Terminal Iron Carbyne Complexes Derived from Arrested CO2 Reductive Disproportionation

The encumbered tetraisocyanide dianion Na₂[Fe(CNAr )₄] reacts with two molecules of CO₂ to effect reductive disproportionation to CO and carbonate ([CO₃]²⁻). When the reaction is performed in the presence of silyl triflates, reductive disproportionation is arrested by silylative esterification of a mono‐CO₂ adduct. This results in the formation of four‐coordinate terminal iron carbynes possessing an aryl carbamate substituent owing to the direct attachment of an C(O)OSiR₃ group to an isocyanide nitrogen atom. Crystallographic, spectroscopic, and computational analyses of these iron–carbon multiply bonded species reveal electronic structure properties indicative of a conformationally locked iron carbyne unit.     

Pentadiynylidyne and Pentacarbido Complexes

The reaction of the halocarbyne [W(≡CBr)(CO)₂(Tp*)] (Tp*=hydrotris(3,5‐dimethylpyrazol‐1‐yl)borate) with trimethylsilyl‐butadiyne, mediated by [Pd(PPh₃)₄] and CuI, affords the first pentadiynylidyne complex [W(≡CC≡CC≡CSiMe₃)(CO)₂(Tp*)]. Desilylation provides a general route to heterobimetallic pentacarbido complexes, including [(Tp*)(CO)₂W(μ‐C₅)(PPh₃)₂Ru(η‐C₅H₅)] and [(Ph₃P)₂(CO)HIr{(μ‐C₅)W(CO)₂(Tp*)}₂].     

Flexible Platinum(0) Coordination to a Ditungsten Ethanediylidyne

The lithiocarbyne [W(≡CLi)(CO)₂(Tp*)] (Tp*=hydrotris(3,5‐dimethylpyrazol‐1‐yl)borate) reacts with [PtCl₂(L₂)] (L₂=1,5‐cyclo‐octadiene, norbornadiene) to furnish ditungsten ethanediylidyne complexes, [W₂{μ‐C₂Pt(L₂)}(CO)₄(Tp*)₂], wherein a trigonal platinum(0) center unsymmetrically ligates one W≡C bond in the solid state but rapidly shimmies between the two W≡C bonds in solution. The η⁴‐dienes are displaced by monodentate CO or isocyanide ligands to provide derivatives where both W≡C bonds coordinate to a single Pt⁰ center, attended by significant distortion of the WCCW spine.     

Effects of acid treatment on activated carbon used as a support for Rb and K catalyst for C2F5I synthesis and its mechanism

In the present work, the activated carbon (AC) support was treated with HCl, HNO₃ and HF solution. The order of catalyst dispersion was as follows: Rb-K/AC-HNO₃ > Rb-K/AC-HF > Rb-K/AC-HCl > Rb-K/AC. The same sequence was also observed for the amount of the acid surface oxygen groups on AC, but not for the basicity of the catalyst. The key role of acid treatment on AC surface chemistry and the basic sites, which are closely related to catalyst dispersion and basicity, is examined to rationalize these findings. On the other hand, a consideration of the reaction mechanism suggests that the reaction proceeds via CF₂ carbenes formed on the catalyst surface as intermediates, followed by carbine disproportionation to CF₃ radicals and CF₃CF₂ radicals, followed by reaction with I₂ to produce CF₃CF₂I, and it was also found that the Rb-K/AC-HCl catalyst with a high dispersion and moderate basicity was helpful for the enhancement of catalytic activity for C₂F₅I synthesis.