SYNTHESIS, STRUCTURE, AND REACTIVITY OF YLIDE RHODIUM(I) AND RHODIUM(III) COMPLEXES

The olefin(ylide) rhodium(I) complexes [(L)(iPr3PCH2)RhCl]2 (3: L = C8H14; 4: L = C2H4) have been prepared from [(L)2RhCl]2 (1, 2) and CH2PiPr3 in almost quantitative yield. Upon treatment of 3 and 4 with LiC5H5, the half-sandwich type compounds [C5H5Rh(CH2PiPr3)(L)] (5, 6) are obtained. Compound 5 (L = C8H14) reacts with carbon monoxide to give [C5H5Rh(CH2PiPr3)(CO)] (7) and with iodine to give [C5H5Rh(CH2PiPr3)I2] (8). Displacement of the olefin ligand also occurs upon treatment of 5 with CH3I, CH2I2 and CH2ClI, leading to the formation of [C5H5RhCH2X(CH2PiPr3)I] (9: X = H; 10: X = I; 11: X = Cl). The bis(ylide) rhodium(III) complexes [C5H5Rh(CH2PR3)(CH2PiPr3)I]I (12-14), [C5H5Rh(CH2PiPr3)(CH2AsPh3)I]I (15) and [C5H5Rh(CH2PiPr3)(CH2NEt3)I]I (16) are obtained by nucleophilic substitution from 10 upon treatment with PR3, AsPh3 and NEt3, respectively. Reaction of 7 with CH3I or CD3I give a mixture of 8 and [C5H5RhCX3(CH2PiPr3)(CO)]I (17a: X = H; 17b: X = D). In contrast, treatment of 7 with dimethylsulfate gives only [C5H5RhCH3(CH2PiPr3)(CO)]SO4Me (17c). The X-ray crystal structure of 17c has been determined. Compound 17c reacts with PiPr3 to give the acetyl(ylide) rhodium(III) complex [C5H5RhCOCH3(CH2PiPr3)(PiPr3)]SO4Me (18).