Aryl Ligands Research Articles

Magnesium 4, 5, and 6 coordinate complexes with ligands bound via sp or sp2 hybridized atoms

As a metallic element of high natural abundance, magnesium finds a wide range of uses in both stoichiometric and more recently catalytic applications. This often takes advantage of the basic or nucleophilic properties of its compounds or their ability to co-complex with other organometallic compounds. However, the homoleptic chemistry of Mg(II) is heavily skewed towards alkyl and aryl ligands bound via sp2 and sp3 hybridized atoms. Here, we report our combined NMR spectroscopic and X-ray crystallographic study into much rarer alternative THF solvates of homoleptic magnesium complexes using ligands which bind via sp (alkynyl) and sp2 (imido) atoms. Specifically, we exploit the high acidity of terminal alkynes and diphenylacetonitrile to prepare tetra-solvated distorted octahedral complexes Mg(CCC6H4R-p)2(THF)4 (R = Me, CF3) and Mg(NCCPh2)2(THF)4 starting from the commercial alkyl reagent MgBu2. Adopting a similar deprotonative strategy using benzophenoneimine Ph2CNH affords the heteroleptic trinuclear complex Mg3(NCPh2)4nBu2(THF)2 with distorted tetrahedral Mg centres. Related imidomagnesium halide complexes can be accessed either by deprotonation of the imine with a Grignard reagent, or nucleophilic addition of a Grignard reagent to a nitrile, but these unusual five-coordinate complexes are unresponsive to a 1,4-dioxane induced Schlenk equilibrium shift. Employing a higher reflux temperature switching from a THF to a toluene medium permits access to the THF solvate of a homoleptic imido complex which also possesses a trinuclear constitution in Mg3(NCPh2)6(THF)2.

Unusual S=1 Four‐Coordinate Fe(IV) Complexes Supported by Bisamide Ligands: Syntheses, Characterization, and Electronic Structures

AbstractThe catalytic relevance of Fe(IV) species in non‐heme iron catalysis has motivated synthetic advances in well‐defined five‐ and six‐coordinate Fe(IV) complexes for a better understanding of their fundamental electronic structures and reactivities. Herein, we report the syntheses of FeDipp2 and FeMes2, a pair of unusual four‐coordinate non‐heme formally Fe(IV) complexes with S=1 ground states supported by strongly donating bisamide ligands. By combining spectroscopic characterization and computational modeling, we found that small variations in ligand aryl substituents resulted in substantial changes in both structures and bonding. This work highlights the strong donor capabilities and modularity of the bisamide ligand set. More broadly, it is a critical contribution to the utilization of ligand design to modulate molecular geometries and electronic structures of low‐coordinate, high‐valent iron complexes.

Unusual S=1 Four-Coordinate Fe(IV) Complexes Supported by Bisamide Ligands: Syntheses, Characterization, and Electronic Structures.

The catalytic relevance of Fe(IV) species in non-heme iron catalysis has motivated synthetic advances in well-defined five- and six-coordinate Fe(IV) complexes for a better understanding of their fundamental electronic structures and reactivities. Herein, we report the syntheses of FeDipp2 and FeMes2, a pair of unusual four-coordinate non-heme formally Fe(IV) complexes with S=1 ground states supported by strongly donating bisamide ligands. By combining spectroscopic characterization and computational modeling, we found that small variations in ligand aryl substituents resulted in substantial changes in both structures and bonding. This work highlights the strong donor capabilities and modularity of the bisamide ligand set. More broadly, it is a critical contribution to the utilization of ligand design to modulate molecular geometries and electronic structures of low-coordinate, high-valent iron complexes.

Tri-aryl antimony(V) hydroximato and hydroxamato complexes: Combining lipophilic Sb(III/V) and hydroxamic acids in combating Leishmania

Six novel tri-aryl antimony(V) hydroximato complexes (3–8) with composition [SbAr3(O2NCR)] (3: Ar = Ph, R = o-(OH)Ph, 4: Ar = Ph, R = Me, 5: Ar = Ph, R = Ph; 6: Ar = Mes, R = Me, 7: Ar = Mes, R = Ph, 8: Ar = Mes, R = o-(OH)Ph (where Ph = phenyl, Me = methyl, Mes = mesityl)), were synthesised and evaluated for anti-parasitic activity towards Leishmania major (L. major) promastigotes and amastigotes. Complexes of the form [SbAr3(O2NCR)], with the dianionic hydroximato ligand binding O,O′-bidentate to the Sb(V) centre, exist in the solid-state for the mesityl-derived complexes. In contrast, the phenyl-ligated Sb(V) complexes crystallise as the hexacoordinate, hydroxamato species [SbPh3(O2NHC(OH))], with the OH ligand derived from entrained H2O in the crystallisation solvent. It is found that both the aryl and hydroximato ligands are found to influence the bioactivity of the Sb(V) complexes. Complexes 3–8 exhibited varied anti-promastigote activity with IC50 values ranging from 1.53 μM for 6 to 36.0 μM for 3, also reflected in varied anti-amastigote activity with a percentage infection range of 5.50% for 6 to 29.00% for 3 at a concentration of 10 μM. The complexes were relatively non-toxic to human fibroblasts with an IC50 value range of 59.3 μM (7) to ≥100 μM (3–6, 8), and exhibited varied toxicity towards J774.1 A macrophages (IC50: 3.97 (6) to ≥100 (8) μM). All complexes showed enhanced activity compared to the parent hydroxamic acids.

Light Activation and Photophysics of a Structurally Constrained Nickel(II)-Bipyridine Aryl Halide Complex.

Transition-metal photoredox catalysis has transformed organic synthesis by harnessing light to construct complex molecules. Nickel(II)-bipyridine (bpy) aryl halide complexes are a significant class of cross-coupling catalysts that can be activated via direct light excitation. This study investigates the effects of molecular structure on the photophysics of these catalysts by considering an underexplored, structurally constrained Ni(II)-bpy aryl halide complex in which the aryl and bpy ligands are covalently tethered alongside traditional unconstrained complexes. Intriguingly, the tethered complex is photochemically stable but features a reversible Ni(II)-C(aryl) ⇄ [Ni(I)···C(aryl)•] equilibrium upon direct photoexcitation. When an electrophile is introduced during photoirradiation, we demonstrate a preference for photodissociation over recombination, rendering the parent Ni(II) complex a stable source of a reactive Ni(I) intermediate. Here, we characterize the reversible photochemical behavior of the tethered complex by kinetic analyses, quantum chemical calculations, and ultrafast transient absorption spectroscopy. Comparison to the previously characterized Ni(II)-bpy aryl halide complex indicates that the structural constraints considered here dramatically influence the excited state relaxation pathway and provide insight into the characteristics of excited-state Ni(II)-C bond homolysis and aryl radical reassociation dynamics. This study enriches the understanding of molecular structure effects in photoredox catalysis and offers new possibilities for designing customized photoactive catalysts for precise organic synthesis.

A Ruthenophosphanorcaradiene as a Synthon for an Ambiphilic Metallophosphinidene.

Reaction of the ruthenium carbene complex Cp*(IPr)RuCl (1) (IPr = 1,3-bis(Dipp)imidazol-2-ylidene; Dipp = 2,6-diisopropylphenyl) with sodium phosphaethynolate (NaOCP) led to intramolecular dearomatization of one of the Dipp substituents on the Ru-bound carbene to afford a Ru-bound phosphanorcaradiene, 2. Computations by DFT reveal a transition state characterized by a concerted process whereby CO migrates to the Ru center as the P atom adds to the π system of the aryl group. The phosphanorcaradiene possesses ambiphilic properties and reacts with both nucleophilic and electrophilic substrates, resulting in rearomatization of the ligand aryl group with net P atom transfer to give several unusual metal-bound, P-containing main-group moieties. These new complexes include a metallo-1-phospha-3-azaallene (Ru─P═C═NR), a metalloiminophosphanide (Ru─P═N─R), and a metallophosphaformazan (Ru─P(═N─N═CPh2)2). Reaction of 2 with the carbene 2,3,4,5-tetramethylimidazol-2-ylidene (IMe4) produced the corresponding phosphaalkene DippP═IMe4.

Unveiling the promising anticancer activity of palladium(II)-aryl complexes bearing diphosphine ligands: a structure-activity relationship analysis.

In continuation of our previous works on the cytotoxic properties of organopalladium compounds, in this contribution we describe the first systematic study of the anticancer activity of Pd(II)-aryl complexes. To this end, we have prepared and thoroughly characterized a wide range of palladium derivatives bearing different diphosphine, aryl and halide ligands, developing, when necessary, specific synthetic protocols. Most of the synthesized compounds showed remarkable cytotoxicity towards ovarian and breast cancer cell lines, with IC50 values often comparable to or lower than that of cisplatin. The most promising complexes ([PdI(Ph)(dppe)] and [PdI(p-CH3-Ph)(dppe)]), characterized by a diphosphine ligand with a low bite angle, exhibited, in addition to excellent cytotoxicity towards cancer cells, low activity on normal cells (MRC5 human lung fibroblasts). Specific immunofluorescence tests (cytochrome c and H2AX assays), performed to clarify the possible mechanism of action of this class of organopalladium derivatives, seemed to indicate DNA as the primary cellular target, whereas caspase 3/7 assays proved that the complex [PdI(Ph)(dppe)] was able to promote intrinsic apoptotic cell death. A detailed molecular docking analysis confirmed the importance of a diphosphine ligand with a reduced bite angle to ensure a strong DNA-complex interaction. Finally, one of the most promising complexes was tested towards patient-derived organoids, showing promising ex vivo cytotoxicity.

Исследование строения -дикетонатов тетраарилсурьмы Ph4Sb[MeC(O)CHC(O)Ph], p-Tol4Sb[MeC(O)CEtC(O)Me] ∙ 1½ PhH, p-Tol4Sb[MeC(O)СHC(O)NHPh

Reaction of pentaphenylantimony and penta(para-tolyl)antimony with -diketones in benzene (100 °C, 1 h) forms tetraarylantimony -diketonates Ph4Sb[MeC(O)CHC(O)Ph] (1), p-Tol4Sb[MeC(O)CEtC(O)Me] ∙ 1½PhH (2), p-Tol4Sb[MeC(O)СHC(O)NHPh] (3), characterized by IR spectra and X-ray diffraction analysis. Crystals 1 [C34H29O2Sb, M 591.32; triclinic system, symmetry group P–1; cell parameters: a = 9.524(13) Å, b = 9.827(10) Å, c = 17.350(18) Å;  = 99.03(3), β = 101.50(6),  = 111.02(4), V = 1438(3) Å3, Z = 2; cal = 1.365 g/cm3], 2 [C44H48O2Sb, M 730.57; triclinic system, symmetry group P–1; cell parameters: a = 9.740(5) Å, b = 14.283(6) Å, c = 15.174(6) Å;  = 107.818(14), β = 90.292(18),  = 105.33(2), V = 1929,7(16) Å3, Z = 2; cal = 1.257 g/cm3], 3 [C34H30NO2Sb, M 606.34; monoclinic system, symmetry group P21/n; cell parameters: a = 9.396(17) Å, b = 10.23(2) Å, c = 29.45(6) Å; β = 95.91(6), V = 2817(10) Å3, Z = 4; cal = 1.430 g/cm3]. The obtained tetraarylantimony -diketonates are crystal-line compounds with a distinct melting point, resistant to moisture and atmospheric oxygen, and highly soluble in aromatic solvents and polyhalide solvents. Complex 2 is a solvate and contains 1½ benzene molecules. According to the X-ray diffraction data, the antimony atoms in complexes 1–3 have a distorted octahedral coordination, with the chelate ring and two aryl substituents locat-ed in the equatorial plane, while two aryl ligands occupy axial positions.

Синтез и строение сольвата бис[3,5-динитробензоата] трис(2-метокси)(5-бром)фенилсурьмы [C6H3(2-OMe)(5-Br)]3Sb[OC(O)C6H3(NO2)2-3,5]2 ∙ PhH ∙ ½ C8H18

Tris(2-methoxy)(5-bromo)phenylantimony bis[3,5-dinitrobenzoate] (1) was obtained from 3,5-dinitrobenzoic acid by oxidative addition to triarylantimony in the presence of tertiary butyl hy-droperoxide in ether, and was isolated by recrystallization from a benzene-octane mixture in the form of a crystal solvate with benzene and octane molecules in its crystal lattice. The structure of solvate 1 was established by the IR spectroscopy and X-ray diffraction analysis (XRD). In the IR spectrum of complex 1, in addition to the absorption bands related to the stretching vibrations of the Sb–C, СAr–О–Ме, and carbonyl groups, there are bands corresponding to the stretching vibra-tions of the C–Br bonds (524 and 555 cm–1). The X-ray diffraction data show that the antimony at-oms in complex 1 have a distorted trigonal bipyramid coordination with carboxylate ligands in the axial position. The antimony atom and two oxygen atoms do not lie on the same straight line and are located in such a way that the OSbO angle is 170.79°. The O…Sb distances (2.134(4) and 2.110(5) Å) are close to the sum of the covalent radii of antimony and oxygen. In addition, accord-ing to the X-ray diffraction data, compound 1 crystallizes in the monoclinic crystal system, space group P21/n. The structural organization in the crystal is formed due to short contacts of oxygen atoms in the nitro groups of the carboxylate ligands with carbon and bromine atoms of the aryl lig-ands of neighboring molecules, as well as hydrogen O...H (2.524–2.715 Å) bonds. In addition, a certain contribution to the formation of the crystal structure is made by the p-p stacking between the aromatic rings of crystallization benzene and the methoxy-bromo-phenyl ligands. The aro-matic rings are displaced in relation to each other and the distance between them is 3.367 Å. Melt-ing point of solvate 1 is 172.6 °C, according to the thermal analysis data. However, further in-crease in temperature is accompanied by decomposition of compound 1, and therefore an exo-thermic peak is observed on the DSC curve at 255.7 °C, corresponding to a mass loss of 31 % ac-cording to the TGA data. Complete tables of atom coordinates, bond lengths, and valence angles are deposited at the Cambridge Crystallographic Data Center (No. 2060562, depos-it@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/data_request/cif)

Interaction and Energy Decomposition Analyses to Predict Stability of Tetraaryl Square Planar Cobalt Complexes

AbstractThe sodium‐mediated cobaltation of pentafluorobenzene using the bimetallic base [NaCo(HMDS)3] (HMDS=N(SiMe3)2) has been reported to afford a novel tetraaryl Co(II) square planar complex. Yet, the preparation of analogue structures with 1,2,3,4‐tetrafluorobenzene, 1,3,5‐trichlorobenzene, and 1,4‐dibromo‐2,5‐difluorobenzene remains elusive. While the metalation step proceeds leading to stable [NaCo(HMDS)2Ar] species, the ligand redistribution process to afford the tetraaryl Co(II) square planar complexes does not take place. Herein we report a density functional theory study in combination with electronic structure and energy decomposition analyses to shed light on the electronic and steric requirements to afford such complexes. Our findings show that the formation of the Co(II) square planar complexes depends on the right balance between intramolecular X⋅⋅⋅X and Na⋅⋅⋅X (X=H, F, Cl, Br) interactions. The latter further induces a ‘seesaw effect’, whereby the aryl ligand acts as a ‘seesaw’ allowing two X atoms in ortho positions to interdependently interact with Na. Only by considering both attractive and repulsive Na(X)⋅⋅⋅X interactions, the correct stability of the square planar complexes observed in experiments can be predicted computationally. We envision these insights to guide the rational design of novel square planar metal complexes for C−C coupling, a field that is still dominated by scarce and expensive precious metals.

Competition between N,C,N-Pincer and N,N-Chelate Ligands in Platinum(II).

Replacement of the chloride ligand of PtCl{κ3-N,C,N-[py-C6HR2-py]} (R = H (1), Me (2)) and PtCl{κ3-N,C,N-[py-O-C6H3-O-py]} (3) by hydroxido gives Pt(OH){κ3-N,C,N-[py-C6HR2-py]} (R = H (4), Me (5)) and Pt(OH){κ3-N,C,N-[py-O-C6H3-O-py]} (6). These compounds promote deprotonation of 3-(2-pyridyl)pyrazole, 3-(2-pyridyl)-5-methylpyrazole, 3-(2-pyridyl)-5-trifluoromethylpyrazole, and 2-(2-pyridyl)-3,5-bis(trifluoromethyl)pyrrole. The coordination of the anions generates square-planar derivatives, which in solution exist as a unique species or equilibria between isomers. Reactions of 4 and 5 with 3-(2-pyridyl)pyrazole and 3-(2-pyridyl)-5-methylpyrazole provide Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N1-[R'pz-py]} (R = H; R' = H (7), Me (8). R = Me; R' = H (9), Me (10)), displaying κ1-N1-pyridylpyrazolate coordination. A 5-trifluoromethyl substituent causes N1-to-N2 slide. Thus, 3-(2-pyridyl)-5-trifluoromethylpyrazole affords equilibria between Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N1-[CF3pz-py]} (R = H (11a), Me (12a)) and Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N2-[CF3pz-py]} (R = H (11b), Me (12b)). 1,3-Bis(2-pyridyloxy)phenyl allows the chelating coordination of the incoming anions. Deprotonations of 3-(2-pyridyl)pyrazole and its substituted 5-methyl counterpart promoted by 6 lead to equilibria between Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N1-[R'pz-py]} (R' = H (13a), Me (14a)) with a κ-N1-pyridylpyrazolate anion, keeping the pincer coordination of the di(pyridyloxy)aryl ligand, and Pt{κ2-N,C-[pyO-C6H3(Opy)]}{κ2-N,N-[R'pz-py]} (R' = H (13c), Me (14c)) with two chelates. Under the same conditions, 3-(2-pyridyl)-5-trifluoromethylpyrazole generates the three possible isomers: Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N1-[CF3pz-py]} (15a), Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N2-[CF3pz-py]} (15b), and Pt{κ2-N,C-[pyO-C6H3(Opy)]}{κ2-N,N-[CF3pz-py]} (15c). The N1-pyrazolate atom produces a remote stabilizing effect on the chelating form, pyridylpyrazolates being better chelate ligands than pyridylpyrrolates. Accordingly, reactions of 4-6 with 2-(2-pyridyl)-3,5-bis(trifluoromethyl)pyrrole yield Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N1-[(CF3)2C4(py)HN]} (R = H (16), Me (17)) or Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N1-[(CF3)2C4(py)HN]} (18), displaying κ1-N1-pyrrolate coordination. Complexes 7-10 are efficient green phosphorescent emitters (488-576 nm). In poly(methyl methacrylate) (PMMA) films and in dichloromethane, they experience self-quenching, due to molecular stacking. Aggregation occurs through aromatic π-π interactions, reinforced by weak platinum-platinum interactions.

Arylation of Nucleophiles Using Diaryliodonium (III) Salts

Diaryliodonium(III) salts (Ar1Ar2I+X−) are hypervalent iodine(III) compounds that function as useful arylation agents forming aryl-carbon and aryl-heteroatom bonds with or without transition metal catalysts. The iodine(III) center of diaryliodonium salts has electrophilic properties, which induces the arylation reactions of nucleophiles. For the cases with Ar1≠Ar2 in diaryliodonium salts, the chemoselectivity of aryl-group transfers depends on the nature of the aryl ligands, including electronic and steric effects. This article describes ligand control strategy leading to unified aryl selectivity and enhanced reactivity for the arylation of various nucleophiles.

Synthesis and Structural Characterization of Phosphanide Gold(III)/Gold(I) Complexes and Their Thallium(III) and Gold(III) Precursors

In this paper, we describe a series of diphenylphosphane and diphenylphosphanide gold(III) and gold(III)/gold(I) complexes containing 3,5-C6Cl2F3 as aryl ligands at gold that have been synthesized due to the arylating and oxidant properties of the new polymeric thallium(III) complex [TlCl(3,5-C6Cl2F3)2]n (1). Its reaction with [Au(3,5-C6Cl2F3)(tht)] (tht = tetrahydrothiophene) produces the gold(III) complex [Au(3,5-C6Cl2F3)3(tht)] (2), which allows the synthesis of the diphenylohosphane derivative [Au(3,5-C6Cl2F3)3(PPh2H)] (3). Its treatment with acetylacetonate gold(I) derivatives leads to two novel AuIII/AuI phosphanido-bridged complexes, [PPN][Au(3,5-C6Cl2F3)3(µ-PPh2)AuCl] (4) and [PPN][{(3,5-C6Cl2F3)3Au(µ-PPh2)}2Au] (5). All these complexes have been characterized, and the crystal structures of 1, 2, 4 and 5 have been established by single crystal X-ray diffraction methods, showing a novel polymeric arrangement in 1.

Особенности строения производных тетра(пара-толил)сурьмы p-Tol4SbX (X = Br, OC(O)Ph∙PhH, OSO2C6H2Me3-2,4,6)

The structure of tetra(para-tolyl)antimony compounds p-Tol4SbX [X = Br (1), OC(O)Ph∙PhH (2), OSO2C6Me3-2,4,6 (3)] was established by X-ray diffraction analysis (XRD). According to the X-ray diffraction data, the antimony atoms in complexes 1–3 have a distorted trigonal bipyramidal coordination with three aryl ligands in the equatorial plane, while the axial angles CSbX are 174.75(8), 175.13(9), and 174.51(6). The X-ray diffraction data: (1) [C28H28BrSb, M = 566.16; monoclinic syngony, sp. gr. P21/n; cell parameters: a = 9.868(6) Å, b = 23.312(11) Å, c = 12.106(6) Å; β = 113.15(2), V = 2561(2) Å3, Z = 4; calc = 1.469 g/cm3;  = 2.649 mm–1; F(000) = 1128.0; region 2q collection: 6.4–56.76; –13 ≤ h ≤ 13, –31 ≤ k ≤ 31, –16 ≤ l ≤ 16; total reflections 42998; independent reflections 6359 (Rint = 0.0346); GOOF = 1.080; R-factor 0.0325]; (2) [C41H39O2Sb, M = 685.47; monoclinic syngony, sp. gr. C2/c; cell parameters: a = 28.186(13) Å, b = 15.116(6) Å, c = 17.629(8) Å; β = 91.73(2), V = 7507(6) Å3, Z = 8; calc = 1.213 g/cm3;  = 0.765 mm–1; F(000) = 2816.0; region 2q collection: 6.572–56.996; –37 ≤ h ≤ 37, –20 ≤ k ≤ 20, –23 ≤ l ≤ 23; total reflections 116806; independent reflections 9489 (Rint = 0.0492); GOOF = 1.102; R-factor 0.0363]; (3) [C37H39O3SSb, M = 685.49; monoclinic syngony, sp. gr. P21/n; cell options: a = 12.172(4) Å, b = 18.802(5) Å, c = 15.433(6) Å; β = 108.744(12), V = 3345(2) Å3, Z = 4; calc = 1.361 g/cm3;  = 0.921 mm–1; F(000) = 1408.0; region 2q collection: 5.96–63.02; –16 ≤ h ≤ 17, –27 ≤ k ≤ 27, –22 ≤ l ≤ 21; total reflections 138835; independent reflections 11081 (Rint = 0.0373); GOOF = 1.045; R-factor 0.0304]. Complete tables of atomic coordinates, bond lengths, and bond angles for compounds 1–3 have been deposited at the Cambridge Crystallographic Data Center (CCDC 2182608, 2149953, 2171918; deposit@ccdc.cam.ac.uk; http://www.ccdc.cam. ac.uk).

Синтез и кристаллическая структура бис(2-метилкарборанил-карбоксилата) трис(3-фторфенил)сурьмы

Oxidation of tris(3-fluorophenyl)antimony with hydrogen hydroperoxide in the presence of 2-methylcarboranylcarboxylic acid leads to the formation of tris(3-fluorophenyl)antimony bis(2-methylcarboranylcarboxylate) (1), the structural features of which have been established by X-ray diffraction analysis. According to X-ray diffraction analysis performed at 293 K on an automatic four-circle diffractometer D8 Quest Bruker (two-coordinate CCD detector, Mo Kα-radiation, λ = 0.71073 Å, graphite monochromator), the crystals are characterized by: C26H38B20F3O4Sb, M 809.52; monoclinic system, space group С2/c; cell parameters: a = 19.050(13), b = 14.441(9), c = 14.568(9) Å;  = 90, β = 98.51(2),  = 90; V = 3964(4) Å3; Z = 4; crystal size 0.8 × 0.55 × 0.29 mm; index ranges –25 ≤ h ≤ 25, –18 ≤ k ≤ 18, –18 ≤ l ≤ 19; total reflections 37401; independent reflections 4709; Rint 0.0545; GOOF 1.108; R1 = 0.0578, wR2 = 0.1482; residual electron density –0.59/1.09 e/Å3. According to X-ray diffraction analysis data, in the molecules of compound 1, the antimony atoms have a distorted trigonal-bipyramidal coordination with the oxygen atoms of the carboxylate ligands in the axial positions. The Sb–C bonds (2.104(4)–2.114(8) Å) are shorter than the Sb–O distances (2.113(3) Å), the OSbО axial angle is 178.48(15)°, the CSbC angles are 109.7(2)°, 118.4(2)°, 131.8(3)°, while a significant increase in one of the angles is associated with the cis-conformation of the carboxylate ligands relative to the equatorial plane. The conformation of aryl ligands with respect to the equatorial plane [C3] is propeller. Structure 1 contains intramolecular Sb•••O=С contacts between the antimony and oxygen atoms of the carbonyl groups of the carboxylate ligands, which are 3.089(3) Å. The formation of a spatial network in the crystal of compound 1 is due to the presence of weak hydrogen bonds with the participation of boron atoms of carboxylate ligands and fluorine of aryl ligands: B•••H (3.19 Å) and F•••B (3.45 Å). Complete tables of atomic coordinates, bond lengths, and bond angles are deposited at the Cambridge Structural Data Center (no. 2178731; deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/data_request/ cif).

Hydrogen Bonding in Platinum Indolylphosphine Polyfluorido and Fluorido Complexes.

The reaction of the Pt complexes cis-[Pt(CH3 )(Ar){Ph2 P(Ind)}2 ] (Ind=2-(3-methyl)indolyl, Ar=4-tBuC6 H4 (1 a), 4-CH3 C6 H4 (1 b), Ph (1 c), 4-FC6 H4 (1 d), 4-ClC6 H4 (1 e), 4-CF3 C6 H4 (1 f)) with HF afforded the polyfluorido complexes trans-[Pt(F(HF)2 )(Ar){Ph2 P(Ind)}2 ] 2 a-f, which can be converted into the fluoride derivatives trans-[Pt(F)(Ar){Ph2 P(Ind)}2 ] (3 a-f) by treatment with CsF. The compounds 2 a-f and 3 a-f were characterised thoroughly by multinuclear NMR spectroscopy. The data reveal hydrogen bonding of the fluorido ligand with HF molecules and the indolylphosphine ligand. Polyfluorido complexes 2 a-f show larger |1 J(F,Pt)|, but lower 1 J(H,F) coupling constants when compared to the fluorido complexes 3 a-f. Decreasing 1 J(P,Pt) coupling constants in 2 a-f and 3 a-f suggest a cis influence of the aryl ligands in the following order: 4-tBuC6 H4 (a) ≈4-CH3 C6 H4 (b)<Ph (c)≪4-FC6 H4 (d)<4-ClC6 H4 (e)<4-CF3 C6 H4 (f). In addition, the larger cis influence of aryl ligands bearing electron-withdrawing groups in the para position correlates with decreasing magnitudes of |1 J(F,Pt)| coupling constants. The interpretation of the experimental data was supported by quantum-chemical DFT calculations.

Au⋅⋅⋅H−C Interactions Support a Robust Thermally Activated Delayed Fluorescence (TADF) Gold(I) Complex for OLEDs with Little Efficiency Roll‐Off and Good Stability

AbstractThe practical use of luminescent mononuclear gold(I) complexes as optoelectronic materials has been limited by their inferior stability. Herein we demonstrate a strategy to improve the stability of gold(I) complexes which display thermally activated delayed fluorescence (TADF). A highly rigid and groove‐like σ‐donating aryl ligand has been used to form dual Au⋅⋅⋅H−C hydrogen bonds. The secondary metal‐ligand interactions have been authenticated by single‐crystal structure, NMR spectroscopy and theoretical simulations. The TADF AuI complex exhibits appealing emission properties (photoluminescence quantum yield=76 %; delayed fluorescence lifetime=1.2 μs) and much improved thermal and photo‐stability. Vacuum‐deposited organic light‐emitting diodes (OLEDs) show promising electroluminescence with a maximum external quantum efficiency (EQE) over 23 % and negligible efficiency roll‐off even at 10 000 cd m−2. An estimated LT50 longer than 77 000 h with initial luminance of 100 cd m−2 reveals good operational stability. This work suggests a way for design of stable luminescent gold(I) complexes.

Au⋅⋅⋅H-C Interactions Support a Robust Thermally Activated Delayed Fluorescence (TADF) Gold(I) Complex for OLEDs with Little Efficiency Roll-Off and Good Stability.

The practical use of luminescent mononuclear gold(I) complexes as optoelectronic materials has been limited by their inferior stability. Herein we demonstrate a strategy to improve the stability of gold(I) complexes which display thermally activated delayed fluorescence (TADF). A highly rigid and groove-like σ-donating aryl ligand has been used to form dual Au⋅⋅⋅H-C hydrogen bonds. The secondary metal-ligand interactions have been authenticated by single-crystal structure, NMR spectroscopy and theoretical simulations. The TADF AuI complex exhibits appealing emission properties (photoluminescence quantum yield=76 %; delayed fluorescence lifetime=1.2 μs) and much improved thermal and photo-stability. Vacuum-deposited organic light-emitting diodes (OLEDs) show promising electroluminescence with a maximum external quantum efficiency (EQE) over 23 % and negligible efficiency roll-off even at 10 000 cd m-2 . An estimated LT50 longer than 77 000 h with initial luminance of 100 cd m-2 reveals good operational stability. This work suggests a way for design of stable luminescent gold(I) complexes.

Multiconfiguration Pair-Density Functional Theory for Chromium(IV) Molecular Qubits.

Pseudotetrahedral organometallic complexes containing chromium(IV) and aryl ligands have been experimentally identified as promising molecular qubit candidates. Here we present a computational protocol based on multiconfiguration pair-density functional theory for computing singlet–triplet gaps and zero-field splitting (ZFS) parameters in Cr(IV) aryl complexes. We find that two multireference methods, multistate complete active space second-order perturbation theory (MS-CASPT2) and hybrid multistate pair-density functional theory (HMS-PDFT), perform better than Kohn–Sham density functional theory for singlet–triplet gaps. Despite the very small values of the ZFS parameters, both multireference methods performed qualitatively well. MS-CASPT2 and HMS-PDFT performed particularly well for predicting the trend in the ratio of the rhombic and axial ZFS parameters, |E/D|. We have also investigated the dependence and sensitivity of the calculated ZFS parameters on the active space and the molecular geometry. The methodologies outlined here can guide future prediction of ZFS parameters in molecular qubit candidates.

Valence-Inverted States of Nickel(II) Complexes Perform Facile C-H Bond Activation.

Valence-inverted reactivity (VIR) is discovered here through high-level computations of excited states of Ni(II) complexes that are generated by triplet energy transfer. For example, the so-generated 3[(Ar)(bpy)NiII(Br)] species possesses a valence-inverted occupancy, dxy1dxz1dx2-y22, wherein the uppermost dx2-y2 orbital is metal-ligand antibonding. This state promotes C-H bond activation of THF and its cross-coupling to the aryl ligand. Thus, due to the metal-ligand antibonding character of dx2-y2, the dxy1dx2-y22 subshell opens a Ni-coordination site by shifting the bidentate bipyridine ligand to monodentate plus a dangling pyridine. The tricoordinate Ni(II) intermediate inserts into a C-H bond of THF, transfers a proton to the dangling pyridine moiety, and eventually generates an arylated THF by reductive-coupling. The calculated high kinetic isotope effect is in accord with experiment, both revealing C-H activation. The VIR pattern is novel, its cross-coupling reaction is highly useful, and it is generally expected to occur in other d8 complexes.