The niobocene formaldehyde complexCp'
2Nb(Cl)(
2-CH
2O) (
1, Cp' =
5-C
5H
4SiMe
3)reacts
with[Ph
3C][BF
4] to give an alkoxide(
2) of formula [Cp'
2Nb(Cl)(OCH
2CPh
3)][BF
4]
and with HBF
4·OEt
2 to giveanalogue
4([Cp'
2Nb(Cl)(OMe)][BF
4]);these processesconstitute examples of electrophilic attack on the formaldehyde carbon, instead of the more typical additionat oxygen. Compound
2 is hydrolyzed toCp'
2Nb(Cl)(OBF
3) (
3), a Le
wis acid adduct of thecorrespondingmetal oxide; both
2 and 3 have been characterizedbyX-ray crystallography.