Zinc Dihalides Research Articles

An isolable, chelating bis[cyclic (alkyl)(amino)carbene] stabilizes a strongly bent, dicoordinate Ni(0) complex

Chelating ligands have had a tremendous impact in coordination chemistry and catalysis. Notwithstanding their success as strongly σ-donating and π-accepting ligands, to date no chelating bis[cyclic (alkyl)(amino)carbenes] have been reported. Herein, we describe a chelating, C2-symmetric bis[cyclic (alkyl)(amino)carbene] ligand, which was isolated as a racemic mixture. The isolation and structural characterization of its isostructural, pseudotetrahedral complexes with iron, cobalt, nickel, and zinc dihalides featuring eight-membered metallacycles demonstrates the binding ability of the bis(carbene). Reduction of the nickel(II) dibromide with potassium graphite produces a dicoordinate nickel(0) complex that features one of the narrowest angles measured in any unsupported dicoordinate transition metal complexes.

Facile Synthesis of Benzimidazole and Benzothiazole Compounds Mediated by a Zinc Precatalyst Supported by an Iminopyrrole‐Morpholine Ligand

AbstractThree zinc complexes, with the general formula {κ2‐C4H3NH[2‐CH=NCH2CH2N(CH2CH2)2O]ZnX2} [X=Cl (2 a), Br (2 b), I (2 c)], supported by a neutral iminopyrrole‐morpholine ligand, were synthesized by the reaction between {C4H3NH‐2‐[CH=NCH2CH2N (CH2CH2)2O]} (1) and anhydrous zinc dihalides (ZnCl2, ZnBr2, ZnI2) at ambient temperature in dry methanol. The zinc complexes were fully characterized using multinuclear NMR spectroscopic techniques and the molecular structures of complexes 2 a and 2 c in their solid states were determined by single‐crystal X‐ray diffraction analysis. The zinc diiodo complex (2 c) proved to be a competent precatalyst in the formation of a wide range of benzimidazole and benzothiazole compounds, via aerobic oxidative condensation of several benzylamines with o‐phenylenediamine, N‐phenyl‐o‐phenylene‐diamine, and o‐mercaptoaniline. The benzimidazole and benzothiazole derivatives were successfully characterized using 1H and 13C{1H} NMR spectroscopy.

Oligo(amylene) from the reaction of fusel oil with zinc dihalide.

Heating mixtures of fusel oil and zinc chloride or zinc bromide to 180 °C gave water, difusel ethers and the hydrocarbon oligo(amylene) as the major coproducts. Separation by chromatography gave oligo(amylene) in 25% yield from fusel oil. The triamylene fraction of the oligo(amylene) had a net heating value of 43.9 kJ g−1 which was 3% greater than specifications for gasoline, diesel #2 and jet A-1. The cetane number of the triamylene was 31.9 so it may not be useful for diesel engines. The triamylene had a flashpoint of 38 °C, viscosity (−20 °C) of 7.85 mm2 s−1, density (15 °C) of 0.78 g mL−1 and melting point below −78 °C which all compared well to the specifications of jet A-1.

Recent Developments on N-Heterocyclic Carbene Supported Zinc Complexes: Synthesis and Use in Catalysis

The present contribution reviews the synthesis, reactivity, and use in catalysis of NHC–Zn complexes reported since 2013. NHC-stabilized Zn(II) species typically display enhanced stability relative to common organozinc species (such as Zn dialkyls), a feature of interest for the mediation of various chemical processes and the stabilization of reactive Zn-based species. Their use in catalysis is essentially dominated by reduction reactions of various unsaturated small molecules (including CO2), thus primarily involving Zn–H and Zn–alkyl derivatives as catalysts. Simple NHC adducts of Zn(II) dihalides also appear as effective catalysts for the reduction amination of CO2 and borylation of alkyl/aryl halides. Stable and well-defined Zn alkoxides have also been prepared and behave as effective catalysts in the polymerization of cyclic esters/carbonates for the production of well-defined biodegradable materials. Overall, the attractive features of NHC-based Zn(II) species include ready access, a reasonable stability/reactivity balance, and steric/electronic tunability (through the NHC source), which should promote their further development.1 Introduction2 NHC-Supported Zinc Alkyl/Aryl Species2.1 Synthesis2.2 Reactivity and Use in Catalysis3 NHC-Supported Zinc Hydride Species3.1 Synthesis3.2 Reactivity and Use in Catalysis4 NHC-Supported Zinc Amido/Alkoxide Species4.1 Synthesis4.2 Use in Catalysis5 NHC-Supported Zinc Dihalide Species5.1 Synthesis5.2 Use in Catalysis6 Other NHC-Stabilized Zn Species7 Conclusion

Zinc Dihydride and Mixed Halo Hydrides Supported by an N‐Heterocyclic Carbene

A series of zinc dihalides [(IMes)ZnX2] [X = Cl (1a) Br (1b), I (1c); IMes = 1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene] is reported. The iodide 1c underwent salt metathesis with NaH as an alternative synthesis of [(IMes)ZnH2]2 (2). 2 readily reacted with (tBu)NCO and Ph2CO under Zn‐H insertion to give [(IMes)Zn(tBuNCHO‐κN)2] (3) and [(IMes)Zn(OCHPh2)2] (4), respectively. Ph2S2 and I2 oxidized the hydride ligands in 2 to give dihydrogen and [(IMes)Zn(SPh)2] (5) and 1c, respectively. A series of mixed halo hydrides [(IMes)Zn(X)(H)]2 [X = Cl (6a), Br (6b), I (6c)] was obtained upon comproportionating 2 with 1a–c. The new compounds were fully characterized, including X‐ray crystallographic analysis of 3 and 6b.

2-Picolylamino(diphenylphosphinoselenoic)amide supported zinc complexes: Efficient catalyst for insertion of N–H bond into carbodiimides, isocyanates, and isothiocyanate

We report here the hydroamination of heterocumulenes such as carbodiimides, isocyanates, and isothiocyanates by zinc complexes supported by the ligand 2-picolylamino-(diphenylphosphinoselenoic)amide [{(Ph2P-(˭Se)}2NCH2(C5H4N)] (1). A series of zinc complexes [κ2-{(Ph2P-(˭Se)}2NCH2(C5H4N)ZnX2] [(X˭Cl (2), Br (3a), I (4)] were prepared from ligand 1 and the corresponding zinc dihalide in a 1:1 molar ratio at 60°C in a chloroform solvent. The reaction of ligand 1 and ZnBr2 in methanol yielded another zinc complex [κ2-{(Ph2P-(˭Se)}2NCH2(C5H4N)ZnBr2(CH3OH)] (3b). The molecular structures of compounds 3a, 3b, and 4 were established through single-crystal X-ray diffraction analyses. The solid-state structures of all the complexes revealed a κ2- chelation through pyridine nitrogen and selenium atoms of ligand 1 to the zinc ion. Complex 2 proved to be a competent pre-catalyst for the addition of the amine N–H bond to carbodiimides, isocyanates, and isothiocyanates. The reaction scope was expanded to reactions of aliphatic and aromatic amines with phenylisocyanate and phenylisothiocyanate in toluene solvents, which proceeded rapidly at room temperature with 5 mol% catalyst loading to yield (up to 99%) the corresponding derivatives of urea and thio-urea. However, a temperature of 90°C was needed for the hydroamination of N,N′ dicyclohexylcarbodiimide. We also report the most plausible mechanism of the hydroamination reaction.

{CH2(PPh2=NSiMe3)(PPh2=S)} and {CH(PPh2=NSiMe3)(Ph2P=S)}– as Ligands in Zinc Chemistry: Synthesis and Structures

AbstractThe (iminophosphoranyl)(thiophosphoranyl)methane zinc complexes [{(PPh2=NSiMe3)(PPh2=S)CH2}ZnX2] (X = Cl, I) have been obtained by the reaction of {CH2(PPh2=NSiMe3)(PPh2=S)} with the corresponding zinc dihalides ZnCl2 and ZnI2. The (iminophosphoranyl)(thiophosphoranyl)methane ligand coordinates as a bidentate ligand through the nitrogen and sulfur atoms to the zinc atom to form a six‐membered metallacycle (N–P–C–P–S–Zn). The reaction of {CH2(PPh2=NSiMe3)(PPh2=S)} with [Zn{N(SiMe3)2}2] and ZnPh2 resulted in the (iminophosphoranyl)(thiophosphoranyl)methanide complexes [{(PPh2=NSiMe3)(PPh2=S)CH}Zn{N(SiMe3)2}] and [{(PPh2=NSiMe3)(PPh2=S)CH}ZnPh], respectively. In addition to the coordination of the phosphinimine nitrogen and sulfur atoms to the zinc atom, a long contact between the methine carbon atom of the P–C–P bridge and the zinc atom was observed in these complexes. The solid‐state structures of all the new compounds were established by single‐crystal X‐ray diffraction.

Bis(phosphinimino)methanides as non-innocent ligand in zinc chemistry: synthesis and structures

Reactions of the bis(phosphinimino)methane {CH2(Ph2PNSiMe3)2} with the zinc dihalides ZnCl2 and ZnI2 afforded the corresponding bis(phosphinimino)methane complexes [{(Me3SiNPPh2)2CH2}ZnCl2] (1) and [{(Me3SiNPPh2)2CH2}ZnI2] (2). In contrast, treatment of {CH2(Ph2PNSiMe3)2} with ZnPh2 in toluene gave the bis(phosphinimino)methanide complex of [{(Me3SiNPPh2)2CH}ZnPh] (3). Further reaction of 3 with the heterocumulenes di(p-tolyl)carbodiimine and diphenyl ketene resulted via a nucleophilic addition of the methine carbon atom of the {CH(Ph2PNSiMe3)2}- ligand to the heterocumulenes in a C-C bond formation. New tripodal phenyl zinc complexes of composition [{(Me3SiNPPh2)2CH)(p-Tol)NC-N(p-Tol)}ZnPh] (4) and [{(Me3SiNPPh2)2CH)(Ph2CC-O)}ZnPh] (5) were obtained.

Synthesis of Tri‐ and Tetraalkynylgermanes

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Synthesis of tri-and tetraalkynylgermanes

A straightforward synthesis of tetra-and trialkynylgermanes by reactions of compounds containing Ge-N or Ge-Cl bonds with alk-1-ynes was proposed. Reactions of appropriate amino-or halogermanes with alk-1-ynes were effective only in the presence of an equivalent amount of zinc dihalide.

An Efficient Route to Regioselective Opening of N‐Tosylaziridines with Zinc(II) Halides.

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An efficient route to regioselective opening of N-tosylaziridines with zinc(II) halides

An efficient route for the regio- and stereoselective ring opening of N-tosylaziridines with zinc dihalides (ZnX 2, X = Cl, Br, I) is described. Depending on the solvent and Zn(II) halide, β-halo amines or imidazolines are obtained selectively in good to excellent yields.

Zinc- and Tin-Mediated C−C Coupling Reactions of Metalated (2-Pyridylmethyl)(trialkylsilyl)amines − Mechanistic, NMR Spectroscopic, and Structural Studies

The zincation of (2-pyridylmethyl)(triisopropylsilyl)amine (1) gives dimeric methylzinc (2-pyridylmethyl)(triisopropylsilyl)amide (2). Further addition of dimethylzinc to a toluene solution of 2 at raised temperatures yields the C−C coupling product [1,2-dipyridyl-1,2-bis(triisopropylsilylamido)ethane]bis(methylzinc) (3). Heating of molten 2, or UV irradiation of 2, results in the formation of 3 and zinc bis[(2-pyridylmethyl)(triisopropylsilyl)amide] (4). The reaction between the zinc dihalide complexes of 1 [5a (X = Cl) and 5b (X = Br)] and methyllithium yields the C−C coupling product 3 and the heteroleptic complex 2, observed by NMR spectroscopy. During this reaction, zinc metal precipitates. The magnesiation of 1 with dibutylmagnesium gives magnesium bis[(2-pyridylmethyl)(triisopropylsilyl)amide] (6) in a quantitative yield. Subsequent addition of dimethylmagnesium results in a dismutation reaction and the formation of heteroleptic methylmagnesium (2-pyridylmethyl)(triisopropylsilyl)amide (7). Treatment of 1 with dimethylmagnesium also gives 7. This complex slowly undergoes an intramolecular metalation during which dark red single crystals of (tetrahydrofuran)magnesium 2-(triisopropylsilylamidomethylidene)-1-azacyclohexa-3,5-dien-1-ide (8) precipitate. In this compound the aromaticity of the pyridyl fragment is abolished. The magnesiation of (tert-butyldimethylsilyl)(2-pyridylmethyl)amine (I) proceeds quantitatively to give methylmagnesium (tert-butyldimethylsilyl)(2-pyridylmethyl)amide (9). This compound also undergoes an intramolecular metalation reaction, which results in the loss of the aromaticity of the pyridyl substituent and the formation of (tetrahydrofuran)magnesium 2-(tertbutyldimethylsilylamidomethylidene)-1-azacyclohexa-3,5dien-1-ide (10). The metalation of 1 with tin(II) bis[bis(trimethylsilyl)amide] yields [bis(trimethylsilyl)amido]tin(II) (2-pyridylmethyl)(triisopropylsilyl)amide (11). The elimination of tin metal occurs even at room temperature, and the C−C coupling product [1,2-dipyridyl-1,2-bis(triisopropylsilylamido)ethane]tin(II) (12) is formed. The metalation of (tert-butyldimethylsilyl)(2-pyridylmethyl)amine with Sn[N(SiMe3)2]2 gives [bis(trimethylsilyl)amido]tin(II) (tert-butyldimethylsilyl)(2-pyridylmethyl)amide (13). Within a few minutes, precipitation of tin metal takes place and the C−C coupled product [1,2-bis(tert-butyldimethylsilylamido)-1,2-dipyridylethane]tin(II) (14) is produced. In order to examine the importance of the pyridyl ligand for the C−C coupling reactions, zinc bis[N-(tert-butyldimethylsilyl)benzylamide] (15) was prepared by means of the metathesis reaction between lithium N-(tert-butyldimethylsilyl)benzylamide and zinc(II) halide. Treatment of 15 with dimethylzinc yields heteroleptic methylzinc N-(tert-butyldimethylsilyl)benzylamide (16). Refluxing of 16 with an excess of dimethylzinc in toluene does not give any C−C coupling reactions.

Polymeric versus monomeric and tetrahedral versus octahedral coordination in zinc(ii) pyridine complexes

The first one-dimensional chain polymers of the type [Zn(μ-Cl)2py]∞ (py⊕=⊕3,5-dichloropyridine and 3,5-dibromopyridine) were synthesized by reaction of the 3,5-dihalopyridines with ZnCl2. In the resulting linear coordination polymer octahedral zinc(II) centres are linked in an edge-sharing fashion by halogen bridges in their pseudo-equatorial plane. In contrast to these findings the analogous reaction between ZnBr2 and the 3,5-dihalopyridines results in the formation of mononuclear tetrahedral complexes. Both of the zinc dihalides react with 3,4,5-trichloropyridine with formation of isotypic molecular crystals which show relatively short halogen⋯halogen contacts; their projections along the [001] direction exhibit a remarkable similarity to those of the chain polymers. From ZnX2 (X⊕=⊕Cl, Br) and 4,4′-bipyridyl (bpy) a zigzag chain coordination polymer of composition [ZnX2(μ-bpy)]∞ was obtained.

Phosphanimin- und Phosphaniminato-Komplexe des Zinks. Kristallstrukturen von [ZnCl2(Me3SiNP(CH2)4CMe3)]2, [ZnI2(Me3SiNPEt3)]2, [ZnI2{Me2Si(NPEt3)2}] und [ZnBr(NPMe3)]4· CH2Cl2/ Phosphaneimine and Phosphoraneiminato Complexes of Zinc. Crystal Structures of [ZnCl2(Me3SiNP(CH2)4CMe3)]2, [ZnI2(Me3SiNPEt3)]2, [Znl2{Me2Si(NPEt3)2}], and [ZnBr(NPMe3)]4· CH2Cl2

Abstract The donor-acceptor complexes [ZnCl2(Me3SiNP(CH2)4CMe3)]2 (1)and [ZnI2(Me3SiNPEt3)]2 (2) have been prepared from the zinc dihalides and the corresponding silylated phosphaneimines in CH2Cl2. Thermolysis of 2 leads to the formation of [ZnI2(Me2Si(NPEt3)2)] (3). Znl2 and ZnBr2 react with the silylated phosphaneimines Me3SiNPR3(R = Me, Et) in the presence of NaF at elavated temperatures to give the phosphoraneiminato complexes [ZnI(NPEt3)]4 (4), [ZnBr(NPMe3)]4 (5) and [ZnBr(NPEt3)]4 (6), respectively, which according to the IR spectra and to a crystal structure determination of 5 form heterocubane structures. The corresponding reactions with the more bulky phosphaneimine Me3SiNP(CH2)4CMe3 do not lead to a phosphoraneiminato complex of zinc. 1: Space group P21/n, Z = 2; lattice dimensions at -60 °C: a = 903.3(2), b = 1217.9(3), c = 1591.6(2) pm, β = 93.94(1)°, R = 0.031. 2: Space group P21/n, Z = 2; lattice dimensions at -70°C: a = 947.9(2), b = 1219.2(2), c - 1527.1(2) pm, 0 = 91.17(1)°, β = 0.045. 1 and 2 form centrosymmetric dimeric molecules via Zn2X2 bridges (X = Cl, I); bond lengths Zn-N = 198.7(2) pm (1) and 199.0(6) pm (2). 3: Space group P412121 Z = 8; lattice dimensions at -90°C: a = b = 965.4(1), c = 2796.9(2) pm, R = 0.019.3 forms monomeric molecules with the Me2Si(NPEt3)2 ligand as chelating agent to give a planar ZnN2Si four-membered ring with Zn-N distances of 207.0(2) pm. 5: Space group P42/nmc, Z = 2; lattice dimensions at -70°C: a = b = 1146.9(6), c = 1437.9(7) pm, R = 0.060.

Photoelectron spectra and valence shell electronic structure of zinc and cadmium difluoride

The He(I)α and He(II)α photoelectron spectra of zinc and cadmium difluoride have been recorded in the vapour phase using a pseudo-molecular beam technique. The spectra were interpreted with the aid of ab initio SCF m.o. calculations on ZnF2. Two different basis sets were used in the calculations and ionization potentials were predicted by both Koopmans' theorem and the ΔSCF method. The electronic structure of the Group IIB difluorides studied was found to be similar to that of the heavier halides except that the ligand-localized m.o.s. appear to have the order σgπuσuπg rather than σgσuπuπg as in the heavier halides. A comparison of the valence electronic structure of the Group IIA and IIB dihalides was made. The d-shell metal-localized ionizations of the Group IIB difluorides studied were observed to be core-like and ligand field effects for the d–1 ionization in the zinc dihalides were considered. In all cases, observations were consistent with largely ionic structures.

Matrix isolation infrared and Raman spectra of binary and mixed zinc dihalides, isotopic effects, force constants, and thermodynamic properties

Raman and infrared matrix solution spectra for all ZnX2 and ZnXY (X,Y=Cl,Br,I) molecules are reported. These spectra complete the vibrational information on the binary dihalides and provide the first experimental evidence for the existence of the mixed zinc dihalides. All three fundamentals are assigned for all molecules. Isotopic effects due to the halogen atoms, the zinc atoms, or both were resolved in the stretching mode bands. From these, stretching, bending, and interaction force constants were evaluated, the criterion for their calculation being the reproduction of band frequencies within experimental error and the best fit of the frequency differences in the resolved isotopic fine structures. The possibility that not all molecules are linear is indicated. The effect of temperature and deviations from linearity on calculated entropies is shown.

Vibrational Spectra, Isotopic Effects, Force Constants and Geometry of Matrix Isolated Binary and Mixed Zinc Dihalides

Vibrational Spectra, Isotopic Effects, Force Constants and Geometry of Matrix Isolated Binary and Mixed Zinc Dihalides