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

The rhodium allenylidenes trans-RhCldouble bond]Cdouble bond]Cdouble 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))Rhdouble bond]Cdouble bond]Cdouble 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)CHCdouble bond]Cdouble bond]CPh(2))(PiPr(3))(2)] (6), which in the presence of CO rearranges to the eta(1)-pentatrienyl derivative trans-Rheta(1)-C(CHdouble bond]CH(2))double bond]Cdouble bond]CPh(2)](CO)(PiPr(3))(2)] (7). Treatment of 7 with acetic acid generates the vinylallene CH(2)double bond]CHbond]CHdouble bond]=C=CPh(2) (8). Compounds 1 and 2 react with HCl to give the five-coordinate allenylrhodium(III) complexes RhCl(2)CHdouble bond]Cdouble bond]C(Ph)R](PiPr(3))(2)] (10, 11). An unusual C(3) + C(2) + P] coupling process takes place upon treatment of 1 with terminal alkynes HCtriple bond]CR', leading to the formation of the eta(3)-allylic compounds RhCleta(3)-anti-CH(PiPr(3))C(R')Cdouble bond]Cdouble bond]CPh(2)](PiPr(3))] R' = Ph (12), p-Tol (13), SiMe(3) (14)]. From 12 and RMgBr the corresponding phenyl and vinyl rhodium(I) derivatives 15 and 16 have been obtained. The previously unknown unsaturated ylide iPr(3)PCHC(Ph)double bond]Cdouble bond]Cdouble bond]CPh(2) (17) was generated from 12 and CO. A C(3) + P] coupling process occurs on treatment of the rhodium allenylidenes 1, 2, and trans-RhCldouble bond]Cdouble bond]Cdouble bond]C(p-Anis)(2)](PiPr(3))(2)] (20) with either Cl(2) or PhICl(2), affording the ylide-rhodium(III) complexes RhCl(3)C(PiPr(3))Cdouble bond]C(R)R'](PiPr(3))] (21-23). The butatrienerhodium(I) compounds trans-RhCleta(2)-H(2)Cdouble bond]Cdouble bond]Cdouble bond]C(R)R'](PiPr(3))(2)] (28-31) were prepared from 1, 20, and trans-RhCldouble bond]Cdouble bond]Cdouble bond]C(Ph)R](PiPr(3))(2)] R = CF(3) (26), tBu (27)] and diazomethane; with the exception of 30 (R = CF(3), R' = Ph), they thermally rearrange to the isomers trans-RhCleta(2)-H(2)Cdouble bond]Cdouble bond]Cdouble bond]C(R)R'](PiPr(3))(2)] (32, 33, and syn/anti-34). The new 1,1-disubstituted butatriene H(2)Cdouble bond]Cdouble bond]Cdouble bond]C(tBu)Ph (35) was generated either from 31 or 34 and CO. The iodo derivatives trans-RhI(eta(2)-H(2)Cdouble bond]Cdouble bond]Cdouble bond]CR(2))(PiPr(3))(2)] R = Ph (38), p-Anis (39)] were obtained by an unusual route from 1 or 20 and CH(3)I in the presence of KI. While the hydrogenation of 1 and 26 leads to the allenerhodium(I) complexes trans-RhCleta(2)-H(2)Cdouble bond]Cdouble bond]C(Ph)R](PiPr(3))(2)] (40, 41), the thermolysis of 1 and 20 produces the rhodium(I) hexapentaenes trans-RhCl(eta(2)-R(2)Cdouble bond]Cdouble bond]Cdouble bond]Cdouble bond]Cdouble bond]CR(2))(PiPr(3))(2)] (44, 45) via C-C coupling. The molecular structures of 3, 7, 12, 21, and 28 have been determined by X-ray crystallography.