Cationic Niobium-Sandwich and Piano-Stool Complexes.

ABSTRACT

The syntheses of the homoleptic bis(arene) niobium cations [Nb(arene)2 ]+ (arene = C6 H3 Me3 , C6 H5 Me) with 16 valence electrons and heteroleptic arene-carbonyl cations [(CO)Nb(arene)2 ]+ (arene = C6 H3 Me3 , C6 H5 Me) and [(arene)M(CO)4 ]+ (arene = C6 H3 Me3 , C6 H6 ) obeying 18 valence electrons are described. Stabilization of these complexes was achieved by using the weakly coordinating anions [Al(ORF )4 ]- or [F{Al(ORF )3 }2 ]- (RF = C(CF3 )3 ). The limits of two synthesis routes starting from neutral Nb(arene)2 (arene = C6 H3 Me3 , C6 H5 Me) or [NEt4 ][M(CO)6 ] (M = Nb, Ta) were investigated. All compounds were analyzed by single crystal X-ray determination, vibrational and NMR spectroscopy. DFT calculations were executed to support the experimental data.