SYNTHETIC, STRUCTURAL, AND THEORETICAL-STUDIES ON A NOVEL RHODIUM(I) COMPLEX CONTAINING A PI-ALLYL-TYPE YLIDE LIGAND

Whereas the reaction of [RhCl(P-i-Pr-3)(2)](n) (1) with [CPh(Me)OH](CO(2)Et)CN2 and PhCHN(2) gives the diazoalkane and dinitrogen complexes trans-[RhCl{N2C(CO(2)Et)(CPh(Me)OH)}(P-i-Pr-3)(2)] (2) and trans-[RhCl(N-2)(P-i-Pr-3)(2)] (3), respectively, the mononuclear yliderhodium(I) compound [RhCl(P-i-Pr-3)(i-Pr3P=CHC(O)Ph)] (4) is obtained on treatment of 1 with PhC(=O)CHN2. It reacts with CO or CN-t-Bu to generate the formerly unknown acyl ylide i-Pr3PCHC(O)Ph (5). The X-ray structure analysis of 4 (monoclinic, space group P2(1)/c (No. 14), with a = 11.280(3) Angstrom, b = 15.201(2) Angstrom, c = 17.041(5) Angstrom, beta = 92.36(1)degrees, and Z = 4) reveals the presence of a eta(3)-allyl-type unit which is coordinated via oxygen and two carbon atoms to the metal center. The nature of the bonding between the modified acyl ylide ligand H3PCHC(=O)CH3 and rhodium(I) has been investigated by ab initio methods at the MP2 level. The calculated structure of the hypothetical molecule [RhCl(PH3){H3PCHC(O)CH3}] (4') is very similar to the geometry of 4 obtained by X-ray analysis. In contrast to 1, the alkynylrhodium(I) compounds trans-[Rh(C=CR)(C2H4)(P-i-Pr-3)(2)] (6, 7) react with PhC(=O)CHN2 to give the diazoalkane complexes trans-[Rh(C=CR)(N2C(H)(COPh))(P-i-Pr-3)(2) (11, 15). The preparation of other derivatives of composition trans-[Rh(C=CR)(N(2)CR'R'')(P-i-Pr-3)(2)] (8-10, 12-14) will also be described.