Syntheses, reactivity, and pi-donating ligand metathesis reaction of five-coordinate sixteen-electron manganese(I) complexes: Crystal structures of [Mn(CO)(3)(-TeC6H4-o-NH-)](-), [(Mn(CO)(3))(2)(mu-SC6H4-o-S-S-C6H4-o-mu-S-)], [(CO)(3)Mn(mu-SC6H4-o-NH2-)](2), and [(CO)(3)Mn(mu-SC8N2H4-o-S-)](2)(2-)

The preparation of the varieties of five-coordinate sixteen-electron mangan ese(I) complexes [Mn(CO)(3)(-EC6H4-o-E ' (-))](-) (E = Te, Se, S, O; E ' = NH, S, O) by (a) oxidative addition of 2-aminophenyl dichalcogenides to ani onic manganese(0)-carbonyl, (b) pi -donating ligand metathesis reaction of complex [Mn(CO)(3)(-TeC6H4-o-NH-)](-), and (c) reduction /deprotonation of the neutral dimetallic [(Mn(CO)(3))(2)(mu -SC6H4-o-S-S-C6H4-o-mu -S-)]/[(Co )(3)Mn(mu -sC(6)H(4)-o-NH2-)](2) proved successful approaches in this direc tion. The IR v(CO) data of the coordinatively and electronically unsaturate d [Mn(CO)(3)(-EC6H4-o-E '-)](-) (E = Te, Se, S, O; E ' = NH, S, O) complexe s suggest the relative order of pi -donating ability of the series of biden tate ligands being [TeC6H4-o-NH](2-) > [SeC6H4-o-NH](2-) > [SC6H4-o-NH](2-) > [SC6H4-o-S](2-) > [SC6H4-o-O](2-) > [OC6H4-o-O](2-). Proton NMR spectra of the [Mn(CO)(3)(-EC6H4-o-NH-)](-) (E = Te, Se, S) derivatives show the lo w-field shift of the amide proton (H-1 NMR (C4D8O): delta 9.66 (br) ppm (E = Te), 9.32 (br) ppm (E = Se), 8.98 (br) ppm (E = S)). The formation of the dimetallic [(CO)(3)Mn(mu -SC8N2H4-o-S-)](2)(2-) can be interpreted as coor dinative association of two units of unstable mononuclear [(CO)(3)Mn(-SC8N2 H4-o-S-)](-) and reflects the pi -donating ability of the bidentate ligand is responsible for the formation of pentacoordinate, sixteen-electron manga nese(I) carbonyl complexes. The neutral bimetallic manganese(I)-bismercapto phenyl disulfide complex [(Mn(CO)(3))(2)(mu -SC6H4-o-S-S-C6H4-o-mu -S)] wit h internal S-S bond length of 2.222(1) Angstrom and the five-coordinate six teen-electron complex [Mn(CO)(3)(-SC6H4-o-S-)](-) are chemically interconve rtible. In a similar fashion, treatment of complex [Mn(CO)(3)(-SC6H4-o-NH-) ](-) with HBF4 yielded neutral dinuclear complex [(CO)(3)Mn(mu -SC6H4-o-NH2 -)](2) and showed that the amine deprotonation is reversible. Investigation s of st-donating ligand metathesis reactions of complex [Mn(CO)(3)(-TeC6H4- o-NH-)](-) revealed that the stable intermediate, not the pi -donating abil ity of bidentate ligands, is responsible for the final protonation/oxidatio n product. This argument is demonstrated by reaction of [Mn(CO)(3)(-TeC6H4- o-NH-)](-) with 1,2-benzenedithiol, hydroxythiophenol, and catechol, respec tively lending to the formation of [Mn(CO)(3)(-EC6H4-o-E '-)](-) (E = S, O; E ' = S, O), although any pi -donor containing the amido group is a more e ffective donor than any other st-donor lacking an amido group. Also, the reactions of [Mn(CO)(3)(-TeC6H4-o-NH-)](-) with electrophiles occ urring at the more electron-rich amide site support that the more electron- rich amide donor of the chelating 2-tellurolatophenylamido occupies an equa torial site as indicated by a shorter Mn-I-N bond length of the distorted t rigonal bipyramidal [Mn(CO)(3)(-TeC6H4-o-NH-)](-).