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By employing X(CH2CH2S-)2 (X = S, tpdt; X = O, opdt; X = NPh, npdt) as bridging ligands, four thiolate-bridged dinickel complexes supported by phosphine ligands, [(dppe)Ni(μ-1SSS':2SS-tpdt)Ni(dppe)][PF6]2 (1[PF6]2, dppe = Ph2P(CH2)2PPh2), [(dppe)Ni(μ-1SSN:2SS-npdt)Ni(dppe)][PF6]2 (2[PF6]2) and [(dppe)Ni(t-Cl)(μ-1SSX:2SS-C4H8S2X)Ni(dppe)][PF6] (3[PF6], X = S; 4[PF6], X = O) were facilely obtained by the salt metathesis reaction. These four thiolate-bridged dinickel complexes have all been fully characterized by spectroscopic methods and X-ray crystallography. In 2[PF6]2, elongation of the Ni-N bond distance, possibly caused by steric hindrance, indicates that the pendant nitrogen group shuttles between the two nickel centers in solution, which is evidenced by 31P{1H} NMR spectroscopic results. Furthermore, these thiolate-bridged dinickel complexes have all been proved to be electrocatalysts for proton reduction to hydrogen. Notably, complex 2[PF6]2 featuring a pendant amine group in the secondary coordination sphere exhibits the best catalytic activity at a relatively low overpotential.

Epoxidation of olefins stands out as a crucial class of reactions and is of great interest in academic research and industry due to the production of various important fine chemicals and intermediates. Manganese complexes have the potential to catalyze the epoxidation of olefins with high efficiency. Magnetic nanocatalysts have attracted significant attention for immobilizing homogeneous transition metal complexes. Easy separation by external magnetic fields, nontoxicity, and a core shell structure are the main advantages of magnetic nanocatalysts over other heterogeneous catalysts. The method of functionalizing magnetic nanoparticles and of anchoring homogeneous metal complexes has significant effects on catalytic performance. Therefore, a critical review of recent research progress on manganese complexes’ immobilization on magnetic nanoparticles for liquid phase olefin epoxidation is necessary. In this work, magnetic nanoparticles are categorized according to their preparation procedures and structures. The physical/chemical properties, catalytic performance for olefin epoxidation, reusability and plausible reaction mechanisms will be discussed, in an attempt to unravel the structure–function relationship and to guide the future study of MNPs’ design for olefin epoxidations.

A base-controlled regiodivergent azidation of trifluoromethyl alkenyl triflates providing either (E)-3-azido-1-aryl-4,4,4-trifluorobut-1-ene (CF3-containing allyl azides) or (Z)-1-azido-1-aryl-4,4,4-trifluorobut-1-ene (CF3-containing alkenyl azides) is described. Catalyzed by Et3N, the azidation of trifluoromethyl alkenyl triflates with TMSN3 gave CF3-containing allyl azides. On the other hand, using stoichiometric DBU, the regioisomeric azidation products, CF3-containing alkenyl azides, were obtained in good yield. A further transformation for CF3-containing amines, triazoles, and azirines highlights the practical applicability of this transition-metal-free protocol.

By employing S(CH2CH2S–)2 (tpdt) and O(CH2CH2S–)2 (opdt) as bridging ligands, two nickel–iron and two nickel–ruthenium heterodimetallic complexes, [Cp*M(μ-1κ3SSS′:2κ2SS-tpdt)Ni(dppe)][PF6] (1, M = Fe; 3, M = Ru) and [Cp*M(μ-1κ3SSO:2κ2SS-opdt)Ni(dppe)][PF6] (2, M = Fe; 4, M = Ru) (Cp* = η5-C5Me5; dppe = Ph2P(CH2)2PPh2), were obtained by a one-pot synthetic method and were identified by spectroscopy and X-ray crystallography. At 1 atm of CO, the pendant oxygen atom dissociated from the iron or ruthenium center and rapidly transferred to the nickel center when a CO molecule attacked the iron or ruthenium center in 2 and 4. However, there was no similar reaction occurring in 1 and 3 with the pendant sulfur atom. We confirmed the solid-state structure of the CO complex [Cp*Fe(t-CO)(μ-1κ2SS:2κ3SSO-opdt)Ni(dppe)][PF6] (5), which represents a possible configuration in the CO-inhibited state of [NiFe]-hydrogenase and exhibits no catalytic activity in electrochemical proton reduction.

A base-controlled regiodivergent azidation of trifluoromethyl alkenyl triflates providing either (E)-3-azido-1-aryl-4,4,4-trifluorobut-1-ene (CF

The novel thioether-dithiolate-bridged diiron complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*] (1, Cp* = η5-C5Me5; tpdt = S(CH2CH2S−)2) has been prepared by the reaction of [Cp*FeCl]2 with Li2(tpdt) in THF. Given the thermodynamic instability of 1, a one-electron oxidation was performed with Fc·PF6 (Fc = ferrocene) affording 1[PF6]. Treatment of 1[PF6] with CO or tBuNC in CH2Cl2 gave complexes [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-CO)}][PF6] (2[PF6]) and [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-tBuNC)}][PF6] (3[PF6]). In addition, complex 1[PF6] can be further oxidized into [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)FeCp*][PF6]2 (1[PF6]2) by Fc·PF6 in THF, while in the presence of MeCN resulting in the formation of complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt){Cp*Fe(η1-MeCN)}][PF6]2 (4[PF6]2). When the solution of complex 1 in THF was warmed to room temperature, thioether-dithiolate-bridged trinuclear iron complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpdt)Fe(μ-2κ2SS:3κ3SSS′-tpdt)FeCp*] (5), which can be oxidized into complex [Cp*Fe(μ-1κ3SSS′:2κ2SS-tpd...