New Octahedral Rhenium(I) Tricarbonyl Amido Complexes

Several new Re(I) octahedral amido complexes fac-[Re(NRR‘)(CO)3(N−N)] (R = aryl; R‘ =
H, aryl; N−N = 2,2‘-bipyridine, bipy; 1,10-phenanthroline, phen) have been synthesized either
by reaction of [Re(OTf)(CO)3(N−N)] precursors with potassium amides or by deprotonation
of [Re(NH2Ar)(CO)3(N−N)]OTf compounds, in turn obtained by reaction of [Re(OTf)(CO)3(N−N)] compounds with amines. The structure of the amido complexes [Re(NHPh)(CO)3(bipy)] (5) and [Re(NPh2)(CO)3(bipy)] (6) have been determined by single-crystal X-ray
diffraction. The results, coupled with the solution NMR behavior of the complexes, indicate
that the delocalization of the nitrogen lone pair of the amido group involves mainly the
N−aryl bonds. Amido complexes [Re(NHp-Tol)(CO)3(N−N)] (4a,b) (p-Tol = 4-methylphenyl)
react with 4-ethylphenol, with ethanothiol, and with diphenylphosphine to give the complexes
[Re(OC6H4-4-C2H5)(CO)3(bipy)] (8), [Re(SCH2CH3)(CO)3(bipy)] (9), and [Re(PPh2)(CO)3(N−N)] (10a,b). The structure of the diphenylphosphido complex [Re(PPh2)(CO)3(phen)] (10b),
determined by X-ray diffraction, was compared with the structure of the homologous
diphenylamido complex 6. The different geometries (pyramidal phosphorus and planar amido
nitrogen) correlate with the higher nucleophilicity of the phosphido complex.