Evgenii V. Baranov

Dialane with a Redox-Active Bis-amido Ligand: Unique Reactivity towards Alkynes

The treatment of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with one equivalent of AlCl(3) and three equivalents of sodium in toluene at 110 °C produced a stable dialane, (dpp-bian)Al-Al(dpp-bian) (1). The reaction of compound 1 with pyridine gave Lewis-acid-base adduct (dpp-bian)(Py)Al-Al(Py)(dpp-bian) (2). Acetylene and phenylacetylene reacted with compound 1 to give cycloaddition products [dpp-bian(R(1)R(2))]Al-Al[(R(2)R(1))dpp-bian] (3: R(1)=R(2)=CH; 4: R(1)=CH, R(2)=CPh). These addition reactions occur across Al-N-C moieties and result in the formation of new C-C and C-Al bonds. At elevated temperatures, compound 4 rearranges into complex 5, which consists of a radical-anionic dpp-bian ligand and two bridging alken-1,2-diyl moieties, (dpp-bian)Al(HCCPh)(2)Al(dpp-bian). This transformation is accompanied by cleavage of the dpp-bian-ligand-alkyne C-C bond, as well as of the Al-Al bond. In contrast to its analogous gallium complex, compound 1 is reactive towards internal alkynes. In the reaction of compound 1 with PhC≡CMe, besides symmetrical addition product [dpp-bian(R(1)R(2))]Al-Al[(R(2)R(1))dpp-bian] (R(1)=CMe, R(2)=CPh; 6), monoadduct [dpp-bian(R(1)R(2))]Al-Al(dpp-bian) (R(1)=CMe, R(2)=CPh; 7) was also isolated. Complexes 1-7 were characterized by IR, (1)H NMR (1-4), and electronic absorption spectroscopy (3-5); the molecular structures of compounds 1-7 were determined by single-crystal X-ray diffraction.

Oxidation by oxygen and sulfur of Tin(IV) derivatives containing a redox-active o-amidophenolate ligand.

Oxidation of tin(IV) o-amidophenolate complexes [Sn(ap)Ph(2)] (1) and [Sn(ap)Et(2)(thf)] (2) (ap=dianion of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (ImQ)) with molecular oxygen and sulfur in toluene solutions was investigated. The reaction of oxygen with 1 at room temperature forms a paramagnetic derivative [Sn(isq)(2)Ph(2)] (3) (isq=radical anion of ImQ) and diphenyltin(IV) oxide [{Ph(2)SnO}(n)]. Interaction of 1 with sulfur gives another monophenyl-substituted paramagnetic tin(IV) complex, [Sn(ap)(isq)Ph] (4), and the sulfide, [Ph(3)Sn](2)S. The oxidation of 2 with oxygen and with sulfur proceeds through the derivative [Sn(isq)(2)Et(2)] (7), which undergoes alkyl elimination to give two new tin(IV) compounds, [Sn(ap)(isq)Et] (5) and [Sn(ap)(EtImQ)Et] (6) (EtImQ=2,4-di-tert-butyl-6-(2,6-diisopropylphenylimino)-3-ethylcyclohexa-1,4-dienolate ligand), respectively, along with the corresponding alkyltin(IV) oxide and sulfide. Complexes 3-5 and 7 were studied by EPR spectroscopy. The structures of 3, 4 and 6 were investigated by X-ray analysis.

Reversible Binding of Molecular Oxygen to Catecholate and Amidophenolate Complexes of SbV: Electronic and Steric Factors

Edge of reactivity: The reactions of reversible binding of molecular oxygen to catecholate and amidophenolate complexes of Sb(V) are investigated by analyzing the position of electronic (E(HOMO)) and steric (G-parameter) factors. The optimal electronic and steric parameters for such type reactions are found.

Dependence of the mutual ligand arrangement in guanidinate complexes of lanthanoids on the ligand solid angles

Mutual ligand arrangement in binuclear lanthanoid complexes of the type [Gu2Ln(μ-H)]2, [Gu2Ln(μ-Cl)]2, and Gu2Ln(μ-Cl)2Li(THF)2, where Gu is a substituted guanidinato ligand, is quantitatively analyzed based on the ligand solid angle approach. In complexes of Nd, Sm, and Gd the Gu ligands shield up to 87% of the metal and the bidentate ligands on opposite metal centers are in the eclipsed arrangement; in complexes of lanthanoids with smaller ionic radii Y, Yb, and Lu the Gu ligands shield over 88.3% of the metal surface and their staggered conformation is observed. The ligand solid angle approach is illustrated and its application to describing multidentate ligands is demonstrated. §Dedicated to Professor Georgy A. Domrachev on the occasion of his 70th birthday

Non-valent interactions and structural features of monomeric guanidinate complexes of rare earth metals: analyses and predictions based on the ligand solid angle

Analysis of steric saturation of rare earth metal centers in monomeric guanidinate coordination complexes with the use of ligand solid angles indicates that the observed optimal metal shielding is 85(3)%. Non-valent ligand–ligand interactions in the metal coordination sphere affect the shielding of the metal and can facilitate or preclude formation of agostic interactions. Analysis of all structurally characterized to date guanidinate complexes of Ln is presented and general and unique features of such complexes are identified.

Synthesis, thermal analysis, and crystal structure of potassium triiodomercurate monohydrate

Single crystals of potassium triiodomercurate monohydrate KHgI3 · H2O are synthesized and studied by X-ray diffraction: space group Pna21; a = 8.57961(11), b = 9.23621(13), and c = 11.38977(16) Å, Z = 4; R= 0.0574. Thermal conditions of decomposition of the compound are studied by differential scanning calorimetry.

Interaction of Azobenzene and Benzalaniline with Strong Amido Bases

The interaction of azobenzene with lithium dicyclohexylamide (Cy2NLi) in THF or Et2O afforded the ion-radical salt of azobenzene (1) structurally characterized for the first time and dicyclohexylaminyl radical, which begins a novel chain of transformations leading eventually to the imino-enamido lithium complex (3). Benzalaniline, being a relative of azobenzene, reacted with Cy2NLi without electron transfer by a proton-abstraction mechanism to form the dilithium salt of N(1),N(2),1,2-tetraphenylethene-1,2-diamine quantitatively.

Crystal structure of the UO2SO4 · 2SO(CH3)2 compound: A new type of uranyl sulfate ribbons and the UO2SO4 · 2SO (CH3)2-UO2SO4 · 2CO(NH2)2 morphotropic transition

Single crystals of bis(dimethyl sulfoxide) uranyl sulfate are prepared, and their crystal structure is determined using X-ray diffraction analysis. The crystals are monoclinic, space group P21/c, a = 12.9189(8) Å, b = 7.9008(5) Å, c = 12.1405(7) Å, β = 95.677(1)°, R1 = 0.0216, wR2 = 0.0468 for 2761 unique reflections with F > 2σ(F). The crystal structure of the UO2SO4 · 2Dmso compound (where Dmso is dimethyl sulfoxide) is built up of infinite uncharged ribbons of the composition [UO2SO4 · 2Dmso]∞, in which the SO4 tetrahedron is tridentately coordinated to two uranyl groups. The differences between the structures of the uranyl sulfate compounds formed upon replacement of dimethyl sulfoxide by other molecules are considered.