H. Schmidbaur, Sybille Lauteschläger, G. Müller
Feb 12, 1985
Citations
0
Influential Citations
19
Citations
Journal
Journal of Organometallic Chemistry
Abstract
Lithiated bis(diphenylphosphino)methane reacts with two equivalents of a dialkylchloro-alane or -gallane (R2MCl; R = CH3, C2H5; M = Al, Ga;) to form coordination compounds (3–6) which have peculiar structure and show unusual fluxional behaviour. A single crystal X-ray diffraction study of the compound ((C6H5)2P]2CH[(C2H5)2Al]2Cl (4) reveals that these complexes can be described as the unsymmetrical adducts of the potential six-electron donor anion [Ph2PCHPPh2]− with the difunctional acceptor cation [Et2AlClAlEt2]+. Through P→ Al and C→ Al donor/acceptor bonds a five-membered ring PCAlClAl is generated, which has an envelope conformation typical for this ring size and a center of chirality at the central carbon atom of the anion. Variable temperature 1H, 13C, and 31P NMR spectroscopy (in toluene) indicates that the acceptor portion R2MClMR2 appears to undergo a rotation around the central P2CAl bond, thereby rendering the PPh2 groups equivalent on the NMR time scale through breaking and re-formation of the AlP bonds. The process is best regarded as a “windshield wiper” motion, which leaves the AIC bonds intact since complete dissociation of R2MCl units is unlikely in the light of the low activation barriers for the fluxionality.