197977-03-0Relevant academic research and scientific papers
Hydroxide-, amide-, and sulfhydrylrhenium(I) tris(alkyne) complexes. Rearrangements to rhenium(III) bis(alkvne) oxo and nitrido compounds
Tahmassebi, Sam K.,McNeil, W. Stephen,Mayer, James M.
, p. 5342 - 5353 (1997)
The rhenium hydroxide and amide complexes Re(OH)(EtC≡CEt)3 (3) and Re(NH2)-(EtC≡CEt)S (10) have been prepared by reaction of the related aquo and ammine complexes with KOH and NaNH2, respectively. The sulfhydryl compound Re(SH)(EtC≡CEt)3 (13) is formed from Re(OSO2CF3)(EtC≡CEt)3 and NaSH. Compound 3 spontaneously rearranges to the oxo-hydride complex Re(O)H(EtC≡CEt)2 (4), and EtC≡CEt in a first-order process (k = (5.6 ± 1.2) × 10-6 s-1 at 294 K). There is a primary isotope effect (kOH/kOD = 5 ± 1), and the rearrangement is unaffected by the presence of 1 M 3-hexyne. These data rule out a mechanism involving initial ligand loss followed by rearrangement. Instead, hydrogen migration from oxygen to rhenium occurs in the coordinatively saturated tris(alkyne) species 3, either synchronously with or prior to the loss of alkyne. Rearrangement is catalyzed by potassium alkoxides, apparently via deprotonation of 3 and concomitant loss of EtC≡CEt to the oxo anion (EtC≡CEt)2ReO- (5), which is reprotonated by ROH. Surprisingly, isolated samples of 5 are not catalysts, apparently due to its slow proton transfer reactions. The amide complex 10 rearranges to the unusual μ-nitrido complex (EtC≡CEt)3Re-N≡Re(H)-(EtC≡CEt)2 (11), which has been characterized spectroscopically. This reaction is similar to that of the hydroxide 3 in that a hydrogen moves from N or O to the rhenium center, with oxidation of the metal. The mechanism of rearrangement is quite different, however, as added alkynes strongly inhibit conversion of 10 to 11, indicating initial 3-hexyne dissociation from 10. No rearrangement has been observed for the sulfhydryl compound 13, which decomposes at 150 °C.
