Synthesis and Structural Characterization of -Carboranylamidine Derivatives.

In this contribution, the first amidinate and amidine derivatives of -carborane are described. Double lithiation of -carborane () with -butyllithium followed by treatment with 1,3-diorganocarbodiimides, R-N=C=N-R (R = Pr, Cy (= cyclohexyl)), in DME or THF afforded the new -carboranylamidinate salts -CHB[C(NPr)Li(DME)] () and -CHB[C(NCy)Li(THF)] (). Subsequent treatment of and with 2 equiv.

Small compound - big colors: synthesis and structural investigation of brightly colored alkaline earth metal 1,3-dimethylviolurates.

A series of brightly colored alkaline earth metal 1,3-dimethylviolurates M(MeVio) have been prepared and fully characterized. The title compounds AE(MeVio)·HO (AE = Mg, = 6 (3); AE = Ca, = 8 (4), AE = Sr, = 6 (5); AE = Ba, = 4 (6)) were obtained by neutralizing 1,3-dimethylvioluric acid monohydrate (=H(MeVio)·HO; 2) with 0.5 equiv.

Rubidium and Cesium Enediamide Complexes Derived from Bulky 1,4-Diazadienes.

The first rubidium and cesium enediamide complexes based on bulky 1,4-diaza-1,3-diene ligands (DADs) have been prepared by metalation of either 1,4-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene (, = DAD) or 1,4-bis(2,6-diisopropylphenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene (, = DAD) with an excess of Rb or Cs metals in coordinating solvents such as tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME). All new complexes were fully characterized by spectroscopic and analytical methods as well as single-crystal X-ray diffraction studies.

An unsymmetrical dinuclear scandium complex comprising salophen ligands [Hsalophen = ,'-bis-(salicyl-idene)-1,2-phenyl-enedi-amine].

Treatment of scandium nitrate tetra-hydrate with the tetra-dentate ligand Hsalophen [,'-bis-(salicyl-idene)-1,2-phenyl-enedi-amine] afforded the yellow dinuclear complex Sc(NO)(μ-salophen)Sc(salophen)(EtOH) or [Sc(CHNO)(NO)(CHO)] (systematic name: (ethanol-κ)bis-(nitrato-κ ,'){μ-2,2'-[1,2-phenyl-enebis(nitrilo-methanylyl-idene)]diphenolato-κ ,',,':κ ,'}{2,2'-[1,2-phenyl-enebis(nitrilo-methanylyl-idene)]diphenolato-κ ,,','}discandium). In this compound, one salophen ligand displays a bridging coordination the two oxygen atoms, while the other salophen ligand is attached to only one Sc center. This arrangement is stabilized by a hydrogen-bonded EtOH co-ligand, and by π-π stacking inter-actions between the two salophen ligands.

Formation and structural characterization of a potassium amidino-guanidinate.

The first potassium amidino-guanidinate complex, -poly[[bis-(μ-1-amidinato-,','','''-tetra-iso-propyl-guanidinato-κ : , : , )dipotassium]-μ-1,2-di-meth-oxy-ethane-κ :'], [K(CHN)(CHO)] or [{ PrN= CHN( Pr)N(N Pr)K}(-DME)] where DME is 1,2-di-meth-oxy-ethane, has been synthesized and structurally characterized. The title compound was isolated in 76% yield from a reaction of ,'-diiso-propyl-carbodi-imide with potassium hydride in DME. The single-crystal X-ray structure determination of the title compound revealed a polymeric chain structure comprising cage-like dimeric units, with the amidino-guanidinate ligand displaying a mixed σ-/π-coordination mode.

Electronic and Geometric Structures of Paramagnetic Diazadiene Complexes of Lithium and Sodium.

The electronic and molecular structures of the lithium and sodium complexes of 1,4-bis(2,6-diisopropylphenyl)-2,3-dimethyl-1,4-diazabutadiene (DAD) were fully characterized by using a multi-frequency electron paramagnetic resonance (EPR) spectroscopy approach and crystallography, together with density functional theory (DFT) calculations. EPR measurements, using relaxation-time-filtered pulse EPR spectroscopy, revealed the diagonal elements of the and tensors for the metal and ligand sites. It was found that the central metals in the lithium complexes had sizable contributions to the SOMO, whereas this contribution was less strongly observed for the sodium complex.

The "Wanderlust" of MeSi groups in rare-earth triple-decker complexes: a combined experimental and computational study.

The migration of Me3Si groups ("Wanderlust") in rare-earth triple-decker sandwich complexes of the type Ln2(COT'')3 (COT'' = bis(trimethylsilyl)cyclooctatetraenyl) has been elucidated by a combined experimental and computational study. For the first time, two isomers of a Ln2(COT'')3 triple-decker have been isolated and characterized in the case of Y2(COT'')3.

High-yield synthesis of a unique Mn(iii) siloxide complex through KMnO oxidation of a Mn(ii) precursor.

A unique trivalent manganese siloxide complex, blue-violet MnLiCl[(PhSiO)O](THF)·2THF (3) has been prepared by a straightforward two-step synthetic protocol. Lithiation of (PhSiOH)O (1) followed by reaction with MnCl(THF) gave the structurally remarkable Mn(ii) precursor MnLiCl[(PhSiO)O](THF)·2THF (2). Surprisingly, the final oxidation step could be achieved using KMnO in THF to provide the Mn(iii) species 3 in high yield (91%).

Scandium-Mediated Formation of a Bis(tetrahydropentalene).

The reactivity of Li[Sc(COT'') ] (1; COT''=1,4-bis(trimethylsilyl)cyclooctatetraenyl) towards CoCl is considerably different from that of related lanthanide triple-decker sandwich complexes. In addition to the expected triple-decker complex Sc (COT'') (2), the complex Sc {μ-BTHP}(COT'') (3) is formed, which comprises the novel BTHP ligand (BTHP =bis(3,5-bis(trimethylsilyl)-1,3a,6,6a-tetrahydropentalene-1-yl)diide or bis(2,7-bis(trimethylsilyl)bicyclo[3.3.

Synthesis and structural study of new metallasilsesquioxanes of potassium and uranium.

The first metallasilsesquioxanes comprising potassium and uranium have been synthesized and structurally characterized by single-crystal X-ray diffraction. (CySiO)K(DME) (2; Cy = cyclohexyl) is a centrosymmetric dimer, in which the two silsesquioxide ligands are interconnected by μ- and μ-bridging siloxide moieties. (CySiO)U (3) represents the first metallasilsesquioxane complex of an actinide element, featuring a U atom that is coordinated by two tridentate silsesquioxide ligands in a distorted octahedral fashion.

Crystal structures of two ytterbium(III) complexes comprising alkynylamidinate ligands.

Two ytterbium(III) complexes comprising alkynylamidinate ligands, namely bis-(η-cyclo-penta-dien-yl)(3-cyclo-propyl-,'-diiso-propyl-propynamidinato-κ,')ytterbium(III), [Yb(CH)(CHN)] or CpYb[( PrN)C-C≡C--CH] () and tris-(3-phenyl-,'-di-cyclo-hexyl-propynamidinato-κ,')ytterbium(III), [Yb(CHN)] or Yb[(CyN)C-C≡C-Ph] (Cy = cyclo-hex-yl) () have been synthesized and structurally characterized. Both complexes are monomers; for complex , the contribution to the scattering from highly disordered toluene solvent molecules in these voids was removed with the SQUEEZE routine [Spek (2015). C, 9-18] in .

Metal complexes of curcumin--synthetic strategies, structures and medicinal applications.

This Tutorial Review presents an overview on the synthesis, characterization and applications of metal complexes containing curcumin (=1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) and its derivatives as ligands. Innovative synthetic strategies leading to soluble and crystallizable metal curcumin complexes are outlined in detail. Special emphasis is placed on the highly promising and exciting medicinal applications of metal curcumin complexes, with the three most important areas being anticancer activity and selective cytotoxicity, anti-Alzheimer's disease activity, and antioxidative/neuroprotective effects.

Heterometallic europium disiloxanediolates: synthesis, structural diversity, and photoluminescence properties.

This contribution presents a full account of a structurally diverse class of heterometallic europium disiloxanediolates. The synthetic protocol involves in situ metalation of (HO)SiPh2OSiPh2(OH) (1) with either (n)BuLi or KN(SiMe3)2 followed by treatment with EuCl3 in suitable solvents such as 1,2-dimethoxyethane (DME) or tetrahydrofuran (THF). Reaction of EuCl3 with 2 equiv of (LiO)SiPh2OSiPh2(OLi) in DME afforded the Eu(III) bis(disiloxanediolate) "ate" complex [{(Ph2SiO)2O}2{Li(DME)}3]EuCl2 (2), which upon attempted reduction with Zn gave the tris(disiloxanediolate) [{(Ph2SiO)2O}3{Li(DME)}3]Eu (3).

Unprecedented formation of polycyclic diazadiborepine derivatives through cage deboronation of m-carborane.

An unprecedented deboronation reaction of icosahedral carboranes is described, in which a BH group of m-carborane is detached from the cage and incorporated into an unusual nido-carborane-anellated diazadiborepine ring system.

Novel inorganic heterocycles from dimetalated carboranylamidinates.

Mono- and dianionic carboranylamidinates are readily available in one-pot reactions directly from o-carborane (1). In situ-monolithiation of 1 followed by treatment with N,N'-diisopropylcarbodiimide, (i)PrN=C=N(i)Pr, or N,N'-dicyclohexylcarbodiimide, CyN=C=NCy, provided the lithium carboranylamidinates (o-C2B10H10C(NH(i)Pr)(=N(i)Pr)-κ(2)C,N)Li(DME) (2a) and (o-C2B10H10C(NH(i)Cy)(=N(i)Cy)-κ(2)C,N)Li(THF)2 (2b). Controlled hydrolysis of 2a,b afforded the free carboranylamidines o-C2B10H11C(NH(i)R)(=N(i)R) (3a: R = (i)Pr, 3b: R = Cy).

Bromidobis[3-(1H-pyrazol-1-yl-κN(2))propionamide-κO]copper(II) bromide methanol monosolvate.

The title copper(II) N-pyrazolylpropanamide (PPA) complex, [CuBr(PPA)(2)]Br, was obtained in 78% yield by treatment of CuBr(2) with an excess of the ligand in methanol. Crystallization from the mother liquid afforded the title compound, i.e.

Unprecedented bending and rearrangement of f-element sandwich complexes induced by superbulky cyclooctatetraenide ligands.

The use of the superbulky cyclooctatetraenide dianion ligand [C(8)H(6)(SiPh(3))(2)](2-) (= COT(BIG)) in organo-f-element chemistry leads to unprecedented effects such as the formation of a significantly bent anionic Ce(III) sandwich complex, a novel cerocene formed by sterically induced SiPh(3) group migration, as well as the first example of a bent uranocene.

Encapsulation of cyclooctatetraenyl dianion in an unusual organic/inorganic lanthanide triple-decker sandwich complex.

Treatment of [(COT)Nd(THF)(2)(mu-Cl)](2) with dilithium tetraphenyldisiloxanediolate, (LiOSiPh(2))(2)O, in a molar ratio of 1 : 4 afforded the novel organic/inorganic triple-decker complex (mu-eta(8):eta(8)-COT)[Nd{(Ph(2)SiO)(2)O}(2){Li(THF)(2)}{Li(THF)}](2) (1) which was structurally characterized by X-ray diffraction.

1,2,3-Triphenyl-1,2-dihydro-quinoxaline.

The title compound, C(26)H(20)N(2), first reported in 1891, was obtained as a by-product in the preparation of benzildianil from benzil and excess aniline. The dihedral angles between the fused benzene ring and the pendant phenyl rings are 17.93 (11), 53.

Unusual inorganic ring systems of scandium and yttrium containing group 13 Metals: coordination of monomeric Me(2)InOMe to yttrium.

Novel transformations of lanthanide(III) disiloxanediolates with group 13 metal trialkyls are reported. Treatment of the scandium metallacrown complex [{(Ph2SiO)2O}2{Li(DME)}2]ScCl.THF (1) with AlMe3 resulted in an Li-Al exchange reaction and the formation of the heterotrimetallic inorganic ring system [{(Ph2SiO)2O}2{Li(THF)2}AlMe2]ScCl.

Structural varieties in heterobimetallic lanthanide disiloxanediolates: "inorganic metallocenes" versus in-plane metallacrowns.

The previously proposed concept of "inorganic metallocenes" of group 3 and rare-earth elements has been tested by preparing a series of novel disiloxanediolates with metals displaying different ionic radii. For the smaller scandium and yttrium, approximately planar arrangements of the disiloxanediolate frameworks with solvent and chloride ligands in trans positions were found. Thus, the compounds [{(Ph2SiO)2O}2{Li(DME)}2]ScCl(THF/DME) (2; DME=1,2-dimethoxyethane and THF=tetrahydrofuran) and [{(Ph2SiO)2O}2{Li(THF)2}2]YCl(THF) (3) can be described as heterobimetallic inorganic ring systems or metallacrown complexes with "in-plane" coordination of the metal.

Unprecedented examples of heterobimetallic cerium(IV) disiloxanediolates.

The first disiloxanediolate complexes of cerium(IV) are reported. Starting from the readily available precursor ((t)BuO)(3)Ce(IV)(NO(3))(THF)(2) (1), we prepared the novel heterobimetallic compounds [{(Ph(2)SiO)(2)O}{K(THF)(2)}](2)Ce(O(t)Bu)(2) (2) and [{(Ph(2)SiO)(2)O}(2){(DME)-KO(t)Bu}{(Ph(2)SiO(2))K}Ce](2) (3) and structurally characterized them by X-ray diffraction.