Анализ путей оптимизации научно-технического обеспечения оборонно-промышленного комплекса Украины

The analysis of ways to optimize scientific and technical support of the military-industrial complex of Ukraine is considered in the article. Main problems and perspective directions of technological development for military purposes are identified. The experience and capacity of higher education institutions in the implementation of scientific and technical developments in this field are studied.У статті проведено аналіз шляхів оптимізації науково-технічного забезпечення оборонно-промислового комплексу України. Визначено основні проблеми та перспективні напрямки розвитку технологій військового призначення. Проаналізовано досвід та можливості вищих навчальних закладів у виконанні науково-технічних розробок у даній сфері.В статье проведён анализ путей оптимизации научно-технического обеспечения оборонно-промышленного комплекса Украины. Определены основные проблемы и перспективные направления развития технологий военного предназначения. Проанализирован опыт и возможности высших учебных заведений в реализации научно-технических разработок в данной сфере

A New Area in Main-Group Chemistry: Zerovalent Monoatomic Silicon Compounds and Their Analogues

ConspectusMonoatomic zerovalent main-group element complexes emerged very recently and attracted increasing attention of both theoretical and experimental chemists. In particular, zerovalent silicon complexes and their congeners (metallylones) stabilized by neutral Lewis donors are of significant importance not only because of their intriguing electronic structure but also because they can serve as useful building blocks for novel chemical species. Featuring four valence electrons as two lone pairs at the central atoms, such complexes may form donor–acceptor adducts with Lewis acids. More interestingly, with the central atoms in the oxidation state of zero, they could pave a way to new classes of compounds and functional groups that are otherwise difficult to realize.In this Account, we mainly describe our contributions in the chemistry of monatomic zerovalent silicon (silylone) and germanium (germylone) supported by a chelate bis-<i>N</i>-heterocyclic carbene (bis-NHC) ligand in the context of related species developed by other groups in the meantime. Utilizing the bis-NHC stabilized chlorosilyliumylidene [:SiCl]⁺ and chlorogermyliumylidene [:GeCl]⁺ as suitable starting materials, we successfully isolated silylone (bis-NHC)Si and germylone (bis-NHC)­Ge, respectively. The electronic structures of the latter complexes established by theoretical calculations and spectroscopic data revealed that they are genuine metallylone species with electron-rich silicon(0) and germanium(0) centers. Accordingly, they can react with 1 molar equiv of GaCl₃ to form Lewis adducts (bis-NHC)­E­(GaCl₃) (E = Si, Ge) and with 2 molar equiv of ZnCl₂ to furnish (bis-NHC)­Si­(ZnCl₂)₂. Conversion of the metallylones with elemental chalcogens affords isolable monomeric silicon­(II) and germanium­(II) monochalcogenides (bis-NHC)­EX­(GaCl₃) (X = Se, Te), representing molecular heavier congeners of CO. Moreover, their reaction with elemental chalcogens can also yield monomeric silicon­(IV) and germanium­(IV) dichalcogenides (bis-NHC)­EX₂ (X = S, Se, Te) as the first isolable complexes of the molecular congeners of CO₂. Moreover, (bis-NHC)­Si could even activate CO₂ to afford the monomolecular silicon dicarbonate complex (bis-NHC)­Si­(CO₃)₂ via the formation of SiO and SiO₂ complexes as intermediates. Furthermore, starting with a chelate bis-<i>N</i>-heterocyclic silylene supported [:GeCl]⁺, we developed two bis-<i>N</i>-heterocyclic silylene stabilized germylone→Fe­(CO)₄ complexes. Our achievements in the chemistry of metallylones demonstrate that the characteristic of monatomic zerovalent silicon and its analogues can provide novel reaction patterns for access to unprecedented species and even extends the series of functional groups of these elements. With this, we can envision that more interesting zerovalent complexes of the main-group elements with unprecedented reactivity will follow in the near future

Iridium-Catalyzed Regioselective Silylation of Secondary Alkyl C–H Bonds for the Synthesis of 1,3-Diols

We report Ir-catalyzed intra­molecular silyl­ation of secondary alkyl C–H bonds. (Hydrido)­silyl ethers, generated <i>in situ</i> by de­hydro­gen­ative coupling of a tertiary or conformationally restricted secondary alcohol with diethyl­silane, undergo regio­selective silyl­ation at a secondary C–H bond γ to the hydroxyl group. Oxidation of the resulting oxa­silol­anes in the same vessel generates 1,3-diols. This method provides a strategy to synthesize 1,3-diols through a hydroxyl-directed, functionalization of secondary alkyl C–H bonds. Mechanistic studies suggest that the C–H bond cleavage is the turnover-limiting step of the catalytic cycle. This silyl­ation of secondary C–H bonds is only 40–50 times slower than the analogous silyl­ation of primary C–H bonds

Copper-Catalyzed Oxidative Dehydrogenative Carboxylation of Unactivated Alkanes to Allylic Esters via Alkenes

We report copper-catalyzed oxidative dehydrogenative carboxyl­ation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV–vis) revealed that the resting state of the catalyst is [(BPI)­Cu­(O₂CPh)] (<b>1-O</b>_<b>2</b><b>CPh</b>), formed from [(BPI)­Cu­(PPh₃)₂], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of <b>1-O</b>_<b>2</b><b>CPh</b> with alkyl radicals and radical probes imply that C–H bond cleavage occurs by a <i>tert</i>-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclo­hexane and <i>d</i>₁₂-cyclo­hexane in separate vessels showed that the turnover-limiting step for the ODC of cyclo­hexane is C–H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amid­ation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper–carboxylate, copper–amidate, and copper–imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu­(II)–amidate > Cu­(II)–imidate > Cu­(II)–benzoate. Consistent with this trend, Cu­(II)–amidates and Cu­(II)–benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclo­hexane led to preliminary investig­ation of copper-catalyzed oxidative dehydrogenative amin­ation of cyclo­hexane to generate a mixture of <i>N</i>-alkyl and <i>N</i>-allylic products

Copper-Catalyzed Oxidative Dehydrogenative Carboxylation of Unactivated Alkanes to Allylic Esters via Alkenes

We report copper-catalyzed oxidative dehydrogenative carboxyl­ation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV–vis) revealed that the resting state of the catalyst is [(BPI)­Cu­(O₂CPh)] (<b>1-O</b>_<b>2</b><b>CPh</b>), formed from [(BPI)­Cu­(PPh₃)₂], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of <b>1-O</b>_<b>2</b><b>CPh</b> with alkyl radicals and radical probes imply that C–H bond cleavage occurs by a <i>tert</i>-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclo­hexane and <i>d</i>₁₂-cyclo­hexane in separate vessels showed that the turnover-limiting step for the ODC of cyclo­hexane is C–H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amid­ation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper–carboxylate, copper–amidate, and copper–imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu­(II)–amidate > Cu­(II)–imidate > Cu­(II)–benzoate. Consistent with this trend, Cu­(II)–amidates and Cu­(II)–benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclo­hexane led to preliminary investig­ation of copper-catalyzed oxidative dehydrogenative amin­ation of cyclo­hexane to generate a mixture of <i>N</i>-alkyl and <i>N</i>-allylic products

Facile Access to Mono- and Dinuclear Heteroleptic N‑Heterocyclic Silylene Copper Complexes

Reaction of the heteroleptic N-heterocyclic chlorosilylene L­(Cl)­Si: (<b>1</b>; L = PhC­(N<i>t</i>Bu)₂) with [Cu­(tmeda)­(CH₃CN)]­[OTf] (<b>2</b>; tmeda = <i>N,N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylenediamine, OTf = OSO₂CF₃ (triflate)) affords the Cu­(I) complex [L­(Cl)­Si:→Cu­(tmeda)]­[OTf] (<b>3</b>) in high yield as the first example of a heteroleptic N-heterocyclic silylene copper complex. Similarly, the reaction of L­(O<i>t</i>Bu)­Si: (<b>4</b>; L = PhC­(N<i>t</i>Bu)₂) with <b>2</b> affords [L­(O<i>t</i>Bu)­Si: → Cu­(tmeda)]­[OTf] (<b>5</b>) and that of L­(NMe₂)­Si: (<b>6</b>) with <b>2</b> leads to [L­(NMe₂)­Si:→Cu­(tmeda)]­[OTf] (<b>7</b>). Complex <b>3</b> shows a rather strong interaction in the solid state between the O atom of the triflate anion and the three-coordinate Cu­(I) center with a Cu···O distance of 2.312 Å. In contrast, complex <b>7</b> features only a weak interaction (ca. 3.28 Å), while in complex <b>5</b> the cation and anion are fully separated. Strikingly, the reaction of the chelating oxo-bridged silylene :Si­(L)­(μ₂-O)­(L)­Si: (<b>8</b>) with the copper source [Cu­(CH₃CN)₄]­[OTf] (<b>9</b>) affords the dinuclear complex salt [Cu₂{η¹:η¹-LSi­(μ₂-O)­SiL}₂]­[OTf]₂ (<b>10</b>), featuring a novel metallacyclooctane dication, selectively in a good yield. Complex <b>10</b> also exhibits a very strong interaction between the copper centers in the dication and the oxygen atoms of triflate anions in the solid state, evidenced by a Cu···O separation of only 2.141 Å. All complexes were fully characterized

An Amplified Ylidic “Half-Parent” Iminosilane LSiNH

The reaction of LSiBr­(NH₂) (<b>4</b>) (L = CH­[(CCH₂)­CMe­(NAr)₂]; Ar = 2,6-<i>i</i>Pr₂C₆H₃) with lithium bis­(trimethylsilyl)­amide in the presence of pyridine or 4-dimethylaminopyridine (DMAP) resulted in the activation of the α C–H bond of pyridine or DMAP, affording the products LSi­(dmap)­NH₂ (<b>6</b>) and LSi­(pyridine)­NH₂ (<b>7a</b>), respectively. Remarkably, this metal-free aromatic C–H activation occurs at room temperature. The emerging aminosilanes were isolated and fully characterized. Isotope labeling experiments and detailed DFT calculations, elucidating the reaction mechanism, were performed and provide compelling evidence of the formation of the “half-parent” iminosilane <b>1</b>, LSiNH, which facilitates this transformation due to its amplified ylidic character by the chelate ligand L. Furthermore, the elusive iminosilane <b>1</b> could be trapped by benzophenone and trimethylsilylazide affording the corresponding products, <b>8</b> and <b>9,</b> respectively, thereby confirming its formation as a key intermediate

Highly Electron-Rich Pincer-Type Iron Complexes Bearing Innocent Bis(metallylene)pyridine Ligands: Syntheses, Structures, and Catalytic Activity

The first neutral bis­(metallylene)­pyridine pincer-type [<b>ENE</b>] ligands (E = Si^II, Ge^II) were synthesized, and their coordination chemistry and reactivity toward iron was studied. First, the unprecedented four-coordinate complexes <b>κ</b>^<b>2</b><i><b>E,E</b></i>′-<b>[ENE]­FeCl</b>_<b>2</b> were isolated. Unexpectedly and in contrast to other related pyridine-based pincer-type Fe­(II) complexes, the N atom of pyridine is reluctant to coordinate to the Fe­(II) site due to the enhanced σ-donor strength of the E atoms, which disfavors this coordination mode. Subsequent reduction of <b>κ</b>^<b>2</b><i><b>Si,Si</b></i>′<b>-[SiNSi]­FeCl</b>_<b>2</b> with KC₈ in the presence of PMe₃ or direct reaction of the [<b>ENE</b>] ligands using Fe­(PMe₃)₄ produced the highly electron-rich iron(0) complexes <b>[ENE]­Fe­(PMe</b>_<b>3</b><b>)</b>_<b>2</b>. The reduction of the iron center substantially changes its coordination features, as shown by the results of a single-crystal X-ray diffraction analysis of <b>[SiNSi]­Fe­(PMe</b>_<b>3</b><b>)</b>_<b>2</b>. The iron center, in the latter, exhibits a pseudosquare pyramidal (PSQP) coordination environment, with a coordinative (pyridine)­N→Fe bond, and a trimethylphosphine ligand occupying the apical position. This geometry is very unusual for Fe(0) low-spin complexes, and variable-temperature ¹H and ³¹P NMR spectra of the <b>[ENE]­Fe­(PMe</b>_<b>3</b><b>)</b>_<b>2</b> complexes revealed that they represent the first examples of configurationally stable PSQP-coordinated Fe(0) complexes: even after heating at 70 °C for >7 days, no changes are observed. The substitution reaction of <b>[ENE]­Fe­(PMe</b>_<b>3</b><b>)</b>_<b>2</b> with CO resulted in the isolation of <b>[ENE]­Fe­(CO)</b>_<b>2</b> and the hitherto unknown <b>κ</b>^<b>2</b><i><b>E,E</b></i>′<b>-[ENE]­Fe­(CO)</b>_<b>2</b><b>L</b> (L = CO, PMe₃) complexes. All complexes were fully characterized (NMR, MS, XRD, IR, and ⁵⁷Fe Mössbauer spectroscopy), showing the highest electron density on the iron center for pincer-type complexes reported to date. DFT calculations and ⁵⁷Fe Mössbauer spectroscopy confirmed the innocent behavior of these ligands. Moreover, preliminary results showed that these complexes can serve as active precatalysts for the hydrosilylation of ketones

Divalent Silicon-Assisted Activation of Dihydrogen in a Bis(N-heterocyclic silylene)xanthene Nickel(0) Complex for Efficient Catalytic Hydrogenation of Olefins

The first chelating bis­(N-heterocyclic silylene)­xanthene ligand [Si^II(Xant)­Si^II] as well as its Ni complexes [Si^II(Xant)­Si^II]­Ni­(η²-1,3-cod) and [Si^II(Xant)­Si^II]­Ni­(PMe₃)₂ were synthesized and fully characterized. Exposing [Si^II(Xant)­Si^II]­Ni­(η²-1,3-cod) to 1 bar H₂ at room temperature quantitatively generated an unexpected dinuclear hydrido Ni complex with a four-membered planar Ni₂Si₂ core. Exchange of the 1,3-COD ligand by PMe₃ led to [Si^II(Xant)­Si^II]­Ni­(PMe₃)₂, which could activate H₂ reversibly to afford the first Si^II-stabilized mononuclear dihydrido Ni complex characterized by multinuclear NMR and single-crystal X-ray diffraction analysis. [Si^II(Xant)­Si^II]­Ni­(η²-1,3-cod) is a strikingly efficient precatalyst for homogeneous hydrogenation of olefins with a wide substrate scope under 1 bar H₂ pressure at room temperature. DFT calculations reveal a novel mode of H₂ activation, in which the Si^II atoms of the [Si^II(Xant)­Si^II] ligand are involved in the key step of H₂ cleavage and hydrogen transfer to the olefin

Copper-Catalyzed Intermolecular Amidation and Imidation of Unactivated Alkanes

We report a set of rare copper-catalyzed reactions of alkanes with simple amides, sulfonamides, and imides (i.e., benzamides, tosylamides, carbamates, and phthalimide) to form the corresponding <i>N</i>-alkyl products. The reactions lead to functionalization at secondary C–H bonds over tertiary C–H bonds and even occur at primary C–H bonds. [(phen)­Cu­(phth)] (<b>1-phth</b>) and [(phen)­Cu­(phth)₂] (<b>1-phth</b>_<b>2</b>), which are potential intermediates in the reaction, have been isolated and fully characterized. The stoichiometric reactions of <b>1-phth</b> and <b>1-phth</b>_<b>2</b> with alkanes, alkyl radicals, and radical probes were investigated to elucidate the mechanism of the amidation. The catalytic and stoichiometric reactions require both copper and <i>t</i>BuOO<i>t</i>Bu for the generation of <i>N</i>-alkyl product. Neither <b>1-phth</b> nor <b>1-phth</b>_<b>2</b> reacted with excess cyclohexane at 100 °C without <i>t</i>BuOO<i>t</i>Bu. However, the reactions of <b>1-phth</b> and <b>1-phth</b>_<b>2</b> with <i>t</i>BuOO<i>t</i>Bu afforded <i>N</i>-cyclohexylphthalimide (Cy-phth), <i>N</i>-methylphthalimide, and <i>tert</i>-butoxycyclohexane (Cy-O<i>t</i>Bu) in approximate ratios of 70:20:30, respectively. Reactions with radical traps support the intermediacy of a <i>tert</i>-butoxy radical, which forms an alkyl radical intermediate. The intermediacy of an alkyl radical was evidenced by the catalytic reaction of cyclohexane with benzamide in the presence of CBr₄, which formed exclusively bromocyclohexane. Furthermore, stoichiometric reactions of [(phen)­Cu­(phth)₂] with <i>t</i>BuOO<i>t</i>Bu and (Ph­(Me)₂CO)₂ at 100 °C without cyclohexane afforded <i>N</i>-methylphthalimide (Me-phth) from β-Me scission of the alkoxy radicals to form a methyl radical. Separate reactions of cyclohexane and <i>d</i>₁₂-cyclohexane with benzamide showed that the turnover-limiting step in the catalytic reaction is the C–H cleavage of cyclohexane by a <i>tert</i>-butoxy radical. These mechanistic data imply that the <i>tert</i>-butoxy radical reacts with the C–H bonds of alkanes, and the subsequent alkyl radical combines with <b>1-phth</b>_<b>2</b> to form the corresponding <i>N</i>-alkyl imide product