Syntheses, Reactivity, and Pi-Donating Ligand Metathesis Reaction of Five-Coordinate Sixteen-Electron manganese(I) Complexes: Crystal Structures of [Mn(CO(3)(-TeC(6)H(4)-o-NH-)](-), [(Mn(CO)(3))2(mu-SC(6)H(4)-o-S--S--C(6)H(4)-o-mu-S--)], [(CO)(3)Mn(mu-SC(6)H(4)-o-NH(2)-)]2, and [(CO)(3)Mn(mu-SC(8)N(2)H(4)-o-S-)](2)(2-)

W F Liaw, C K Hsieh, G Y Lin, G H Lee

Inorg Chem. 2001 Jul 2;40(14):3468-75.

PMID: 11421694

Abstract:

The preparation of the varieties of five-coordinate sixteen-electron manganese(I) complexes [Mn(CO)(3)(-EC(6)H(4)-o-E'-)](-) (E = Te, Se, S, O; E' = NH, S, O) by (a) oxidative addition of 2-aminophenyl dichalcogenides to anionic manganese(0)-carbonyl, (b) pi-donating ligand metathesis reaction of complex [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-), and (c) reduction /deprotonation of the neutral dimetallic [(Mn(CO)(3))(2)(mu-SC(6)H(4)-o-S-S-C(6)H(4)-o-mu-S-)]/[(CO)(3)Mn(mu-SC(6)H(4)-o-NH(2)-)](2) proved successful approaches in this direction. The IR nu(CO) data of the coordinatively and electronically unsaturated [Mn(CO)(3)(-EC(6)H(4)-o-E'-)](-) (E = Te, Se, S, O; E' = NH, S, O) complexes suggest the relative order of pi-donating ability of the series of bidentate ligands being [TeC(6)H(4)-o-NH](2)(-) > [SeC(6)H(4)-o-NH](2)(-) > [SC(6)H(4)-o-NH](2)(-) > [SC(6)H(4)-o-S](2)(-) > [SC(6)H(4)-o-O](2)(-) > [OC(6)H(4)-o-O](2)(-). Proton NMR spectra of the [Mn(CO)(3)(-EC(6)H(4)-o-NH-)](-) (E = Te, Se, S) derivatives show the low-field shift of the amide proton ((1)H NMR (C(4)D(8)O): 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-SC(8)N(2)H(4)-o-S-)](2)(2-) can be interpreted as coordinative association of two units of unstable mononuclear [(CO)(3)Mn(-SC(8)N(2)H(4)-o-S-)](-) and reflects the pi-donating ability of the bidentate ligand is responsible for the formation of pentacoordinate, sixteen-electron manganese(I) carbonyl complexes. The neutral bimetallic manganese(I)-bismercaptophenyl disulfide complex [(Mn(CO)(3))(2)(mu-SC(6)H(4)-o-S-S-C(6)H(4)-o-mu-S-)] with internal S-S bond length of 2.222(1) A and the five-coordinate sixteen-electron complex [Mn(CO)(3)(-SC(6)H(4)-o-S-)](-) are chemically interconvertible. In a similar fashion, treatment of complex [Mn(CO)(3)(-SC(6)H(4)-o-NH-)](-) with HBF(4) yielded neutral dinuclear complex [(CO)(3)Mn(mu-SC(6)H(4)-o-NH(2)-)](2) and showed that the amine deprotonation is reversible. Investigations of pi-donating ligand metathesis reactions of complex [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-) revealed that the stable intermediate, not the pi-donating ability of bidentate ligands, is responsible for the final protonation/oxidation product. This argument is demonstrated by reaction of [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-) with 1,2-benzenedithiol, hydroxythiophenol, and catechol, respectively leading to the formation of [Mn(CO)(3)(-EC(6)H(4)-o-E'-)](-) (E = S, O; E' = S, O), although any pi-donor containing the amido group is a more effective donor than any other pi-donor lacking an amido group. Also, the reactions of [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-) with electrophiles occurring at the more electron-rich amide site support that the more electron-rich amide donor of the chelating 2-tellurolatophenylamido occupies an equatorial site as indicated by a shorter Mn(I)-N bond length of the distorted trigonal bipyramidal [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-).

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