–Li bonds involving phenolate oxygen donor atoms whereas that of Li4(LPh)2(OEt2)3 revealed a C2-symmetric structure in which the two biphenolate phosphane ligands are linked with four lithium atoms that bind to three diethyl ether molecules. Treatment of FeCl2 with one or two equivalents of Na2(LPh)(DME)2 in THF at –35 °C generates binuclear Fe2(LPh)2(THF)2 or mononuclear Fe(HLPh)2(THF)2, respectively. The two iron(II) centers in Fe2(LPh)2(THF)2 are antiferromagnetically coupled.

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