Oxidatively-induced C(sp3)-C(sp3) bond formation at a tucked-in iron(iii) complex

Carbon-carbon (C-C) bond formation is a cornerstone of synthetic chemistry, relying on routes such as transition-metal mediated cross-coupling for the introduction of new carbon-based functionality. For {[M] n+-C} (M = metal) structural units, studies that offer well-defined relationships between metal oxidation state, hydrocarbon strain, and {[M] n+-C} bond thermochemistry are thus informative, providing a means to reliably access new product classes. Here, we show that one-electron oxidation of the iron tucked-in complex [(η6-C5Me4[double bond, length as m-dash]CH2)Fe(dnppe)] (dnppe = 1,2-bis(di-n-propylphosphino)ethane) results in C(sp3)-C(sp3) bond formation giving unique {Fe2} dimers. Freeze-quenched CW X-band EPR spectroscopy allowed for spectroscopic identification of the reactive [(η6-C5Me4[double bond, length as m-dash]CH2)Fe(dnppe)]+ intermediate. Density functional theory (DFT) calculations reveal a primarily Fe-centered radical and a weak {[Fe]-C} bond (BDE[Fe]-C = 24.5 kcal mol-1, c.f. BDEC-C(ethane) = 90 kcal mol-1). For comparison, a structurally analogous Fe(iii) methyl complex was prepared, [Cp*Fe(dnppe)(CH3)]+ (Cp* = C5Me5 -), where C(sp3)-C(sp3) coupling was not observed, consistent with a larger calculated BDE[Fe]-C value of 47.8 kcal mol-1. These data are analogized to the simple hydrocarbons ethane and cyclopropane, where a strain-induced BDEC-C decrease of 33 kcal mol-1 is witnessed on cyclization.

Nonaqueous Electrochemistry of Uranium Complexes: A Guide to Structure-Reactivity Tuning

Uranium complexes can be stabilized in a wide range of oxidation states, ranging from U^II to U^VI and a very recent example of a U^I complex. This review provides a comprehensive summary of electrochemistry data reported on uranium complexes in nonaqueous electrolyte, to serve as a clear point of reference for newly synthesized compounds, and to evaluate how different ligand environments influence experimentally observed electrochemical redox potentials. Data for over 200 uranium compounds are reported, together with a detailed discussion of trends observed across larger series of complexes in response to ligand field variations. In analogy to the traditional Lever parameter, we utilized the data to derive a new uranium-specific set of ligand field parameters ^UE_L(L) that more accurately represent metal-ligand bonding situations than previously existing transition metal derived parameters. Exemplarily, we demonstrate ^UE_L(L) parameters to be useful for the prediction of structure-reactivity correlations in order to activate specific substrate targets.

Bis(1-Bora-4-phosphorinane) Ring Closure at Cp*M (M = Fe, Co) Complexes

Bis(1-bora-4-phosphorinane) metal complexes have been synthesized using a Cp*M-protecting (M = Fe, Co, Cp* = C5Me5-) strategy and structurally authenticated by NMR spectroscopy and single crystal X-ray diffraction. Synthesis of...

Bridging cyanides from cyanoiron metalloligands to redox-active dinitrosyl iron units

Cyanide, as an ambidentate ligand, plays a pivotal role in providing a simple diatomic building-block motif, for controlled metal aggregation, M–CN–M′.

Optimised Syntheses of the Half-Sandwich Complexes FeCl(dppe)Cp*, FeCl(dppe)Cp, RuCl(dppe)Cp*, and RuCl(dppe)Cp

Thanks to their synthetic versatility, the half-sandwich metal chlorides MCl(dppe)(η5-C5R5) [M = Fe, Ru; dppe = 1,2-bis(diphenylphosphino)ethane, R = H (cyclopentadiene, Cp), CH3 (pentamethylcyclopentadiene, Cp*)] are staple starting materials in many organometallic laboratories. Here we present an overview of the synthetic methods currently available for FeCl(dppe)Cp*, FeCl(dppe)Cp, RuCl(dppe)Cp*, and RuCl(dppe)Cp, and describe in detail updated and optimised multigram syntheses of all four compounds.

Highly nucleophilic dipropanolamine chelated boron reagents for aryl-transmetallation to iron complexes

New arylborates chelated by dipropanolamine are readily synthesised from boronic acids and demonstrated to be highly nucleophilic reagents.