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This report describes the Na2PtCl4 catalyzed C-H arylation of arene substrates with diaryliodonium salts. The site selectivity of these reactions is predominantly controlled by steric factors. Remarkably, Na2PtCl4-catalyzed naphthalene arylation proceeds with opposite site selectivity compared to that obtained with Na2PdCl4 as the catalyst. Preliminary mechanistic studies provide evidence for a Pt(II)/Pt(IV) catalytic cycle involving rate-limiting C-C bond-forming reductive elimination.

Amino alcohols are important ligands for the asymmetric catalytic hydroamination of aminoallenes to form chiral pyrrolidines. The amino alcohol d-N-cyclohexyl-diphenylvalinol was synthesized and crystallized by slow evaporation from a 7:1 ether:ethanol mixture. The molecule crystallizes in the monoclinic space group P2 1 with unit cell parameters a = 8.0724(8) A, b = 14.4327(14) A, c = 8.6752(9) A and β = 107.098(2)° and contains one molecule in the asymmetric unit with all constituent atoms being on general positions. Close inspection of the solid-state structure revealed a strong intramolecular hydrogen bond between the hydrogen atom of the hydroxyl group and the amine nitrogen. Herein we report the solid state structure of the chiral amino alcohol D-N-cyclohexyl-diphenylvalinol, a molecule which can serve as a ligand for transition metal complexes that function as asymmetric hydroamination catalysts .

Sterically encumbered chiral l -amino alcohols with secondary amines and tertiary alcohols catalyze the enantioselective alkylation of benzaldehyde with diethyl zinc. Using 2 mol % of amino alcohol catalyst predominantly gave (R)-1-phenylpropanol with enantiomeric excesses of up to 61%. Using the in situ prepared titanium complex at 2 mol % as catalyst also favored the (R)-enantiomer with enantiomeric excesses of up to 73%. In almost all cases, the addition catalyzed by the titanium complex exhibited higher enantioselectivity than that of the amino alcohol ligand alone.

This report describes a comparison of the reactivity of a series of diimine PtII complexes as catalysts for H/D exchange between benzene and RCO2D. Substitution at the 2- and 6-positions of the N-aryl group and especially incorporation of halogens at these sites lead to significant increases in catalyst reactivity. Interestingly, marked differences in the structure activity relationship were observed in this catalytic study compared to previously reported stoichiometric investigations of C–H activation at PtII diimine complexes.

This letter describes a new method for the highly site- and chemoselective Pd-catalyzed direct arylation of naphthalene. Tuning the structure of the diimine-ligated Pd catalyst results in formation of the α-arylated product in high yield and >50:1 selectivity. This is, to our knowledge, the first systematic evaluation of catalyst control in the C−H arylation of an unactivated aromatic substrate. Preliminary studies implicate an unusual mechanism involving sequential naphthalene π-coordination/metalation at PdIV.

This paper describes an efficient synthesis of the cationic platinum complex [(N-CH3-bpym)PtCl2]+ (N-CH3-bpym = N-methylbipyrimidinium) and evaluation of its catalytic activity in H/D exchange reactions of CH4 (with D2SO4) and benzene (with CF3CO2D). With both substrates [(N-CH3-bpym)PtCl2]+ shows C−H activation reactivity comparable to that of its neutral analogue (bpym)PtCl2 (bpym = bipyrimidine). The origin of this similar reactivity is proposed to be the in situ formation of the same active catalyst in both cases.

This paper describes a protocol for the direct comparison of diverse Pt catalysts in the H/D exchange between C6H6 and TFA-d1, CD3CO2D, and TFE-d3 using turnover number (TON) as a standard metric. An initial survey of Pt complexes, including commercial Pt salts (PtCl2, K2PtCl4) and Pt chloride complexes containing bidentate and tridentate nitrogen donor ligands, has been conducted. These studies have established that the addition of AgOAc (in TFA-d1) or AgBF4 (in CD3CO2D and TFE-d3) displaces the Cl ligands on the Pt precatalyst, which leads to dramatically increased turnover numbers. In general, PtCl2 and K2PtCl4 provided the fewest turnovers, and species containing bidentate ligands afforded higher turnover numbers than those with tridentate ligands. A diimine Pt complex was found to be a top performing catalyst for H/D exchange with all deuterium sources examined. Interestingly, the relative reactivity of many of the catalysts varied dramatically upon changing the deuterium source, highlighting the nee...

A variety of sterically encumbered amino alcohol ligands were prepared in a two-step modular synthesis. The titanium complexes of these ligands were prepared in situ and used as catalysts for hydroamination. The intramolecular hydroamination of 6-methyl-hepta-4,5-dienylamine at 135 °C with 5 mol % catalyst gave exclusively 2-(2-methyl-propenyl)-pyrrolidine with enantiomeric excesses up to 16%.

The first example of a Pt-catalyzed direct C—H arylation of simple arenes (I), (IV), and (VI) with diaryliodonium salts (II) is described.

Advances in the chemistry of high-oxidation-state copper and palladium demonstrate their great potential as catalysts. Homogeneous copper and palladium catalysts are used to synthesize a broad range of organic molecules, including pharmaceuticals, commodity chemicals and polymers. Improvements in the activity, selectivity and scope of these catalysts have the potential to increase their usefulness and reduce the environmental impact of the chemical reactions. In this Review, Amanda Hickman and Melanie Sanford summarize recent advances by organometallic chemists working with a subset of catalysts that operate through an intermediate containing palladium in the +3 or +4 oxidation state or copper in the +3 oxidation state. Copper and palladium catalysts are critically important in numerous commercial chemical processes. Improvements in the activity, selectivity and scope of these catalysts could drastically reduce the environmental impact, and increase the sustainability, of chemical reactions. One rapidly developing strategy for achieving these goals is to use ‘high-valent’ organometallic copper and palladium intermediates in catalysis. Here we describe recent advances involving both the fundamental chemistry and the applications of these high-valent metal complexes in numerous synthetically useful catalytic transformations.

High reversibility during crystallization leads to relatively defect-free crystals through repair of nonperiodic inclusions, including those derived from impurities. Microporous coordination polymers (MCPs) can achieve a high level of crystallinity through a related mechanism whereby coordination defects are repaired, leading to single crystals. In this work, we discovered and exploited the fact that this process is far from perfect for MCPs and that a minority ligand that is coordinatively identical to but distinct in shape from the majority linker can be inserted into the framework, resulting in defects. The reaction of Zn(II) with 1,4-benzenedicarboxylic acid (H(2)BDC) in the presence of small amounts of 1,3,5-tris(4-carboxyphenyl)benzene (H(3)BTB) leads to a new crystalline material, MOF-5(O(h)), that is nearly identical to MOF-5 but has an octahedral morphology and a number of defect sites that are uniquely functionalized with dangling carboxylates. The reaction with Pd(OAc)(2) impregnates the metal ions, creating a heterogeneous catalyst with ultrahigh surface area. The Pd(II)-catalyzed phenylation of naphthalene within Pd-impregnated MOF-5(O(h)) demonstrates the potential utility of an MCP framework for modulating the reactivity and selectivity of such transformations. Furthermore, this novel synthetic approach can be applied to different MCPs and will provide scaffolds functionalized with catalytically active metal species.

Advances in the chemistry of high-oxidation-state copper and palladium demonstrate their great potential as catalysts. Homogeneous copper and palladium catalysts are used to synthesize a broad range of organic molecules, including pharmaceuticals, commodity chemicals and polymers. Improvements in the activity, selectivity and scope of these catalysts have the potential to increase their usefulness and reduce the environmental impact of the chemical reactions. In this Review, Amanda Hickman and Melanie Sanford summarize recent advances by organometallic chemists working with a subset of catalysts that operate through an intermediate containing palladium in the +3 or +4 oxidation state or copper in the +3 oxidation state. Copper and palladium catalysts are critically important in numerous commercial chemical processes. Improvements in the activity, selectivity and scope of these catalysts could drastically reduce the environmental impact, and increase the sustainability, of chemical reactions. One rapidly developing strategy for achieving these goals is to use ‘high-valent’ organometallic copper and palladium intermediates in catalysis. Here we describe recent advances involving both the fundamental chemistry and the applications of these high-valent metal complexes in numerous synthetically useful catalytic transformations.