Hydridic character and reactivity of Di[1,2-bis(dimethylphosphino)ethane]hydridonitrosylmolybdenum(0)

The synthesis of the tetraphosphine-substituted molybdenum hydride complex trans-Mo-(dmpe)(2)(H)(NO) (3) (dmpe = bis(dimethylphosphino)ethane) is described, which is obtained by starting from the known compound Mo(CO)(4)(NO)(ClAlCl3) via the isolable chloride trans-Mo(Cl)(dmpe)(2)(NO) (1) and the borohydride trans-Mo(eta(1)-BH4)(dmpe)(2)(NO) (2). Two deuteride complexes trans-Mo(dmpe)(2)(D)(NO) (3a) and mer-Mo(CO)(D)(NO)(PMe3)(3) (4) have been prepared. From these the Mo-D bond ionicities of both deuterides were obtained via determinations of the deuterium quadrupole coupling constants (DQCC) in solution from T-1min measurements of the H-2 nucleus and in solid state from static H-2 NMR spectra. A strongly polar character of the Mo-D(H) bond was found for 3 and 4. In agreement with its enhanced hydridicity 3 revealed a very high propensity for hydride transfer reactions. It reacted readily with benzophenone, acetophenone, and acetone to afford the corresponding alkoxide complexes trans-Mo(dmpe)(2)(NO)(OCHRR') (R = R' = Ph (5); R = Me, R' = Ph (6); R = R' = Me (7)). 3 also underwent rapid insertion with Fe(CO)(5) and Re-2(CO)(10) to afford mu-formyl complexes Mo(dmpe)(2)(NO)[(mu-OCH)Fe(CO)(4)] (8) and Mo(dmpe)(2)(NO)[(mu-OCH)Re-2-(CO)(9)] (9), respectively. Furthermore, reversible double insertion of 3 into Re-2(CO)(10) was observed, which furnished the (ON)(dmpe)(2)Mo(mu-OCH)Re-2(CO)(8)(mu-CHO)Mo(dmpe)(2)(NO) complex (10). For this reaction equilibrium constants were determined by VT-NMR measurements. DeltaH and DeltaS amount to -58.8 +/- 2.7 kJ mol(-1) and -48 +/- 2 J.K-1.mol(-1). The reaction of 3 with Mn-2(CO)(10) gave the mu-carbonyl complex Mo(dmpe)(2)(NO)[(mu-OC)Mn(CO)(4)] (12) via the intermediacy of Mo(dmpe)(2)(NO)[(mu-OCH)Mn-2(CO)(9)] (11). The structures of compounds 1, 2, 8, 9, 10, and 12 were studied by single-crystal X-ray diffraction.