Cyclometalated Iridium Bipyridine Complexes with Peripheral Antimony Substituents

As part of our ongoing efforts in the development of main group Lewis acids as anion receptors, we have investigated the synthesis of cyclometalated bipyridine iridium(III) complex decorated by antimony moieties. Reaction of 4-(diphenylstibino)-2,2'-bipyridine ( L ) with [(ppy)₂Ir(μ-Cl)]₂ afforded the corresponding tris-chelate iridium complex [(ppy)₂Ir L ]⁺ ([ 1 ]⁺), which was isolated as a hexafluorophosphate salt ([ 1 ][PF₆]). Reaction of [ 1 ][PF₆] with excess PhICl₂ in DMSO induced the conversion of the diphenylantimony moiety of [ 1 ]⁺ into an anionic diphenyltrichloroantimonate leading to a zwitterionic complex referred to as 2 -Cl. Complexes [ 1 ][PF₆] and 2 -Cl were characterized by NMR and the structure of 2 -Cl confirmed using X-ray diffraction. DFT calculations and electrochemical measurments show that the electron-rich diphenyltrichloroantimonate moiety in 2 -Cl cathodically shifts the Ir(III/IV) redox couple. Luminescence measurements also show that 2 -Cl is less emissive than [ 1 ]⁺.     

Promoting the Hydrosilylation of Benzaldehyde by Using a Dicationic Antimony‐Based Lewis Acid: Evidence for the Double Electrophilic Activation of the Carbonyl Substrate

The concomitant activation of carbonyl substrates by two Lewis acids has been investigated by using [1,2‐(Ph₂MeSb)₂C₆H₄]²⁺ ([ 1 ]²⁺), an antimony‐based bidentate Lewis acid obtained by methylation of the corresponding distibine. Unlike the simple stibonium cation [Ph₃MeSb]⁺, dication [ 1 ]²⁺ efficiently catalyzes the hydrosilylation of benzaldehyde under mild conditions. The catalytic activity of this dication is correlated to its ability to doubly activate the carbonyl functionality of the organic substrate. This view is supported by the isolation of [ 1 ‐μ₂‐DMF][OTf]₂, an adduct, in which the DMF oxygen atom bridges the two antimony centers.     

[Sb(12-Krone-4)2(CH3CN)][SbCl6]3 und [Bi(12-Krone-4)2(CH3CN)][SbCl6]3, die ersten Trikationen von Antimon(III) und Bismut(III)

[Sb(12-Crown-4)₂(CH₃CN)][SbCl₆]₃ and [Bi(12-Crown-4)₂(CH₃CN)][SbCl₆]₃, first Trications of Antimony(III) and Bismuth(III) The crown ether complexes [M(12-crown-4)₂(CH₃CN)][SbCl₆]₃ with M = Sb and Bi are formed by the reaction of antimony trichloride and bismuth trichloride, respectively, with antimony pentachloride in acetonitrile solution in the presence of 12-crown-4. They form colourless, moisture sensitive crystals, which were characterized by X-ray structure determinations and by IR spectroscopy. The complex with M = Sb was also characterized by ¹²¹Sb Mössbauer spectroscopy. Both complexes crystallize isotypically in the orthorhombic space group Pbcn with four formula units per unit cell. M = Sb: 3 483 observed unique reflections, R = 0.038. M = Bi: 2 958 observed unique reflections, R = 0.036. The compounds consist of SbCl₆^? ions and trications [M(12-crown-4)₂(CH₃CN)]³⁺, in which the M³⁺ ions are ninefold coordinated by the eight oxygen atoms of the crown ether molecules and by the nitrogen atom of the acetonitrile molecule. The lone pair of the M³⁺ ions has no steric effect.     

Oxidative Addition von N‐Chlortriphenylphosphanimin an Phosphortrichlorid und Antimontrichlorid. Kristallstrukturen von (Cl3PNPPh3)2[PCl6][ClHCl],[SbCl4(HNPPh3)2][SbCl6] und [Sb(NPPh3)4][SbCl6]

Oxidative Addition of N‐chlorotriphenylphosphoraneimine onto Phosphorus(III) Chloride and Antimony(III) Chloride. Crystal Structures of (Cl₃PNPPh₃)₂[PCl₆][ClHCl], [SbCl₄(HNPPh₃)₂][SbCl₆], and [Sb(NPPh₃)₄][SbCl₆] Phosphorus(III) chloride reacts with N‐chlorotriphenylphosphoraneimine, ClNPPh₃, in CH₂Cl₂ solution strongly exothermically via oxidative addition to give (Cl₃PNPPh₃)₂[PCl₆][ClHCl] ( 1 ). As a by‐product, Ph₃PNP(O)Cl₂ can be obtained, which is formed from PCl₃ and ClNPPh₃ in the presence of POCl₃. In contrast to these results, antimony(III) chloride reacts with ClNPPh₃ in CH₂Cl₂ solution to give a mixture of the phosphoraneimine complex [SbCl₄(HNPPh₃)₂][SbCl₆] ( 2 ) and the phosphoraneiminato complex [Sb(NPPh₃)₄][SbCl₆] ( 3 ). The complexes 1 ‐ 3 were characterized by IR spectroscopy and by single crystal X‐ray determinations. 1 : Space group C2/c, Z = 4, lattice dimensions at 193 K: a = 3282.0(2), b = 798.7(1), c = 1926.1(2) pm, β = 107.96(1)°, R₁ = 0.0302. 1 contains [Cl₃PNPPh₃]⁺ cations with PN bond lengths of 152.5(2) and 160.9(2) pm, and a PNP bond angle of 140.5(1)°. 2 ·CH₂Cl₂: Space group , Z = 2, lattice dimensions at 193 K: a = 1031.2(1), b = 1448.3(2), c = 1811,4(2) pm, α = 70.96(1)°, β = 87.67(1)°, γ = 75.37(1)°, R₁ = 0.0713. 2 ·CH₂Cl₂ contains cations [SbCl₄(HNPPh₃)₂]⁺ with octahedrally coordinated Sb atom and the HNPPh₃ ligand molecules being in trans‐position. Sb–N bond lengths are 207.6(6) and 209.3(6) pm, PN bond lengths 162.3(7) and 160.8(7), which approximately corresponds with double bonds. 3 ·0.5CH₂Cl₂: Space group P4/n, Z = 2, lattice dimensions at 193 K: a = b = 1678.8(1), c = 1244.3(1) pm, R₁ = 0.0618. 3 ·0.5CH₂Cl₂ contains [Sb(NPPh₃)₄]⁺ cations with tetrahedrally coordinated Sb atom and short Sb–N bond lengths of 193.7(6) pm. The PN distances of the phosphoraneiminato ligands, (NPPh₃)^? with 156.5(6) pm, correspond with double bonds, the SbNP bond angles are 130.6(3)°.     

Achieving Near-unity Photoluminescence Quantum Yields in Organic-Inorganic Hybrid Antimony (III) Chlorides with the [SbCl5] Geometry

Hybrid organic–inorganic antimony halides have attracted increasing attention due to the non-toxicity, stability, and high photoluminescence quantum yield (PLQY). To shed light on the structural factors that contribute to the high PLQY, five pairs of antimony halides with general formula A₂SbCl₅ and A₂Sb₂Cl₈ are synthesized via two distinct methods and characterized. The A₂SbCl₅ type adopts square pyramidal [SbCl₅] geometry with near-unity PLQY, while the A₂Sb₂Cl₈ adopts seesaw dimmer [Sb₂Cl₈] geometry with PLQY≈0 %. Through combined data analysis with the literature, we have found that A₂SbCl₅ series with square pyramidal geometry generally has much longer Sb⋅⋅⋅Sb distances, leading to more expressed lone pairs of Sb^III. Additional factors including Sb−Cl distance and stability of antimony chlorides may also affect PLQY. Our targeted synthesis and correlated insights provide efficient tools to precisely form highly emissive materials for optoelectronic applications.     

Untersuchungen zur Sb–Sb‐Bindungsknüpfung in der Koordinationssphäre von Übergangsmetallen

Investigations of Sb–Sb Bond Formation Reactions in the Coordination Sphere of Transition Metals The reaction of SbCl₃ with various transition metal metalates of the type K[ML_n] [ML_n = Ni(CO)Cp*, Fe(CO)Cp′, Co(CO)₄; Cp* = η⁵‐C₅Me₅, Cp′ = η⁵‐C₅H₄Me] in the presence of [Cr(CO)₅thf] have been studied. With K[Ni(CO)Cp*] and K[Fe(CO)₂Cp′] the trigonal‐pyramidal complexes [(μ₃‐Sb){Ni(CO)Cp*}₃] ( 1 ) and [(μ₃‐Sb){Fe · (CO)₂Cp′}₃] ( 2 ), respectively, are obtained. The reaction with K[Co(CO)₄] leads to the tetrahedral cluster [Co₃(CO)₉(μ₃‐Sb{Cr(CO)₅})] ( 3 ) and the butterfly cluster [Co₂(CO)₆(μ‐SbCl)(μ‐SbCl{Cr(CO)₅})] ( 4 ). All products are characterised by X‐ray crystal structure determination. In contrast to the corresponding [(CO)₅CrPCl₃] system forming P–P bonds, starting from SbCl₃/[Cr(CO)₅thf] does not cause a Sb–Sb bond formation.     

Antimony(III) Halide-Assisted Stereospecific Coordination of Thione

The antimony halide-aided stereospecific coordination of a cyclic thiourea-type of ligand is observed for the first time. The antimony(III) imidazole thione complexes syn-[( L¹ )SbCl₃] ( syn- 1 ) and anti-[( L¹ )SbBr₃] ( anti- 2 ) have been synthesized in very good yield by the reaction between the spatially defined steric impact ligand [(IPaul)S] ( L¹ ) ([(IPaul)S]=1,3-bis(2,4-methyl-6-diphenyl phenyl)imidazole thione) and corresponding antimony halide. The stereoselective formation of complexes syn- 1 and anti- 2 has been confirmed by both NMR and single-crystal X-ray diffraction studies. Interestingly the stereospecific nature of syn- 1 and anti- 2 remains intact in solution. Furthermore, the thermal stability of antimony(III) imidazole thione complexes were examined by TGA analysis.     

Synthesis,Characterization, and Singlet Oxygen Sensitization by Antimony (III/V) Corrole Complexes

The synthesis, structural, spectroscopic characterization, and DFT/TD-DFT calculations of antimony corroles are reported herein. The studied complexes can be described as [(Corr)Sb^III] and [(Corr)(oxo)Sb^V]₂, where Corr is the trianion of corrole. All these complexes are diamagnetic in nature as is evident from sharp peaks with normal chemical shifts in the ¹H NMR spectra. Single crystal XRD analysis reveals that the antimony(V) corrole complex is the bis-μ-oxo-bridged dinuclear antimony(V). Both the tetra and hexa-coordinated [(Corr)Sb^III] and [(Corr)(oxo)Sb^V]₂ antimony complexes adopt domed-structure with weak d-π electron coupling. The Sb−O bond distances in the co-facial dimer of [(Corr)(oxo)Sb^V]₂ are 1.9802(16) Å (DFT: 2.0141 Å ) (for Sb1−O1), and 1.9639(17) Å (DFT: 1.9957 Å ) (for Sb2−O2) respectively. We observed that even though iodosobenzene is frequently used to oxidize [(Corr)Sb^III] species, the oxidation of [(Corr)Sb^III] is indeed very facile in nature and it even occurred in the air-equilibrated CHCl₃ solution while storing for few days. Excitation of these antimony (III/V) corrole complexes in DCM/MeOH (1 : 1) at 77 K results in red emission with maxima at 640–720 nm. The singlet oxygen production of [(Corr)(oxo)Sb^V]₂ has a quantum yield of 69 % and is two times higher than the analogous [(Corr)Sb^III] derivatives.     

Reactions of 1,4,7-trithiacyclononane, [9]aneS3, with early transition metal halides: synthesis and X-ray structure of {Fe([9]aneS3)2}[Sb2Cl8]

Summary The reactions of titanium(III) and (IV) chlorides with the crown thioether [9]aneS₃ were investigated. [TiCl_3- (MeCN)₃] gives a purple 1:1 adduct with a proposed octahedral structure involving tridentate fac-attachment of the ligand. With [TiCl₄(MeCN)₂] the identity of the yellow 1∶1 adduct obtained is discussed in terms of a six-coordinate species with bidentate ligand chelation. The title compound was isolated from the reactions of [9]aneS₃ with [TiCl₃(MeCN)₃] [SbCl₆] (by accident) and iron filings/SbCl₅ in MeCN solution and characterised crystallographically. The cation has two macrocyclic ligands coordinated facially to a six-coordinate Fe²⁺ ion; the anion comprises dimeric [(SbCl₄)₂] units linked together into a polymeric chain by weak halogen bridging.     

Phosphaniminato-Komplexe des Antimons. Die Kristallstrukturen von [Sb2Cl5(NPMe3)2][SbCl6] · CH3CN und [SbCl(NPPh3)]2[SbCl6]2 · 6 CH3CN

Phosphorane Iminato Complexes of Antimony. The Crystal Structures of [Sb₂Cl₅(NPMe₃)₂][SbCl₆] · CH₃CN and [SbCl(NPPh₃)]₂[SbCl₆]₂ · 6 CH₃CN The title compounds are formed by reaction of antimony pentachloride in acetonitrile solution with the phosphorane iminato complexes SbCl₂(NPMe₃) and SbCl₂(NPPh₃), respectively, which themselves are synthesized by reaction of antimony trichloride with Me₃SiNPR₃ (R = Me, Ph). The complexionic compounds are characterized by ¹²¹Sb Mössbauer spectroscopy and by crystal structure determinations. [Sb₂Cl₅(NPMe₃)₂][SbCl₆] · CH₃CN: Space group P4₁, Z = 4, 3 698 observed unique reflections, R = 0.022. Lattice dimensions at ?60°C: a = b = 1 056.0(1), c = 2 709.6(2) pm. The structure consists of SbCl₆^? ions and cations [Sb₂Cl₅(NPMe₃)₂(CH₃CN)]⁺, in which one Sb^III atom and one Sb^V atom are bridged by the N atoms of the phosphorane iminato ligands. [SbCl(NPPh₃)]₂[SbCl₆]₂ · 6 CH₃CN: Space group P1 , Z = 2, 5 958 observed unique reflections, R = 0.033. Lattice dimensions at ?60°C: a = 989.4(11), b = 1 273(1), c = 1 396(1) pm, α = 78.33(7), β = 77.27(8)°, γ = 86.62(8)°. The structure consists of SbCl₆^? ions and centrosymmetric cations [SbCl(NPPh₃)(CH₃CN)₂]₂²⁺, in which the antimony atoms are bridged by the N atoms of the phosphorane iminato ligands.     

Octahedral distortion caused by hydrogen bonding in tris(diethylammonium) hexachloridoantimonate(III)

The factors influencing the distortion of inorganic anions in the structures of chloridoantimonates(III) with organic cations, in spite of numerous structural studies on those compounds, have not been clearly described and separated. The title compound, [(C₂H₅)₂NH₂]₃[SbCl₆], consisting of isolated distorted [SbCl₆]³⁻ octahedra that have C₃ symmetry and [(C₂H₅)₂NH₂]⁺ cations, unequivocally shows the role played by hydrogen bonding in the geometry variations of inorganic anions. The organic cations, which are linked to the inorganic substructure through N—H...Cl hydrogen bonds, are clearly responsible for the distortion of the octahedral coordination of Sb^III in terms of differences (Δ) in both Sb—Cl bond lengths [Δ = 0.4667 (6) Å] and Cl—Sb—Cl angles [Δ = 9.651 (17)°].     

Enhanced Electrochemiluminescence from a Stoichiometric Ruthenium(II)–Iridium(III) Complex Soft Salt

Electrochemiluminescence (ECL) and electrochemistry are reported for a heterometallic soft salt, [Ru(dtbubpy)₃][Ir(ppy)₂(CN)₂]₂ ( [Ir][Ru][Ir] ), consisting of a 2:1 ratio of complementary charged Ru and Ir complexes possessing two different emission colors. The [Ru]²⁺ and [Ir]^? moieties in the [Ir][Ru][Ir] greatly reduce the energy required to produce ECL. Though ECL intensity in the annihilation path was enhanced 18× relative to that of [Ru(bpy)₃]²⁺, ECL in the co‐reactant path with tri‐n‐propylamine was enhanced a further 4×. Spooling spectroscopy gives insight into ECL mechanisms: the unique light emission at 634 nm is due to the [Ru]²⁺* excited state and no [Ir]^?* was generated in either route. Overall, the soft salt system is anticipated to be attractive and suitable for the development of efficient and low‐energy‐cost ECL detection systems.     

Elusive Antimony‐Centered Radical Cations: Isolation,Characterization, Crystal Structures,and Reactivity Studies

One‐electron oxidation of the stibines Aryl₃Sb ( 1 , Aryl=2,6‐ⁱ Pr₂‐4‐OMe‐C₆H₂; 2 , Aryl=2,4,6‐ⁱ Pr₃‐C₆H₂) with AgSbF₆ and NaBAryl^F₄ (Aryl^F=3,5‐(CF₃)₂C₆H₃) afforded the first structurally characterized examples of antimony‐centered radical cations 1 ^.+[BAryl^F₄]⁻ and 2 ^.+[BAryl^F₄]⁻. Their molecular and electronic structures were investigated by single‐crystal X‐ray diffraction, electron paramagnetic resonance spectroscopy (EPR) and UV/Vis absorption spectroscopy, in conjunction with theoretical calculations. Moreover, their reactivity was investigated. The reaction of 2 ^.+[BAryl^F₄]⁻ and p ‐benzoquinone afforded a dinuclear antimony dication salt 3 ²⁺[BAryl^F₄]₂⁻, which was characterized by NMR spectroscopy and X‐ray diffraction analysis. The formation of the dication 3 ²⁺ further confirms that the isolated stibine radical cations are antimony‐centered.     

Elusive Antimony‐Centered Radical Cations: Isolation,Characterization, Crystal Structures,and Reactivity Studies

One‐electron oxidation of the stibines Aryl₃Sb ( 1 , Aryl=2,6‐ⁱ Pr₂‐4‐OMe‐C₆H₂; 2 , Aryl=2,4,6‐ⁱ Pr₃‐C₆H₂) with AgSbF₆ and NaBAryl^F₄ (Aryl^F=3,5‐(CF₃)₂C₆H₃) afforded the first structurally characterized examples of antimony‐centered radical cations 1 ^.+[BAryl^F₄]⁻ and 2 ^.+[BAryl^F₄]⁻. Their molecular and electronic structures were investigated by single‐crystal X‐ray diffraction, electron paramagnetic resonance spectroscopy (EPR) and UV/Vis absorption spectroscopy, in conjunction with theoretical calculations. Moreover, their reactivity was investigated. The reaction of 2 ^.+[BAryl^F₄]⁻ and p ‐benzoquinone afforded a dinuclear antimony dication salt 3 ²⁺[BAryl^F₄]₂⁻, which was characterized by NMR spectroscopy and X‐ray diffraction analysis. The formation of the dication 3 ²⁺ further confirms that the isolated stibine radical cations are antimony‐centered.     

Synthesis and Crystal Structures of Antimony(III) Complexes With a Bis(amino)silane Ligand

Bis(amino)silane bearing bulky substituents on nitrogen, LH₂ [L = Me₂Si(NDipp)₂, Dipp = 2, 6‐diisopropylphenyl] was reacted with nBuLi (ratio 1:1 and 1:2) in toluene. The Me₂Si(LiNDipp)₂ was treated with SbCl₃ in a 1:1 ratio to yield the four‐membered SiN₂Sb ring compound of composition [η²(N,N)‐Me₂Si(NDipp)₂SbCl] ( 1 ). The mono lithiated bis(amino)silane was used to synthesize the monodentate heterotetraatomic complex [(η¹‐Me₂SiNDipp)NHDippSbCl₂] ( 2 ) by the reaction with SbCl₃. The complexes were characterized by ¹H and ¹³C NMR, elemental analysis, IR, and single‐crystal X‐ray structural analysis.     

[Sb(NPPh3)4]+SbF6−: Synthese,Kristallstruktur und 121Sb-Mößbauer-Spektrum

[Sb(NPPh₃)₄]⁺SbF₆^?: Synthesis, Crystal Structure, and ¹²¹Sb Mössbauer Spectrum The title compound as well as the hexachloro antimonate [Sb(NPPh₃)₄]⁺SbCl₆^? have been prepared by the reaction of Me₃SiNPPh₃ with SbF₅ and SbCl₅, respectively, in acetonitrile solutions. The compounds form colourless, moisture sensitive crystals, which were characterized by IR spectroscopy, by ¹²¹Sb Mössbauer spectroscopy, and by crystal structure analyses. A complete crystal structure analysis, however, could be carried out with [Sb(NPPh₃)₄]⁺SbF₆^? only. The compound crystallizes orthorhombically in the space group Pccn with four formula units per unit cell. The structure determination was done with 3 972 observed unique reflections, R = 0.053. Lattice dimensions at 19°C: a = 1 658,6; b = 1 698.9, c = 2 361.9 pm. In the cation [Sb(NPPh₃)₄]⁺ the antimony atom is tetrahedrally coordinated by the four nitrogen atoms of the phosphoraneiminato ligands with extremely short Sb? N bond lengths of 193 pm.     

An Antimony(V) Dication as a Z‐Type Ligand: Turning on Styrene Activation at Gold

With the intent to demonstrate that the charge of Z‐type ligands can be used to modulate the electrophilic character and catalytic properties of coordinated transition metals, we are now targeting complexes bearing polycationic antimony‐based Z‐type ligands. Toward this end, the dangling phosphine arm of ((o‐(Ph₂P)C₆H₄)₃)SbCl₂AuCl ( 1 ) was oxidized with hydrogen peroxide to afford [((o‐(Ph₂P)C₆H₄)₂(o‐Ph₂PO)C₆H₄)SbAuCl₂]⁺ ([ 2 a ]⁺) which was readily converted into the dicationic complex [((o‐(Ph₂P)C₆H₄)₂(o‐Ph₂PO)C₆H₄)SbAuCl]²⁺ ([ 3 ]²⁺) by treatment with 2 equiv AgNTf₂. Both experimental and computational results show that [ 3 ]²⁺ possess a strong Au→Sb interaction reinforced by the dicationic character of the antimony center. The gold‐bound chloride anion of [ 3 ]²⁺ is rather inert and necessitates the addition of excess AgNTf₂ to undergo activation. The activated complex, referred to as [ 4 ]²⁺ [((o‐(Ph₂P)C₆H₄)₂(o‐Ph₂PO)C₆H₄)SbAuNTf₂]²⁺ readily catalyzes both the polymerization and the hydroamination of styrene. This atypical reactivity underscores the strong σ‐accepting properties of the dicationic antimony ligand and its activating impact on the gold center.     

Amino­guanidinium(2+) amino­guanidinium(1+) hexa­chloro­antimonate(III) at 295 and 92 K

The crystal and molecular structure of the title compound, (CH₇N₄)(CH₈N₄)[SbCl₆], has been determined at 295 and 92 K. It is composed of isolated [SbCl₆]^3? octahedra and amino­guanidinium mono‐ and dications. One of four of the crystallographically inequivalent amino­guanidinium cations is disordered at both temperatures. Two crystallographically inequivalent [SbCl₆]^3? octahedra were found to possess three significantly longer Sb—Cl bonds than three other octahedra. The shorter bonds are in the range 2.456 (2)–2.577 (2) Å, whereas the longer ones are between 2.705 (2) and 2.931 (2) Å. Each short Sb—Cl bond is located trans to a long bond. It is argued that this deformation is caused by N—H?Cl hydrogen bonds.     

Structural,Spectroscopic and Computational Examination of the Dative Interaction in Constrained Phosphine–Stibines and Phosphine–Stiboranes

A series of phosphine–stibine and phosphine–stiborane peri‐substituted acenaphthenes containing all permutations of pentavalent groups ?SbCl_nPh_4–n ( 5 – 9 ), as well as trivalent groups ?SbCl₂, ?Sb(R)Cl, and ?SbPh₂ ( 2 – 4 , R=Ph, Mes), were synthesised and fully characterised by single crystal diffraction and multinuclear NMR spectroscopy. In addition, the bonding in these species was studied by DFT computational methods. The P–Sb dative interactions in both series range from strongly bonding to non‐bonding as the Lewis acidity of the Sb acceptor is decreased. In the pentavalent antimony series, a significant change in the P–Sb distance is observed between ?SbClPh₃ and ?SbCl₂Ph₂ derivatives 6 and 7 , respectively, consistent with a change from a bonding to a non‐bonding interaction in response to relatively small modification in Lewis acidity of the acceptor. In the Sb^III series, two geometric forms are observed. The P–Sb bond length in the SbCl₂ derivative 2 is as expected for a normal (rather than a dative) bond. Rather unexpectedly, the phosphine–stiborane complexes 5 – 9 represent the first examples of the σ⁴P→σ⁶Sb structural motif.     

Stoichiometry-dependent oxidation of tris(2-methoxyphenyl)antimony with diiodine

The reaction of 2-methoxyphenyllithium with SbCl₃ affords tris(2-methoxyphenyl)antimony. Its treatment with equimolar amount of I₂ results in stiborane (2-MeOC₆H₄)₃SbI₂, while heating with 2 equivalents of I₂ leads to iodotris(2-methoxyphenyl)stibonium triiodide [(2-MeOC₆H₄)₃SbI]⁺ [I₃]^– featuring halogen bonding in solid state.