Syntheses and X-ray structures of complexes with (η3-allyl)Mo-units in oxygen-rich coordination spheres

The reaction of Mo(eta(3)-C3H4(CH3))(CH3CN)(2)(CO)(2)Cl with AgBF4 in THF yields the cationic complex [Mo(eta(3)-C3H4(CH3))(CH3CN)(2)(CO)(2)(THF)](+)[BF4](-), 1, whose X-ray structure has been determined. Oxo nucleophiles are capable of replacing the weakly bound THF molecule in 1 and under simultaneous loss of CH3CN the resulting complexes aggregate to oligonuclear compounds. Accordingly, the reactions with NaOMe and KOH yield [Na(THF)(4)](+)[(eta(3)-C3H4(CH3))(CO)(2)Mo(mu-OCH3)(3)Mo(CO)(2)(eta(3)-C3H4(CH3))](-), 2 and [K(18-crown-6)](+)[[Mo(eta(3)-C3H4(CH3))(CO)(2)](3)(mu(2)-OH)(3)(mu(3)-OH)](-), 3, which were characterized by means of single crystal X-ray diffraction. Due to fluoride abstraction from BF4- the reaction of 1 with KOH also yields fluorinated derivatives of 3 but incorporation of fluorine in 3 can be avoided if AgO3SCF3 rather than AgBF4 is used to generate the cation of 1. For purposes of comparison the dinuclear complex [K(18-crown-6)](+)[[Mo(eta(3)-C3H4(CH3))(CO)(2)](2)(mu(2)-F)(3)](-), 4, has been prepared, too, showing fluoride bridges and K ... F bonding. The chemical properties and the structures of these compounds in solution as well as their role as structural models for intermediates during molybdenum oxide catalysed propene oxidation are discussed. (C) 1999 Elsevier Science S.A. All rights reserved.