Unusual pathways for metal-assisted C[bond]C and C[bond]P coupling reactions using allenylidenerhodium complexes as precursors.

The rhodium allenylidenes trans-[RhCl[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))(2)] [R = Ph (1), p-Tol (2)] react with NaC(5)H(5) to give the half-sandwich type complexes [(eta(5)-C(5)H(5))Rh[[double bond]C[double bond]C[double bond]C(Ph)R](PiPr(3))] (3, 4). The reaction of 1 with the Grignard reagent CH(2)[double bond]CHMgBr affords the eta(3)-pentatrienyl compound [Rh(eta(3)-CH(2)CHC[double bond]C[double bond]CPh(2))(PiPr(3))(2)] (6), which in the presence of CO rearranges to the eta(1)-pentatrienyl derivative trans-[Rh[eta(1)-C(CH[double bond]CH(2))[double bond]C[double bond]CPh(2)](CO)(PiPr(3))(2)] (7). Treatment of 7 with acetic acid generates the vinylallene CH(2)[double bond]CH[bond]CH[double bond]=C=CPh(2) (8).

Coordination and Coupling of OH-Functionalized C Units at a Single Metal Center: The Synthesis of Alkynyl(Vinylidene), Alkynyl(Enyne), Bis(Alkynyl)Hydrido, Enynyl, and Hexapentaene Rhodium Complexes from Propargylic Alcohols as Precursors.

The reaction of [Rh(η -C H )-(PiPr ) ] (1) with HCCCH(Ph)OH yields the alkynyl(vinylidene) complex trans-[Rh{CCCH(Ph)OH}{CCH-CH(Ph)OH}(PiPr ) ] (2), while from 1 and HCCCPh OH the alkynyl-(enyne)metal derivative trans-[Rh(CCCPh OH){n -(E)-Ph (OH)CCCCHCH-CPh OH} (PiPr ) ] (3) is obtained. On treatment with 1-alkyn-3-ols HCCCR OH (R = Me, Ph, iPr), the highly reactive π-benzyl compound [Rh(n -CH Ph)(PiPr ) ] (4) yields the five-coordinate complexes [RhH(CCCR OH) (PiPr ) ] (5-7) of which those with R = Me and Ph can be converted to the alkynyl(vinylidene)metal isomers trans-[Rh(CCCR OH)(CCH-CR OH)-(PiPr ) ] (8, 9). Compounds 8 and 9 react with L' = CO and isocyanides by migration of the alkynyl ligand to the vinylidene unit to give the enynylrhodium(I) complexes trans-[Rh{n -(Z)-C(CCCR OH)CH-CR OH}(L')(PiPr ) ] (10, 11: L' = CO; 12-15: L' = CNR').