1,3,5-Tris(thiocyanatomethyl)mesitylene as a Ligand. Pseudooctahedral Molybdenum, Manganese, and Rhenium Carbonyl Complexes and Copper and Silver Dimers. Copper-Catalyzed Carbene- and Nitrene-Transfer Reactions

Recent Advances in Catalytic Alkyne Transformation via Copper Carbene Intermediates

As one of the abundant and inexpensive metals on the earth, copper has demonstrated broad applications in synthetic chemistry and catalysis. Among these copper-catalyzed advances, copper carbenes are versatile and reactive intermediates that can mediate a variety of transformations, which have attracted much attention in the past decades. The present review summarizes two different reaction models that take place between a copper carbene intermediate and alkyne species, including the cross-coupling reaction of copper carbene intermediate with terminal alkyne, and the addition of copper carbene intermediate onto the C–C triple bond. This article will cover the profile from 2010 to 2021 by placing emphasis on the detailed catalytic models and highlighting the synthetic applications offered by these practical and mild methods.

Binding Interactions in Copper, Silver and Gold π-Complexes

The copper(I), silver(I), and gold(I) metals bind π‐ligands by σ‐bonding and π‐back bonding interactions. These interactions were investigated using bidentate ancillary ligands with electron donating and withdrawing substituents. The π‐ligands span from ethylene to larger terminal and internal alkenes and alkynes. Results of X‐ray crystallography, NMR, and IR spectroscopy and gas phase experiments show that the binding energies increase in the order Ag<Cu<Au and the binding energies are slightly higher for alkynes than for alkenes. Modulation of the electron density at the metal using substituents on the ancillary ligands shows that the π‐back bonding interaction plays a dominant role for the binding in the copper and gold complexes.

Nucleophilic Migratory Cyclopropenation of Activated Alkynes: A Nonmetal Approach to Unbiased Cyclopropenes

An unprecedented reductive [2 + 1] annulation of α-keto esters with alkynones mediated by P(NMe₂)₃ is described. Although this nonmetal cyclopropenation is a nucleophilic process, attributed to the ester migration via a formal [2 + 2] cycloaddition reaction of Kukhtin-Ramirez adducts and alkynones followed by a fragmentation, cyclopropenes with an unbiased alkene scaffold are formed in good to excellent yields, thus providing a promising complementarity to electrophilic metal-catalyzed cyclopropenation.

Isolable Copper(I) η2-Cyclopropene Complexes

Treatment of bis(pyrazolyl)borate ligand supported [(CF₃)₂Bp]Cu(NCMe) with 1,2,3-trisubstituted cyclopropenes produced thermally stable copper(I) η²-cyclopropene complexes amenable to detailed solution and solid-state analysis. The [(CF₃)₂Bp]Cu(NCMe) also catalyzed [2 + 1]-cycloaddition chemistry of terminal and internal alkynes with ethyl diazoacetate affording cyclopropenes, including those used as ligands in this work. The tris(pyrazolyl)borate [(CF₃)₂Tp]Cu(NCMe) is a competent catalyst for this process as well. The treatment of [(CF₃)₂Tp]Cu with ethyl 2,3-diethylcycloprop-2-enecarboxylate substrate gave an O-bonded rather than a η²-cyclopropene copper complex.

Recyclable heterogeneous metal foil-catalyzed cyclopropenation of alkynes and diazoacetates under solvent-free mechanochemical reaction conditions

Silver and copper foil were found to be effective, versatile and selective heterogeneous catalysts for the cyclopropenation of terminal and internal alkynes under mechanochemical reaction conditions.

Silver and copper foil were found to be effective, versatile and selective heterogeneous catalysts for the cyclopropenation of terminal and internal alkynes under mechanochemical reaction conditions. This methodology enables the functionalization of a wide range of terminal or internal alkynes under ambient, aerobic, and solvent-free conditions. Finally, we have demonstrated a unique and versatile one-pot domino Sonogashira-cyclopropenation mechanochemical reaction for the formation of complex cyclopropenes.

Cyclopropenation of internal alkynylsilanes and diazoacetates catalyzed by copper(i) N-heterocyclic carbene complexes

Copper(i) N-heterocyclic carbene (CuNHC) complexes are effective catalysts for the cyclopropenation of internal alkynylsilanes and diazoacetates compounds.

Exploring the coordinative adaptation and molecular shapes of trinuclear CuII2MII (M = Zn/Cd) complexes derived from salen type Schiff bases: structural and theoretical studies

Structural analyses and DFT studies of three new hetero-metallic compounds established that a slight modification in the ligand system or changes in the central metal ion can stabilize interesting novel structures with thiocyanate ion.

Crystal structures of two bis-(iodo-meth-yl)benzene derivatives: similarities and differences in the crystal packing

The isomeric derivatives 1,2-bis-(iodo-meth-yl)benzene, (I), and 1,3-bis-(iodo-meth-yl)benzene (II), both C8H8I2, were prepared by metathesis from their di-bromo analogues. The ortho-derivative, (I), lies about a crystallographic twofold axis that bis-ects the C-C bond between the two iodo-methyl substituents. The packing in (I) relies solely on C-H⋯I hydrogen bonds supported by weak parallel slipped π-π stacking inter-actions [inter-centroid distance = 4.0569 (11) Å, inter-planar distance = 3.3789 (8) Å and slippage = 2.245 Å]. While C-H⋯I hydrogen bonds are also found in the packing of (II), type II, I⋯I halogen bonds [I⋯I = 3.8662 (2) Å] and C-H⋯π contacts feature prominently in stabilizing the three-dimensional structure.