THE SYNTHESIS AND CHARACTERIZATION OF ORGANOIMIDO-RE(V) COMPLEXES - THE X-RAY CRYSTAL-STRUCTURES OF [RECL(NC(6)H(4)ME-4) (OME)((T)BUNC)(2)(PPH(3))][BPH(4)] AND [RECL2(NC(6)H(4)ME-4)(PPH(3)) (4-CLC6H4(O)CNNCHPH-O,N)]

Reaction of [ReCl3(NAr)(PPh(3))(2)] (NAr = NC(6)H(4)Me-4, NC(6)H(3)Me( 2)-2,6) with excess tertiary-butyl isocyanide, ((t)BuNC), in methanol yielded the red-brown Re(V) arylimido- complexes, [ReCl(NAr)(OMe)((t)B uNC)(2)(PPh(3))][BPh(4)] where NAr = NC(6)H(4)Me-4, (1) or NAr = NC(6) H(3)Me-2,6, (2). The X-ray crystal structure of (1) revealed a distort ed octahedral configuration about the central rhenium atom. The isocya nide ligands are disposed in a cis configuration and the chloride and phosphine ligands trans. The remaining sites are occupied by the tolyl imido- and methoxide ligands. The Re-N(I) bond length of 1.739(3) Angs trom and Re-N(1)-C(11) angle of 164.8(3)degrees are consistent with th e imido- ligand functioning as a linear four-electron donor (assuming the imido-ligand to be neutral). The reaction between the tolylimido- Re(V) complex, [ReCl3(NC(6)H(4)Me-4)(PPh(3))(2)], and aroylhydrazones, Ar(O)CNHNCRR'(Ar = Ph, R = R(1) = Me; Ar = 4-ClC6H4, R = H, R(1) = Ph ), in a 1 : 1 toluene/ethanol mixture under reflux yielded the green R e(V) complexes [ReCl2(NC(6)H(4)Me-4)(PPh(3)){Ar(O)CNNCRR'-ON}] were Ar = Ph, R = R' = Me (3) or Ar = 4-ClC6H4, R = H, R' = Ph (4). Complex ( 3) can also be synthesized from the reaction of [ReCl3(NC(6)H(4)Me-4) (PPh(3))(2)] and the hydrazone generated in situ from benzoic hydrazid e in a 1:1 toluene/acetone mixture. The X-ray crystal structure of (4) showed a distorted octahedral geometry with the oxygen and nitrogen a toms of the chelated hydrazone (1-) ligand being mutually cis. The nit rogen atom of the tolylimido- ligand is trans to the chelated oxygen a nd the phosphorus atom of the triphenylphosphine ligand is trans to th e chelated nitrogen. The remaining sites are filled by the two chlorid e ligands. The Re-N(3) bond length of 1.706(5) Angstrom and Re-N(3)-C( 11) angle of 175.7(5)degrees are consistent with the imido- ligand fun ctioning as a linear four-electron donor.