| Abstract
| - The octahedral hydride Mo(CO)H(NO)(PMe3)3 has been prepared from a η1-BH4 precursor. The highly activated Mo−H bond of this complex inserts various types of carbonyl compounds.
- The synthesis of the mer-Mo(CO)H(NO)(PMe3)3 complex 3 is described, which is obtainedfrom Mo(CO)4(NO)AlCl4 via the isolable intermediates MoCl(CO)(NO)(PMe3)3 (1) and theborohydride complex Mo(η1-BH4)(CO)(NO)(PMe3)3 (2). The reactivity of 3 with respect toinsertions has been probed. 3 thus reacts with benzaldehyde, benzophenone, acetophenone,and acetone to afford the corresponding alkoxide complexes Mo(CO)(NO)(PMe3)3(OCHR‘R‘‘)(R‘ = H, R‘‘ = Ph (4a); R‘, R‘‘ = Ph (4b); R‘ = Me, R‘‘ = Ph (4c), and R‘, R‘‘ = Me (4d)). Ahigh propensity of 3 to undergo carbonyl insertion was also manifested in its transformationswith CO2 and metal carbonyl compounds. The conversion of 3 with CO2 leads to the formato-O-complex Mo(CO)(NO)(PMe3)3(OCHO) (5), while CO induces PMe3 substitution withformation of the nonisolable Mo(CO)2(NO)(PMe3)2H compound (6). Fe(CO)5 readily insertsto yield the dinuclear formyl species (Me3P)3(ON)(OC)Mo(μ-OCH)Fe(CO)4 (7a), and Re2(CO)10is transformed to the related μ-formyl complex (Me3P)3(ON)(OC)Mo(μ-OCH)Re2(CO)9 (7b)in an equilibrium reaction lying far to the formyl side. Temperature-dependent NMRmeasurements allowed us to derive equilibrium constants and ΔH = −46.5 ± 0.6 kJ/moland ΔS = −103 ± 2 eu. These values for 7b were approximately reproduced by accurateDFT calculations and investigated further via an incremental analysis of bond dissociationenergies. Finally insertion reactions of 3 with various imines were studied. Only in the caseof a bisdihydroproline ester did an insertion take place, however, across the ester carbonylgroup. Concomitant elimination of a phosphine moiety was observed with formation of theisolable chelate complex (8). The structuresof complexes 2, 3, 4b, 7a, 7b, and 8 were studied by X-ray diffraction.
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