Fundamental Study on Arsenic(III) Halides (AsX3; X = Br, I) toward the Construction of C3-Symmetrical Monodentate Arsenic Ligands

Arsenic ligands have attracted considerable attention in coordination chemistry. Arsenic(III) halides are the most important starting materials in the preparation of monodentate arsenic ligands. In this work, we optimized the synthetic methodologies of arsenic(III) halides (AsX₃; X = Br, I) and examined the difference of their physical properties such as solubility to organic solvent and reactivity to nucleophiles. In addition, a wide variety of monodentate arsenic ligands were prepared with the obtained AsX₃. Finally, the obtained monodentate arsenic ligands were utilized for copper-free Sonogashira cross-coupling reaction in the reaction system with porphyrin. The results showed that monodentate arsenic ligands have higher catalytic activity compared with triphenylphosphine because of the difference of the electronic features of lone pairs between arsenic and phosphorus atoms.

Substituent-dependent reactivity of triarylantimony(iii) toward I2: isolation of [Ar3SbI]+ salt

The outcome of reactions of triarylantimony (Ar₃Sb) with diiodine in benzene is strongly affected by the identity of the substituents.

On the Redox Reactivity of a Geometrically Constrained Phosphorus(III) Compound

The reactivity of a geometrically constrained phosphorus(III) complex bearing the N,N-bis(3,5-di-tert-butyl-2-phenolate)amide pincer ligand (P(ONO); 1) towards oxidants and reductants is explored. This compound can be readily oxidized to the phosphorus(V) dihalo-derivatives P(ONO)X₂ where X=Cl (2), Br (3) and I (4). Attempts at isolating the analogous difluoride through oxidation of 1 were unsuccessful yielding only the hydrofluoride P(ONO)(H)F (5), however P(ONO)F₂ (6) can be accessed via a halide exchange reaction of 2 with KF. Compound 2 can be employed as a precursor to novel cationic species through chloride ion displacement using strong Lewis bases. Thus, reaction of 2 with two or three molar equivalents of dimethylaminopyridine (DMAP) affords [P(ONO)(Cl)(DMAP)₂ ]⁺ (7) and [P(ONO)(DMAP)₃ ]²⁺ (8). Reaction of 2 with the weaker bidentate base 2,2'-bipyridine (bipy) affords [P(ONO)(Cl)(bipy)]⁺ (9), although this species was only accessible upon addition of a halide abstracting agent. The dicationic tris(pyridine) adduct [P(ONO)(py)₃ ]²⁺ (10) is also accessible by reaction of 4 with pyridine. Oxidation of 1 using oxygen gas proceeds slowly and allows for the observation of two compounds, a mixed valence dimeric phosphorus(III)/phosphorus(V) compound [P(ONO)(μ² -O)(μ² :κ¹ ,κ² -ONO)P] (11) and the fully oxidized species [P(ONO)(μ² -O)(μ² :κ¹ ,κ² -ONO)P(O)] (12). Finally, reaction of 1 using KC₈ results in the dimerization of the putative radical anion [P(ONO)]^.- through formation of a P-P bond to afford [P(ONO)]₂^2- (13). Reactions with TEMPO result in the formation of the trigonal bipyramidal species P(ONO)(TEMPO)₂ (14).

Adducts of Donor-Functionalized Ar3P with the Soft Lewis Acid I2: Probing Simultaneous Lewis Acidity and Basicity at Internally Solvated P(III) Centers

The enhancement of donor strength of ortho-functionalized triarylphosphanes is shown to occur via different mechanisms for O- and N-donor substituents, with internal solvation of the phosphorus center observed for N donors. Nevertheless, the steric congestion about the P center is shown to significantly oppose the increase in donor ability, leading to donation weaker than that expected. A series of mono- and bis-aryl-substituted Ar₃PI₂ adducts (Ph_3-n(o-OMe-C₆H₄)_nPI₂, Ph_3-n(o-NMe₂-C₆H₄)_nPI₂, Ph_3-n(o-CH₂NMe₂-C₆H₄)_nPI₂ (n = 1, 2)) have been synthesized via the 1:1 reaction of donor-functionalized phosphanes with diiodine. These soft Lewis acid/base adducts exhibit apparent internal solvation of the donor phosphorus by the pendant donor moieties, giving rise to five- or six-coordinate phosphorus atoms acting as both Lewis base and Lewis acid; the first neutral six-coordinate simultaneous P(III) Lewis acid and Lewis base adduct is reported. Single-crystal X-ray diffraction studies reveal unexpectedly weak donor strength for one of the phosphanes, indicating significant steric hindrance as a consequence of internal solvation. Crystallographic interrogation of the corresponding iodophosphonium salts [Ar₃PI]X (X = I₃, BAr^F) shows that the cationic complexes experience a still greater influence of the steric bulk of the donor moieties than their neutral precursors. The steric and electronic contributions to bonding have been analyzed through computational studies, determining the factors governing the basicity of these donor-functionalized phosphanes, and show that enhancement of P-centered donor strength occurs by conjugation of lone pairs through the arene rings for oxygen substituents and via internal solvation for the nitrogen donors.

A family of cis-macrocyclic diphosphines: modular, stereoselective synthesis and application in catalytic CO2/ethylene coupling

The stereoselective synthesis of a family of cis-macrocyclic diphosphines was achieved in only three steps from white phosphorus and commercial materials. These new ligands showed activity in the nickel-catalyzed coupling of CO₂ and ethylene.

A family of cis-macrocyclic diphosphines was prepared in just three steps from white phosphorus and commercial materials using a modular synthetic approach. Alkylation of bicyclic diphosphane 3,4,8,9-tetramethyl-1,6-diphosphabicyclo(4.4.0)deca-3,8-diene, or P₂(dmb)₂, produced phosphino-phosphonium salts [R-P₂(dmb)₂]X, where R is methyl, benzyl and isobutyl, in yields of 90–96%. Treatment of these salts with organolithium or Grignard reagents yielded symmetric and unsymmetric macrocyclic diphosphines of the form cis-1-R-6-R′-3,4,8,9-tetramethyl-2,5,7,10-tetrahydro-1,6-DiPhospheCine, or R,R′-DPC, in which R′ is methyl, cyclohexyl, phenyl or mesityl, in yields of 46–94%. Alternatively, symmetric diphosphine Cy₂-DPC was synthesized in 74% yield from the dichlorodiphosphine Cl₂P₂(dmb)₂. As a first application, these cis-macrocyclic diphosphines were used as ligands in the nickel-catalyzed synthesis of acrylate from CO₂ and ethylene, for which they showed promising catalytic activity.

The Halogen Bond

The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

Synthesis and solid-state structures of gold(i) complexes of diphosphines

A series of diphosphine bis(gold) complexes were synthesised and the importance of aurophilic interactions for their structure formation was studied.

Synthesis, spectral characterization and crystals structure of some arsane derivatives of gold (I) complexes: a comparative density functional theory study

A series of complexes of the type LAuCl where L = tris(p-tolylarsane), tris(m-tolylarsane), bis(diphenylarsano)ethane, and tris(naphthyl)arsane have been synthesized. All of the new complexes, 1-4, have been fully characterized by means of ¹H NMR and ¹³C NMR spectroscopy and single crystal X-ray crystallography. The structures of complexes 1-4 have been determined from X-ray diffraction data. The linear molecules have an average bond distance between gold-arsenic and gold-chlorine of 2.3390Å and 2.2846Å, respectively. Aurophilic interaction was prominent in complex 1 and 3, whereas complex 2 and 4 do not show any such interaction. The intermolecular gold interaction bond length was affected by the electronegativity of the molecule. The computed values calculated at DFT level using B3LYP function are in good agreement with the experimental results.

Structural isomerism in tris-tolyl halo-phosphonium and halo-arsonium tri-halides, [(CH3C6H4)3EX][X3], (E = P, As; X = Br, I)

The group 15 ligands (o-CH(3)C(6)H(4))(3)P, (m-CH(3)C(6)H(4))(3)P, (p-CH(3)C(6)H(4))(3)P, Ph(3)As, (o-CH(3)C(6)H(4))(3)As and (p-CH(3)C(6)H(4))(3)As have been reacted with two equivalents of di-iodine or di-bromine to yield complexes of formula R(3)EX(4) (E = P, As; X = I, Br). These halogenated group 15 compounds are ionic, [R(3)EX][X(3)] consisting of halo-phosphonium or halo-arsonium cations and trihalide anions. These adducts exhibit structural isomerism and may exist either as simple 1:1 ion pairs, [R(3)EX][X(3)], isomer (A), which display a weak XX interaction between cation and anion, or as a 2:1 complex, which consists of a [{R(3)EX}(2)X(3)](+) cationic species made up of two [R(3)EX](+) cations interacting with one [X(3)](-) anion. The overall charge is balanced by a second [X(3)](-) anion. These 2:1 species also exhibit structural isomerism due to subtle differences in the connectivity of the [{R(3)EX}(2)X(3)](+) fragment, as the {R(3)EX}(+) units may either interact at the same end of the [X(3)](-) ion, to give a Y-shaped motif, isomer (B), or at opposite ends, giving a Z-shaped motif, isomer (C). The type of structural isomer formed is related to the way in which [Ar(3)EX](+) cations pack together via aryl embraces. Isomer (A) and (C) structures form chains of side-to-side, anti-parallel embracing cations. In (A) and (C) structures a square-like stacking motif of cations is observed. In contrast, isomer (B) structures feature side-to-side, parallel embracing cations, and do not exhibit the square motif.

Synthesis of gold(I) fluoroalkyl and fluoroalkenyl-substituted phosphine complexes and factors affecting their crystal packing

A series of gold(I) phosphine complexes of the type [AuCl{PR(2)(R(f))}] (R = Et, i-Pr, Cy; R(f) = CF = CF(2); R = Ph, R(f) = C = CFH, CCl = CF(2), C ≡ CCF(3), CF(3), i-C(3)F(7), s-C(4)F(9)) have been prepared and most have been structurally characterised. All of the complexes are monomeric in the solid state, and a number of secondary interactions are observed--including short intramolecular AuF distances, metal-bound Au-ClH non-classical hydrogen bonds, fluorous domains and phenyl embraces. Only in the case of [AuCl{PEt(2)(CF = CF(2))}] is an aurophilic interaction with an AuAu contact less than the sum of the van der Waals radii observed. Even then, the distance, 3.3458(10) Å, is longer than that previously observed for the related complex with R = Ph; R(f) = CF = CF(2).