Iron-Intercalated Zirconium Diselenide Thin Films from the Low-Pressure Chemical Vapor Deposition of [Fe(η⁵-C₅H₄Se)₂Zr(η⁵-C₅H₅)₂]₂

Transition metal chalcogenide thin films of the type FexZrSe2 have applications in electronic devices, but their use is limited by current synthetic techniques. Here, we demonstrate the synthesis and characterization of Fe-intercalated ZrSe2 thin films on quartz substrates using the low-pressure chemical vapor deposition of the single-source precursor [Fe(η5-C5H4Se)2Zr(η5-C5H5)2]2. Powder X-ray diffraction of the film scraping and subsequent Rietveld refinement of the data showed the successful synthesis of the Fe0.14ZrSe2 phase, along with secondary phases of FeSe and ZrO2. Upon intercalation, a small optical band gap enhancement (Eg(direct)opt = 1.72 eV) is detected in comparison with that of the host material

Accessing new 2D semiconductors with optical band gap: synthesis of iron-intercalated titanium diselenide thin films via LPCVD

Fe-doped TiSe2 thin-films were synthesized via low pressure chemical vapor deposition (LPCVD) of a single source precursor: [Fe(η⁵-C₅H₄Se)₂Ti(η⁵-C₅H₅)₂]₂ (1). Samples were heated at 1000 °C for 1–18 h and cooled to room temperature following two different protocols, which promoted the formation of different phases. The resulting films were analyzed by grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and UV/vis spectroscopy. An investigation of the Fe doping limit from a parallel pyrolysis study of FeₓTiSe₂ powders produced in situ during LPCVD depositions has shown an increase in the Fe–TiSe₂–Fe layer width with Fe at% increase. Powders were analyzed using powder X-ray diffraction (PXRD) involving Rietveld refinement and XPS. UV/vis measurements of the semiconducting thin films show a shift in band gap with iron doping from 0.1 eV (TiSe₂) to 1.46 eV (Fe₀.₄₆TiSe₂)

Introduction of selenium and tellurium into reaction systems

Abstract There are several commercial selenium and tellurium compounds that are useful in synthetic chemistry. The introduction of selenium and tellurium into both organic and inorganic compounds frequently begins with the elements. This chapter provides an overview of the main reactivity of the hexagonal allotropes of selenium and tellurium, which are the most stable form of the elements under ambient conditions. While the two elements have very similar chemical properties, there are also notable differences. Upon reduction, both elements form mono- and poly-chalcogenides, which are useful nucleophilic reagents in several reactions. The elements also react with many main group compounds as well as with transition metal complexes. They also form homopolyatomic cations upon oxidation. Both selenium and tellurium react with Grignard reagents and organyllithium compounds affording organylchalcogenolates, which upon oxidation form dichalcogenides that are themselves useful reagents in organic synthetic chemistry as well as in materials applications. This chapter provides a short introduction to the various topics that will be developed further in the subsequent chapters of this book.This article has previously been published in the journal Physical Sciences Reviews, Volume 4, Issue 4, 20180059, ISSN (Online) 2365-659X, DOI: https://doi.org/10.1515/psr-2018-0059

Experimental and Computational Investigations of Platinum Complexes of Selenium Diimide and Some Novel Selenium-Nitrogen Ligands

The reaction of selenium diimide Se[N(t-Bu)]2 and PtCl2 afforded an N,N’-chelated complex [PtCl2{N,N’-Se[N(t-Bu)]2}] (1) in good yield and [PtCl2{N,N’-SeO[NH(t-Bu)]2}] (2) as a minor product. Attempts to prepare 2 by direct reaction of SeOCl2 with Li[NH(t-Bu)] in toluene followed by addition of PtCl2 produced cyclic Se4[N(t-Bu)]4 in solution (77Se NMR spectrum) and a small amount of the complex [PtCl3{Se,Se’,Se”-Se4[N(t-Bu)]4}][Pt2Cl5{Se,Se’,Se”-Se3[N(t-Bu)]2}]∙3MeCN (3∙3MeCN), which contains tridentate Se4[N(t-Bu)]4 in the cation and the novel, acyclic bridging ligand [SeN(t-Bu)SeN(t-Bu)Se]2- in the anion. The reaction of Se[N(t-Bu)]2 with [PtCl2(NCPh)2] in THF produced the dinuclear complex [Pt2Cl6{SeN(t-Bu)C(Ph)NH}2]∙2C4H8O (4∙2THF) as the major product and only a few crystals of 1. The possible formation of SeO[NH(t-Bu)]2 or 2 by the reaction of Se[N(t-Bu)]2 or 1, respectively, with adventitious water and the pathway for the production of 4 were investigated through revPBE GGA/def2-TZVP calculations. The X-ray structures of 1, 2, 3∙3MeCN, and 4∙2THF have been determined.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Chalcogen‐Bonding Interactions in Telluroether Heterocycles [Te(CH₂)ₘ]ₙ (n=1–4; m=3–7)

Abstract The Te⋅⋅⋅Te secondary bonding interactions (SBIs) in solid cyclic telluroethers were explored by preparing and structurally characterizing a series of [Te(CH₂)ₘ]ₙ (n=1–4; m=3–7) species. The SBIs in 1,7‐Te₂(CH₂)₁₀, 1,8‐Te₂(CH₂)₁₂, 1,5,9‐Te₃(CH₂)₉, 1,8,15‐Te₃(CH₂)₁₈, 1,7,13,19‐Te₄(CH₂)₂₀, 1,8,15,22‐Te₄(CH₂)₂₄ and 1,9,17,25‐Te₄(CH₂)₂₈ lead to tubular packing of the molecules, as has been observed previously for related thio‐ and selenoether rings. The nature of the intermolecular interactions was explored by solid‐state PBE0‐D3/pob‐TZVP calculations involving periodic boundary conditions. The molecular packing in 1,7,13,19‐Te₄(CH₂)₂₀, 1,8,15,22‐Te₄(CH₂)₂₄ and 1,9,17,25‐Te₄(CH₂)₂₈ forms infinite shafts. The electron densities at bond critical points indicate a narrow range of Te⋅⋅⋅Te bond orders of 0.12–0.14. The formation of the shafts can be rationalized by frontier orbital overlap and charge transfer

Experimental and computational investigation on the formation pathway of [RuCl₂(CO)₂(ERR′)₂] (E = S, Se, Te; R, R′ = Me, Ph) from [RuCl₂(CO)₃]₂ and ERR′

Abstract The pathways to the formation of the series of [RuCl₂(CO)₂(ERR′)₂] (E = S, Se, Te; R, R′ = Me, Ph) complexes from [RuCl₂(CO)₃]₂ and ERR′ have been explored experimentally in THF and CH2Cl2, and computationally by PBE0-D3/def2-TZVP calculations. The end-products and some reaction intermediates have been isolated and identified by NMR spectroscopy, and their crystal structures have been determined by X-ray diffraction. The relative stabilities of the [RuCl₂(CO)₂(ERR′)₂] isomers follow the order cct > ccc > tcc > ttt ≈ ctc (the terms c/t refer to cis/trans arrangement of the ligands in the order of Cl, CO, and ERR′). The yields were rather similar in both solvents, but the reactions were significantly faster in THF than in CH₂Cl₂. The highest yields were observed for the telluroether complexes, and the yields decreased with lighter chalcogenoethers. PBE0-D3/def2-TZVP calculations indicated that the reaction path is independent of the nature of the solvent. The substitution of one CO ligand of the intermediate [RuCl₂(CO)₃(ERR′)] by the second ERR′ shows the highest activation barrier and is the rate-determining step in all reactions. The observed faster reaction rate in THF than in CH₂Cl₂ upon reflux can therefore be explained by the higher boiling point of THF. At room temperature the reactions in both solvents proceed equally slowly. When the reaction is carried out in THF, the formation of [RuCl₂(CO)₂(THF)] is also observed, and the reaction may proceed with the substitution of THF by ERR′. The formation of the THF complex, however, is not necessary for the dissociation of the [RuCl₂(CO)₂]₂. Thermal energy at room temperature is sufficient to cleave one of the bridging Ru–Cl bonds. The intermediate thus formed undergoes a facile reaction with ERR′. This mechanism is viable also in non-coordinating CH₂Cl₂

Macrocycles containing 1,1’-ferrocenyldiselenolato ligands on group 4 metallocenes

Abstract Macrocyclic [Fe(η⁵-C₅H₄Se)₂M(η⁵-C₅H₄R)₂]₂ [M = Ti (1), Zr (2), Hf (3), R = H; and M = Zr (4), Hf (5), R = tBu] were prepared and characterized by ⁷⁷Se NMR spectroscopy and the crystal structures of 1–3 and 5 were determined by single-crystal X-ray diffraction. The crystal structure of 4 is known and the complex is isomorphous with 5. 1–5 form mutually similar macrocyclic tetranuclear complexes in which the alternating Fe(C₅H₄Se)₂ and M(C₅H₄R)₂ centers are linked by selenium bridges. The thermogravimetric analysis (TGA) of 1–3 under a helium atmosphere indicated that the complexes undergo a two-step decomposition upon heating. The final products were identified using powder X-ray diffraction as FexMSe₂, indicating their potential as single-source precursors for functional materials

Competitive Te-Te and C-Te bond cleavage in the oxidative addition of diaryl and dialkyl ditellurides to Pt(0) centers

Abstract The oxidative addition reaction of ditellurides R₂Te₂ [R = ⁿBu, Ph, Th (2-thienyl, C4H3S)] to [Pt(η²-nb)(dppn)] (nb = norbornene, dppn = 1,2-bis(diphenylphosphano)naphthalene) was found to afford [Pt(TeR)₂(dppn)] [R = ⁿBu (1), Ph (2), Th (3)] and [Pt(TeR)(R)(dppn)] [R = Ph (4), Th (5)] as a result of the cleavage of the Te-Te or C-Te bond, respectively. The reactions and the product distributions were monitored by 31P{1H} NMR spectroscopy. The spectral interpretation was assisted by the high-yield preparation of [Pt(TePh)₂(dppn)] (2) and [Pt(TeTh)₂(dppn)] (3) by ligand exchange reactions from [PtCl₂(dppn)], and by the crystal structure determinations and spectral characterizations of 2 and 3. Two series of reactions were carried out both at room temperature and at −80 °C. One involved the addition of the toluene solution of R₂Te₂ to that of [Pt(η²-nb)(dppn)], and the other the addition of [Pt(η²-nb)(dppn)] solution to the R₂Te₂ solution. The oxidative addition of ⁿBu₂Te₂ to [Pt(η²-nb)(dppn)] yielded solely [Pt(TenBu)₂(dppn)]. In case of Ph₂Te₂ and Th₂Te₂, the reaction of equimolar amounts of ditelluride and [Pt(η²-nb)(dppn)] afforded only [Pt(TeR)(R)(dppn)] (R = Ph, Th), but when an excess of R₂Te₂ was used, the addition of [Pt(η²-nb)(dppn)] to the ditelluride resulted in the formation of a mixture of [Pt(TeR)₂(dppn)] and [Pt(TeR)(R)(dppn)] with the latter the main component. An excess of R₂Te₂ and the lowering of the temperature favoured the formation of [Pt(TeR)₂(dppn)]. The reaction energetics in toluene was calculated at revPBE/def2-TZVP(-f) level of theory. The increase of the electron withdrawing nature of the organic substituent rendered [Pt(TeR)(R)(dppn)] increasingly stable with respect to [Pt(TeR)₂(dppn)]. The computation of the energy profiles of the likely pathways of the oxidative addition indicated that concurrent formation of [Pt(TeR)₂(dppn)] and [Pt(TeR)(R)(dppn)] (R = Ph, Th) may be more likely than the formation of the latter due to the decomposition of the former. This was verified experimentally by stirring pure [Pt(TeR)₂(dppn)] in toluene for a prolonged time at room temperature. No decomposition was observed

Accessing new 2D semiconductors with optical band gap: synthesis of iron-intercalated titanium diselenide thin films via LPCVD

Abstract Fe-doped TiSe2 thin-films were synthesized via low pressure chemical vapor deposition (LPCVD) of a single source precursor: [Fe(η5-C5H4Se)2Ti(η5-C5H5)2]2 (1). Samples were heated at 1000 °C for 1–18 h and cooled to room temperature following two different protocols, which promoted the formation of different phases. The resulting films were analyzed by grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and UV/vis spectroscopy. An investigation of the Fe doping limit from a parallel pyrolysis study of FexTiSe2 powders produced in situ during LPCVD depositions has shown an increase in the Fe–TiSe2–Fe layer width with Fe at% increase. Powders were analyzed using powder X-ray diffraction (PXRD) involving Rietveld refinement and XPS. UV/vis measurements of the semiconducting thin films show a shift in band gap with iron doping from 0.1 eV (TiSe2) to 1.46 eV (Fe0.46TiSe2)

Iron-intercalated zirconium diselenide thin films from the low-pressure chemical vapor deposition of [Fe(η⁵-C₅H₄Se)₂Zr(η⁵-C₅H₅)₂]₂

Abstract Transition metal chalcogenide thin films of the type FexZrSe₂ have applications in electronic devices, but their use is limited by current synthetic techniques. Here, we demonstrate the synthesis and characterization of Fe-intercalated ZrSe₂ thin films on quartz substrates using the low-pressure chemical vapor deposition of the single-source precursor [Fe(η⁵-C₅H₄Se)₂Zr(η⁵-C₅H₅)₂]₂. Powder X-ray diffraction of the film scraping and subsequent Rietveld refinement of the data showed the successful synthesis of the Fe0.14ZrSe₂ phase, along with secondary phases of FeSe and ZrO₂. Upon intercalation, a small optical band gap enhancement (Eg(direct)opt = 1.72 eV) is detected in comparison with that of the host material