D. P. Krut'ko

Tetramethyl(2-methylthioethyl)cyclopentadienyl complexes of zirconium(iv): synthesis, crystal structure, and dynamic behavior in solutions

Chelating sulfur-containing cyclopentadienyl ligand tetramethyl(2-methylthioethyl)cyclopentadiene (1), was synthesized for the first time. Its sodium (2a) and lithium (2b) derivatives were isolated in the crystalline state. Starting from compound1 some novel ZrIV complexes were prepared: [tetramethyl(2-methylthioethyl)cyclopentadienylltriclllorozirconium (3), bis[tetramethyl(2-methylthioethyl)cyclopentadienylldichlorozirconium (4), and [pentamethylcyclopentadienyll [tetramethyl(2-methylthioethyl)cyclopentadienylldichlorozirconium (5). The crystal structures of3 and5 were determined by X-ray diffraction analysis. The dynamic behavior of complex3 in various solvents was investigated by1H and13C N MR spectroscopy. The S→Zr coordination bond was shown to exist in complex3 both in the crystalline state and in solution. No coordination of this type was found in compounds4 and5.

On the reduction behaviour of 2-methoxyethyl and 2-methylthioethyl substituted zirconocene dichlorides: crystal structure of (η5,σ-C5Me4CH2CH2S)2Zr

Abstract A reduction of previously reported 2-methoxyethyl and 2-methylthioethyl functionalized zirconocenedichlorides (η5-C5Me4CH2CH2EMe)(η5-C5Me5)(ZrCl2 (E = O, S) and (η5-C5Me4CH2CH2EMe)(η5-C5Me4CH2CH2E′Me)ZrCl2 (E = O, S; E′ = O, S) with Mg/Hg in THF leads unexpectedly to the products of OMe and SMe bond cleavage (η5,σ-C5Me4CH2CH2E)(η5-C5Me5)ZrMe (E = O, S), (η5,σ-C5Me4CH2CH2E)(η5-C5Me4CH2CH2E′Me)ZrMe (E = O, S; E′ = O), and (η5,σ-C5Me4CH2CH2S)2Zr respectively. The crystal structure of (η5,σ-C5Me4CH2CH2S)2Zr was established by X-ray analysis. At that same time the reduction of (ηsu5-C5Me4CH2CH2EMe)(η5-C5Me5)ZrCl2 (E> = O, S) under 1 atm of CO gives either only the dicarbonyl derivative (η5-C5Me4CH2CH2EMe) (η5-C6Me5)Zr(CO)2 (E = O) or a complex mixture of products (E = S).

Structures of lithium salts of substituted 1-phenylpropynes: 13C NMR and MNDO study

Abstract 13C NMR spectroscopy has been used to study the structure of ambident carbanions in contact (CIP) and solvent-separated (SSIP) ion pairs of lithium salts of substituted 1-phenylpropynes. It was shown that the structures of carbanions in SSIP are close to the propargylic type, whereas, with the decrease in delocalizing ability of substituents at the propargylic centre, their structure shifts to the allenylic type, in fair agreement with theoretical predictions by the MNDO semi-empirical method. In CIP, the structures of carbanions are progressively changed from near-to-propargylic to allenylic with decrease of delocalizing ability of the substituents.

Tetramethyl(2-methoxyethyl)cyclopentadienyl complexes of zirconium(iv). Crystal structure of [η5:η1−C5(CH3)4(CH2CH2OCH3)]ZrCl3

Several novel zirconium(iv) complexes with the chelating oxygen-containing cyclopentadienyl ligand, tetramethyl(2-methoxyethyl)cyclopentadiene, have been synthesized. [η5:η1-Tetra-methyl(2-methyl)cyclopentadienyl]trichlorozirconium (2), bis[η5-tetramethyl(2-methoxyethyl)cyclopentadienyl]dichlorozirconium (3), [η5-pentamethylcyclopentadienyl][η5-tetra-methyl(2-methoxyethyl)cyclopentadienyl]dichlorozirconium (4), and [η5-tetra-methyl(2-methylthioethyl)cyclopentadienyl][η5-tetramethyl(2-methoxyethyl)-cyclopentadienyl]dichlorozirconium (5) have been prepared from the corresponding lithium cyclopentadienide (l). The crystal structure of cyclopentadienyl complex2 has been established by X-ray analysis. The coordination O→Zr bond in compound2 exists both in the crystalline state and in solutions. No coordination of this type was observed in complexes3–5. Synthesized complexes2–5 are discussed in comparison with their sulfur-containing analogs.

Ferrocenylsubstituted α,β-unsaturated ketones in the synthesis of dihydropyrimidinethiones

Abstract The reaction has been studied of ferrocenylsubstituted α,β-unsaturated ketones with thiourea in alkaline ethanol leading to the corresponding dihydropyrimidinethiones. Products were isolated as yellow or orange crystals with yields of 65–95%. Structures were proved by high resolution 1 H NMR spectra. Ferrocenylsubstituted dihydropyrimidinethiones have been shown to convert quantitatively into the initial α,β-unsaturated ketones under heating with alkaline ethanol in the presence of water.

Alkyl derivatives of platinum and rhodium as intermediates in homogeneous reactions of olefin hydrogenation and isomerisation

Abstract Literature data and results obtained on the mechanisms of olefin hydrogenation and isomerisation using platinum and rhodium complexes, in particular, with PtSn and RhSn bonds were analysed. The role of alkyl derivatives of platinum and rhodium in these reactions is discussed.

LITHIUM 5-(2-DIPHENYLPHOSPHINOETHYL)-1,2,3,4-TETRAMETHYLCYCLOPENTADIENIDE : REGIOSELECTIVITY OF ALKYLATION OF THE TETRAMETHYLCYCLOPENTADIENIDE ANION

Treatment of a mixture of isomeric (2-chloroethyl)-1,2,3,4-tetramethylcyclopentadienes with lithium diphenylphosphide leads to novel 4,5,6,7-tetramethylspiro[2,4]hepta-4,6-diene among the reaction products. The reaction of spiroheptadiene obtained with excess LiPPh2 at elevated temperature affords lithium 5-(2-diphenylphosphinoethyl)-1,2,3,4-tetramethylcyclopentadienide in almost quantitative yield. the regioselectivity of alkylation of the tetramethylcyclopentadienide anion is estimated from quantum-chemical calculations performedab initio for C5Mc4H−. The full charges on the ring carbon atoms are determined within the framework of Baders theory of atomic fragments in molecules.

SYNTHESIS OF NEW ELEMENTSUBSTITUTED DERIVATIVES OF 3H-PYRROLIZINES

Abstract The anion of 3H-pyrrolizine was isolated as its lithium 2a and thallium salts 3 and the anion of 1-methyl-3H-pyrrolizine as its lithium salt 2b . Reaction of the lithium anions with Group 14 electrophiles led to a number of substituted derivatives of the 3H-pyrrolizine ring system. In the case of 2b it was shown that the number of isomers obtained was strongly dependent on the reaction solvent.

Reaction of Some Dibromomethyl-Substituted Cyclohexadienones with Molecular Bromine

Abstract4-Dibromomethyl-4-methyl-2,5-cyclohexadienone and its 2- and 3-methyl-substituted derivatives react with an equimolar amount of molecular bromine in carbon tetrachloride, yielding vinyl bromination products at the α-position with respect to the carbonyl group. The reaction of 4-dibromomethyl-3,4-dimethyl-2,5-cyclohexadienone with a large excess of bromine, apart from the vinyl bromination product, gives the corresponding 3-bromomethyl and 3-dibromomethyl derivatives. 4-Dibromomethyl-2,4-dimethyl-2,5-cyclohexadienone takes up bromine molecule at the C2ÍC3 double bond.

Bis-(2-diphenylphosphinoethyl)cyclopentadienylchlorolutetium: synthesis and dynamic behavior in solution

The new biscyclopentadienyl lutetium complex (η5:η1-C5H4CH2CH2PPh2)2LuCl was synthesized by the reaction of LuCl3(THF)3 with lithium (2-diphenylphosphinoethyl)cyclopentadienide. Its behavior in solution was investigated by dynamic NMR spectroscopy. It was shown that the coordination of both phosphino groups to the lutetium center is retained over the whole temperature range studied. The barrier to pseudo-rotation for the trigonal bipyramid, which governs the intramolecular dynamics of this complex, was determined.