The 17e(-) monoradical [Mn(CO)5 ] is widely recognized as an unstable organometallic transient and is known to dimerize rapidly with the formation of a MnMn single bond. As a result of this instability, isolable analogues of [Mn(CO)5 ] have remained elusive. Herein, we show that two sterically encumbering isocyanide ligands can destabilize the MnMn bond leading to the formation of the isolable, manganese(0) monoradical [Mn(CO)3 (CNAr(Dipp2) )2 ] (Ar(Dipp2) =2,6-(2,6-(iPr)2 C6 H3 )2 C6 H3 ). The persistence of [Mn(CO)3 (CNAr(Dipp2) )2 ] has allowed for new insights into nitrosoarene spin-trapping studies of [Mn(CO)5 ].

The preparation of 3D and 2D Cu(I) coordination networks using ditopic m-terphenyl isocyanides is described. The incorporation of sterically encumbering substituents enables the controlled, solid-state preparation of Cu(I) tris-isocyanide nodes with a labile solvent ligand in a manner mirroring solution-phase chemistry of monomeric complexes. The protection afforded by the m-terphenyl groups is also shown to engender significant stability towards heat as well as acidic or basic conditions, resulting in robust single-metal-node networks that can transition from 3D to 2D extended structures.

The development of catalysts capable of fast, robust C-H bond amination under mild conditions is an unrealized goal despite substantial progress in the field of C-H activation in recent years. A Mn-based metal-organic framework (CPF-5) is described that promotes the direct amination of C-H bonds with exceptional activity. CPF-5 is capable of functionalizing C-H bonds in an intermolecular fashion with unrivaled catalytic stability producing >10 turnovers.

No abstract

A permanently porous, three-dimensional metal-organic material formed from zero-valent metal nodes is presented. Combination of ditopic m-terphenyl diisocyanide, [CNAr], and the d Ni(0) precursor Ni(COD), produces a porous metal-organic material featuring tetrahedral [Ni(CNAr)] structural sites. X-ray absorption spectroscopy provides firm evidence for the presence of Ni(0) centers, whereas gas-sorption and thermogravimetric analysis reveal the characteristics of a robust network with a microdomain N-adsorption profile.

To circumvent complications with redox-active ligands commonly encountered in the study of manganese electrocatalysts for CO reduction, we have studied the electrochemistry of the manganese mixed carbonyl/isocyanide complexes XMn(CO)(CNAr) (X = counteranion), to evaluate the pairing effects of the counteranion and their influence over the potential necessary for metal-based reduction. The complexes described herein have been shown to act as functional analogues to the known homoleptic carbonyl manganese complexes [Mn(CO)] (n = 1-, 0, 1+). The m-terphenyl isocyanide ligand CNAr improves the kinetic stability of the resulting mixed carbonyl/isocyanide systems, such that conversion among all three oxidation states is easily effected by chemical reagents. Here, we have utilized an electrochemical study to fully understand the redox chemistry of this system and its ability to facilitate CO reduction and to provide comparison to known manganese-based CO electrocatalysts. Two complexes, BrMn(CO)(CNAr) and [Mn(THF)(CO)(CNAr)]OTf, have been studied using infrared spectroelectrochemistry (IR-SEC) to spectroscopically characterize the redox states of these complexes during the course of electrochemical reactions. A striking difference in the necessary potential leading to the first one-electron reduction has been found for the halide and triflate species, respectively. Complete selectivity for the formation of CO and CO is observed in the reactivity of [Mn(CO)(CNAr)] with CO, which is deduced via the trapping and incorporation of liberated CO into the zerovalent species Mn(CO)(CNAr) to form the dimers Mn(CO)(CNAr) and Mn(CO)(CNAr).

The dimeric bridging carbonyl complexes [(μ-CO) 2 [CpCo] 2 ] n (n = 0, 1−) have occupied a central position in the understanding of metal−metal bonding interactions when bridging ligands are present. Based on simple electron-counting formalisms, these dimers have been proposed to possess formal Co−Co bond orders of 2 and 1.5, respectively. However, this simple bonding scheme has been contrasted by molecular orbital theory considerations, as well as spectroscopic data that probes M−M bonding interactions generally. While this system has received considerable attention, there has been a long-standing synthetic limitation in that the doubly reduced dianionic dimer, [(μ-CO) 2 [CpCo] 2 ] 2− , has not been amenable to isolation, thereby precluding an analysis of ostensible full-integer reduction in a homologous series. Accordingly, herein is presented the synthesis of a homologous, three-membered series of bridging-isocyanide [(μ-CNAr) 2 [CpCo] 2 ] n dimers, including the dianionic member. Structural and spectroscopic analyses of these [(μ-CNAr) 2 [CpCo] 2 ] n dimers, which feature the m-terphenyl isocyanide CNAr Mes2 (Ar Mes2 = 2,6-(2,4,6-Me 3 C 6 H 2 ) 2 C 6 H 3 ), reveal that this series possesses similar overall properties to the bridging carbonyl counterparts. However, high-resolution X-ray crystallographic studies have revealed important structural differences that were not discernible in older studies of the carbonyl complexes. Also presented is the synthesis of the bridging-isocyanide/η 6arene dimers [Co 2 ((η 6 -Mes)(μ-CNAr Mes )) 2 ] n (n = 0, 1+), which are valence isoelectronic to the mono-and dianionic [(μ-CNAr) 2 [CpCo] 2 ] n derivatives. Structural and spectroscopic studies of these η 6 -arene complexes, as well as the related neutral nickel dimer (μ-CNAr Mes ) 2 [CpNi] 2 provide evidence for an electronic structure environment dominated by M→(CN)π* backbonding interactions, rather than direct M−M bonding. This conclusion is supported by DFT-derived molecular orbital analysis on the bridging-isocyanide [(μ-CNAr Mes2 ) 2 [CpCo] 2 ] n dimers.

For decades,t ransiently generated 17e À monoradicals have occupied ac entral role in the development of atom-transfer and radical-mediated processes in organometallic chemistry. [1][2][3] Ap rototypical example of this class is the zerovalent manganese pentacarbonyl radical [Mn(CO) 5 ]which has been extensively investigated for its role in radical-type olefin hydrogenation, [4,5] [7][8][9][10] or at higher temperatures by using either ultrafast spectroscopic [11] or nitrosoarene spin-trapping techniques. [12][13][14] Importantly,efforts to prepare stabilized variants of [Mn(CO) 5 ]bysubstitution of one or more CO ligands with more encumbering ligands such as phosphines (PR 3 )h ave been shown to extend the lifetime of [MnL 5 ]-type radicals to the order of hours in solution. [15][16][17][18] However,such derivatized [Mn(CO) 5Àn L n ]c omplexes have remained susceptible to facile dimerization/redistributionp rocesses when concentrated and isolable examples remain unknown. Additionally, investigations into the one-electron activation chemistry of [Mn(CO) 5Àn L n ]s pecies with small molecule substrates are limited. [16,17] Given the challenges faced in exploring the properties of [Mn (CO) ) 2 ]( Ar Dipp2 = 2,6-(2,6-(iPr) 2 C 6 H 3 ) 2 C 6 H 3 )f eaturing two m-terphenyl isocyanide ligands. [22,23] Thesterically encumbering nature of these isocyanidel igands effectively prevents the formation of MnÀMn single bonds,thus rendering this 17eÀ radical both isolable in the solid state and persistent in solution. Additionally,asaresult of the isolobal analogy between carbon monoxide (CO) and organoisocyanides (C NR), [22,24] ) 2 ]delivers 1 most cleanly and in the highest yield after isolation (92 %; Figure 1A). Upon isolation, 1 is stable for days in solution at elevated temperatures (C 6 D 6 ,808 8C) and shows no sign of dimerization and/or ligand redistribution when concentrated to asolid.In both solution and the solid state,c omplex 1 possesses several spectroscopic and structural features consistent with ad 7 monoradical formulation. The 1 HNMR spectrum of 1 in C 6 D 6 features broad, shifted resonance signals characteristic of ap aramagnetic species,w hereas determination of the