Bis(imino)carbazolide Complexes of Rhodium:  Highly Nucleophilic Ligands Exerting a Dramatic Accelerating Effect on MeI Oxidative Addition

Abstract

Rhodium(I) complexes bearing a bis(imino)carbazolide ligand L and an additional neutral donor [LRh(C 2 H 4 ), 2; LRh(CO), 3] have been prepared via a salt metathesis reaction between NaL and the dimeric rhodium precursors [RhCl(C 2 H 4 ) 2 ] 2 and [RhCl(CO) 2 ] 2 , respectively. Complex 3 was also prepared by reaction of the free ligand with [RhCl(CO) 2 ] 2 , whereas a related reaction with [RhCl(C 2 H 4 ) 2 ] 2 afforded the dinuclear Rh I -Rh III ethyl complex 4. The X-ray crystal structure of 4 showed octahedral [bis(imino)carbazolide]Rh III (Cl)Et linked to square-planar bis(ethylene)Rh I Cl via chloride bridges. Kinetic studies on the oxidative addition of MeI to 3 to form the LRh III I(CO)Me complex 5 revealed a second-order rate constant of 1.66 M -1 s -1 in CH 2 Cl 2 at 25 °C, which corresponds to a reaction rate approximately 50 000 times faster than that observed for [RhI 2 (CO) 2 ] -.

Oxidative addition of MeI to cationic Rh(I) carbonyl complexes with pyridyl bis(carbene) ligands

“…The clean second-order kinetics for disappearance of 1a-c are consistent with a bimolecular reaction with MeI, but do not provide information about subsequent product isomerisation steps. The apparent activation entropies are all large and negative, as frequently found for oxidative addition of MeI to square planar d 8 metal complexes, which is generally thought to proceed via an S N 2 mechanism [10,11,[13][14][15][16].…”

“…We recently reported that the bis(imino)carbazolide complex, 6 has very high reactivity towards MeI [16]. Its rate constant for oxidative addition is ca.…”

“…It is of interest how the steric and electronic properties of the ancillary ligands can affect the rates of the oxidative addition and migratory insertion steps. Recent examples in the literature have investigated the effects of monodentate [10,11], bidentate [12][13][14] and tridentate ligands [15,16] on the reactivity of neutral rhodium(I) carbonyl complexes.…”

Dicarbonylrhodium(I) Complexes of Bipyridine Ligands with Proximate H‐Bonding Substituents and Their Application in Methyl Acetate Carbonylation

“…[59][60][61] [Rh(1)(CO) 2 ]SbF 6 was dissolved in a 3.2 m solution of MeI in acetonitrile, and the carbonyl region of the IR spectrum was monitored at 25°C over 900 min (Figure 7). During the course of the reaction, the ν(CO) bands of [Rh (1) [38] The IR spectra in Figure 7, which were determined in acetonitrile because of the poor solubility of the ionic 3 ], before CO migratory insertion can take place.…”

Controlled Friedel‐Crafts Acylation of 3,6‐Disubstituted‐9H‐carbazole

“…7,8 It was also shown that the rhodium bis(imino)carbazolide carbonyl complexes experienced a dramatically fast rate of MeI oxidative addition reaction. 9 The electrochemical studies of Pd analogue were also reported. 11 Bis(imino)carbazolyl moiety has been employed as a bridge linking two porphyrins to form a new type of Pacman porphyrin system.…”