Triple hydrogen atom abstraction from Mn-NH complexes results in cyclophosphazenium cations.

All hydrogen atoms of the NH3 in [Mn(depe)2(CO)(NH3)]+ are abstracted by 2,4,6-tri-tert-butylphenoxyl radical, resulting in the isolation of a rare cyclophosphazenium cation, [(Et2P(CH2)2PEt2)N]+, in 76% yield. An analogous reaction is observed for [Mn(dppe)2(CO)(NH3)]+. Computations suggest insertion of NHx into a Mn-P bond provides the thermodynamic driving force.

Catalytic Ammonia Oxidation to Dinitrogen by Hydrogen Atom Abstraction.

Catalysts for the oxidation of NH are critical for the utilization of NH as a large-scale energy carrier. Molecular catalysts capable of oxidizing NH to N are rare. This report describes the use of [Cp*Ru(P N )( NH )][BAr ], (P N =1,5-di(phenylaza)-3,7-di(tert-butylphospha)cyclooctane; Ar =3,5-(CF ) C H ), to catalytically oxidize NH to dinitrogen under ambient conditions.

Evaluating the impacts of amino acids in the second and outer coordination spheres of Rh-bis(diphosphine) complexes for CO hydrogenation.

To explore the influence of a biologically inspired second and outer coordination sphere on Rh-bis(diphosphine) CO2 hydrogenation catalysts, a series of five complexes were prepared by varying the substituents on the pendant amine in the P(Et)2CH2NRCH2P(Et)2 ligands (PEtNRPEt), where R consists of methyl ester modified amino acids, including three neutral (glycine methyl ester (GlyOMe), leucine methyl ester (LeuOMe), and phenylalanine methyl ester (PheOMe)), one acidic (aspartic acid dimethyl ester (AspOMe)) and one basic (histidine methyl ester (MeHisOMe)) amino acid esters. The turnover frequencies (TOFs) for CO2 hydrogenation for each of these complexes were compared to those of the non-amino acid containing [Rh(depp)2]+ (depp) and [Rh(PEtNMePEt)2]+ (NMe) complexes. Each complex is catalytically active for CO2 hydrogenation to formate under mild conditions in THF.

Anion control of tautomeric equilibria: Fe-H N-H influenced by NH···F hydrogen bonding.

Counterions can play an active role in chemical reactivity, modulating reaction pathways, energetics and selectivity. We investigated the tautomeric equilibrium resulting from protonation of Fe(PNP)(CO) (PNP = (EtPCH)NMe) at Fe or N. Protonation of Fe(PNP)(CO) by [(EtO)H][B(CF)] occurs at the metal to give the iron hydride [Fe(PNP)(CO)H][B(CF)].

H Binding, Splitting, and Net Hydrogen Atom Transfer at a Paramagnetic Iron Complex.

While diamagnetic transition metal complexes that bind and split H have been extensively studied, paramagnetic complexes that exhibit this behavior remain rare. The square planar S = 1/2 Fe(PN) cation (Fe) reversibly binds H/D in solution, exhibiting an inverse equilibrium isotope effect of K/ K = 0.58(4) at -5.

H Oxidation Electrocatalysis Enabled by Metal-to-Metal Hydrogen Atom Transfer: A Homolytic Approach to a Heterolytic Reaction.

Oxidation of H in a fuel cell converts the chemical energy of the H-H bond into electricity. Electrocatalytic oxidation of H by molecular catalysts typically requires one metal to perform multiple chemical steps: bind H , heterolytically cleave H , and then undergo two oxidation and two deprotonation steps. The electrocatalytic oxidation of H by a cooperative system using Cp*Cr(CO) H and [Fe(diphosphine)(CO) ] has now been invetigated.

Frustration across the periodic table: heterolytic cleavage of dihydrogen by metal complexes.

This perspective examines frustrated Lewis pairs (FLPs) in the context of heterolytic cleavage of H by transition metal complexes, with an emphasis on molecular complexes bearing an intramolecular Lewis base. FLPs have traditionally been associated with main group compounds, yet many reactions of transition metal complexes support a broader classification of FLPs that includes certain types of transition metal complexes with reactivity resembling main group-based FLPs. This article surveys transition metal complexes that heterolytically cleave H, which vary in the degree that the Lewis pairs within these systems interact.

Preparation and Protonation of Fe2(pdt)(CNR)6, Electron-Rich Analogues of Fe2(pdt)(CO)6.

The complexes Fe2(pdt)(CNR)6 (pdt(2-) = CH2(CH2S(-))2) were prepared by thermal substitution of the hexacarbonyl complex with the isocyanides RNC for R = C6H4-4-OMe (1), C6H4-4-Cl (2), Me (3). These complexes represent electron-rich analogues of the parent Fe2(pdt)(CO)6. Unlike most substituted derivatives of Fe2(pdt)(CO)6, these isocyanide complexes are sterically unencumbered and have the same idealized symmetry as the parent hexacarbonyl derivatives.

Models of the Ni-L and Ni-SIa States of the [NiFe]-Hydrogenase Active Site.

A new class of synthetic models for the active site of [NiFe]-hydrogenases are described. The Ni(I/II)(SCys)2 and Fe(II)(CN)2CO sites are represented with (RC5H4)Ni(I/II) and Fe(II)(diphos)(CO) modules, where diphos = 1,2-C2H4(PPh2)2(dppe) or cis-1,2-C2H2(PPh2)2(dppv). The two bridging thiolate ligands are represented by CH2(CH2S)2(2-) (pdt(2-)), Me2C(CH2S)2(2-) (Me2pdt(2-)), and (C6H5S)2(2-).

Ni(I)/Ru(II) model for the Ni-L state of the [NiFe]hydrogenases: synthesis, spectroscopy, and reactivity.

This study describes the characterization of a mixed-valence Ru(II)/Ni(I) complex, a structural model for the Ni-L state of the [NiFe]hydrogenases. One-electron oxidation of (cymene)Ru(μ-pdt)Ni(diphos) ([1](0), diphos = dppe, C2H4(PPh2)2; [2](0), diphos = dcpe, C2H4(P(C6H11)2)2] affords the mixed-valence cations [(cymene)Ru(pdt)Ni(diphos)](+) ([1](+) and [2](+)). Crystallographic and spectroscopic measurements indicate that these cations are described as Ru(II)/Ni(I).