Scorpionate Complex Research Articles

Utilizing the Perfluoronaphthalene Radical Cation as a Selective Deelectronator to Access a Variety of Strongly Oxidizing Reactive Cations.

A selective deelectronation reagent with very high potential of +2.00 (solution)/+2.41 V (solid-state) vs. Fc+/0 and based on a room temperature stable perfluoronaphthalene (naphthaleneF) radical cation salt was developed and applied. The solid-state deelectronation of commercial naphthaleneF with [NO]+[F{Al(ORF)3}2]- generates [naphthaleneF]+⋅[F{Al(ORF)3}2]- (ORF=OC(CF3)3) in gram scale. Thermochemical analysis unravels the solid-state deelectronation potential of the starting [NO]+-reagent to be +2.34 V vs. Fc+/0 with [F{Al(ORF)3}2]- counterion, but only +1.14 V vs. Fc+/0 with the small [SbF6]- ion. Selective reactions demonstrate the selectivity of [naphthaleneF]+⋅ for deelectronation of a multitude of organ(ometall)ic molecules and elements in solution: providing the molecular structures of the acene dications [tetracene]2+, [pentacene]2+ or spectroscopic evidence for the carbonyl complex of the ferrocene dication [Fc(CO)]2+, the [P9]+ cation from white phosphorus, the solvent-free copper(I) salt starting from copper metal and the dicationic Fe(IV)-scorpionate complex [Fe(sc)2]2+.

Ligand and Substrate Effects on Regio‐ and Stereoselective Ru(II)‐Catalyzed Hydroacyloxylations to Vinylic Esters

AbstractTwo Ru(II)‐catalytic systems were developed for anti‐Markovnikov regioselective hydroacyloxylations of terminal alkynes to vinylic esters. [Ru(NCCH3)6][(BF4)2] favors (E)‐vinylic ester products with arylacetylenes and select carboxylic acids, whereas a Ru scorpionate complex with two electron‐withdrawing ligands favors (Z)‐vinylic ester isomers.

Substrate-dependent spin crossover in an Fe(ii) scorpionate complex

A new spin-crossover complex based on a heteroscorpionate ligand was synthesized and characterized.

Tris(2-Pyridyl)Arsine as a New Platform for Design of Luminescent Cu(I) and Ag(I) Complexes.

The coordination behavior of tris(2-pyridyl)arsine (Py3As) has been studied for the first time on the example of the reactions with CuI, CuBr and AgClO4. When treated with CuI in CH2Cl2 medium, Py3As unexpectedly affords the scorpionate complex [Cu(Py3As)I]∙CH2Cl2 only, while this reaction in MeCN selectively leads to the dimer [Cu2(Py3As)2I2]. At the same time, the interaction of CuBr with Py3As exclusively gives the dimer [Cu2(Py3As)2Br2]. It is interesting to note that the scorpionate [Cu(Py3As)I]∙CH2Cl2, upon fuming with a MeCN vapor (r.t., 1 h), undergoes quantitative dimerization into the dimer [Cu2(Py3As)2I2]. The reaction of Py3As with AgClO4 produces complex [Ag@Ag4(Py3As)4](CIO4)5 featuring a Ag-centered Ag4 tetrahedral kernel. At ambient temperature, the obtained Cu(I) complexes exhibit an unusually short-lived photoluminescence, which can be tentatively assigned to the thermally activated delayed fluorescence of (M + X) LCT type (M = Cu, L = Py3As; X = halogen). For the title Ag(I) complexes, QTAIM calculations reveal the pronounced argentophilic interactions for all short Ag∙∙∙Ag contacts (3.209–3.313 Å).

A Diverse Array of C-C Bonds Formed at a Tantalum Metal Center.

We demonstrate the formation of a diverse array of organic and organometallic products containing newly formed C-C bonds via successive methyl transfers from di-, tri-, and tetramethyl Ta(V) precursors to unsaturated small molecule substrates under mild conditions. The reactions of Ta(V) methyl complexes 1-X [H2B(MesIm)2]TaMe3X (X = Me, Cl; Im = imidazole, Mes = 2,4,6-trimethylphenyl) with CO led to oxo enolate Ta(V) products, in which the enolate ligands were constructed from Ta-Me groups and two equivalents of CO. Similarly, the reaction of 1-Me with CNXyl yielded an imido enamine Ta(V) product. Surprisingly, 1-Cl reacted with CNXyl (1 equiv) at the borate backbone of the [H2B(MesIm)2] ligand with concomitant methyl transfer from the metal center to form a new, dianionic scorpionate ligand that supported a Ta(V) dimethyl chloro complex (6). Treatment of 1-Cl with further CNXyl led to an azaallyl scorpionate complex, and an imido isocyanide scorpionate complex, along with propene and xylyl ketenimine. Complex 6 reacted with CO to yield a pinacol scorpionate complex 10-a new reaction pathway in early transition metal chemistry. Mechanistic studies revealed that this proceeded via migratory insertion of CO into a Ta-Me group, followed by methyl transfer to form an η2-acetone intermediate. Elimination of acetone furnished a CO-stabilized Ta(III) intermediate capable of rebinding and subsequently coupling two equivalents of CO-derived acetone to form the pinacol ligand in 10.

Hungry for charge – how a beryllium scorpionate complex “eats” a weakly coordinating anion

Abstract We present the reaction of a tris(pyrazolyl) beryllium scorpionate (TpBe) complex with a weakly coordinating anion (WCA), which yields the heteroleptic complex TpBeOC(CF3)3 1 (TpBeOR F). The product 1 has been characterized by multinuclear NMR spectroscopy (1H, 9Be, 13C) and single-crystal X-ray diffraction (scXRD). Quantum chemical calculations (DFT, NPA, LOL) were performed to study the bonding nature in 1.

Solvent-induced ion separation of a beryllium scorpionate complex.

Spontaneous ion separation of the scorpionate beryllium complex, TpBeI 1 (Tp = 1-trispyrazolylborate), occurs upon treatment with THF, yielding [TpBe(thf)]I 2, which was characterized by heteronuclear NMR spectroscopy (1H, 9Be, 13C) and structurally characterized by single crystal X-ray diffraction. 2 represents a rare example of a structurally characterized monocationic beryllium complex, and to the best of our knowledge, the synthesis of 2 by a solvent-induced ion separation has previously only been observed in the reactions of beryllium dihalides with strong Lewis bases.

N2O-Free single-pot conversion of cyclohexane to adipic acid catalysed by an iron(ii) scorpionate complex

Iron catalysed efficient single-pot adipic acid synthesis by cyclohexane oxidation with ozone in a solvent-, heating-, radiation- and N2O-free protocol.

Synthesis and Reactivity of a Cerium(III) Scorpionate Complex Containing a Redox Non-Innocent 2,2′-Bipyridine Ligand

The Ce(III) hydrotris(3,5-dimethylpyrazolyl)borate complex [Ce(TpMe2)2(κ2-dmpz)] (1) (TpMe2 = {HB(dmpz)3}−; dmpz = 3,5-dimethylpyrazolide) was isolated in fair yield from the reaction of [Ce(I)3(THF)4] with two equivalents of [K(TpMe2)] via the facile decomposition of TpMe2. [Ce(TpMe2)2(bipy)] (2) was synthesized in poor yield by the “one-pot” reaction of [Ce(I)3(THF)4], bipy (bipy = 2,2′-bipyridine), KC8 and two equivalents of [K(TpMe2)] in tetrahydrofuran (THF). The reaction of 2 with N-methylmorpholine-N-oxide produced the known decomposition product [Ce(TpMe2)(μ-BOpMe2)]2 (3) (BOpMe2 = {HBO(dmpz)2}2−) in poor yield, presumably by N–O and B–N bond cleavage of a reactive intermediate. The reaction of 2 with trimethylsilylazide gave [Ce(TpMe2)2(N3)] (4) in poor yield; the fate of bipy and the trimethylsilyl group is unknown. Complexes 1–4 were characterized by single crystal XRD, NMR and FTIR spectroscopy and elemental analysis. Complex 2 was additionally probed by UV/Vis/NIR and Electron Paramagnetic Resonance (EPR) spectroscopies, Cyclic Voltammetry (CV) and magnetometry, which together indicate a formal 4f1 Ce(III) center coordinated by a bipy·− radical anion in this system.

ChemInform Abstract: Silver(I)‐Catalyzed Reaction Between Pyrazole and Propargyl Acetates: Stereoselective Synthesis of the Scorpionate Ligands (E)‐Allyl‐gem‐dipyrazoles (ADPs).

The reaction between readily accessible pyrazole and propargyl acetates in the presence of Ag(I) catalyst yielded a new class of (E)-allyl-gem-dipyrazole scorpionate ligands: 1-aryl-2-N-pyrazolyl allyl acetates and 1,3-dipyrazolyl-3-arylpropene. The reaction showed broad substrate scope, and various functional and protecting groups were tolerated under the reaction conditions. The palladium(II) scorpionate complex could thus be easily prepared and successfully employed in Suzuki–Miyaura cross-couplings in water.

Silver(I)-Catalyzed Reaction between Pyrazole and Propargyl Acetates: Stereoselective Synthesis of the Scorpionate Ligands (E)-Allyl-gem-dipyrazoles (ADPs)

The reaction between readily accessible pyrazole and propargyl acetates in the presence of Ag(I) catalyst yielded a new class of (E)-allyl-gem-dipyrazole scorpionate ligands: 1-aryl-2-N-pyrazolyl allyl acetates and 1,3-dipyrazolyl-3-arylpropene. The reaction showed broad substrate scope, and various functional and protecting groups were tolerated under the reaction conditions. The palladium(II) scorpionate complex could thus be easily prepared and successfully employed in Suzuki-Miyaura cross-couplings in water.

A tris(pyrazolyl)borate rhodium phosphite complex that undergoes an Arbusov-like rearrangement

Tp'Rh[P(OMe)3](Me)H, loses methane in pentane solution containing CH2F2 to give the scorpionate complex bis(μ-dimethyl phosphito)-κ(2)P:O;κ(2)O:P-bis{methyl[tris(3,5-dimethyl-1H-pyrazol-1-yl-κN(2))borato]rhodium(III)}, [Rh2(CH3)2(C2H6O3P)2(C15H22BN6)2], in which the phosphine O-Me bond is cleaved. The product is dimeric and resembles the Arbusov-type rearrangement product known to form from trimethyl phosphite.

Solvothermal syntheses, high- and low-temperature crystal structures, and thermochromic behavior of [1,2-diethyl-3,4,5-trimethyl-pyrazolium] 4[Bi 4I 16] and [1,10-phenanthrolinium][BiI 4]·(H 2O)

A new iron(II) scorpionate complex, {Fe[HC(3,4,5-Me 3pz) 3] 2}(I) 2 (pz = pyrazolyl) ( 1), and two novel compounds containing low-dimensional poly(iodobismuthate) anions [1,2-Et 2-3,4,5-Me 3pz] 4[Bi 4I 16] ([1,2-Et 2-3,4,5-Me 3pz] + = [1,2-diethyl-3,4,5-trimethyl-pyrazolium] +) ( 2), and [H(1,10-phen)][BiI 4]·(H 2O) ([H(1,10-phen)] + = [1,10-phenanthrolinium] +) ( 3), have been synthesized and characterized by single crystal X-ray diffraction. Crystals of 2 resulted from the solvothermal reaction of BiI 3 and {Fe[HC(3,4,5-Me 3pz) 3] 2}(I) 2 in an ethanol/water solvent mixture. The anion of this compound is discrete (0-D) and consists of four slightly distorted BiI 6 octahedra joined in an edge-sharing arrangement, and the cation is a decomposition/solvent attack product of the iron scorpionate complex. Crystals of 3 resulted from the solvothermal reaction of BiI 3, 1,10-phenanthroline, and CuI in an ethanol/water solvent mixture. [H(1,10-phen)][BiI 4]·(H 2O) contains 1-D chains of BiI 6 octahedra and a protonated phenanthroline/water molecule complex. Both 2 and 3 are thermochromic compounds as their colors change, respectively, from orange at 296 K to yellow upon cooling to 100 K and from red-orange at 296 K to orange at 100 K. Crystallographic data at both temperatures were recorded for each sample and are reported here. The crystallographic data indicate that interatomic distances (Bi–I and Bi⋯Bi) within the inorganic anions change as a function of temperature, and it is believed that these changes are associated with the observation of thermochromism. {Fe[HC(3,4,5-Me 3pz) 3] 2}(I) 2 ( 1) crystallizes in the monoclinic space group P2 1/ n with the following lattice parameters at 150(1) K: a = 10.8489(5) Å, b = 17.6642(9) Å, c = 15.4131(8) Å, β = 102.4860(10)°. [Et 2Me 3pz] 4[Bi 4I 16] ( 2) and [H(1,10-phen)][BiI 4]·(H 2O) ( 3) both crystallize in the triclinic space group P 1 ¯ with the following lattice parameters for 2 at 296(1) K and 100(1) K, respectively: a = 11.2923(4) Å, b = 13.6412(5) Å, c = 15.0824(6) Å, α = 78.2090(10)°, β = 71.9670(10)°, and γ = 67.4020(10)°; a = 11.0963(7) Å, b = 13.4158(8) Å, c = 14.9840(9) Å, α = 79.1450(10)°, β = 71.1310(10)°, and γ = 68.1360(10)°. Lattice parameters for 3 at 296(1) K and 100(1) K, respectively, are as follows: a = 7.7590(4) Å, b = 11.1477(5) Å, c = 12.0731(6) Å, α = 77.6570(10)°, β = 79.1900(10)°, and γ = 71.2950(10)°; a = 7.7000(4) Å, b = 10.9265(6) Å, c = 11.9748(7) Å, α = 78.1020(10)°, β = 79.9940(10)°, and γ = 71.8380(10)°.

Dramatically Enhanced Carbon Acidity of the Nitrobenzyl Fragment in a Nickel(II) Scorpionate Complex

The -CH(2)- group of the 2-nitrobenzyl pendant arm of the scorpionate complex I deprotonates in basic aqueous solution (pK(a) = 10.6), due to the coordination of the nitronate group to the nickel(II) center. Metal coordination enhances 2-nitrobenzene acidity by 10 orders of magnitude. [reaction: see text]

A silver-catalyzed Büchner reaction

A silver scorpionate complex, derived from the highly fluorinated [HB(3,5-(CF 3) 2Pz) 3] −, catalyzes the addition of ethyl diazoacetate to benzene rings, providing norcaradienes, which undergo electrocyclization to provide the corresponding cycloheptatriene. These reactions are surprisingly selective for addition to the aromatic moiety rather than C–H insertion.

Pushing the frontiers of hard and soft scorpionate chemistry.

The preparation and structure of the first scorpionate complex of a group 16 element, [Te(kappa(2)-Tm(Me))(2)], is reported. It displays square planar geometry at the Te atom and two distinct ligand conformations. In addition, the first pyrazolylborate complex of a group 15 element, [Bi(Tp)(2)(pzH)Cl], has been synthesized and characterized.