Tristhiolatomolybdenum nitrides, (RS)3Mo≡N where R = iPr and tBu, preparation, characterization and comparisons with related trialkoxymolybdenumnitrides

The addition of thiols to ((BuO)-Bu-t)(3)ModropN in toluene leads to the formation of (RS)(3)ModropN compounds as yellow, air-sensitive compounds, where R = Pr-i and Bu-t. The single-crystal structure of ((BuS)-Bu-t)(3)ModropN reveals a weakly associated dimeric structure where two ((BuS)-Bu-t)(3)ModropN units (Mo-N = 1.61 Angstrom, Mo-S = 2.31 Angstrom (av)) are linked via thiolate sulfur bridges with long 3.03 Angstrom (av) Mo-S interactions. Density functional theory calculations employing Gaussian 98 B3LYP (LANL2DZ for Mo and 6-31 G* for N, O, S, and H) have been carded out for model compounds (HE)(3)ModropN and (HE)(3)MoNO, where E = O and S. A comparison of the structure and bonding within the related series ((BuE)-Bu-t)(3)ModropN and ((BuE)-Bu-t)(3)MoNO is made for E = O and S. In the thiolate compounds, the highest energy orbitals are sulfur lone-pair combinations. In the alkoxides, the HOMO is the N 2p lone-pair which has M-N sigma and M-O pi* character for the nitride. As a result of greater O ppi to Mo pi interactions, the M-N pi orbitals of the Mo-N triple bond are destabilized with respect to their thiolate counterpart. For the nitrosyl compounds, the greater O ppi to Mo dpi interaction favors greater back-bonding to the nitrosyl pi* orbitals for the alkoxides relative to the thiolates. The results of the calculations are correlated with the observed structural features and spectroscopic properties of the related alkoxide and thiolate compounds.