The insertion chemistry of the hydride complex trans-Mo(dmpe)2(H)(NO) (1) (dmpe = bis(dimethylphosphino)ethane) with imines has been investigated. It was found that disubstituted aromatic imines RCH=NR' (R, R' = Ar) insert into the Mo-H bond of 1, while a series of various mono- and other disubstituted imines do not react. The insertion products trans-Mo(dmpe)(2)(NO) [NR'(CH2R)] (R = R' = Ph (2); R = Cp2Fe, R' = Ph (3); R = Ph, R' = Cp2Fe (4); R = 1-naphthyl, R' = Ph (5)) have been isolated and fully characterized by elemental analysis, IR and NMR spectroscopy, and mass spectrometry. The imine PhCH=NC10H7 (C10H7 = 1-naphthyl) reacted with 1 establishing an equilibrium to produce the nonisolable complex trans-Mo(dmpe)(2)(NO)[NC10H7(CH2Ph)] (6). The equilibrium constant for this reaction has been derived from VT-NMR measurements, and the DeltaH and DeltaS values of this reaction were calculated to be -48.8 +/- 0.4 kJ.mol(-1) and -33 +/- 1 J.K-1.mol(-1) reflecting a mild exothermic process and its associative nature. Single-crystal X-ray diffraction analyses were carried out on 2-5.