Linkage Isomerization of MSCN(CDOH)₂(CDO)BMe to MNCS(CDOH)₂(CDO)BMe (M = Tc, Re). Crystal Structures of TcNCS(CDOH)₂(CDO)BMe, ReNCS(CDOH)₂(CDO)BMe, and ReSCN(CDOH)₂(CDO)BMe

Abstract

The 7-coordinate technetium(III) and rhenium(III) monocapped tris(dioxime) complexes [MX(dioxime) 3 BR] have been prepared in which the seventh ligand, X, is thiocyanate or hydroxide (M ) Tc, Re; R ) Me, Et). Both the N-and S-bound thiocyanate linkage isomers are produced during the syntheses, however, the S-bound complex isomerizes to the N-bound analogue. The synthetic routes employed allowed isolation of sufficient quantities of the technetium and rhenium S-bound isomers to be identified; however, full characterization was not possible. The linkage isomerization reaction of TcSCN(CDOH) 2 (CDO)BMe to TcNCS(CDOH) 2 (CDO)BMe was monitored in dichloromethane by UV-visible spectrophotometry, with four isosbestic points observed, consistent with the formation of a single product. The N-bound isomers for both Tc and Re, and the S-bound isomer of Re were characterized by single-crystal X-ray diffraction analysis. The two N-bound complexes were found to be isostructural. TcNCS(CDOH) 2 (CDO)BMe crystallized in the orthorhombic space group P2 1 2 1 2 1 with a ) 15.814-(2) Å, b ) 17.855(3) Å, c ) 17.997(5) Å, Z ) 8, R ) 0.054, and R W ) 0.057. ReNCS(CDOH) 2 (CDO)BMe crystallized in the orthorhombic space group P2 1 2 1 2 1 with a ) 15.795(1) Å, b ) 17.843(2) Å, c ) 18.014(3) Å, Z ) 8, R ) 0.054, and R W ) 0.073. In both cases two independent molecules per unit cell were observed. ReSCN(CDOH) 2 (CDO)BMe crystallized in the monoclinic space group P2 1 /c with a ) 10.0866(6) Å, b ) 26.301-(2) Å, c ) 12.4592(7) Å, β ) 100.5(1) deg, Z ) 4, R ) 0.100, and R W ) 0.141.

Novel rhenium(iii, iv, and v) tetradentate N2O2 Schiff base mononuclear and dinuclear complexes

“…The Re–NCS (2.097 Å) bond is within typical ranges for Re(V) complexes with a coordinated thiocyanate and is on the long end of the reported Re–NCS and Tc–NCS bond distances for Re(III) complexes. 22, 55–59 The Re–P (2.424 Å) bond distance is comparable to those observed in other Re(III) complexes. 20, 25, 38, 40, 60, 61 …”

Novel 99m Tc(III)-azide complexes [ 99m Tc(N 3 )(CDO)(CDOH) 2 B-R] (CDOH 2 = cyclohexanedione dioxime) as potential radiotracers for heart imaging

“…The structural characterization of complexes [M(N 3 )(CDO)(CDOH) 2 B-R] (M = Tc and Re) is difficult because organic azides and heavy metal azide salts tend to be highly heat and shock-sensitive explosives (https://en.wikipedia.org/wiki/Azide). Due to the similarity (isoelectronic) between SCN − and ${\mathrm{normalN}}_3^{-}$, it is reasonable to believe that complexes [ 99m Tc(N 3 )(CDO)(CDOH) 2 B-R] would share very similar structures with those of [M(NCS)(CDO)(CDOH) 2 B-Me] (M = Tc and Re), which have been determined by X-ray crystallography [48]. This assumption is completely consistent with the fact that 99m Tc-Teboroxime-NCS and 99m Tc-Teboroxime-N 3 shared almost identical HPLC retention times of under the same chromatographic conditions [44].…”

“…Structures of complexes [ 99m TcCl(CDO)(CDOH) 2 B-R] were derived from those of complexes [ReCI(CDO)CDOH) 2 BPh], [TcX(dioxime) 3 B-R] (X = Cl, Br; dioxime = dimethylglyoxime, cyclohexanedione dioxime; R = CH 3 and C 4 H 9 ) and [Tc(NCS) (CDO) (CDOH) 2 BMe] [46-48]. …”

2,2′-[(1E,2E)-1,2-Bis(hydroxyimino)ethane-1,2-diyl]dipyridinium hexachloridorhenate(IV)

“…In the crystallographic literature many metal complexes with dioximes have been reported. In the case of rhenium compounds there are three crystal structures with coordinated monooximes (Jurisson et al, 1991;Jurisson et al, 1998), while the complexes of Re with dioximes were not reported. Therefore, it seemed an attractive idea to obtain new compounds of rhenium with dioximes.…”

“…For the structure of the [ReCl 6 ] 2À ion, see: Takazawa et al (1990); Hołyń ska et al (2007). For structures of rhenium compounds with monooximes, see: Jurisson et al (1991Jurisson et al ( , 1998. For background tointeractions, see: Janiak (2000).…”