The synthesis and characterization of organoimido- Re(V) complexes. The x-ray crystal structures of [ReCl(NC6H4Me-4) (OMe)(tBuNC)2(PPh3)][BPh4] and [ReCl2(NC6H4Me-4)(PPh3)4-ClC6H4(O)CNNCHPh-O,N]

Abstract Reaction of [ReCl 3 (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 BuNC) 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 distorted octahedral configuration about the central rhenium atom. The isocyanide ligands are disposed in a cis configuration and the chloride and phosphine ligands trans . The remaining sites are occupied by the tolylimido- and methoxide ligands. The Re—N(I) bond length of 1.739(3) A and Re—N(1)—C(11) angle of 164.8(3) are consistent with the imido- ligand functioning as a linear four-electron donor (assuming the imido-ligand to be neutral). The reaction between the tolylimido- Re(V) complex, [ReCl 3 (NC 6 H 4 Me-4)(PPh 3 ) 2 ], and aroylhydrazones, Ar(O)CNHNCRR′(Ar = Ph, R = R 1 = Me: Ar = 4-ClC 6 H 4 , R = H, R 1 = Ph), in a 1 : 1 toluene/ethanol mixture under reflux yielded the green Re(V) complexes [ReCl 2 (NC 6 H 4 Me-4)(PPh 3 )Ar(O)CNNCRR′-O,N], where Ar = Ph, R = R′= Me ( 3 ) or Ar = 4-ClC 6 H 4 , R = H, R′ = Ph ( 4 ). Complex ( 3 ) can also be synthesized from the reaction of [ReCl 3 (NC 6 H 4 Me-4)(PPh 3 ) 2 ] and the hydrazone generated in situ from benzoic hydrazide in a 1:1 toluene/acetone mixture. The X-ray crystal structure of ( 4 ) showed a distorted octahedral geometry with the oxygen and nitrogen atoms of the chelated hydrazone (1-) ligand being mutually cis . The nitrogen atom of the tolylimido- ligand is trans to the chelated oxygen and the phosphorus atom of the triphenylphosphine ligand is trans to the chelated nitrogen. The remaining sites are filled by the two chloride ligands. The Re—N(3) bond length of 1.706(5) A and Re—N(3)—C(11) angle of 175.7(5) are consistent with the imido- ligand functioning as a linear four-electron donor.