3-Chloro-1,2,3,4-tetraphenylcyclobutenyl-Ennea-chloro-μ-Oxo-di-Niobat(V),[C4Cl(Ph)4]⊕[Nb2OCl9]⊖ Synthese und Kristallstruktur

3-Chloro-1,2,3,4-tetraphenylcyclobutenyl-Ennea-chloro-μ-Oxo-di-Niobate(V), [C₄Cl(Ph)₄]^⊕[Nb₂OCl₉]^?. Synthesis and Crystal Structure The title compound yields from a one step reaction of niobium pentachloride and niobium oxide trichloride with diphenyl acetylene in dichloro methane, forming dark green crystals. The new complex is characterized by the i.r. spectrum and a crystal structure determination by X-ray methods. The compound crystallizes triclinic in the space group P1 with two formula units per unit cell (2253 independent observed reflexions, R = 4.7%). The lattice dimensions are a = 1199, b = 1034, c = 1453 pm; α = 87.0°, β = 108.6°, γ = 96.6°. The cyclobutenyl cation forms an almost planar C₄-ring with two pairs of neighbouring C? C bonds of 139 pm and 153 pm. The anion [Nb₂OCl₉]^? displays a nearly linear NbONb axis (bond angle 174°) in which the NbO bond lengths are 176 pm and 208 pm. Two anions are linked via asymmetric chloro bridges with Nb? Cl bond lengths of 248 pm and 270 pm to form a centrosymmetric dimer.