180620-06-8Relevant articles and documents
Unusual pathways for metal-assisted C-C and C-P coupling reactions using allenylidenerhodium complexes as precursors
Werner, Helmut,Wiedemann, Ralf,Laubender, Matthias,Windmueller, Bettina,Steinert, Paul,Gevert, Olaf,Wolf, Justin
, p. 6966 - 6980 (2007/10/03)
The rhodium allenylidenes trans-[RhCl{=C=C=C(Ph)R}(P/Pr3)2] [R = Ph (1), p-Tol (2)] react with NaC5H5 to give the half-sandwich type complexes [(η5-C5H5)Rh{=C=C=C(Ph)R} (P/Pr3)] (3, 4). The reaction of 1 with the Grignard reagent CH2=CHMgBr affords the η3-pentatrienyl compound [Rh(η3- CH2CHC=C=CPh2)(P/Pr3)2] (6), which in the presence of CO rearranges to the η1-pentatrienyl derivative trans-[Rh{η1-C(CH=CH2)=C=CPh2} (CO)(P/Pr3)2] (7). Treatment of 7 with acetic acid generates the vinylallene CH2=CH-CH=C=CPh2 (8). Compounds 1 and 2 react with HCl to give the five-coordinate allenylrhodium(III) complexes [RhCl2{CH=C=C(Ph)R}(P/Pr3)2] (10, 11). An unusual [C3 + C2 + P] coupling process takes place upon treatment of 1 with terminal alkynes HC=CR′, leading to the formation of the η3-allylic compounds [RhCl{η3-anti-CH(P/Pr3)C(R′) C=C=CPh2}(P/Pr3)] [R′ = Ph (12), p-Tol (13), SiMe3 (14)]. From 12 and RMgBr the corresponding phenyl and vinyl rhodium(I) derivatives 15 and 16 have been obtained. The previously unknown unsaturated ylide /Pr3PCHC(Ph)=C=C=CPh2 (17) was generated from 12 and CO. A [C3 + P] coupling process occurs on treatment of the rhodium allenylidenes 1, 2, and trans-[RhCl{=C=C=C(p-Anis)2}(P/Pr3)2] (20) with either Cl2 or PhlCl2, affording the ylide-rhodium(III) complexes [RhCl3(C(P/Pr3)C=C(R)R′}(P/Pr3)] (21-23). The butatrienerhodium(I) compounds trans-[RhCl{η2-H2C=C=C=C(R)R′} (P/Pr3)2] (28-31) were prepared from 1, 20, and trans-[RhCl{=C=C=C(Ph)R}(P/Pr3)2] [R = CF3 (26), tBu (27)] and diazomethane; with the exception of 30 (R = CF3, R′ = Ph), they thermally rearrange to the isomers trans-[RhCl{η2-H2C=C=C=C=(R)R′} (P/Pr3)2] (32, 33, and syn/anti-34). The new 1,1-disubstituted butatriene H2C=C=C=C(tBu)Ph (35) was generated either from 31 or 34 and CO. The iodo derivatives trans-[Rhl(η2-H2C=C=C=CR2) (P/Pr3)2] [R = Ph (38), p-Anis (39)] were obtained by an unusual route from 1 or 20 and CH3l in the presence of KI. While the hydrogenation of 1 and 26 leads to the allenerhodium(I) complexes trans-[RhCl{η2-H2C=C=C=C(Ph)R} (P/Pr3)2] (40, 41), the thermolysis of 1 and 20 produces the rhodium(I) hexapentaenes trans-[RhCl(η2-R2C=C=C=CR2) (P/Pr3)2] (44, 45) via C-C coupling. The molecular structures of 3, 7, 12, 21, and 28 have been determined by X-ray crystallography. (Abbreviations used: p-Tol = p-tolyl, 4-C6H4CH3; p-Anis = p-anisyl, 4-C6H4OCH3.).
