Controlled Expansion of a Strong-Field Iron Nitride Cluster: Multi-Site Ligand Substitution as a Strategy for Activating Interstitial Nitride Nucleophilicity.

Multimetallic clusters have long been investigated as molecular surrogates for reactive sites on metal surfaces. In the case of the µ4 -nitrido cluster [Fe4 (µ4 -N)(CO)12 ]- , this analogy is limited owing to the electron-withdrawing effect of carbonyl ligands on the iron nitride core. Described here is the synthesis and reactivity of [Fe4 (µ4 -N)(CO)8 (CNArMes2 )4 ]- , an electron-rich analogue of [Fe4 (µ4 -N)(CO)12 ]- , where the interstitial nitride displays significant nucleophilicity. This characteristic enables rational expansion with main-group and transition-metal centers to yield unsaturated sites. The resulting clusters display surface-like reactivity through coordination-sphere-dependent atom rearrangement and metal-metal cooperativity.

A Metal-Organic Framework with Exceptional Activity for C-H Bond Amination.

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 >105 turnovers.

Crystalline Coordination Networks of Zero-Valent Metal Centers: Formation of a 3-Dimensional Ni(0) Framework with m-Terphenyl Diisocyanides.

A permanently porous, three-dimensional metal-organic material formed from zero-valent metal nodes is presented. Combination of ditopic m-terphenyl diisocyanide, [CNArMes2]2, and the d10 Ni(0) precursor Ni(COD)2, produces a porous metal-organic material featuring tetrahedral [Ni(CNArMes2)4]n 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 N2-adsorption profile.

Comparison of nucleophilic- and radical-based routes to the formation of manganese-main group element single bonds.

Using the stable metalloradical Mn(CO)3(CNArDipp2)2, we report the formation of manganese-main group complexes via the single-electron functionalization of main group halides. The reactions occur in a simple 1 : 1 stoichiometry, and demonstrate the utility of using stable open-shelled organometallics as precursors for metal-main group compounds. This has enabled the preparation of manganese complexes bearing terminal -EXn substituents, as shown through the isolation of Mn(SnCl)(CO)3(CNArDipp2)2 and Mn(BiCl2)(CO)3(CNArDipp2)2 from SnCl2 and BiCl3, respectively. Through this approach, we have also isolated Mn(SbF2)(CO)3(CNArDipp2)2 from SbF3, which serves as a unique example of a terminal -SbF2 complex. Although the metalloradical functionalization of binary main group halides provides the desired main group adduct in yields comparable to nucleophilic activation using the manganate Na[Mn(CO)3(CNArDipp2)2], the former approach is shown to be far more atom-economical with respect to Mn. Additionally, we have found that Mn(CO)3(CNArDipp2)2 also serves as a convenient precursor to MnF(CO)3(CNArDipp2). The latter is an analogue to the elusive monofluoride FMn(CO)5.

Electrochemical Properties and CO2-Reduction Ability of m-Terphenyl Isocyanide Supported Manganese Tricarbonyl Complexes.

To circumvent complications with redox-active ligands commonly encountered in the study of manganese electrocatalysts for CO2 reduction, we have studied the electrochemistry of the manganese mixed carbonyl/isocyanide complexes XMn(CO)3(CNArDipp2)2 (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)5]n (n = 1-, 0, 1+). The m-terphenyl isocyanide ligand CNArDipp2 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 CO2 reduction and to provide comparison to known manganese-based CO2 electrocatalysts. Two complexes, BrMn(CO)3(CNArDipp2)2 and [Mn(THF)(CO)3(CNArDipp2)2]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 CO32- is observed in the reactivity of [Mn(CO)3(CNArDipp2)2]- with CO2, which is deduced via the trapping and incorporation of liberated CO into the zerovalent species Mn(CO)3(CNArDipp2)2 to form the dimers Mn2(CO)7(CNArDipp2)3 and Mn2(CO)8(CNArDipp2)2.

Robust, Transformable, and Crystalline Single-Node Organometallic Networks Constructed from Ditopic m-Terphenyl Isocyanides.

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.

Kinetic Destabilization of Metal-Metal Single Bonds: Isolation of a Pentacoordinate Manganese(0) Monoradical.

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 ].