The Fluoro Analogue of Wilkinson's Catalyst and Unexpected Ph−Cl Activation

Activation of SO2F2 at a Rhodium PNP Pincer Complex: Ligand Supported S-F Bond Cleavage to Generate NSO2F Derivatives

The κ2-(P,N)-phosphine ligand precursor NH(CH2CH2PCy2)2 can be used for the synthesis of the rhodium(I) complex [Rh(CO){ĸ3-(P,N,P)-Cy2PC2H4NHC2H4PCy2}][Cl] (1). The deprotonated complex [Rh(CO){ĸ3-(P,N,P)-Cy2PC2H4NC2H4PCy2}] (2) shows a cooperative reactivity of the PNP ligand in the activation reaction of SO2F2 to yield the rhodium fluorido complex trans-[Rh(F)(CO){ĸ2-(P,P)-Cy2PC2H4N(SO2F)C2H4PCy2}]2 (3) by S-F bond cleavage. It is remarkable that no reaction was observed when 3 was treated with hydrogen sources e. g. dihydrogen, organosilicon compounds such as triethylsilane or TMS-CF3 and different fluorine sources such as SF4 or Selectfluor®. However, the treatment of complex 3 with XeF2 in the presence of CsF resulted in the formation of the unique fluorido rhodium(III) complex cis,trans-[Rh(F)3(CO){ĸ2-(P,P)-Cy2PC2H4N(SO2F)C2H4PCy2}]2 (4). In the presence of pyridine(HF)X or BF3 the fluorido complex 3 converted into the dicationic complexes [Rh(CO){ĸ2-(P,P)-Cy2PC2H4N(SO2F)C2H4PCy2}]2[XF]2, X=HF (5) or BF3 (6), respectively.

Oxidative Addition of Biphenylene and Chlorobenzene to a Rh(CNC) Complex

The synthesis and organometallic chemistry of rhodium(I) complex [Rh(CNC-Me)(SOMe2)][BArF 4], featuring NHC-based pincer and labile dimethyl sulfoxide ligands, is reported. This complex reacts with biphenylene and chlorobenzene to afford products resulting from selective C-C and C-Cl bond activation, [Rh(CNC-Me)(2,2'-biphenyl)(OSMe2)][BArF 4] and [Rh(CNC-Me)(Ph)Cl(OSMe2)][BArF 4], respectively. A detailed DFT-based computational analysis indicates that C-H bond oxidative addition of these substrates is kinetically competitive, but in all cases endergonic: contrasting the large thermodynamic driving force calculated for insertion of the metal into the C-C and C-Cl bonds, respectively. Under equivalent conditions the substrates are not activated by the phosphine-based pincer complex [Rh(PNP-iPr)(SOMe2)][BArF 4].

Rhodium-catalyzed, P-directed selective C7 arylation of indoles

The indole scaffold will continue to play a vital role in the future of drug discovery and agrochemical development. Regioselective direct arylation of indoles on the benzenoid moiety is a challenging task due to the inherent reactivity of the C2 and C3 positions. Here, we have developed an effective strategy for the regioselective direct arylation of indoles at the C7 position with (hetero)aryl bromides by the rational design of a directing group. The key to the high selectivity and reactivity of this method is the appropriate selection of a class of directing groups, N-PR2 (R = t Bu and c Hex), that are easily removed in the presence of the Wilkinson's catalyst. Using the present method as a key step, formal synthesis of marine alkaloid dictyodendrin B has also been demonstrated.

Structure and dynamic NMR behavior of rhodium complexes supported by Lewis acidic group 13 metallatranes

Z-type complexes featuring Rh → Al and Rh → Ga interactions show distorted Rh centers and fluxionality on the NMR timescale.

Rhodium-catalyzed transformation of heteroaryl aryl ethers into heteroaryl fluorides

A rhodium complex catalyzed the conversion of the C-O bond of heteroaryl aryl ethers to the C-F bond. The reaction of (4-chlorophenylthio)pentafluorobenzene with heteroaryl aryl ethers provided heteroaryl fluorides and heteroaryl (4-chlorophenylthio)tetrafluorophenyl ethers; this involved the cleavage of a single heteroaryl C-O bond under equilibrium conditions. The reaction of heteroaryl aryl ethers with 2-fluorobenzothiazole in which two heteroaryl and aryl C-O bonds were cleaved provided heteroaryl fluorides and aryl fluorides. The reactions were applicable to five-membered and six-membered heteroaryl aryl ethers and also to diaryl ethers possessing one or two electron-withdrawing groups.

Synthesis and reductive elimination of arylPd(ii) trifluoromethyl complexes: a remarkable concentration effect on chemoselectivity

A remarkable and unprecedented concentration effect on chemoselectivity is observed for the thermal decomposition of Pd(ii) aryl trifluoromethyl complexes. As the concentration increases, the Ar–CF₃ cross-coupling is suppressed gradually whilst the Ar–Ar homocoupling increases steadily.

Exceedingly Facile Ph-X Activation (X = Cl, Br, I) with Ruthenium(II): Arresting Kinetics, Autocatalysis, and Mechanisms

[(Ph3P)3Ru(L)(H)2] (where L = H2 (1) in the presence of styrene, Ph3P (3), and N2 (4)) cleave the Ph-X bond (X = Cl, Br, I) at RT to give [(Ph3P)3RuH(X)] (2) and PhH. A combined experimental and DFT study points to [(Ph3P)3Ru(H)2] as the reactive species generated upon spontaneous loss of L from 3 and 4. The reaction of 3 with excess PhI displays striking kinetics which initially appears zeroth order in Ru. However mechanistic studies reveal that this is due to autocatalysis comprising two factors: 1) complex 2, originating from the initial PhI activation with 3, is roughly as reactive toward PhI as 3 itself; and 2) the Ph-I bond cleavage with the just-produced 2 gives rise to [(Ph3P)2RuI2], which quickly comproportionates with the still-present 3 to recover 2. Both the initial and onward activation reactions involve PPh3 dissociation, PhI coordination to Ru through I, rearrangement to a η(2)-PhI intermediate, and Ph-I oxidative addition.

4a,8a-Azaboranaphthalene-4-yl phosphine ligands: synthesis and electronic modulation in Suzuki–Miyaura coupling reactions

Design, synthesis and characterization of new BN-aromatic phosphine ligands are presented, demonstrating moderate catalytic activity in Suzuki reactions of C–Cl bond.

The mechanism, electronic and ligand effects for reductive elimination from arylPd(ii) trifluoromethyl complexes: a systematic DFT study

Detailed reaction mechanisms and ligand effects have been studied for reductive elimination of Ar–CF₃ from Pd(ii) centers.

Fluoride, bifluoride and trifluoromethyl complexes of iridium(i) and rhodium(i)

New methods for the preparation of a range of NHC-based Ir(i) and Rh(i) fluoride, bifluoride and trifluoromethyl complexes are reported.