Electrophilic Attack on the Carbon Terminus of a Niobium-Bound Formaldehyde Ligand

Abstract

The niobocene formaldehyde complex Cp‘ 2 Nb(Cl)(η 2 -CH 2 O) ( 1, Cp‘ = η 5 -C 5 H 4 SiMe 3 ) reacts with [Ph 3 C][BF 4 ] to give an alkoxide ( 2 ) of formula [Cp‘ 2 Nb(Cl)(OCH 2 CPh 3 )][BF 4 ] and with HBF 4 ·OEt 2 to give analogue 4 ([Cp‘ 2 Nb(Cl)(OMe)][BF 4 ]); these processes constitute examples of electrophilic attack on the formaldehyde carbon, instead of the more typical addition at oxygen. Compound 2 is hydrolyzed to Cp‘ 2 Nb(Cl)(OBF 3 ) ( 3 ), a Lewis acid adduct of the corresponding metal oxide; both 2 and 3 have been characterized by X-ray crystallography.