1415966-23-2

Upstream product

• 1079-66-9 chloro-diphenylphosphine 
• 69506-91-8 1,3-bis(1H-imidazol-1-yl)benzene 

Relevant academic research and scientific papers

P(CH)P pincer rhodium(I) complexes: The key role of electron-poor imidazoliophosphine extremities

The coordination chemistry of a potentially pincer-type dicationic meta-phenylene-bis(imidazoliophosphine) ligand 3 to neutral and cationic carbonylrhodium(I) centers has been investigated. Similarly to what was observed previously for its ortho-phenylene counterpart, 3 was found to bind to the RhCl(CO) fragment in a trans-chelating manner that makes possible a weak Rh-C(H) interaction, inferred from the nonbonding but relatively short Rh-C and Rh-H contacts observed in the solid state structure of the dicationic adduct (3)RhCl(CO) (5). Formation of the target PCP-type pincer complex could not be triggered despite multiple attempts to deprotonate the central C-H moiety in the initial dicationic adduct 5, or in the tricationic species [(3)Rh(CO)] + (8) generated by abstraction of the chloride ion from 5. Complex 8 was identified on the basis of NMR and IR analyses as a Rh(I)-stabilized P(CH)P-intermediate en route to the anticipated classical PCP-type pincer complex. Analysis of the electronic structure of this intermediate computed at the density functional level of theory (DFT level) revealed a bonding overlap between a Rh d-orbital and π-orbitals of the m-phenylene ring. NBO analyses and calculated Wiberg indices confirm that this interaction comprises an η1-C-Rh bonding mode, with only secondary contributions from the geminal C and H atoms. Although the target PCP-type pincer complex could not be generated, treatment of the tricationic intermediate with methanol induced a P-CN2 bond cleavage at both imidazoliophosphine moieties, resulting in the formation of a dicationic open pincer species, that is, a nonchelated bis((MeO)PPh2)-stabilized aryl-Rhodium complex that is the κC-only analogue of the putative κP,κC,κP-PCP complex sought initially. Theoretical studies at the DFT level of experimental or putative species relevant to the final C-H activation process ruled out the oxidative addition pathway. Two alternative pathways are proposed to explain the formation of the open pincer complex, one based on an organometallic α-elimination step, the other based on an organic aromatization-driven β-elimination process.

Effect of positive-charges in diphosphino-imidazolium salts on the structures of Ir-complexes and catalysis for hydroformylation

The effect of positive charges in the diphosphino-imidazolium salts of L2 was investigated in terms of coordinating character, structures of corresponding Ir-complexes and catalysis for hydroformylation. It was found that the involved positive charges exhibited strong electron-withdrawing effect on the neighbored phosphine fragment, rendering L2 more π-acceptor ability than the corresponding neutral counterpart of L1. Consequently, the changed coordinating ability of L1 and L2 led to the variety in the structures and components for the Ir-complexes (Ir-L1a, Ir-L1b, Ir-L2a, and Ir-L2b). The complexation of L2 with Ir(acac)(CO)2 led to a novel five-coordinate Ir(II)-complex of Ir-L2a chelated by a PCC (phosphine-carboanion-carbene) pincer in tripodal mode, whereas the complexation of L1 with Ir(acac)(CO)2 led to a four-coordinate square-planar Ir(I)-complex of Ir-L1a chelated by a PCP (phosphine-carboanion-phosphine) pincer. In addition, the different catalytic performances of these Ir-complexes ligated by L1 and L2 for hydroformylation of olefins were investigated.

Phosphane-ligated ionic palladium complexes: Synthesis, characterization and application as efficient and reusable precatalysts for the homogeneous carbonylative sonogashira reaction under CuI-free conditions

The stable ionic PdII complexes 1A-4A were synthesized through the complexation of PdCl2(MeCN)2 with the phosphane-functionalized ionic liquids (FILs) 1-4 with π-acceptor character. Single-crystal X-ray diffraction analyses showed that 1A-4A were all composed of PdII-centred square-planar cations and triflate (OTf-, CF3SO3-) counteranions. The complex cations in 1A-3A possessed structural similarity to trans-PdCl2(PPh 3)2. The cation in 4A was a new PdII-centered planar complex ligated by the phosphane-carbon anion-carbene (PCC) pincer in a tripodal manner. The stabilities of 1A-4A were improved due to the intensive π-backbonding interaction between the Pd and P atoms. When complexes 1A-4A were used as precatalysts for homogeneous carbonylative Sonogashira coupling of PhI with phenylacetylene free of CuI, 1A-3A exhibited excellent catalytic behaviour with a TON of up to 1700 at a CO pressure of 0.5 MPa and moderate temperature of 100 °C, whereas 4A exhibited poor activity towards the transformation of PhI due to the high stability of 4A. The recycling experiments of 3A in [Bpy]BF4 (as a solvent) indicated that 3A could be recycled for 5 runs with neither activity loss nor metal leaching into the organic phase. Complex 3A also proved to be a general precatalyst for the carbonylative Sonogashira couplings of a wide range of aryl iodides with phenylacetylene. The selectivity of the desired carbonylation product depended more on electronic effects than the steric effects of the substituents of the aryl iodides. The ionic palladium complexes 1A-4A ligated by imidazolium-based-phosphanes were prepared and shown, by single-crystal X-ray diffraction analyses, to be composed of PdII-centered square-planar cations and OTf- counteranions. The complexes were tested as precatalysts for the homogeneous carbonylative Sonogashira coupling of aryl iodides with phenylacetylene. Copyright

Phosphane-ligated ionic palladium complexes: Synthesis, characterization and application as efficient and reusable precatalysts for the homogeneous carbonylative sonogashira reaction under CuI-free conditions

The stable ionic PdII complexes 1A-4A were synthesized through the complexation of PdCl2(MeCN)2 with the phosphane-functionalized ionic liquids (FILs) 1-4 with π-acceptor character. Single-crystal X-ray diffraction analyses showed that 1A-4A were all composed of PdII-centred square-planar cations and triflate (OTf-, CF3SO3-) counteranions. The complex cations in 1A-3A possessed structural similarity to trans-PdCl2(PPh3)2. The cation in 4A was a new PdII-centered planar complex ligated by the phosphane-carbon anion-carbene (PCC) pincer in a tripodal manner. The stabilities of 1A-4A were improved due to the intensive π-backbonding interaction between the Pd and P atoms. When complexes 1A-4A were used as precatalysts for homogeneous carbonylative Sonogashira coupling of PhI with phenylacetylene free of CuI, 1A-3A exhibited excellent catalytic behaviour with a TON of up to 1700 at a CO pressure of 0.5 MPa and moderate temperature of 100 °C, whereas 4A exhibited poor activity towards the transformation of PhI due to the high stability of 4A. The recycling experiments of 3A in [Bpy]BF4 (as a solvent) indicated that 3A could be recycled for 5 runs with neither activity loss nor metal leaching into the organic phase. Complex 3A also proved to be a general precatalyst for the carbonylative Sonogashira couplings of a wide range of aryl iodides with phenylacetylene. The selectivity of the desired carbonylation product depended more on electronic effects than the steric effects of the substituents of the aryl iodides.