| Abstract
| - Seven-coordinate Tc(III) and Re(III)monocapped boronic acid adducts of tris(cyclohexanedionedioxime)were prepared where X = OH-,NCS-, SCN-. BothN- and S-bound thiocyanate isomers resulted in the syntheses from the X= OH- precursors. The S-bound linkage isomer wasfound to convert to the more favorable N-bound isomer. X-raycrystal structures are reported for the Tc−NCS and both Re−SCN andRe−NCS complexes. To our knowledge, these are the first examplesof S-bound coordination of thiocyanate to Tc andRe.
- The 7-coordinate technetium(III) and rhenium(III)monocapped tris(dioxime) complexes[MX(dioxime)3BR] havebeen prepared in which the seventh ligand, X, is thiocyanate orhydroxide (M = Tc, Re; R = Me, Et). Both theN- and S-bound thiocyanate linkage isomers are produced during thesyntheses, however, the S-bound complexisomerizes to the N-bound analogue. The synthetic routes employedallowed isolation of sufficient quantities ofthe technetium and rhenium S-bound isomers to be identified; however,full characterization was not possible.The linkage isomerization reaction ofTcSCN(CDOH)2(CDO)BMe toTcNCS(CDOH)2(CDO)BMe wasmonitoredin dichloromethane by UV−visible spectrophotometry, with fourisosbestic points observed, consistent with theformation of a single product. The N-bound isomers for both Tc andRe, and the S-bound isomer of Re werecharacterized by single-crystal X-ray diffraction analysis. Thetwo N-bound complexes were found to beisostructural. TcNCS(CDOH)2(CDO)BMecrystallized in the orthorhombic space groupP212121 witha = 15.814(2) Å, b = 17.855(3) Å, c =17.997(5) Å, Z = 8, R = 0.054, andRW= 0.057.ReNCS(CDOH)2(CDO)BMecrystallized in the orthorhombic space groupP212121 witha = 15.795(1) Å, b = 17.843(2) Å,c = 18.014(3) Å,Z = 8, R = 0.054, andRW = 0.073. In both cases two independentmolecules per unit cell were observed.ReSCN(CDOH)2(CDO)BMe crystallized inthe monoclinic space group P21/c witha = 10.0866(6) Å, b =26.301(2) Å, c = 12.4592(7) Å, β = 100.5(1) deg,Z = 4, R = 0.100, andRW = 0.141.
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