Further studies of phosphine adducts of niobium(IV) and tantalum(IV) chlorides: New seven- and eight-coordinate compounds with trimethylphosphine: NbCl4(PMe3)3 and Ta2Cl8(PMe3)4 |
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| Authors: | FAlbert Cotton Michael P Diebold Wieslaw J Roth |
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| Institution: | Department of Chemistry and Laboratory for Molecular Structure and Bonding, Texas A & M University, College Station, TX 77843, U.S.A. |
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| Abstract: | The reaction of NbCl4(THF)2 with an excess of PMe3 in toluene solution afforded a 70% isolated yield of green NbCl4(PMe3)3. When a slurry of TaCl5 in toluene containing a slight excess of PMe3 was reduced with sodium amalgam overnight, a 60% yield of orange to red (depending on crystal size) Ta2Cl8(PMe3)4 was obtained. Both compounds have been fully characterized by X-ray crystallography. NbCl4(PMe3)3 forms monoclinic crystals (P21/c) with unit cell dimensions a = 15.061(3) Å, b = 11.677(4) Å, c = 11.583(4) Å, β = 91.71(3)°, V = 2036(2) Å3, and Z = 4. It is isomorphous with its TaCl4(PMe3)3 homolog, and the bond lengths and angles are very similar. Ta2Cl8(PMe3)4 forms cubic crystals (Im3) with a = 16.377(2), V = 4392(2) Å3 and Z = 6. It is thus isomorphous with its niobium homolog, and the internal dimensions are quite comparable. The Ta-Ta distance is 2.830(1) Å, consistent with the existence of a single bond. |
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| Keywords: | Author to whom correspondence should be addressed |
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