Reactions of monocyclopentadienylniobium(III) complexes with α-diketones. Crystal structure of the phosphonium salt [P{C(OH)MeC(O)Me} Me 2Ph]Cl

Abstract

The reactions of Nb(η 5-C 5H 5)Cl 2(CO)L 2 ( PMe 3, PMe 2Ph) with α-diketones RCOCOR (R  Me, Ph) and 3,5-di-t-butyl- o-quinone have been studied. When L  PMe 2Ph and R  Ph the reaction in a molar ratio 1 1 gives Nb(η 5-C 5H 5)Cl 2(O 2C 2Ph 2)(PMe 2Ph) 2 (I) whereas the same reaction for R  Me gives the phosphonium salt [P{C(OH)MeC(O)Me}Me 2Ph]Cl (VII). When L  PMe 3 only the phosphonium salts [P{C(OH)RC(O)R}Me 3]Cl are obtained for R  Me (V) and Ph (VI), but the complex Nb(η 5-C 5H 5)Cl 2(O 2C 2Ph 2)PMe 3 (II) can be isolated by previous addition of MeI. Similar reactions with 3,5-di-t-butyl- o-quinone give Nb(η 5-C 5H 5)Cl 2( o-O 2C 6H 2Bu t)L, L  PMe 3 (III), PMe 2Ph (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 P2 1/ c with a 7.440(2), b 10.377(3), c 17.644(4) Å, β 96.94(2)° and D cal 1.039 g cm −3 for Z = 4. A final R value of 0.046 ( R w = 0.049) based on 2309 observed reflections was obtained. The geometry around the P atom is tetrahedral.