Abstract
The Rh(I) complex [Rh(CO)(PEt 3 )(mnt)] - generated in situ by the addition of PEt 3 to [Rh(CO) 2 (mnt)] - reacts with various alkyl halides R-X (X = I, R = Me, Et, n-Pr, n-Bu, n-C 10 H 21 , i-Pr, i-Bu; X = Br, R = Et, n-Pr, n-Bu, Bz, allyl, propargyl; X = Cl, R = allyl) in the presence of excess phosphine to form a series of stable neutral Rh(III) acyl species of formula Rh(COR)(PEt 3 ) 2 (mnt). These complexes have been characterized by IR and 1 H NMR spectroscopy, and the structure of a representative member of the series (R = n-Pr) has been determined by single-crystal X-ray diffraction methods. The structure determination of Rh(CO-n-Pr)(PEt 3 ) 2 (mnt) shows that the complex crystallizes in space group D 2h 15 -Pbca in a cell of dimensions a = 20.47 (4) Å, b = 13.61 (3) Å, and c = 18.44 (4) Å with eight molecules per unit cell (ρ exptl = 1.40 (2) g/cm 3 ; ρ calcd = 1.421 g/cm 3 ). The coordination geometry of the complex is square pyramidal with the butanoyl group occupying the apical position at a distance of 2.002 (7) Å from the Rh(III) ion. The complex possesses nearly C s symmetry in the solid state with the triethylphosphine conformations related by a noncrystallographic mirror. The Rh-S and Rh-P bond lengths average 2.320 and 2.348 Å, respectively. In the presence of excess PEt 3 , addition of perchloric acid to a solution of [Rh(CO)(PEt 3 )(mnt)] - results in the formation of the rhodium(III) hydride Rh(H)(CO)(PEt 3 ) 2 (mnt). In contrast, the addition of acid to the rhodium(I) complex in acetonitrile in the presence of ethylene leads slowly to the formation of an acyl complex which is isolated as Rh(COEt)(PEt 3 ) 2 (mnt) upon adding excess PEt 3 . © 1979 American Chemical Society.