A. V. Piskunov

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.

Free radical fixation by tin(IV) diphenylcatecholate complexes

The reactions of sodium and thallium catecholates CatM2 (Cat is the 3,6-di-tert-butylpyrocatechol dianion; M = Na, T1) with tin diphenyl dichloride afford new tin catecholate complexes Ph2SnCat · THF (I) and Ph2SnCat (II). The molecular structure of pentacoordinated complex I is determined by X-ray diffraction analysis. The synthesized complexes are capable of fixating both short-lived (PhC(O)O., (CH3)2NC(S)S., and NC(CH3)2C.) and stable free radicals (aroxyl, nitroxyl, triphenylmethyl, and phenoxazinyl) to form stable o-semiquinone tin derivatives.

The new C–C bond formation in the reaction of o-amidophenolate indium(III) complex with alkyl iodides

The reaction of bis(4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-amidophenolato)indium(III) anion with alkyl iodides is reported. This process includes oxidative addition of two RI (R = Me, Et) molecules to the non-transition metal complex and results in an alkyl transfer to ring carbon atoms with the formation of two new C-C bonds. The interaction proceeds at mild conditions and gives new indium(III) derivatives containing iminocyclohexa-1,4-dienolate type ligands.

Zinc and cadmium complexes based on 3,6-di-tert-butyl-o-benzoquinone

Zinc and cadmium bis-o-semuquinolate and catecholate complexes are synthesized by the reduction of 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) with amalgamated metals in a medium of various solvents. The oxidation of the metal catecholate derivatives results in the corresponding mono-o-semiquinone complexes, which undergo symmetrization to form the metal bis-o-semiquinolates. The molecular structures of the complexes (3,6-SQ)2Zn · Py, (3,6-SQ)2Zn · H2O, and (3,6-SQ)2Cd · α,α′-Bipy (3,6-SQ is the radical anion of 3,6-Q) are studied by X-ray diffraction analysis. Magnetochemical studies are carried out for the zinc and cadmium bis-o-semiquinone complexes.

Indium(III) complexes with o-iminobenzoquinone in different redox states

The indium(III) complexes containing 4,6-di-tert-butyl-N-(2,6-di-iso-propyl-phenyl)-o-iminobenzoquinone (imQ) in dianion o-amidophenolate (AP) (1) or radical-anion o-iminobenzosemiquinolate (imSQ) (3) form and iodide ligands (one in the case of 1 or two in the case of 3) have been obtained in the presence of donor agent (tetramethylethylenediamine (TMED)). The 4,6-di-tert-butyl-N-(2,6-di-iso-propyl-phenyl)-o-amidophenolate-ethyl-indium(III) (2) was obtained by the exchange reaction of disodium o-amidophenolate (APNa2) with I2InEt. Structures of complexes 1, 2 and 3 were determined by X-ray diffraction analysis.

Formation of a new carbon-carbon bond in the reaction of allyl halides with tin(iv) bis-o-amidophenolate

A reaction of tin(IV) bis-o-amidophenolate complex based on redox-active 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-aminophenol with various allyl halides was studied. This process includes the addition of 1 equiv. of allyl halide to the starting complex and is accompanied by the change in the redox state of one of the redox-active ligands. The reaction results in the formation of a new carbon—carbon bond between the allylic fragment and the carbon atom at position 5 of the ligand o-iminoquinone ring, as well as a tin—halogen bond. The structure and composition of compounds synthesized were confirmed by ESR, NMR, and IR spectroscopy and elemental analysis.

The reactivity of o-amidophenolate indium(III) complexes towards different oxidants

The reactivity of o-amidophenolate indium(III) complexes towards different oxidants was investigated. The oxidation reactions were found to proceed through the stage of paramagnetic o-iminobenzosemiquinonato indium(III) derivative formation. The monoradical intermediates undergo symmetrization. The final products of the oxidation processes are corresponding biradical o-iminobenzosemiquinonato indium(III) complexes. In order to understand the reasons for the symmetrization processes steric factors (G-parameters) were evaluated for all intermediates and final products by a method based on the ligand solid angle approach.

The interaction of N,N′-bis(2,6-dimethylphenyl)imidazol-2-ylidene with o-benzosemiquinonato zinc(II) and indium(III) complexes

The N-heterocyclic carbene N,N′-bis(2,6-dimethylphenyl)imidazol-2-ylidene (NHC) interacts with non-transition metal complexes bearing redox-active o-benzosemiquinonato ligands in two ways: as a neutral donor or as a reducer. The reaction of NHC with (3,6-SQ)2Zn·Et2O gives the carbene adduct (3,6-SQ)2Zn·{CN(Me2Ph)(CH)2N(Me2Ph)} (1) while reaction with (3,6-SQ)3In forms the ionic complex [(3,6-SQ)2(3,6-Cat)In]− {HCN(Me2Ph)(CH)2N(Me2Ph)}+ (2) as the main product.

Novel germanium(IV) catecholate complexes

The interaction of germanium(II) chloride dioxanate with 3,6-di-tert-butyl-o-benzoquinone or with its mono-and dianion derivatives is attended by the redox transformations. The novel germanium bis-catecholate complexes were synthesized that contained coordinated ether molecules (THF (I), Et2O (II)) irrespective of the initial redox form of o-quinone. The germanium complex was also synthesized by the exchange reaction between GeCl4 and sodium catecholate. Complexes (I), (II) were characterized by NMR and IR spectroscopies, elemental and X-ray diffraction analyses.

New paramagnetic tin(IV) complexes based on o-iminoquinone ligands: Synthesis and thermal transformation

A series of new paramagnetic tin(IV) complexes based on sterically hindered o-iminobenzoquinones (R)ImQ differed in fragments (R) in the N-aryl fragment is synthesized. The thermal transformation of the tin(IV) complex, (iso-Pr)ImSQSn(tert-Bu)2Cl ((iso-Pr)ImSQ is the radical anion of 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinone), is studied. The thermal transformation of the paramagnetic complex in nonane results in the formation of a new tin(II) bis(aminophenolate) derivative. The synthesized complexes and the thermolysis product are characterized by EPR, IR, and 1H, 13C, and 119Sn NMR spectroscopy and elemental analysis. The structures of the (tert-Bu)ImSQSn(tert-Bu)2Cl complex and the thermal decomposition product, {(iso-Pr)AmPh}2Sn ((iso-Pr)AmPh is 2-(2,6-di-iso-propylphenyl)amino-4,6-di-tert-butylphenolate), are determined by X-ray diffraction analysis.