Synthesis and characterization of new imidorhenium(V) and imidorhenium(VI) complexes of pyridyltriazines and pyrazinyltriazine with halide coligands including rare iodide

The blue colored imido complexes [Re(NC6H4Cl)X3(L)] have been synthesized by three methods: (i) reaction of [ReVOX3(L)] with p-ClC6H4NH2, (ii) reaction of [ReIII(OPPh3)X3(L)] with p-ClC6H4NH2 and (iii) reaction of [ReVOX3(PPh3)2] with L followed by the addition of p-ClC6H4NH2 in boiling toluene. Here, X = Cl, Br, I and L are 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine (L2) and its dimethyl (L1) and pyrazinyl (L3) analogues. The [Re(NC6H4Cl)Cl3(L1)] (1a), [Re(NC6H4Cl)Cl3(L2)] (1b), [Re(NC6H4Cl)Br3(L2)] (1c), [Re(NC6H4Cl)I3(L2)] (1d), [Re(NC6H4Cl)Cl3(L3)] (1e), [Re(NC6H4Cl)Br3(L3)] (1f), [Re(NC6H4Cl)I3(L3)] (1g), complexes have been characterized electrochemically and spectroscopically. The X-ray structures of [Re(NC6H4Cl)Cl3(L2)] and [Re(NC6H4Cl)I3(L3)] reveal that the ReCl3 fragment is meridionally disposed and that the L ligand is N,N-coordinated such that the pyridine/pyrazine nitrogen lies trans to the imide nitrogen. The feasibility of generating the rhenium(VI) congener of the imidorhenium(V) complex is also examined with the help of six-line EPR spectra at room temperature.