Search

A series of new six-coordinate silicon, germanium, and tin complexes based on 3,6-di-tert-butyl-o-benzoquinone with N-donor ligands (1,10-phenanthroline and 2,2′-bipyridine) were synthesized and structurally and spectrally characterized. According to the results of electrochemical measurements, the complexes can be oxidized or reduced (they are redox amphoteric) due to the presence of redox-active ligands. The electronic absorption spectra of the compounds show absorption in the 450–500 nm range, which accounts for their intense color. This absorption band is blue-shifted with increasing solvent polarity. The combination of the spectral characteristics and results of quantum chemical calculations indicates that the synthesized silicon, germanium, and tin complexes can be considered as donor-acceptor chromophores with photoinduced ligand-to-ligand charge transfer between the diimine moiety and catechols. [ABSTRACT FROM AUTHOR]

New metal-organic coordination polymers (MOCPs) of cadmium(II) based on chelate-type ligands have been synthesized. The structural features of the obtained zigzag polymer derivatives [Cd(pQ)(1,2-PG)]⋅2DMF, [Cd(pQ)⋅2DMAA], [Cd(pQ)⋅2NMP], [Cd(pQ)(1,2-PG)]⋅2NMP, [Cd(CA)⋅2NMP], and [Cd(CA)(1,3-PG)]⋅2NMP (where pQ is the dianion of 2,5-di-hydroxy-3,6-di-tert-butyl-p-benzoquinone, CA is the dianion of chloranilic acid, 1,2-PG is 1,2-propanediol, 1,3-PG is 1,3-propanediol, DMF is N,N-dimethylformamide, DMAA is N,N-dimethylacetamide, NMP is N-methyl-2-pyrrolidone) are studied. The molecular and crystal structures of the synthesized MOCPs were established by X-ray diffraction analysis of single crystals. [ABSTRACT FROM AUTHOR]

New tin(IV) complexes based on various pyrocatechols containing tert-butyl and tert-octyl substituents in the aromatic ring are synthesized and structurally characterized. Reduction of spatially hindered o-quinones with tin amalgam in tetrahydrofuran allows the preparation of compounds with the trans-position of catecholate ligands in the metal coordination sphere. In the further reaction of synthesized tin(IV) biscatecholates with N-donor ligands (pyridine (Py), α,α′-dipyridyl (dipy), 1,10-phenanthroline (phen), pyrazino-[2,3-f][1-10]-phenanthroline (DPQ), dipyrido-[3,2-a:2′3′-c]-phenazine (DPPZ)) the respective six-coordinated complexes are obtained. The introduction of bidentate ligands naturally results in the cis-position of dioxolene ligands in the tin coordination sphere. The possibility of intramolecular ligand–ligand charge transfer (LL′CT) between catecholate and diimine moieties in the synthesized octahedral metal derivatives is shown by electronic absorption spectroscopy. The effect of substituents in catecholate ligands and acceptor properties of diimines on the shift of a long-wave absorption band is determined. The electronic transition corresponding to LL′CT is revealed to undergo a bathochromic shift in the electronic absorption spectrum with a decrease in the polarity of the solvent used. [ABSTRACT FROM AUTHOR]

O,N-Heterocyclic phospholenes (tBuAp)PCl, (PhAp)PCl, (PhAp)PPh and (PhenoxAp)PCl based on sterically hindered 4,6-di-tert-butyl-N-(R)-о-aminophenols (RAp, R = tBu, Ph) and 2,4,6,8-tetra-tert-butyl-1H-phenoxazin-1-one (PhenoxAp) were synthesized and structurally characterized. The diverse reactivity of the synthesized compounds towards reducing, oxidizing agents and Lewis acids was observed. Reduction of (tBuAp)PCl leads to a dimeric diphosphole. The oxidative addition of 3,6-di-tert-butyl-o-benzoquinone and 4,6-di-tert-butyl-N-(2,6-di-isopropyl-phenyl)-o-iminoquinone to the phosphorus in (PhAp)PCl gives new pentacoordinated PV compounds containing two different dianionic redox-active ligands. Bis-o-amidophenolate (PhenoxAp)2PBr was prepared by the reaction of 2,4,6,8-tetra-tert-butyl-1H-phenoxazin-1-one with PBr3 and cyclohexene. Dissolution of (PhenoxAp)2PBr in THF promotes the ring opening reaction of the cyclic ether. The reaction of (PhAp)PCl with Ni(CO)4 and Fe2(CO)9 leads to the stable PIII adducts (PhAp)P(Cl)–Ni(CO)3 and (PhAp)P(Cl)–Fe(CO)4. [ABSTRACT FROM AUTHOR]

Novel heteroleptic lanthanum, praseodymium, and neodymium metal-organic coordination polymers (MOCPs) containing two types of anionic organic ligands as organic units are prepared by a two-step solvothermal synthesis in N,N-dimethylformamide. Framework derivatives with the [Ln2(CA)(fdc)2·4DMF]· ·2DMF composition are prepared (Ln = La, Pr, Nd; CA is a dianion of the chloranilic acid; fdc is a dianion of the 2,5-furandicarboxylic acid; DMF is N,N-dimethylformamide). The structure of the compounds is studied by XRD (CCDC CIF file No. 2251285 (I), 2251286 (II), 2251287 (III)). [ABSTRACT FROM AUTHOR]

The paper reviews data reported on the synthesis, molecular and electronic structure of heterocyclic derivatives of low valent silicon, germanium, tin, and lead for the period from 2016 to 2021. The main pathways of chemical transformations of these compounds are considered. [ABSTRACT FROM AUTHOR]

New complex of low-valent germanium PhenoxAPGe (I) based on the redox-active ligand 2,4,6,8-tetra-tert-butylphenoxazin-1-one is synthesized and structurally characterized. Its versatile reactivity is demonstrated for the acid-base and redox transformations. The reaction of germylene I with Ni(COD)2 is found to result in the substitution of both cyclooctadiene molecules, coordination of four germylene fragments to zero-valent nickel, and formation of compound (PhenoxAPGe)4Ni (II). The reaction of compound I with [CpNi(CO)]2 in a toluene solution affords complex (PhenoxAPGe)2(NiCp)2 (III), being the substitution product of two carbonyl groups by two isolobal germylene fragments. The reaction with the one-electron oxidant (3,6-di-tert-butyl-2-methoxyphenoxyl radical) generates labile paramagnetic germylene IV characterized by EPR spectroscopy. Digermylene oxide V synthesized by the hydrolysis of the starting germylene Iin situ reacts with N-heterocyclic carbene and KC8 to form ionic derivatives VI and VII containing the Ge(II)–O–Ge(II) fragment. Germylene I is tested as a catalyst for the hydroboration of benzaldehyde. The molecular structures of the compounds are determined by X-ray diffraction (СIF files CCDC nos. 2117783 (I), 2124277 (II), 2125357 (III), and 2118393 (VII)). [ABSTRACT FROM AUTHOR]

A series of new paramagnetic six-coordinate gallium complexes based on 3,6-di-tert-butyl-o-benzoquinone with N-donor ligands, such as pyridine (Py), 2,2′-dipyridyl (2,2′-dipy), and 4,4′-di-tert-butyl-2,2′-dipyridyl (But-dipy), were synthesized and structurally characterized. The molecular structures of the synthesized compounds were established by single-crystal X-ray diffraction. The complexes with bidentate N-donor ligands have the cis arrangement of the o-quinone ligands, whereas the compound with coordinated pyridine molecules has the trans arrangement of the diolate moieties. The synthesized compounds are characterized by spin density delocalization between the differently charged redox-active ligands. Regardless of the metal coordination environment, the near-IR region of the electronic absorption spectra of all the synthesized complexes show a low-intensity charge-transfer band between the catecholate and o-semiquinolate ligands, which was confirmed by DFT calculations. [ABSTRACT FROM AUTHOR]

New bimetallic complexes PhAPGe[M(CO)nCp]2 (PhAP is 3,5-di-tert-butyl-N-(phenyl)-o-ami-nophenolate dianion; M = Fe, n = 2 (II); M = W, n = 3 (III)) are synthesized by the insertion of O,N-heterocyclic germylene PhAPGe (I) at the metal–metal bond in dimers [Fe(CO)2Cp]2 and [W(CO)3Cp]2. The oxidation of compounds II and III with silver(I) triflate affords paramagnetic germanium(IV) o-iminosemiquinolates detected by EPR spectroscopy. The oxidative addition of 3,6-di-tert-butyl-o-benzoquinone to germylene I proceeds via the oxidation of the low-valence center to the tetravalent state and is accompanied by symmetrization with the formation of the corresponding bis-o-amidophenolate and bis(catecholate) derivatives of germanium(IV). Digermylene oxide Ia synthesized by the hydrolysis of starting germylene I acts as the oxidant in the reaction with the nickel cyclopentadienylcarbonyl dimer and forms an eight-membered metallocycle supporting four Ge(II)–Ni(II) donor–acceptor bonds in compound (CpNi)2[PhAP-GeOGePhAmP]2 (PhAmP is 3,5-di-tert-butyl-N-(phenyl)-o-aminophenolate anion) (IV). The molecular structures of compounds II–IV are determined by X-ray diffraction (XRD) (СIF files CCDC nos. 2118153–2118155, respectively). [ABSTRACT FROM AUTHOR]

New paramagnetic tin(IV) derivatives containing the radical-anion of 2,4,6,8-tetra-tert-butylphenoxazin-1-one redox-active ligand (phenox-imQ) are synthesized and studied by EPR spectroscopy. Complexes I–V are paramagnetic in the crystalline state and in solution. The geometry of the obtained paramagnetic species and spin density distribution in them are studied by the Density functional theory. Diamagnetic complex VI is synthesized from the phenox-imQ dianion, and its one-electron oxidation is studied. The molecular structure of complex VI · ТHF is determined by X-ray diffraction analysis (CIF file CCDC no. 2000962 (VI · ТHF)). [ABSTRACT FROM AUTHOR]