MULTIPLE RE-C BONDS AT THE [(MEC(CH(2)PPH(2))(3))RE(CO)(2)](+) AUXILIARY

After displacement of the eta(2)-H-2 ligand from [(triphos)Re(CO)(2)(e ta(2)-H-2)]BF4 (2), ethyne and various 1-alkynes, HC=CR, are tautomeri zed at the Re(I) center to vinylidene ligands (R=H, Ph, p-tolyl, COOEt n-C6H13, SiMe(3)). A kinetic pi-alkyne adduct is intercepted at low t emperature during the reaction between 2 and ethyne. The primary vinyl idene complex [(triphos)Re(CO)(2)(C=CH2)]BF4 (7-BF4) can also be obtai ned by reaction of the (trimethylsilyl)vinylidene complex [(triphos)Re (CO)(2){C=C(H)SiMe(3)}]BF4 with stoichiometric water. Unprecedented ex amples of addition of either water or alcohols to Re-vinylidene moieti es to give hydroxycarbene or alkoxycarbene complexes are presented. In particular, an excess of water transforms 7-BF4 into the secondary hy droxycarbene complex [(triphos)Re(CO)(2){C(OH)CH3}]BF4 (II), which can be isolated in the solid state. Upon thermolysis in refluxing tetrahy drofuran, 11 selectively converts to the tricarbonyl complex [(triphos )Re(CO)(2)]BF4 and methane. Deprotonation of 11 by mild bases gives th e acetyl derivative (triphos)Re(CO)(2)(COCH3), which regenerates the h ydroxycarbene precursor by protonation with strong acids. The ethoxyca rbene complexes [(triphos)Re(CO)(2){C(OEt)CH(2)R}]BPh(4)(R=H, COOEt) a re prepared by nucleophilic addition of ethanol across the C=C double bond of the corresponding vinylidene derivatives. Neutral sigma-alkyny l complexes of the general formula (triphos)Re(CO)(2)(C=CR)(R=Ph, p-to lyl, COOEt, n-C6H13, H) are obtained by reaction of the vinylidene der ivatives with strong bases, The reaction of the sigma-alkynyl complexe s with various methylating agents affords disubstituted, vinylidene de rivatives, herein exemplified by [(triphos)Re(CO)(2){C=C(Me)Ph}](OSO2C F3). The structural identities in the solid state of the phenylvinylid ene complex [(triphos)Re(CO)(2){C=C(H)Ph}]BF4 and of the ethoxycarbene complex [(triphos)Re(CO)(2){C(OEt)CH3}]BPh(4) have been determined by X-ray diffraction analyses. In both complexes the metal center is oct ahedrally coordinated by a fac triphos ligand, by two mutually cis ter minal carbonyls, and by the organyl ligand.