Synthesis and onwards coordination of an As(I) centered zwitterion

Very close I⋯As and I⋯Sb interactions in trimethylpnictogen-pentafluoroiodobenzene cocrystals

The unusually short, for any experimentally characterized molecular (co)crystal, directional C–I⋯As and C–I⋯Sb halogen bonds have been engineered in the supramolecular reactions of the in situ cocrystallized (CH3)3E (E = As or Sb) with C6F5I.

Recent Developments in the Chemistry of Pn(I) (Pn=N, P, As, Sb, Bi) Cations

The Group 15 Pn(I) cations (Pn=N, P, As, Sb and Bi), which are isoelectronic with the donor-stabilized carbones, have emerged recently. Despite the presence of two lone pair of electrons, the Pn(I) cations are weakly nucleophilic due to their inherent positive charge. Strongly electron-donating supporting ligands including zwitterionic forms have been used to enhance their Lewis basicity. Furthermore, the chelating effect of cyclic ligand systems proved effective in increasing their nucleophilicity. The strategies involved in successfully isolating the fleeting Sb(I) and Bi(I) cations as the recent most achievements in this field have been discussed. The syntheses, structure, bonding situations and reactivity of the Pn(I) cations are discussed. An outlook on the periodic trends and future applications of these electronically unique electron-rich cationic moieties have been provided.

Phosphine-Stabilized Pnictinidenes

The reaction of the intramolecular germylene‐phosphine Lewis pair (o‐PPh₂)C₆H₄GeAr* (1) with Group 15 element trichlorides ECl₃ (E=P, As, Sb) was investigated. After oxidative addition, the resulting compounds (o‐PPh₂)C₆H₄(Ar*)Ge(Cl)ECl₂ (2: E=P, 3: E=As, 4: E=Sb) were reduced by using sodium metal or LiHBEt₃. The molecular structures of the phosphine‐stabilized phosphinidene (o‐PPh₂)C₆H₄(Ar*)Ge(Cl)P (5), arsinidene (o‐PPh₂)C₆H₄(Ar*)Ge(Cl)As (6) and stibinidene (o‐PPh₂)C₆H₄(Ar*)Ge(Cl)Sb (7) are presented; they feature a two‐coordinate low‐valent Group 15 element. After chloride abstraction, a cyclic germaphosphene [(o‐PPh₂)C₆H₄(Ar*)GeP] [B(C₆H₃(CF₃)₂)₄] (8) was isolated. The ³¹P NMR data of the germaphosphene were compared with literature examples and analyzed by quantum chemical calculations. The phosphinidene was treated with [iBu₂AlH]₂, and the product of an Al−H addition to the low‐valent phosphorus atom (o‐PPh₂)C₆H₄(Ar*)Ge(H)P(H)Al(C₄H₉)₂ (9) was characterized.

(2-Pyridyloxy)arsines as ligands in transition metal chemistry: a stepwise As(iii) → As(ii) → As(i) reduction

Neutral inherently tri- and tetradentate ligands of the type Ph_3-xAs(PyO)_x (x = 2 (1), 3 (2)) have been synthesized and characterized. Reaction of 1 with [RuCl₂(PPh₃)₃] affords complex [PhAs(μ-PyO)₂RuCl₂(PPh₃)] (3), whereas 2 and [RuCl₂(PPh₃)₃] react with formation of [As(μ-PyO)₂RuCl(PPh₃)₂] (5) and [Ph₃P(PyO)]Cl (6). Treatment of complex 5 with [AuCl(tht)] (tht = tetrahydrothiophene) results in liberation of tht and formation of [AuCl(As(PyO)₂)RuCl(PPh₃)₂] (7), featuring an (Au-As-Ru) core. For compounds 3, 5, and 7 the As-Ru and As-Au bond situation has been investigated using NBO, AIM and ELF analysis, allowing the assignment of pronounced canonical forms of σ-(As^III→Ru^II) to 3, σ-(As^II-Ru^I) to 5 and σ-(Au^I←As^I→Ru^II) to 7.

An Acyclic Arsenium Cation Stabilised by a Single P-As π-Interaction and a Cyclic Diphosphinophosphonium Salt

Stable acyclic arsenium cations R₂ As⁺ , isoelectronic analogues of germylenes, are rare in comparison to the corresponding phosphenium cations. The first example of a diphosphaarsenium salt, [{(Dipp)₂ P}₂ As][Al{OC(CF₃ )₃ }₄ ]⋅1 1 / 2  PhMe, is described. This salt exhibits remarkable stability due to the delocalisation of a lone pair from a planar phosphorus centre into the vacant p-orbital at arsenic; the bonding in 2 has been probed by DFT calculations. An attempt to synthesise an analogous diphosphaphosphenium salt unexpectedly generated the cyclic phosphonium salt [cyclo-{(Mes)P}₂ P(Mes)₂ ][BAr^F ₄ ]⋅CyMe through the cyclisation of a putative phosphine-substituted diphosphene cation intermediate.

Synthesis of Heavy Dicyanamide Homologues from Air-Stable Precursors

A convenient synthesis of dicyanophosphide and dicyanoarsenide anions is reported. These heavy homologues of the long-known and fundamentally important dicyanamide anion were formed through the nucleophilic displacement of bis(diphenylphosphino)ethane (dppe) from the pnictogen⁺ transfer agents [dppePn][BPh₄ ] (Pn=P, As) by exposure to cyanide salts. The protocol requires three synthetic steps from commercially available materials and the [dppePn][BPh₄ ] salts are remarkably temperature, air, and moisture stable. All products have been fully characterized by spectroscopic methods and by single-crystal X-ray diffraction, and the electronic structures of the DCPn anions have been assessed computationally.

A comparative study of the structure and bonding in heavier pnictinidene complexes [(ArE)M(CO)n] (E = As, Sb and Bi; M = Cr, Mo, W and Fe)

N,C,N-Chelated pnictinidenes ArE [where E = As (1), Sb (2) or Bi (3); Ar = C₆H₃-2,6-(CH[double bond, length as m-dash]Nt-Bu)₂] were used as ligands for the coordination of transition metal carbonyls. Thus, the reaction of 1-3 with [M(CO)₅THF] (where M = Cr, W) or [Mo(CO)₅(Me₃N)] gave complexes [(ArE)M(CO)₅] [where E = As and M = Cr (1a), Mo (1b), W (1c); E = Sb and M = Cr (2a), Mo (2b), W (2c); E = Bi and M = Cr (3a), Mo (3b), W (3c)]. Analogously, the treatment of 1-3 with [Fe₂(CO)₉] resulted in the formation of the complexes [(ArE)Fe(CO)₄] [where E = As (1d), Sb (2d) or Bi (3d)]. All compounds were characterized by ¹H and ¹³C NMR spectroscopy, Raman, IR and UV-Vis spectroscopy. The molecular structures of the majority of the compounds (except 1b and 1c) were also determined by the single-crystal X-ray diffraction analysis. Furthermore, the structure and bonding of the title compounds have also been thoroughly investigated using a computational approach.

Utilizing a zwitterionic approach for the synthesis of late transition metal – triphosphenium ion coordination compounds

Zwitterionic dicoordinate phosphorus(I) compounds (1 and 2), formally a charge neutral triphosphenium ion or phosphanide, are shown to coordinate to a variety of late transition metals. The reaction of the phosphanide proligands with {Rh(COD)Cl}2 results in an equilibrium process that varies as a function of temperature or reaction stoichiometry. Palladium(II) compounds have a tendency to chlorinate the borate backbone while giving dimeric coordination compounds (1Pd) and also a decomposition product (3) where the P(I) atom was replaced. Both “lone pairs” of electrons on phosphorus are utilized simultaneously in the dominant product from the reaction of 1 and [PtMe2(μ-SMe2)]2, while each platinum center ortho-metallated a phenyl substituent on the flanking phosphorus atoms (1Pt). Stable, isolable, and fully characterized dimeric mercury complexes (1Hg and 2Hg) are produced nearly quantitatively from the reaction of the phosphanide proligand with HgCl2. All compounds described were structurally characterized using single crystal X-ray diffraction and represent a growing series of zwitterionic P(I) coordination compounds that cannot be isolated when a cationic triphosphenium ion is used.

Synthesis of quaternary heterocyclic salts

The microwave synthesis of twenty quaternary ammonium salts is described. The syntheses feature comparable yields to conventional synthetic methods reported in the current literature with reduced reaction times and the absence of solvent or minimal solvent.