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The first example of a triply cyclometalated homopolynuclear tri-Ir(III) complex with additional carbene donors is presented. Cooperative catalysis and the interplay between homogenous and heterogeneous catalyses are discussed for the tri-Ir(III) complex and a related non-cyclometalated tri-Pd(II) complex.

Complexes of mesoionic carbene (MIC) ligands are gaining immense popularity in organometallic chemistry and homogeneous catalysis. We present here a series of palladium(II) complexes that are comprised of MIC donor ligands, and we demonstrate their applications in α-arylation, α-methylation, and Suzuki-Miyaura coupling reactions. All the complexes have been structurally characterized by X-ray crystallographic analysis. These palladium(II) complexes are potent precatalysts and they deliver good to excellent yields for both αarylation and Suzuki-Miyaura coupling reactions. A palladium(II) complex bearing two MIC units in a trans fashion is [a] 111 used for chemoselective Suzuki-Miyaura coupling reaction. This complex delivers lower yields in α-arylation reactions compared with PEPPSI-type complexes, however, it gives an α-methylated product when the reaction is conducted in N,N-dimethylformamide. Mercury poisoning experiments suggest that the Suzuki-Miyaura coupling reaction likely proceeds via Pd nanoparticles. However, the α-arylation reaction proceeds homogeneously, as shown by the negative mercury poison test. The present results thus open up new avenues for MIC ligands in catalytic α-arylation and α-methylation reactions.recently been used in photophysical applications. [14] In addition, substituted 1,2,3-triazoles can easily be synthesized by the 1,3-dipolar cycloaddition reaction of an azide to an alkyne (click reaction). [15] Alkylation of the triazoles results in the formation of the corresponding 1,2,3-triazolium salts, which are the precursors for the 1,2,3-triazol-5-ylidenes.We present here the synthesis of PEPPSI-type palladium(II) 1,2,3-triazol-5-ylidene complexes and Pd(MIC) 2 X 2 (X = halide) type complexes along with their applications in α-arylation, αmethylation, and Suzuki-Miyaura cross coupling reactions. All the complexes have been characterized by 1 H, 13 C{ 1 H}, 2D correlation NMR spectroscopy, mass spectrometry, and also by Xray crystallography. Results and Discussion Synthesis and Characterization of ComplexesThe triazolium salts (R)-1 and (S)-1 were prepared from the corresponding triazoles by using methyl iodide as methylating agent under heating conditions by using a reported procedure. [16] The reaction of the triazolium salt (R)-1 with PdCl 2 and K 2 CO 3 in pyridine or with the corresponding chloro-substituted pyridines resulted in the formation of PEPPSI-type palladium(II) complexes (R)-[2], (R)-[3] and (R)-[4] (Scheme 1). Full Paper Scheme 1. Preparation of complexes (R)-[2], (R)-[3] and (R)-[4].The triazolium salts as well as the palladium(II) complexes were isolated in pure enantiomeric forms. All the complexes were obtained in reasonable yields of 52-63.5 %, they were well soluble in chlorinated solvents such as dichloromethane and chloroform and they were all stable towards both air and moisture. The formation of these complexes was easily monitored by 1 H NMR spectroscopy, which showed the disappearance of the triazolium C-H proton signal (δ = 9.20 ppm) [16] for the triazol...

Heat shock proteins of 70 kDa (Hsp70s) partner with structurally diverse Hsp40s (J proteins), generating distinct chaperone networks in various cellular compartments that perform myriad housekeeping and stress-associated functions in all organisms. Plants, being sessile, need to constantly maintain their cellular proteostasis in response to external environmental cues. In these situations, the Hsp70:J protein machines may play an important role in fine-tuning cellular protein quality control. Although ubiquitous, the functional specificity and complexity of the plant Hsp70:J protein network has not been studied. Here, we analyzed the J protein network in the cytosol of Arabidopsis thaliana and, using yeast genetics, show that the functional specificities of most plant J proteins in fundamental chaperone functions are conserved across long evolutionary timescales. Detailed phylogenetic and functional analysis revealed that increased number, regulatory differences, and neofunctionalization in J proteins together contribute to the emerging functional diversity and complexity in the Hsp70:J protein network in higher plants. Based on the data presented, we propose that higher plants have orchestrated their “chaperome,” especially their J protein complement, according to their specialized cellular and physiological stipulations.