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This work details the synthesis and characterization of low-coordinate Zn(II)-based organocations [(NHC)Zn(R)]+ incorporating extremely bulky NHCs [ITr] and [IAd] ([ITr] = ([ITr] = [(HCNCPh3)2C:]; [IAd] = [(HCNAd)2C:], Ad = adamantyl)). Their structural features and particularities are thoroughly assessed as well as their air and water tolerance. Neutral ITr and IAd adducts [(ITr)Zn(R)2] (1, R = Me; 2, R = Et) and [(IAd)Zn(R)2] (3, R = Me; 4, R = Et) were synthesized by reaction of carbene [ITr] or [IAd] with a stoichiometric amount of [ZnR2] and isolated in good yields. Despite the steric bulk of [ITr] and [IAd], neutral compounds 1–4 are robust and the solid state structure of adduct 3 was established through X-ray crystallographic studies as a trigonal monomer Zn(II) species. Adducts 1–4 may readily be ionized by [Ph3C][B(C6F5)4] to afford two-coordinate Zn(II) alkyl cations [(ITr)Zn(Me)]+ ([5]+) and [(ITr)Zn(Et)]+ ([6]+), [(IAd)Zn(Me)]+ ([7]+) and [(IAd)Zn(Me)]+ ([8]+), all isolated in high yields (>80%) as [B(C6F5)4]− salts, which were fully characterized. Remarkably, cation [(ITr)Zn(C6F5)]+ ([9]+), prepared by reaction of [5][B(C6F5)4] with [B(C6F5)3], features π–arene interactions with the electrophilic Zn(II), as deduced from solid state data and further completed by DFT-estimated non-covalent interactions (NCI), indicating that [ITr] may provide substantial steric and electrostatic stabilization. The latter certainly explains the remarkable stability of [(ITr)Zn(C6F5)]+ ([9]+) towards hydrolysis at RT, as it only coordinates H2O to afford an unprecedented stable Zn–OH2 organocation [10]+. Also noteworthy, H2O coordination is reversible allowing recovery of [(ITr)Zn(C6F5)]+ cation, even after prolonged air exposure. Yet, controlled hydrolysis of [(ITr)Zn(C6F5)]+ may occur upon heating with selective protonolysis of the Zn–C6F5 bond to afford structurally characterized dication [(ITr)Zn(OH)]22+ [11]2+. Interestingly, despite steric hindrance, the air-/water-tolerant cation [(ITr)Zn(C6F5)]+ is an effective CO2 hydrosilylation catalyst, and was also shown to mediate imine hydrogenation catalysis. [ABSTRACT FROM AUTHOR]

This document provides an overview of a special issue published in the Organic and Polymer Chemistry section of the journal Catalysts. The issue includes contributions from 18 members of the journal's Editorial Board and covers a wide range of topics in the fields of homogeneous catalysis, organometallic chemistry, and polymer chemistry. The special issue consists of three review articles and four scientific papers, covering subjects such as gold chemistry, transition metal phosphide nanoparticle catalysts, and cobalt complexes. The document also mentions the importance of communication and academic exchanges among researchers in the field of chemistry. [Extracted from the article]

We herein report the first use of thiosquaramides as polymerization catalysts, which are shown to be effective for the controlled ROP of lactide in the presence of an alcohol source and NEt3. Comparison of their catalytic performances with the less acidic squaramides are also discussed. The observed catalytic activity of variously N‐substituted thiosquaramides suggest that a balanced NH Brønsted acidity is required for optimal performance. Most interestingly and rather unexpectedly, DFT‐supported calculations on thiosquaramide‐mediated lactide ROP catalysis suggest that secondary interactions between the thiosquaramide N‐substituents and the incoming lactide (presently of type C‐H⋅⋅⋅π‐arene) are crucial for catalytic activity. Though this type of interactions is quite common in organo‐catalysis, it has rarely been evidenced to play a key role in the area of organo‐catalyzed polymerizations. Such catalyst substituents/substrate interactions may well play a significant role in the catalytic performances of various other systems. [ABSTRACT FROM AUTHOR]

We herein report on the synthesis, structure, and use in alkyne hydroboration catalysis of [(IPrCl)Zn−R]+ and [(ItBu)Zn−R]+ cations bearing IPrCl (IPrCl=1,3‐bis[2,6‐bis(1‐methylethyl)phenyl]‐4,5‐dichloro‐1,3‐dihydro‐imidazol‐2‐ylidene) and the sterically demanding ItBu carbene (ItBu=1,3‐bis(1,1‐dimethylethyl)−1,3‐dihydro‐imidazol‐2‐ylidene). Ionization of neutral precursors [(IPrCl)ZnR2] (1 a, R=Et; 1 b, R=Me) and [(ItBu)ZnEt2] (2) with one equivalent of [Ph3C][B(C6F5)4] led to with robust and stable two‐coordinate ZnII cations [(IPrCl)Zn−R]+ (3 a, R=Et; 3 b, R=Me) and [(ItBu)Zn−Et]+ (4), respectively, all isolated as [B(C6F5)4]− salts. Further derivatization of alkyl cations 3 b and 4 by reaction with one equivalent of [B(C6F5)3] afforded cations [(IPrCl)Zn−C6F5]+ (5) and [(ItBu)Zn−C6F5]+ (6) as [B(C6F5)4]− salts, with cation 6 displaying a limited stability in solution. The molecular structures of cations 3 b, 4 and 5 were confirmed through X‐ray diffraction studies. Among stable cations, Fluoride ion affinity (FIA) estimations agree with cation 5 being the most Lewis acidic in thus far reported [(IPrCl)Zn−R]+ cations. In the presence of pinacol borane and 1‐octyne, cations 3 a–b, 5 and [(IPrCl)Zn−C6F5]+ (5 mol%) slowly catalyze the selective cis‐hydroboration of 1‐octyne to the vinylborane product A. Cation 5 also mediates 2‐hexyne hydroboration to afford a mixture of hydroboration products B and C. In the case of hydroboration catalysis mediated by cations 5 and [(IPrCl)Zn−C6F5]+, experimental data and preliminary DFT calculations are consistent a Lewis‐acid‐type catalysis. [ABSTRACT FROM AUTHOR]