E–H Bond Activations and Hydrosilylation Catalysis with Iron and Cobalt Metalloboranes

An exciting challenge in transition metal catalyst design is to explore whether earth-abundant base metals such as Fe, Co, and Ni can mediate two-electron reductive transformations that their precious metal counterparts (e.g., Ru, Rh, Ir, and Pd) are better known to catalyze. Organometallic metalloboranes are an interesting design concept in this regard because they can serve as organometallic frustrated Lewis pairs. To build on prior studies with nickel metalloboranes featuring the DPB and ^(Ph)DPB^(Mes) ligands in the context of H_2 and silane activation and catalysis (DPB = bis(o-diisopropylphosphinophenyl)phenylborane, ^(Ph)DPB^(Mes) = bis(o-diphenylphosphinophenyl)mesitylborane), we now explore the reactivity of iron, [(DPB)Fe]_2(N_2), 1, and cobalt, (DPB)Co(N_2), 2, metalloboranes toward a series of substrates with E–H bonds (E = O, S, C, N) including phenol, thiophenol, benzo[h]quinoline, and 8-aminoquinoline. In addition to displaying high stoichiometric E–H bond activation reactivity, complexes 1 and 2 prove to be more active catalysts for the hydrosilylation of ketones and aldehydes with diphenylsilane relative to (^(Ph)DPB^(Mes))Ni. Indeed, 2 appears to be the most active homogeneous cobalt catalyst reported to date for the hydrosilylation of acetophenone under the conditions studied

A perspective of solutions for membrane instabilities in olefin/paraffin separations: a review

Light olefins are mainly produced by naphtha steam cracking, which is among the more energy intensive processes in the petrochemical industry. To save energy, some alternatives have been proposed to partially replace or combine with cryogenic distillation the conventional technology to separate olefins and paraffins. Within this aim, facilitated transport membranes, mainly with Ag+cations as selective carriers, have received great attention owing to the high selectivity and permeance provided. However, to be used industrially, the undesirable instability associated with the Ag+ cation should be considered. Poisonous agents and polymer membrane materials are sources of Ag+ deactivation. In recent years, great achievements on the separation performance have been reported, but the current challenge is to maintain the selectivity in long-term separation processes. This work presents a critical analysis of the potential causes of Ag+ deactivation and points out some alternatives that have been proposed to overcome the hurdle. This review highlights and critically analyses some perspectives of the ongoing development and application of facilitated transport membranes.The authors thank the Brazilian Federal Agency for Support and Evaluation of Graduate Education − CAPES (PDSE Grant 88881.134232/2016-01) and the Spanish Ministry of Economy, Industry and Competitiveness (CTQ2015-66078-R and CTQ2016-75158-R projects, Spain-FEDER 2014-2020) for financial support