Substitution and Isomerization of Asymmetric β-Diketonato Rhodium(I) Complexes: A Crystallographic and Computational Study

Abstract

Ligand substitution of PPh 3 for CO in the asymmetric square-planar β-diketonato complex [Rh-(PhCOCHCOCH 2 CH 3 )(CO) 2 ] leads to formation of the monosubstituted [Rh(PhCOCHCOCH 2 -CH 3 )(CO)(PPh 3 )] product. Two geometrical product isomers are possible, which unexpectedly crystallize in the same crystal lattice. DFT calculations of the substitution reaction support a twostep mechanism, involving temporary dissociation of a β-diketonato ligand and formation of a square-planar intermediate. Analysis of the mechanisms involved in product isomerization suggests several noncatalyzed and solvent-assisted interconversion pathways.

Mechanistic Studies on the Catalytic Oxidative Amination of Alkenes by Rhodium(I) Complexes with Hemilabile Phosphines

“…The addition of a large excess of styrene to a dissolution of 5 in THF-d 8 (160 : 1) resulted in the formation of a symmetric species 12 which was observed at δ 33.93 ppm (J P-Rh = 204.1 Hz) in the 31 P{ 1 H} NMR spectrum at 273 K. The spectroscopic data for 12 suggest the formation of an olefin adduct [Rh{Ph 2 P(CH 2 ) 3 OEt} 2 (styrene) n ] + . It is worth of note that this species has never been observed by 31 P{ 1 H} NMR under catalytic conditions. In agreement with this, the addition of 40 equiv.…”

“…In a parallel experiment, a THF-d 8 solution containing catalyst 5, piperidine and styrene and in a 1 : 40 : 160 molar ratio was heated in a thermostathized bath at 338K and monitored regularly by 31 P{ 1 H} NMR spectra at 273K. After 20 min, a mixture of the cationic piperidine complex 8 and the neutral species 9 was observed.…”

“…The substitution processes have been assumed to require low activation energy values. 29,30,31 The neutral square planar rhodium(I) amino-amido complex 9 is the precursor for the catalytic active species: the olefin-amido intermediate [Rh{Ph 2 P(CH 2 ) 3 OEt} 2 (NC 5 H 10 )(styrene)] (a, Figure 10). The resulting complex a presents a distorted square planar geometry where the amido N-atom forms an angle of 95.08 o with the C-C centroid of the olefin group which lies roughly perpendicular to the coordination plane.…”

An experimental and DFT study of the packing and structure of dithenoylmethane monocarbonylphosphine Rhodium(I) complex [Rh((C 4 H 3 S)COCHCO(C 4 H 3 S))(CO)(PPh 3 )]

“…Density functional theory (DFT) calculations of this study done with the Gaussian 09 program package [8]. A selection of functionals were used, namely the GGA (Generalized Gradient Approximation) functional PW91 [9] and LC-BLYP [10,11,12,13] (long range corrected BLYP), meta-GGA functional M06-D3 [14] (M06 with the Grimme empirical dispersion correction D3 [15]) and the hybrid functionals B3LYP (Becke 1993 and Lee-Yang-Parr) [16,17] and CAM-B3LYP [18] (long range corrected version of B3LYP), with the triple-ζ basis set 6-311G (d,p) [20,21,22]. The LC-BLYP optimised gas phase structures were used to further conduct a natural bond orbital (NBO) analysis (using the NBO 3.1 module [23] in Gaussian 09), as well as an electronic density analysis (using Bader's quantum theory of atoms in molecules (QTAIM) [24,25,26], as implemented in ADF2017 [27,28,29]).…”

Rhodium-rhodium interactions in [Rh(β-diketonato)(CO)2] complexes

“…The electronic density analysis was performed using QTAIM [31], as implemented in ADF2013 [32], at the same level of theory. The 6-311G (d,p)/Lanl2dz basis set proved to give reliable geometries and energies for rhodium-dicarbonyl complexes containing a β-diketonato ligand [33,34,35].…”