Synthesis and Characterization of [Fe3 (As3 )3 (As4 )]3- , a Binary Fe/As Zintl Cluster With an Fe3 Core

We report here the synthesis and structural characterization of the first binary iron arsenide cluster anion, [Fe₃ (As₃ )₃ (As₄ )]^3- , present in both [K([2.2.2]crypt)]₃ [Fe₃ (As₃ )₃ (As₄ )] (1) and [K(18-crown-6)]₃ [Fe₃ (As₃ )₃ (As₄ )]⋅en (2). The cluster contains an Fe₃ triangle with three short Fe-Fe bond lengths (2.494(1) Å, 2.459(1) Å and 2.668(2) Å for 1, 2.471(1) Å, 2.473(1) Å and 2.660(1) Å for 2), bridged by a 2-butene-like As₄ unit. An analysis of the electronic structure using DFT reveals a triplet ground state with direct Fe-Fe bonds stabilizing the Fe₃ core.

Conversion of E4 (E4 =P4 , As4 , AsP3 ) by Ni(0) and Ni(I) Synthons - A Comparative Study

The reactivity of white phosphorus and yellow arsenic towards two different nickel nacnac complexes is investigated. The nickel complexes [(L¹ Ni)₂ tol] (1, L¹ =[{N(C₆ H₃ ⁱ Pr₂ -2,6)C(Me)}₂ CH]^- ) and [K₂ ][(L¹ Ni)₂ (μ,η^1 : 1 -N₂ )] (6) were reacted with P₄ , As₄ and the interpnictogen compound AsP₃ , respectively, yielding the homobimetallic complexes [(L¹ Ni)₂ (μ-η² ,κ¹ :η² ,κ¹ -E₄ )] (E=P (2 a), As (2 b), AsP₃ (2 c)), [(L¹ Ni)₂ (μ,η^3 : 3 -E₃ )] (E=P (3 a), As (3 b)) and [K@18-c-6(thf)₂ ][L¹ Ni(η^1 : 1 -E₄ )] (E=P (7 a), As (7 b)), respectively. Heating of 2 a, 2 b or 2 c also leads to the formation of 3 a or 3 b. Furthermore, the reactivity of these compounds towards reduction agents was investigated, leading to [K₂ ][(L¹ Ni)₂ (μ,η^2 : 2 -P₄ )] (4) and [K@18-c-6(thf)₃ ][(L¹ Ni)₂ (μ,η^3 : 3 -E₃ )] (E=P (5 a), As (5 b)), respectively. Compound 4 shows an unusual planarization of the initial Ni₂ P₄ -prism. All products were comprehensively characterized by crystallographic and spectroscopic methods.

Structural diversity of mixed polypnictogen complexes: dicationic E2E'2 (E ≠ E' = P, As, Sb, Bi) chains, cycles and cages stabilized by transition metals

The reactivity of the tetrahedral dipnictogen complexes [{CpMo(CO)₂}₂(μ,η²:η²-EE′)] (E, E′ = P, As, Sb, Bi; “Mo₂EE′”) towards different one-electron oxidation agents is reported. Oxidation with [Thia][TEF] (Thia⁺ = C₁₂H₈S₂⁺; TEF⁻ = Al{OC(CF₃)₃}₄⁻) leads to the selective formation of the radical monocations [Mo₂EE′]˙⁺, which immediately dimerize to the unprecedented dicationic E₂E′₂ ligand complexes [{CpMo(CO)₂}₄(μ₄,η²:η²:η²:η²-E′EEE′)]²⁺via E–E bond formation. Single crystal X-ray diffraction revealed that, in the case of Mo₂PAs and Mo₂PSb, P–P bond formation occurs yielding zigzag E₂P₂ (E = As (1), Sb (2)) chains, whereas Mo₂SbBi forms a Sb₂Bi₂ (5) cage, Mo₂AsSb an unprecedented As₂Sb₂ unit representing an intermediate stage between a chain- and a cage-type structure, and Mo₂AsBi a novel planar As₂Bi₂ (4a) cycle. Therefore, 1–5 bear the first substituent-free, dicationic hetero-E₄ ligands, stabilized by transition metal fragments. Furthermore, in the case of Mo₂AsSb, the exchange of the counterion causes changes in the molecular structure yielding an unusual, cyclic As₂Sb₂ ligand. The experimental results are corroborated by DFT calculations.

Unique dicationic hetero-tetrapnictogen E₂E′₂ (E ≠ E′ = P, As, Sb, Bi) chains and cages are obtained via oxidation of the tetrahedranes [{CpMo(CO)₂}₂(μ,η²:η²-EE′)]. Exchange of the counterion causes an unusual cyclization of the As₂Sb₂ ligand.

Reactivity of Cu(I) Nacnac Complexes Toward Polypnictogen Compounds

The nacnac Cu(I) compound [LCu(MeCN)] (2) (L = [{N(C₆H₃Me₂-2,6)C(Me)}₂CH]^-) was reacted with complexes containing aromatic cyclo-E₅ ([Cp*Fe(η⁵-E₅)], E = P (1a), As (1b), Cp* = η⁵-C₅Me₅), cyclo-P₄ ([Cp‴Co(η⁴-P₄)] (3), Cp‴ = η⁵-C₅H₂^tBu₃) and cyclo-E₃ ligands ([Cp‴Ni(η³-E₃)], E = P (4a), As (4b)) yielding the heterometallic complexes [(Cp*Fe)(μ,η^5:2-E₅)(LCu)] (E = P (5a), As (5b)), [(Cp*Fe)(μ₃,η^5:2:1-E₅)(LCu)₂] (E = P (6a), As (6b)), [(Cp‴Co)(μ,η^4:2-P₄)(LCu)] (7), [(Cp‴Co)(μ₃,η^4:2:1-P₄)(LCu)₂] (8), and [(Cp‴Ni)(μ,η^3:2-E₃)(LCu)] (E = P (9a), As (9b)). These complexes are rare examples of the coordination of a group 11 metal to aromatic cyclo-E_n (E = P, As; n = 3-5) ligands. All products were comprehensively characterized by crystallographic and spectroscopic methods. Their dynamic behavior in solution was studied by VT (variable-temperature) NMR spectroscopy, and their electronic structures were elucidated by DFT calculations.