@article {42755, title = {Highly air-stable anionic mononuclear and neutral binuclear palladium(ii) complexes for C-C and C-N bond-forming reactions}, journal = {Inorganic Chemistry}, volume = {46}, year = {2007}, month = {NOV}, pages = {11316{\textendash}11327}, type = {Article}, abstract = {

The short-bite aminobis(phosphonite), PhN{P(-OC10H6(μ-S)C10H6O-)}2 (2), containing a mesocyclic thioether backbone is synthesized by either treating PhN(PCl2)2 with 2 equiv of thiobis(2,2{\textquoteleft}-naphthol) or reacting chlorophosphite (-OC10H6(μ-S)C10H6O-)PCl (1) with aniline in the presence of a base. Treatment of 2 with an equimolar amount of Pd(COD)Cl2 in the presence of H2O affords a P-N-P-bridged and P,S-metalated binuclear complex, [PhN(P(-OC10H6(μ-S)C10H6O-)-κP)2Pd2Cl2{P(-OC10H6(μ-S)C10H6O-)(O)-κP,κS}2] (3), whereas the same reaction with 2 equiv of Pd(COD)Cl2 in the presence of H2O and Et3N produces the mononuclear anionic complex [{(-OC10H6(μ-S)C10H6O-)P(O)-κP,κS}PdCl2](Et3NH) (5). By contrast, reaction of 2 with 2 equiv of Pd(COD)Cl2 and H2O in the absence of Et3N gives the hydrogen phosphonate coordinated complex [{(-OC10H6(μ-S)C10H6O-)P(OH)}PdCl2] (4) which converts to the anionic complex in solution or in the presence of a base. Compound 2 on treatment with Pt(COD)X2 (X = Cl or I) afforded P-coordinated four-membered chelate complexes [PhN(P(-OC10H6(μ-S)C10H6O-)-κP)2PtX2] (6 X = Cl, 7 X = I). The crystal structures of compounds 2, 3, 5, and 7 are reported. Compound 3 is the first example of a crystallographically characterized binuclear palladium complex containing a bidentate bridging ligand and its hydrolyzed fragments forming metallacycles containing a palladium-phosphorus σ bond. All palladium complexes proved to be very good catalysts for the Suzuki-Miyaura and Mizoroki-Heck cross-coupling and amination reactions with excellent turnover numbers (TON up to 1.46 {\texttimes} 105 in the case of the Suzuki-Miyaura reaction).

}, doi = {10.1021/ic701674x}, author = {Punji, Benudhar and Mague, Joel T. and Balakrishna, Maravanji S.} } @article {42746, title = {Highly stable adamantyl-substituted pincer-ligated iridium catalyst for alkane dehydrogenation}, journal = {Organometallics}, volume = {29}, year = {2010}, month = {MAY}, pages = {2702{\textendash}2709}, abstract = {

The adamantyl-substituted pincer-ligand precursor AdPCP-H [(AdPCP = κ3-C6H3-2,6-(CH2PAd2)2); Ad = 1-adamantyl] has been synthesized by the reaction of 1,3-dibromoxylene with di-1-adamantylphosphine in the presence of triethylamine. Treatment of AdPCP-H with [Ir(COD)Cl]2 (COD = 1,5-cyclooctadiene) affords the pincer-ligated complex (AdPCP)IrHCl, which was crystallographically characterized. Dehydrohalogenation of (AdPCP)IrHCl either with LiBEt3H or with KOtBu, under hydrogen atmosphere, yields the hydrides (AdPCP)IrH2 and (AdPCP)IrH4. (AdPCP)IrH2 catalyzes dehydrogenation of alkanes with a level of activity comparable to that of the previously reported (tBuPCP)IrH2, while it is thermally much more robust than the tBuPCP analogue, as well as iPrPCP or tBuPOCOP pincer complexes.

}, doi = {10.1021/om100145q}, author = {Punji, Benudhar and Emge, Thomas J. and Goldman, Alan S.} } @article {49551, title = {Hybrid pincer (PNN)Ni(II) complex catalyzed selective C-H alkylation of pyridones using unactivated alkyl chlorides}, journal = {ACS Catalysis}, volume = {15}, year = {2025}, month = {FEB}, pages = {2987-2999}, type = {Article}, abstract = {

The use of readily accessible unactivated alkyl chlorides in the alkylation reaction to install valuable alkyl and methyl motifs into privileged heterocycles is an underdeveloped area. Herein, we report the regioselective C-H alkylation of diverse pyridones employing challenging unactivated alkyl chlorides as coupling partners, enabled by a strategically developed quinolinyl-based pincer (Ph2PNNQ)Ni(II) complex. The air-stable nickel catalyst is highly effective for the selective alkylation of functionalized 2-pyridones with both primary and secondary alkyl chlorides as well as for the unexpected C6 methylation, furnishing a wide range of 6-alkyl-2-pyridone scaffolds (78 examples). Remarkably, the alkyls bearing biologically and pharmacologically significant motifs, such as pterostilbene, nonyl phenol, sesamol, estrone, vitamin E, stigmasterol, cholesterol, and diosgenin, were compatible under this catalytic approach. The insights into the mechanism suggest that the alkylation reaction follows a Ni(II)/Ni(III)/Ni(IV) pathway involving the crucial two-step, one-electron oxidative addition of alkyl chloride. Several control studies, kinetics, and EPR analyses were performed to understand the detailed reaction pathway, further supported by density functional theory calculations.

}, keywords = {alkyl chlorides, C-H/C-Cl activation, hybrid pincer ligand, Mechanism, Nickel, pyridones}, issn = {2155-5435}, doi = {10.1021/acscatal.4c07173}, author = {Verma, Suryadev K. and Samal, Pragnya Paramita and Pradhan, Chandini and Pandey, Dilip K. and Krishnamurty, Sailaja and Punji, Benudhar} }