Reactions of monocyclopentadienylniobium(III) complexes with α-diketones. Crystal-structure of the phosphonium salt [P{C(OH)MeC(O)Me}Me2Ph]Cl

Abstract

The reactions of Nb(η5-C5H5)Cl2(CO)L2 (= PMe3, PMe2Ph) with α-diketones RCOCOR (R = Me, Ph) and 3,5-di-t-butyl-o-quinone have been studied. When L = PMe2Ph and R = Ph the reaction in a molar ratio 1/1 gives Nb(η5-C5H5)Cl2(O2C2Ph2)(PMe2Ph)2 (I) whereas the same reaction for R = Me gives the phosphonium salt [P{C(OH)MeC(O)Me}Me2Ph]Cl (VII). When L = PMe3 only the phosphonium salts [P{C(OH)RC(O)R}Me3]Cl are obtained for R = Me (V) and Ph (VI), but the complex Nb(η5-C5H5)Cl2(O2C2Ph2)PMe3 (II) can be isolated by previous addition of MeI. Similar reactions with 3,5-di-t-butyl-o-quinone give Nb(η5-C5H5)Cl2(o-O2C6H2But)L, L = PMe3 (III), PMe2Ph (IV). All the compounds have been characterized by IR, 1H, 13C, 31P NMR spectroscopy and the crystal structure of VII has been determined by X-ray diffraction. VII crystallizes in the monoclinic space group P21/c with a 7.440(2), b 10.377(3), c 17.644(4) Å, β 96.94(2)° and Dcal 1.039 g cm−3 for Z = 4. A final R value of 0.046 (Rw = 0.049) based on 2309 observed reflections was obtained. The geometry around the P atom is tetrahedral.