Dichromium and dimolybdenum complexes with tertiary phosphines, and new iron(II) chloride complexes with oxygen donor ligands

Abstract

In appropriate solvents at reflux temperatures, anhydrous chromium(III) chloride reacts with the monodentate tertiary phosphines PMe3 and PEt3, and with the bidentate tertiary phosphine, bis(dimethylphosphino)- methane [dmpm] to form Cr2Cl6(PMe3)4, Cr2Cl6 (PEt3)4 and Cr2Cl6(dmpm)2, respectively. The reaction of two equivalents of Na(Hg) with Cr2Cl6(dmpm)2 yields Cr2Cl4(dmpm)2 in which we expected to find multiple Cr-Cr bonds. However, the dichromium(II) compound, Cr2Cl4 (dmpm)2, avoids any Cr-Cr bond formation by adopting a bizarre structure. Cr2Cl4(dmpm)2 reacts with methanol to yield Cr2Cl4(/Li-OMe)2(dmpm)2. All of the dinuclear chromium species have an edge-sharing bioctahedral structure except for Cr2Cl4(dmpm)2, where each Cr atom is in a trigonal bipyramidal coordination sphere, with a common Cl...Cl edge. The reaction of MoC13(THF)3 with two equivalents of the phosphine in THF yields two sorts of compound, Mo2Cl6(PEt3)4 and Mo2Cl6(PEt3)3, and at room temperature, Mo2Cl6(PEt3)3 becomes the principal product. Mo2Cl6(PEt3)3 exhibits a significant metal-metal interaction, whereas Mo2Cl6(Pet3)4 does not. Several new iron(II) chloride complexes with oxygen donor ligands have been prepared and structurally characterized by X-ray crystallography, namely, Fe4Cl8(THF)6, [FeCl2(OPMe3)]n, and FeCl2(OPMe3)2. Fe4Cl8(THF)6 has been isolated from a solution of iron(II) chloride in THF which was obtained by reacting FeCl3 in THF with metallic iron. Either polymeric compound [FeCl2(OPMe3)]n or monomeric compound FeCl2(OPMe3)2 can be obtained from the reaction of a usefully reactive solution of iron(II) chloride in THF with OPMe3 by adjustment of the OPMe3 concentration. Full details about the syntheses, structure, characterization and magnetic properties of these tertiary phosphine complexes of dichromium and dimolybdenum, and of the iron(II) chloride compounds with oxygen donor ligands are given.