μ-Chlorobis(diethylaluminium)bis(diphenylphosphino)methanide, a complex with windshield wiper fluxionality☆

摘要: 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 the compound ((C6H5)2P]2CH[(C2H5)2Al]2Cl (4) reveals that these complexes can be described as unsymmetrical adducts potential six-electron donor anion [Ph2PCHPPh2]− difunctional acceptor cation [Et2AlClAlEt2]+. Through P→ Al C→ donor/acceptor bonds five-membered ring PCAlClAl is generated, has an envelope conformation typical for this size center chirality at central carbon atom anion. Variable temperature 1H, 13C, 31P NMR spectroscopy (in toluene) indicates portion R2MClMR2 appears undergo rotation around P2CAl bond, thereby rendering PPh2 groups equivalent on time scale through breaking re-formation AlP bonds. The process best regarded “windshield wiper” motion, leaves AIC intact since complete dissociation R2MCl units unlikely in light low activation barriers fluxionality.