Electrophilic benzylidene(pentacarbonyl)-chromium(0) and -tungsten(0) complexes: isolation, characterization, and an unusual thermolytic reaction of the tungsten compounds

The reaction of the anionic alkyl complexes of chromium and tungsten, NEt4+[(CO)5M{CH(OMe)(p-C6H4R)}]–(M = Cr, R = OMe; M = W, R = OMe, Me, H) with HBF4·Et2O yields isolable, strongly electrophilic benzylidene(pentacarbonyl) complexes, (CO)5MCH(p-C6H4R); thermolysis of the tungsten compounds gives µ-benzylidenebis(pentacarbonyltungsten) complexes, [(CO)5W]2[µ-CH(p-C6H4R)].