REACTIONS OF NITRILES WITH BINUCLEAR RHODIUM HYDRIDES - THE STEPWISE REDUCTION OF A CARBON NITROGEN TRIPLE BOND AT 2 METAL CENTERS

{The reaction of simple nitriles, R’CN (R’ = CH3, Ph, o-tol) with the electron-rich binuclear rhodium hydride derivatives [(R2PCH2CH2PR2)Rh]2(mu-H)2 (R = Pr(i): [(dippe) Rh]2(mu-H)2: R = OPri: [(dipope)Rh]2(mu-H)2) results in the formation of alkylideneimido derivatives [(R2PCH2CH2PR2)Rh]2(mu-H)(mu-N=CHR’), apparently by insertion of the nitrile moiety into a bridging hydride bond: this was confirmed by the reaction of nitriles with the dideuteride [(dippe)Rh]2(mu-D)2, which resulted in the formation of [(dippe)Rh]2(mu-D)(mu-N=CHR’). Further reduction can take place by addition of H-2 to generate the corresponding amide hydride derivatives [(dippe)Rh]2(mu-H)(mu-NHCH2R’); this represents an overall stoichiometric reduction of a nitrile to a coordinated amide at a binuclear centre. These same amido-hydride complexes can be accessed by addition of amine to the starting binuclear rhodium hydride derivatives. The X-ray structure of [(Pri2PCH2CH2PPri2)Rh]2(mu-H)(mu-N=CHCH3) was undertaken to confirm the structure of these particular intermediates. Crystals of this material are monoclinic