Facile Addition of B-H and B-B Bonds to an Iron(IV) Nitride Complex.

The nitride ligand in the iron(IV) complex PhB( i Pr 2 Im) 3 Fe≡N reacts with boron hydrides to afford PhB( i Pr 2 Im) 3 FeN( B )H ( B = 9-BBN ( 1 ), Bpin ( 2 )) and with (Bpin) 2 to afford PhB( i Pr 2 Im) 3 FeN(Bpin) 2 ( 3 ). The iron(II) borylamido products have all been structurally and spectroscopically characterized, demonstrating facile insertion into B-H and B-B bonds by PhB( i Pr 2 Im) 3 Fe≡N. Density functional theory (DFT) calculations reveal that the quintet state ( S = 2) is significantly lower in energy than the singlet ( S = 0) and triplet ( S = 1) states for all products. Stoichiometric reaction with (Bpin) 2 does not produce the mono-borylated iron imido species PhB( i Pr 2 Im) 3 FeN(Bpin). DFT calculations suggest that this is because PhB( i Pr 2 Im) 3 FeN(Bpin) is unstable toward disproportionation to the starting iron(IV) nitride and PhB( i Pr 2 Im) 3 FeN(Bpin) 2 . Attempts at B-C bond insertion using phenyl- and benzyl-pinacol borane were unsuccessful, which we attribute to unfavorable kinetics.