Crystal Structures and ⁷⁷Se NMR Spectra of Molybdenum(IV) Areneselenolates Having Intramolecular NH···Se Hydrogen Bonds

Salts of the monooxomolybdenum(IV,V) areneselenolates having intramolecular NH···Se hydrogen bonds, [MoIVO(Se-2-RCONHC6H4)4]2- (R = t-Bu, CH3, CF3) and [MoVO(Se-2-t-BuCONHC6H4)4]-, were synthesized and characterized by 1H nuclear magnetic resonance (NMR), 77Se NMR, electron spin resonance (ESR), UV−visible spectra, X-ray analysis, and electrochemical measurements. 77Se−1H correlated spectroscopy (COSY) indicated a significant correlation between amide 1H and selenolate 77Se atoms through an NH···Se hydrogen bond with 1J(77Se−1H) = 5.4 Hz coupling. The hydrogen bonds contribute to the positive shift in the Mo(V)/Mo(IV) redox potential. In the crystal structure of (PPh4)2[MoIVO(Se-2-CH3CONHC6H4)4], an NH···OMo hydrogen bond was found. Ab inito calculations support the presence of intramolecular NH···OMo and NH···Se hydrogen bonds.