Complexes of organoaluminium compounds. Part VIII. Crystal and molecular structure, infrared and nuclear magnetic resonance spectra, and reactions of di-µ-(tricarbonyl-η5-cyclopentadienyltungsten-OO′)bisdimethylaluminium and the characterisation of some phosphine derivatives

Abstract

The compound [{(η-C₅H₅)W(CO)₃(AlMe₃)}₂], made from trimethylaluminium or dimethylaluminium hydride and the hydride [(η⁵-C₅H₅)W(CO)₃H], crystallises in space group C2/c with a= 18.120(4), b= 6.188(2), c= 22.266(5)Å, β= 93.29(2)°, and Z= 4. The structure, determined by the heavy-atom method from X-ray diffractometer data (1 175 reflections), was refined by least-squares techniques to R 4.2%. The molecules have slightly puckered twelve-membered rings, in which carbonyl groups [C–O,1.22(2)Å] are linked through carbon to tungsten [W–C, 1.851 (14)Å] and through oxygen to aluminium [Al–O,1.81(1), Al–C,1.94(2)Å;: C–Al–C 123(1)°]. Co-ordination round tungsten is completed by cyclopentadienyl groups (W–C 2.31–2.36 Å) and by terminal carbonyl groups [W–C 1.97(2), C–O 1.19(3)Å]. Absorptions at ca. 1 550 cm^–1 are associated with bridging carbonyl groups. The ring is easily broken by protonic species HX [X = Cl, OH, MeCOCHCOMe (acac)], yielding the hydride [(C₅H₅)W(CO)₃H] and the compounds (Me₂AlX)_n, and by donors D (D = NMe₃ or OEt₂) giving complexes [(C₅H₅)W(CO)₃(AlMe₂)],D. The compounds [{(C₅H₅)WL(CO)₂(AlMe₂)}_m](L = PPh₃, PMe₂Ph, or PEt₂Ph) were made from trimothylaluminium and the hydrides [(C₅H₅)WL(CO)₂H] : spectroscopic data suggest bridging carbonyl groups in the compounds where L = PMe₂Ph or PEt₂Ph, similar to those where L = CO. The reaction between dimethylaluminium hydride and pentacarbonylhydridorhenium gives the known hydride [Re₃-(CO)₁₄H].