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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.