Oxidative addition of methyl iodide to [Rh(CH3COCHCOCH3)(CO)(P(OCH2)3CCH3)]

(Acetyl-acetonato-κ(2)O,O')carbon-yl[tris-(4-chloro-phen-yl)phosphane-κP]rhodium(I)

The title compound, [Rh(C(5)H(7)O(2))(C(18)H(12)Cl(3)P)(CO)], contains the bidentate acetyl-acetonate ligand coordinated to the Rh(I) atom, forming a chelate ring [Rh-O = 2.0327 (15) and 2.0613 (14) Å]. The Rh(I) atom is additionally coordinated by one P [Rh-P = 2.2281 (6) Å] and one carbonyl C [Rh-C = 1.812 (2) Å] atom, resulting in a slightly distorted square-planar geometry. The mol-ecules are packed to minimize steric hindrance with the phosphanes positioned above and below the slightly distorted square geometrical plane.

Oxidative addition of methyl iodide to [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)]: an experimental and computational study

The reaction rate of the oxidative addition and CO insertion steps of methyl iodide with [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)] are presented. Large negative experimental values for the activation entropy and results from a density functional theory computational chemistry study indicated trans addition of the CH3I to [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)]. A study of the molecular orbitals gives insight into the flow of electrons during the oxidative addition reaction. CO insertion leads to a square pyramidal [Rh(PhCOCHCOPh)(P(OCH2)3CCH3)(COCH3)(I)] acyl product with the COCH3 moiety in the apical position. The strong electron donation of the P(OCH2)3CCH3 ligand accelerates the oxidation addition step of methyl iodide to [Rh(PhCOCHCOPh)(CO)(P(OCH2)3CCH3)] by ca. 265 times faster (at 35°C) than that of the Monsanto catalyst, but inhibits the CO insertion step.