Synthesis and Reactivity of N-Heterocyclic Carbene Coordinated Formal Germanimidoyl-Phosphinidenes

Treatment of N-heterocyclic carbene (NHC) ligated germylidenylphosphinidene MsFluidtBu-GeP(NHCiPr) (where MsFluidtBu is a bulky hydrindacene substituent, and NHCiPr is 1,3-diisopropyl-4,5-dimethyl-imidazolin-2-ylidene) with mesityl azide and 4-tertbutylphenyl azide afforded NHC coordinated formal germanimidoyl-phosphinidenes, which represent the first compounds bearing both Ge═N double bond and phosphinidene functionalities. Studies of the chemical properties revealed that the reactions preferred to occur at the Ge═N double bond, which underwent [2 + 2] cycloadditions with CO2 and ethyl isocyanate, and coordinated with coinage metals through the nitrogen atom.

A soft molecular 2Fe-2As precursor approach to the synthesis of nanostructured FeAs for efficient electrocatalytic water oxidation

An unprecedented molecular 2Fe-2As precursor complex was synthesized and transformed under soft reaction conditions to produce an active and long-term stable nanocrystalline FeAs material for electrocatalytic water oxidation in alkaline media. The 2Fe2As-centred β-diketiminato complex, having an unusual planar Fe2As2 core structure, results from the salt-metathesis reaction of the corresponding β-diketiminato FeIICl complex and the AsCO- (arsaethynolate) anion as the monoanionic As- source. The as-prepared FeAs phase produced from the precursor has been electrophoretically deposited on conductive electrode substrates and shown to act as a electro(pre)catalyst for the oxygen evolution reaction (OER). The deposited FeAs undergoes corrosion under the severe anodic alkaline conditions which causes extensive dissolution of As into the electrolyte forming finally an active two-line ferrihydrite phase (Fe2O3(H2O) x ). Importantly, the dissolved As in the electrolyte can be fully recaptured (electro-deposited) at the counter electrode making the complete process eco-conscious. The results represent a new and facile entry to unexplored nanostructured transition-metal arsenides and their utilization for high-performance OER electrocatalysis, which are also known to be magnificent high-temperature superconductors.

The Chemistry of Yellow Arsenic

The generation and handling of the light-sensitive and metastable yellow arsenic (As₄) is extremely challenging. In view of recent breakthroughs in synthesizing As₄ storage materials and transfer reagents, the more intensive use of yellow arsenic as a source for further reactions can be expected. Given these aspects, the current stage of knowledge of the direct use of As₄ is comprehensively summarized in the present review, which lists the activation of As₄ by main group elements as well as transition metal compounds (including the f-block elements). Moreover, it also partly compares the reaction outcomes in relation to the corresponding reactions of P₄. The possibility of using alternative sources for generating arsenic moieties and compounds is also discussed. The release of As₄ molecules from precursor compounds and the use of transfer reagents for polyarsenic entities open up new synthetic pathways to avoid the direct generation of yellow arsenic solutions and to ensure its smooth usage for subsequent reactions.

From As-Zincoarsasilene (LZn-As=SiL') to Arsaethynolato (As≡C-O) and Arsaketenylido (O=C=As) Zinc Complexes

The reactivity of the As-zincosilaarsene LZn-As=SiL' A (L=[CH(CMeNDipp)₂ ]^- , Dipp=2,6-ⁱ Pr₂ C₆ H₃ , L'=[{C(H)N(2,6-ⁱ Pr₂ -C₆ H₃ )}₂ ]^2- ) towards small molecules was investigated. Due to the pronounced zwitterionic character of the Si=As bond of A, it undergoes addition reactions with H₂ O and NH₃ , forming LZnAs(H)SiOH(L') 1 and LZnAs(H)SiNH₂ (L') 2. Oxygenation of A with N₂ O at -60 °C furnishes the deep blue 1,2-disiloxydiarsene, [LZnOSi(L')As]₂ 4, presumably via dimerization of the arsinidene intermediate LZnOSi(L')As 3. Oxygenation of A with CO₂ leads to the monomeric arsaethynolato siloxido zinc complex LZnOSi(L')(OC≡As) 5, essentially trapping the intermediary arsinidene 3 with liberated CO following initial oxidation of the Si=As bond. DFT calculations confirm the ambident coordination mode of the anionic [AsCO] ligand in solution, with the O-arsaethynolato [As≡C-O]^.- in 5, and the As-arsaketenylido ligand mode [O=C=As]^- present in LZnO-Si(L')(-As=C=O) 5' akin to the analogous phosphorus system, [PCO]^- .

Cyaarside (CAs- ) and 1,3-Diarsaallendiide (AsCAs2- ) Ligands Coordinated to Uranium and Generated via Activation of the Arsaethynolate Ligand (OCAs- )

Reaction of the trivalent uranium complex [((^Ad,Me ArO)₃ N)U(DME)] with one molar equiv [Na(OCAs)(dioxane)₃ ], in the presence of 2.2.2-crypt, yields [Na(2.2.2-crypt)][{((^Ad,Me ArO)₃ N)U^IV (THF)}(μ-O){((^Ad,Me ArO)₃ N)U^IV (CAs)}] (1), the first example of a coordinated η¹ -cyaarside ligand (CAs^- ). Formation of the terminal CAs^- is promoted by the highly reducing, oxophilic U^III precursor [((^Ad,Me ArO)₃ N)U(DME)] and proceeds through reductive C-O bond cleavage of the bound arsaethynolate anion, OCAs^- . If two equiv of OCAs^- react with the U^III precursor, the binuclear, μ-oxo-bridged U₂ ^IV/IV complex [Na(2.2.2-crypt)]₂ [{((^Ad,Me ArO)₃ N)U^IV }₂ (μ-O)(μ-AsCAs)] (2), comprising the hitherto unknown μ:η¹ ,η¹ -coordinated (AsCAs)^2- ligand, is isolated. The mechanistic pathway to 2 involves the decarbonylation of a dimeric intermediate formed in the reaction of 1 with OCAs^- . An alternative pathway to complex 2 is by conversion of 1 via addition of one further equiv of OCAs^- .