PHOSPHINE ADDUCTS OF THE OPEN METALLOCENES OF ZIRCONIUM, HAFNIUM, NIOBIUM, AND MOLYBDENUM - SYNTHESES, STRUCTURES, AND REACTIONS WITH CARBON-MONOXIDE

The reactions of MCl4(PEt3)2 complexes (M = Zr, Hf, Nb, Mo) with 4 equiv of K(2,4-C7H11) lead to the formation of M(2,4-C7H11)2PEt3 Complexes. Other related phosphine adducts may be prepared similarly, while phosphite complexes may be prepared by ligand substitution reactions. For the zirconium phosphine complex, exposure to CO generates both the monocarbonyl and the dicarbonyl complexes. Structural data have been obtained for three of the M(2,4-C7H11)2PEt3 complexes (M = Zr, Nb, Mo), as well as for Zr(2,4-C7H11)2(CO)n (n = 1, 2). The M(2,4-C7H11)2PEt3 complexes for M = Zr and Nb are isomorphous, adopting space group P1BAR with Z = 2 and respective cell constants of a = 7.988(4) angstrom, b = 8.631(4) angstrom, c = 15.649(7) angstrom, a = 87.98(4)-degrees, beta = 103.46(4)-degrees, gamma = 91.70(4)-degrees, and V = 1048.3(8) angstrom3, and a = 7.936(2) angstrom, b = 8.735(2) A, c = 15.511(5) A, a = 87.82(2)-degrees, beta = 103.79(2)-degrees, gamma = 92.12(2)-degrees, and V = 1043.0(5) A3. Crystals of the molybdenum complex are orthorhombic, belonging to space group Pbca with a = 11.244(2) angstrom, b = 14.516(2) angstrom, c = 24.963(4) angstrom, and V = 4074.5(11) angstrom3 for Z = 8. Crystals of the zirconium monocarbonyl complex are also orthorhombic, adopting space group P2(1)2(1)2(1), with a = 11.827(2) angstrom, b = 12.158(2) angstrom, c = 10.328(2) angstrom, and V = 1485.1 angstrom3 for Z = 4. Crystals of the dicarbonyl are triclinic, space group P1BAR, with a = 8.552(3) angstrom, b = 9.243(3) angstrom, c = 20.419(8) angstrom, alpha = 93.34(3)-degrees, beta = 83.88(3)-degrees, gamma = 87.97(3)-degrees, and V = 1600.7 angstrom3 for Z = 4 (two independent molecules). Except for the molybdenum complex, all mono(ligand) adducts possess the expected syn-eclipsed oriented dienyl ligands. The molybdenum complex is unusual, having one eta5-S (S = sickle) bound dienyl ligand, while the zirconium dicarbonyl has an unsymmetric orientation of tWo eta5-U bound ligands, with one carbonyl by the open edge of one dienyl ligand, the other carbonyl being by the backside of the other dienyl ligand.