VINYLIDENE TRANSITION-METAL COMPLEXES .22. ALKYNE, ALKYNYL(HYDRIDO)-COMPLEX, VINYLIDENE-COMPLEX, AND VINYLVINYLIDENE COMPLEX OF RHODIUM FROM OH-FUNCTIONALIZED, NH2-FUNCTIONALIZED, AND CL-FUNCTIONALIZED ALKYNES

The reaction of [RhCl(PiPr3)2]n with gamma-functionalized 1-alkynes HC = C-CRR'X (X = OH, OMe, Cl, NH2) at room temperature leads to the formation of either alkyne-, alkynyl(hydrido)-, or vinylidenerhodium complexes. The alkyne and alkynyl(hydrido) derivatives rearrange thermally or in the presence of deactivated Al2O3 to the isomeric vinylidenerhodium compounds in almost quantitative yield. On treatment of the gamma-functionalized vinylidenerhodium complexes trans[RhCl(=C=CH-CRR'X)(PiPr3)2] with Al2CO3 or traces of acids, elimination of HX occurs and (for R H, CH3; R' = CH3; X = OH, Cl, NH2) the (vinylvinylidene)rhodium compounds trans-[RhCl(= C= CH-CR = CH2)(PiPr3)2] are formed. In contrast, the reaction of trans-[RhCl(= C = CHCPh2OH)(PiPr3)2] with either Al2O3 or acid gives the allenylidene complex trans-[RhCl(= C = C = CPh2)(PiPr3)2]. The 1-hexyne derivatives HC = C[CH2]3CH2X (X = OH, Cl) react with [RhCl(PiPr3)2], to give alkyne-, alkynyl(hydrido)-, and vinylidenerhodium compounds; attempts to form the cyclic vinylidene complex trans-[RhCl(= C = C(CH2)3CH2)(PiPr3)2] by HX elimination from trans-[RhCl(= C = CH[CH2]3CH2X)(PiPr3)2] (X = OH, Cl) failed. The half-sandwich-type (vinylvinylidene)rhodium compounds [C5H5Rh(= C = CH-CR = CH2)(PiPr3)] (R = H, Me) are obtained from [RhH(C = C-CR = CH2)Cl(py)(PiPr3)2] and NaC5H5.