HYDROXIDERHENIUM(I), AMIDERHENIUM(I), AND SULFHYDRYLRHENIUM(I) TRIS(ALKYNE) COMPLEXES - REARRANGEMENTS TO RHENIUM(III) BIS(ALKYNE) OXO AND NITRIDO COMPOUNDS

The rhenium hydroxide and amide complexes Re(OH)(EtC=CEt)(3) (3) and R e(NH2)(EtC=CEt)(3) (10) have been prepared by reaction of the related aquo and ammine complexes with KOH and NaNH2, respectively. The sulfhy dryl compound Re(SH)(EtC=CEt)(3) (13) is formed from Re(OSO2CF3)(EtC=C Et)(3) and NaSH. Compound 3 spontaneously rearranges to the oxo-hydrid e complex Re(O)H(EtC=CEt)(2) (4), and EtC=CEt in a first-order process (k = (5.6 +/- 1.2) x 10(-6) s(-1) at 294 K). There is a primary isoto pe effect (k(OH)/k(OD) = 5 +/- 1), and the rearrangement is unaffected by the presence of 1 M 3-hexyne, These data rule out a mechanism invo lving initial ligand loss followed by rearrangement, Instead, hydrogen migration from oxygen to rhenium occurs in the coordinatively saturat ed tris(alkyne) species 3, either synchronously with or prior to the l oss of alkyne. Rearrangement is catalyzed by potassium alkoxides, appa rently via deprotonation of 3 and concomitant loss of EtC=CEt to the o xo anion (EtC=CEt)(2)ReO- (5), which is reprotonated by ROH. Surprisin gly, isolated samples of 5 are not catalysts, apparently due to its sl ow proton transfer reactions. The amide complex 10 rearranges to the u nusual mu-nitrido complex (EtC=CEt)(3)Re-N=Re(H)-(EtC=CEt)(2) (11), wh ich has been characterized spectroscopically. This reaction is similar to that of the hydroxide 3 in that a hydrogen moves from N or O to th e rhenium center, with oxidation of the metal, The mechanism of rearra ngement 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 degrees C.