Neutral Donor Ligands Research Articles

Sequestration of Np4+ and NpO22+ ions by using diglycolamide-functionalized azacrown ethers in C8mim·NTf2 ionic liquid: Extraction, spectroscopic, electrochemical and DFT studies

Complexation of Np4+ and NpO22+ ions was studied in a room temperature ionic liquid (C8mim•NTf2) using two multiple diglycolamide (DGA) ligands with three and four DGA arms tethered to the nitrogen atoms of the aza-9-crown-3 and -12-crown-4 scaffolds termed as LI and LII, respectively. The studies include solvent extraction, UV–visible spectrophotometry, cyclic voltammetry, and density functional theory (DFT). While the extraction of NpO22+ ion, as a function of the nitric acid concentration, resembled that of the ‘solvation’ mechanism, seen in case of neutral donor ligands in molecular diluent, an opposite trend was observed for the Np4+ ion suggesting a ‘cation-exchange’ mechanism often operating in the case of ionic liquid-based solvent systems. Slope analysis suggested formation of Np(NO3)]3+•L and NpO2(NO3)2•L extracted species for the extraction of Np4+ and NpO22+, respectively, in both the ligand systems. The complexation of the metal ions was supported by peak shifts in the UV–visible spectrophotometric as well as cyclic voltammetric studies. DFT studies were carried out to get structural information of the complexes.

Heteroligand α-Diimine-Zn(II) Complexes with O,N,O′- and O,N,S-Donor Redox-Active Schiff Bases: Synthesis, Structure and Electrochemical Properties

A number of novel heteroligand Zn(II) complexes (1-8) of the general type (Ln)Zn(NN) containing O,N,O'-, O,N,S-donor redox-active Schiff bases and neutral N,N'-chelating ligands (NN) were synthesized. The target Schiff bases LnH2 were obtained as a result of the condensation of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with substituted o-aminophenols or o-aminothiophenol. These ligands with combination with 2,2'-bipyridine, 1,10-phenanthroline, and neocuproine are able to form stable complexes upon coordination with zinc(II) ion. The molecular structures of complexes 4∙H2O, 6, and 8 in crystal state were determined by means of single-crystal X-ray analysis. In the prepared complexes, the redox-active Schiff bases are in the form of doubly deprotonated dianions and act as chelating tridentate ligands. Complexes 6 and 8 possess a strongly distorted pentacoordinate geometry while 4∙H2O is hexacoordinate and contains water molecule coordinated to the central zinc atom. The electrochemical properties of zinc(II) complexes were studied by the cyclic voltammetry. For the studied complexes, O,N,O'- or O,N,S-donor Schiff base ligands are predominantly involved in electrochemical transformations in the anodic region, while the N,N'-coordinated neutral nitrogen donor ligands demonstrate the electrochemical activity in the cathode potential range. A feature of complexes 5 and 8 with sterically hindered tert-butyl groups is the possibility of the formation of relatively stable monocation and monoanion forms under electrochemical conditions. The values of the energy gap between the boundary redox orbitals were determined by electrochemical and spectral methods. The parameters obtained in the first case vary from 1.97 to 2.42 eV, while the optical bang gap reaches 2.87 eV.

Sulfinyl-aminotroponiminates: alkali- (Li, Na, K) and heavy-metal (Bi) complexes.

The installation of electron-withdrawing functional groups at the carbocyclic backbone of aminotroponiminate (ATI) ligands is a versatile method for influencing the electronic properties of the resulting ATI complexes. We report here Li, Na, and K salts of an ATI ligand with a phenylsulfinyl substituent in the backbone. It is demonstrated that the sulfinyl group actively contributes to the coordination chemistry of these complexes, effectively competing with neutral donor ligands such as thf or pyridine in the solid state (XRD), in solution (DOSY NMR spectroscopy), and in the gas phase (DFT). The impact of the phenylsulfinyl group on the redox properties of the complexes have been investigated and access to sodium sodiate species through ligand-induced disproportionation has been studied. Transfer of the ATI ligand to the heavy p-block element bismuth has been demonstrated. Analytical techniques applied in this work include multinuclear and DOSY NMR spectroscopy, cyclic voltammetry, DFT calculations, and single-crystal X-ray diffraction analysis.

Tungsten(VI) selenide tetrachloride, WSeCl4 - synthesis, properties, coordination complexes and application of [WSeCl4(SenBu2)] for CVD growth of WSe2 thin films.

WSeCl4 was obtained in good yield by heating WCl6 and Sb2Se3in vacuo. Green crystals grown by sublimation were shown by single crystal X-ray structure analysis to contain square pyramidal monomers with apical WSe, and powder X-ray diffraction (PXRD) analysis confirmed this to be the only form present in the bulk sample. Density functional theory (DFT) calculations using the B3LYP-D3 functional replicated the structure, identified the key bonding orbitals, and were used to aid assignment of the IR spectrum of WSeCl4. Reaction of WSeCl4 with ligands L gave [WSeCl4(L)] (L = MeCN, DMF, thf, py, OPPh3, 2,2'-bipy, SeMe2, SenBu2), whilst the dimers [(WSeCl4)2(μ-L-L)] were formed with L-L = Ph2P(O)CH2P(O)Ph2, 1,4-dioxane and 4,4'-bipyridyl. The complexes were characterised by microanalysis, IR and 1H NMR spectroscopy, and single crystal X-ray structures determined for [WSeCl4(L)] (L = OPPh3, MeCN, DMF) and [(WSeCl4)2(μ-L-L)] (L-L = 1,4-dioxane, 4,4'-bipyridyl). All except the 2,2'-bipy complex, which is probably seven-coordinate, contain six-coordinate tungsten with the neutral donor trans to WSe. Alkylphosphines, including PMe3 and PEt3, decompose WSeCl4 upon contact, forming phosphine selenides (SePR3). In contrast, the selenoether complexes [WSeCl4(SeMe2)] and [WSeCl4(SenBu2)] were isolated and characterised. The crystal structure of the minor W(VI) by-product, [(WSeCl4)2(μ-SeMe2)], was determined and using SMe2, a few crystals of the W(V) species, [{WCl3(SMe2)}2(μ-Se)(μ-Se2)], were obtained and structurally characterised. The isolated W(VI) complexes are compared with those of WOCl4 and WSCl4 and the combination of experimental and computational data are consistent with WSeCl4 being a weaker Lewis acid and its complexes significantly less stable than those of the lighter analogues, especially in solution. Low pressure chemical vapour deposition (LPCVD) using [WSeCl4(SenBu2)] in the range 660-700 °C (0.1 mmHg) produced highly reflective thin films, which were identified to be WSe2 by grazing incidence X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. XRD analysis of the thinner films revealed them to be highly oriented in the <00l> direction.

The versatile roles of neutral donor ligands in tuning catalyst performance for the ring-opening polymerization of cyclic esters

The use of neutral donor ligands is an effective strategy to modify catalyst structure and performance in the synthesis of sustainable polymers through the ring-opening polymerization (ROP) of cyclic esters.

Modulating extraction and retention of fluorinated β-diketonate metal complexes in perfluorocarbons through the use of non-fluorinated neutral ligands

Extraction of metal ions into perfluorocarbon solvent with a fluorinated acac ligand is described as well as synergistic extraction with neutral nitrogen donor ligands. Applications include catalysis, nuclear fuels reprocessing, and medical imaging.

Low-Symmetry β-Diketimine Aryloxide Rare-Earth Complexes: Flexible, Reactive, and Selective.

We report the synthesis, characterization, and reactivity of a new low-symmetry β-diketimine featuring a pendant amino(methyl)phenol donor and its corresponding heteroleptic rare-earth (RE) complexes. This includes the first structurally characterized examples of alcoholysis and insertion from an isolated REIII amide in a β-diketimine framework. The flexible methylene linkage leads to REIII complexes with tunable dynamic solution behavior that defines their stoichiometric and catalytic reactivity. The addition of a strong neutral donor ligand, tricyclohexylphosphine oxide, suppresses a prevalent catalyst degradation pathway (base-promoted elimination) and dramatically enhances the catalyst performance in the stereospecific ring-opening polymerization of rac-β-butyrolactone. Our results further demonstrate the importance of ligand reorganization in the stoichiometric and catalytic activity of REIII ions.

Effect of Ligand Fields on the Reactivity of O2‐Activating Iron(II)‐Benzilate Complexes of Neutral N5 Donor Ligands

Three new iron(II)-benzilate complexes [(N4Py)Fe II (benzilate)]ClO 4 ( 1 ), [(N4Py Me2 )Fe II (benzilate)]ClO 4 ( 2 ) and [(N4Py Me4 )Fe II (benzilate)]ClO 4 ( 3 ) of neutral pentadentate nitrogen donor ligands have been isolated and characterized to study their dioxygen reactivity. Single crystal X-ray structures reveal a mononuclear six-coordinate iron(II) centre in each case, where benzilate binds to the iron center in monodentate mode via one carboxylate oxygen. Introduction of methyl groups in the 6-positions of the pyridine rings makes the N4Py Me2 and N4Py Me4 ligands weaker field compared to the parent N4Py ligand. All the complexes ( 1-3 ) react with dioxygen to decarboxylate the coordinated benzilate to benzophenone quantitatively. The decarboxylation takes lesser time for the complex of more sterically hindered ligand and follows the order 3 > 2 > 1 . The complexes display oxygen atom transfer reactivity to thioanisole and also exhibit hydrogen atom transfer reactions with substrates containing weak C-H bonds. Based on interception studies with external substrates, labelling experiment and Hammett analysis, a nucleophilic iron(II)-hydroperoxo species is proposed to form upon two-electron reductive activation of dioxygen by each iron(II)-benzilate complex. The nucleophilic oxidants are converted to the corresponding electrophilic iron(IV)-oxo oxidant upon treatment with a protic acid. The high-spin iron(II)-benzilate complex with the weakest ligand field results in the formation of a more reactive iron-oxygen oxidant.

Synthesis, structure and thermal behavior of volatile mononuclear mixed ligand complexes of rare-earth dipivaloylmethanates with diethylenetriamine

Highly volatile and stable complexes of rare-earth elements with mononuclear structure are of great importance for gas phase deposition of functional thin film materials. Mixed ligand complexes with β-diketonate anions (e.g. thd− = 2,2,6,6-tetrametylheptane-3,5-dionate) and ancillary neutral donor ligands demonstrate mononuclear structure and sufficient volatility, however, they are unstable to neutral ligand elimination especially in case of light rare earth elements. Here diethylenetriamine (deta) has been applied as tridentate neutral ligand to improve the stability of mixed ligand complexes due to macrochelate effect and additional weak intramolecular interactions, e.g. hydrogen bonds. Synthesis of a series of mixed-ligand [Ln(thd)3(deta)], Ln = La (1L), Pr (2L), Nd (3L), Sm (4L) and Gd (5L) complexes, their X-ray single crystal structure characterization, DFT calculations, and thermal behavior study have been performed. Compounds 1L-5L demonstrate similar mononuclear molecular structure, but different molecular packing of three types, which may undergo mutual transformation. Compounds 1L-4L sublime intact in temperature range of 140–160 °C in vacuum without decomposition. 1L was successfully applied as volatile precursors for MOCVD preparation of epitaxial complex oxide thin films, (0 0 l) LaMnO3 and (0 0 l) LaAlO3, on (0 0 l) MgO and (0 0 l) SrTiO3 substrates.

The role of neutral donor ligands in the isoselective ring-opening polymerization of rac-β-butyrolactone.

Isoenriched poly-3-hydroxybutyrate (P3HB) is a biodegradable material with properties similar to isotactic polypropylene, yet efficient routes to this material are lacking after 50+ years of extensive efforts in catalyst design. In this contribution, a novel lanthanum aminobisphenolate catalyst (1-La) can access isoenriched P3HB through the stereospecific ring-opening polymerization (ROP) of rac-β-butyrolactone (rac-BBL). Replacing the tethered donor group of a privileged supporting ligand with a non-coordinating benzyl substituent generates a catalyst whose reactivity and selectivity can be tuned with inexpensive achiral neutral donor ligands (e.g. phosphine oxides, OPR3). The 1-La/OPR3 (R = n-octyl, Ph) systems display high activity and are the most isoselective homogeneous catalysts for the ROP of rac-BBL to date (0 °C: Pm = 0.8, TOF ∼190 h−1). Combined reactivity and spectroscopic studies provide insight into the active catalyst structure and ROP mechanism. Both 1-La(TPPO)2 and a structurally related catalyst with a tethered donor group (2-Y) operate under chain-end stereocontrol; however, 2-RE favors formation of P3HB with opposite tacticity (syndioenriched) and its ROP activity and selectivity are totally unaffected by added neutral donor ligands. Our studies uncover new roles for neutral donor ligands in stereospecific ROP, including suppression of chain-scission events, and point to new opportunities for catalyst design.

Synthesis of titanium(iv) 3,6-di-tert-butylcatecholate complexes

Two synthetic approaches were used for the synthesis of 3,6-di-tert-butylcatecholate derivatives of titanium(iv). These approaches are based on the exchange reaction between sodium catecholate and titanium(iv) chloride and the reaction of 3,6-di-tert-butylpyrocatechol with titanium tetrabutoxide. Depending on the reaction conditions, the former method allows the synthesis of the titanium monocatecholate complex 3,6-CatTiCl2(THF)2 (3,6-Cat is doubly deprotonated 3,6-di-tert-butylpyrocatechol) or bimetallic sodium titanium catecholate derivatives. Using the latter method, it is possible to synthesize six-coordinate titanium(iv) bis-cate-cholate complexes in high yields after the introduction of neutral bidentate donor ligands (TMEDA, DME, 2,2′-bipyridyl) to the reaction mixture.

Triphenylantimony(V) catecholato complexes with 4-(2,6-dimethylphenyliminomethyl)pyridine. Structure, redox properties: The influence of pyridine ligand

The complexation of triphenylantimony(V) catecholates (3,6-DBCat)SbPh3 (1), (4,5-pip-3,6-DBCat)SbPh3 (2) and (4,5-Cl2-3,6-DBCat)SbPh3 (3) with neutral 4-(2,6-dimethylphenyliminomethyl)pyridine (Py-CHN–Ar) leads to the formation of hexacoordinated complexes (3,6-DBCat)SbPh3·(Py-CHN–Ar) (4), (4,5-pip-3,6-DBCat)SbPh3·(Py-CHN–Ar) (5) and (4,5-Cl2-3,6-DBCat)SbPh3·(Py-CHN–Ar) (6) (where 3,6-DBCat is 3,6-di-tert-butyl-catecholate, 4,5-pip-3,6-DBCat is 4,5-(N,N′-piperazine-1,4-diyl)-3,6-di-tert-butyl-catecholate, 4,5-Cl2-3,6-DBCat is 4,5-dichloro-3,6-di-tert-butyl-catecholate) containing NPyridine-coordinated neutral donor ligand Py-CHN–Ar. In the absence of donor ligands chlorine-containing catecholate 3 undergoes rearrangement in acetonitrile to form ionic complex [Ph4Sb]+[(4,5-Cl2-3,6-DBCat)2SbPh2]- (7). Complexes have been isolated and characterized by spectroscopic methods and cyclic voltammetry. The pyridine-containing catecholate (3,6-DBCat)SbPh3·Py (8) was also synthesized in order to compare it's the electrochemical behaviour with those of iminopyridine complexes 4–6. The presence of NPyridine-coordinated iminopyridine ligand changes the mechanism of catecholate oxidation in 4 and 6: the first oxidation wave (at Eox1p = 0.94 V for 4 and 0.99 V for 6) is two-electron and corresponds to the oxidation of dianionic catecholate ligand to a coordinated o-benzoquinone. In contrast to catecholates 4 and 6, the electrochemical behaviour of piperazine-containing catecholate 5 does not practically differ from that one for initial catecholate 2. The molecular structures of complexes 3–7 in crystals have been determined by single-crystal X-ray analysis.

Two Carbenes versus One in Magnesium Chemistry: Synthesis of Terminal Dihalide, Dialkyl, and Grignard Reagents

Substantial progress has been made in the coordination chemistry of main-group elements with neutral donor ligands, largely ushered in by the development of stable N-heterocyclic carbenes (NHCs). There is growing interest in the synthesis of well-defined coordination compounds containing s-block metals; however, examples of molecular compounds containing “normal” NHCs bound to magnesium remain relatively understudied. We report that NHCs react with magnesium halides, MgX2 (X = Cl, Br, I), to afford (IPr)MgCl2(THF) (1), [(IPr)MgCl2]2 (2), (sIPr)2MgCl2 (3), (sIPr)2MgBr2 (4), and (sIPr)2MgI2 (5), where IPr is 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidine and sIPr is 1,3-diisopropyl-4,5-dimethylimidizol-2-ylidine. Using the IPr ligand, weak NHC coordination and dynamic interaction with THF are observed in solution. In contrast, the coordination of two sIPr ligands results in higher purity, enhanced stability, and no observation of THF coordination. Dual carbene complexation with commercially available Mgn...

Extraction of lanthanides(III) from Perchlorate Solutions with Carbamoyl- and Phosphorylmethoxymethylphosphine Oxides and Tetrabutyldiglycolamide

ABSTRACT The solvent extraction of Ln(III) ions from perchlorate aqueous solutions into an organic phase containing neutral polyfunctional organophosphorus ligands R2P(O)CH2OCH2C(O)NBu2 R = Bu (I), R = Ph (II) and R2P(O)CH2OCH2P(O)R1 2 R = R1 = Bu (III); R = Bu, R1 = Ph (IV); R = R1 = Ph(V) has been studied. Their extraction behavior was compared with that of tetrabutyldiglycolamide (TBDGA), tetrabutylmethylenediphosphine dioxide (VI), P,P-dibutyl-P’P’-diphenylmethylenediphosphine dioxide (VII), tetraphenylmethylenediphosphine dioxide (VIII), dibutyl-N,N-dibutylcarbamoylmethylphosphine oxide (IX) and diphenyl-N,N-dibutylcarbamoylmethylphosphine oxide (X). The extraction equilibrium was investigated, and the equilibrium constants were calculated. It was found that the lanthanide(III) ions are extracted with the studied extractants from perchlorate solutions as LnL3(ClO4)3 complexes. In the NaClO4 media, TBDGA was found to possess a higher extraction efficiency towards Ln(III) ions than other neutral donor ligands studied. A successive replacement of the C(O)NBu2 groups in the diglycolamide extractant molecule by phosphoryl ones leads to a decrease in the extraction efficiency of Ln(III) ions. In the NaClO4 media, compounds II, IV and V with phenyl radicals at the P(O) group demonstrate a lower extraction efficiency towards Ln(III) ions than their butyl-substituted analogs. In contrast, phenyl-substituted diphosphine dioxides VIII, VII and carbamoylmethylphosphine oxide (X) extract Ln(III) ions more effectively than their butyl-substituted analogs VI and IX. The extraction of Ln(III) ions from HClO4 solutions is accompanied by HClO4 interaction with neutral donor extractants, which leads to a decrease of the free extractant concentration in the organic phase. By this reason, an increase in the HClO4 concentration higher than 0.1 M is accompanied by a decrease of the Ln(III) extraction with TBDGA. In the 3 M HClO4 system, diphosphine dioxide VIII outperforms TBDGA at the Ln(III) extraction.

From lithium to sodium: design of heterometallic molecular precursors for the NaMO2 cathode materials.

Based on the well-established model structure of Li2M2(tbaoac)6, the first series of heterometallic molecular precursors Na2M2(tbaoac)6(THF)2 (M = Fe, Co, and Ni) have been designed and successfully utilized for the preparation of NaMO2 oxide cathode materials of sodium-ion batteries.

Strengths of different Lewis bases in stabilizing titanium fluorides: A theoretical insight

Detailed investigations of the electronic structure and bonding scenario in various cis-TiF4D2 and [TiF5D]– (D = neutral donor ligand) complexes have been presented using computational methods (R-M06-L/6-311++G(d,p)//R-M06-L/6-311 + G(d)). We have also computed the formation energies of these complexes for different reaction routes in the gas phase and acetonitrile solvent medium. The donor-acceptor nature of the TiD1 and TiD2 bonds in the cis-TiF4D2 complexes are confirmed by QTAIM calculations. Moreover, EDA-NOCV analysis was performed to gain better insight into the bonding situation in this class of complexes and also to obtain a relative scale of both intrinsic and overall Lewis basicity for the ligands, considering TiF4 as reference Lewis acid. The calculations reveal that with respect to TiF4, abnormal N-heterocyclic carbene (aNHC) exhibits both overall and intrinsically strongest Lewis basicity, whereas intrinsically and overall weakest Lewis basicity are shown by CO and AsH3, respectively. Furthermore, the isomerism of mixed chloro and fluoro titanium complexes supported by neutral ligands is extensively studied to shed light on the dependence of the relative stabilities of these isomers on intrinsic Lewis base strength of the ligands.

Butylamine-Catalyzed Synthesis of Nanocrystal Inks Enables Efficient Infrared CQD Solar Cells.

The best-performing colloidal-quantum-dot (CQD) photovoltaic devices suffer from charge recombination within the quasi-neutral region near the back hole-extracting junction. Graded architectures, which provide a widened depletion region at the back junction of device, could overcome this challenge. However, since today's best materials are processed using solvents that lack orthogonality, these architectures have not yet been implemented using the best-performing CQD solids. Here, a new CQD ink that is stable in nonpolar solvents is developed via a neutral donor ligand that functions as a phase-transfer catalyst. This enables the realization of an efficient graded architecture that, with an engineered band-alignment at the back junction, improves the built-in field and charge extraction. As a result, optimized IR CQD solar cells (Eg ≈ 1.3 eV) exhibiting a power conversion efficiency (PCE) of 12.3% are reported. The strategy is applied to small-bandgap (1 eV) IR CQDs to augment the performance of perovskite and crystalline silicon (cSi) 4-terminal tandem solar cells. The devices show the highest PCE addition achieved using a solution-processed active layer: a value of +5% when illuminated through a 1.58 eV bandgap perovskite front filter, providing a pathway to exceed PCEs of 23% in 4T tandem configurations with IR CQD PVs.

Aldehyde Reduction by a Pyridone Borane Complex through Boron‐Ligand‐Cooperation: Concerted or Not?

The reduction of benzaldehyde by a pyridone borane complex was investigated by NMR, X‐ray analysis as well as DFT and DLPNO‐CCSD(T) computations. The reaction leads to the formation of a pyridone boronic ester complex stabilized by an NH···O hydrogen bond. The computations show that the hydrogenation takes place in a concerted fashion, yielding a transient benzyl alcohol boroxypyridine complex that undergoes a barrierless O–H addition. The concerted hydrogen transfer is associated with a transformation of a pyridone borane to a boroxypyridine, and thus with the interconversion of a neutral donor ligand to a covalently bound substituent.

Sodium Aminotroponiminates: Ligand‐Induced Disproportionation, Mixed‐Metal Compounds, and Exceptional Activity in Polymerization Catalysis

AbstractSodium complexes of aminotroponiminate (ATI) ligands have been reacted with a range of neutral donor ligands. Upon addition of crown ethers, they undergo an unusual ligand‐induced disproportionation reaction with formation of [Na(ATI)2]− sodiate complex anions. The same structural motif has also been found in the first well‐defined mixed‐metal ATI complexes, which have been accessed starting from monometallic sodium and potassium species. The mixed‐metal compounds confirm the possibility of ATIs to act as ditopic ligands. Using the polymerization of ϵ‐caprolactone as a model system, structure‐reactivity‐relationships in sodium and mixed‐metal ATI compounds have been studied by comparing the reactivity of [Na(ATI)] and [Na(ATI)2]− structural motifs. These studies revealed trends in the catalyst activity depending on the nuclearity of the complex and the substitution pattern at the ATI ligand. Exceptionally high activities were obtained for dinuclear sodium sodiates of type [Na(crown)2][Na(ATI)2], making them the most active alkali metal initiators for this reaction. The organometallic and polymeric compounds presented in this work have been characterized by techniques including (VT‐)NMR spectroscopy, single‐crystal X‐ray diffraction, gel permeation chromatography, mass spectrometry, and DFT calculations.

Mechanism of Charged, Neutral, Mono-, and Polyatomic Donor Ligand Coordination to Perchlorinated Cyclohexasilane (Si6Cl12).

We report the detailed computational study of several perchlorinated cyclohexasilane (Si6Cl12)-based inverse sandwich compounds. It was found that regardless of the donor ligand size and charge, for example, Cl- and CN- anions or neutral HCN and NCPh nitriles, their coordination to the puckered Si6Cl12 ring results in its flattening. The NBO and CDA studies of the complexes showed that coordination occurs due to hybridization of low-lying antibonding σ*(Si-Cl) and σ*(Si-Si) unoccupied molecular orbitals (UMOs) of Si6Cl12 and occupied molecular orbitals (OMOs) of donor molecules (predominantly lone-pair-related), resulting in donor-to-ring charge transfer accompanied by complex stabilization and ring flattening. It is known that the Si6 ring distortion results from vibronic coupling of OMO and UMO pairs (pseudo-Jahn-Teller effect, PJT). Consequently, the Si6 ring flattening most probably occurs due to suppression of the PJT effect in all of the studied compounds. In this paper, the stabilization energy E(2) associated with donor-acceptor charge transfer (delocalization) was estimated using NBO analysis for [Si6Cl12·2Cl]2-, [Si6Cl12·2(NC)]2-, Si6Cl12·2(NCH), and Si6Cl12·2(NCPh). It was found that the polarizability of the donor might significantly affect the stabilization energy value (Cl- > CN- > HCN). For the neutral complexes, the E(2) value is correlated with the charge on the nitrogen atoms. All of these factors, that is, specific donor E(2) value, charge transfer, complex MO energy diagrams, and so on, should be taken into account when choosing the ligands suitable for forming Si-based 1D compounds and other nanoscale materials.