B. A. Dolgoplosk

Study of the reactions of bis-cyclopentadienyl-nickel with titanium and aluminum halides and their use for the polymerization of butadiene

1. In the interaction of CPN with AlBr3 and TiCl4, donor-acceptor type complexes are formed, in which both cyclopentadienyl groups are bonded to a nickel atom. These complexes induce stereospecific polymerization of butadiene and its copolymerization with styrene. 2. The reaction of C5H5NiCl · PPh3 with AlBr3 leads to the formation of the complex C5H5NiCl · AlBr3, which catalyzes the polymerization of butadiene. 3. The mechanism of the formation of π-allyl-type active centers, which catalyze stereospecific polymerization, was discussed on the basis of the experimental data.

CONVERSIONS OF HYDROCARBONS TREATED WITH NEODYMIUM METAL UNDER THE CONDITIONS OF MECHANOCHEMICAL ACTIVATION AT ROOM TEMPERATURE

The conversions of cyclohexene and 1,3- and 1,4-cyclohexadiencs treated with neodymium metal under the conditions of mechanochemical activation at 20 °C have been studied. A complicated cycle of conversions, including isomerization, disproportionation, and polymerization, occurs under the reaction conditions. A mechanism for the conversion of the hydrocarbons involving organornetallic intermediates is proposed.

Oligodienyl compounds of d- and f-transition metals: synthesis and stability

The results of investigations performed in the Laboratory of Organometallic Catalysis of the A. V. Topchiev Institute of Petrochemical Synthesis of the RAS are reviewed. The oligodienyl compounds of a series of transition metals, RnolM and RnolMXm (Rol= R′(diene)3–10, where R′ is an alkyl, allyl, alkenyl, or H; (diene)3–10 is an oligodienyl group with 3–10 monomeric diene units; M = Ti3+, Cr2+, Mn2+, Co2+, Ni2+, Nd3+, Pr3+, Sm3+, and Gd3+; X is a halogen or an electronegative group), have been synthesized for the first time and some of their properties have been studied. The stability of oligodienyl compounds is much higher than that of the corresponding π-alkenyl derivatives. The IR spectra of the compounds synthesized allowed us to conclude that their stability and some peculiarities of the reactions of these compounds can be explained by π-coordination of the isolated double bond of the oligodienyl chain to the transition metal.

Formation of carbene species in the reaction of lithium alkyls with molybdenum, tungsten, and cobalt chlorides

Ethyl derivatives of Mo and W and amyl derivatives of Mo undergo not only β-cleavage with the formation of equimolar amounts of the corresponding alkane and alkene but also α-cleavage accompanied by the generation of carbene species (methyl- and butylcarbenes) in these systems. The latter decomposition pathway is also proposed for ethyl and amyl cobalt derivatives.

Mechanism of decomposition of transition-metal organometallic compounds and the role of the intermediate products in catalysis

Conclusions1.The composition of the products of decomposition of organic compounds of a number of transition metals at the time of their formation was investigated, and it was found that: a) decomposition of methyl derivatives of Mo and W primarily takes place based on the mechanism of α-disproportionation with formation of carbene and carbyne fragments; b) decomposition of benzyl and neophyl derivatives of neodymium and yttrium in THF quantitatively takes place with formation of stable carbene (carbyne) complexes; c) decomposition of trimethylsilyl(germyl)methyl derivatives of W, Mo, Ta, Re, Nb, Rh, Pd, and Pt is accompanied by formation of complexes containing carbene fragments of two types: (CH3)3SiCH: and CH2: (in the case of W, Mo, Ta, Nb, and Rh compounds, this pathway of decomposition is determining); d) in the reaction of benzylmagnesium chloride with Mo, W, Re, Rh, Pt, and Pd chlorides, significant quantities of toluene, the product of α-disproportionation of benzyl groups, and some quantities of stilbene and tolan, the products of recombination of carbene and carbyne fragments, are formed.2.Based on the data in the literature and the data obtained in the present study concerning the mechanism of decomposition of organic compounds of transition metals, hypotheses were advanced concerning the chemistry of the elemental events in catalytic reactions taking place through organometallic compounds (hydrogenation, dehydrogenation, skeletal isomerization, and deuterium exchange).

Polymerization of cycloolefins in the presence of catalysts containing tungsten halides and allylsilanes

1. Allyl compounds of silicon in combination with tungsten halides effectively catalyze the ring-opening polymerization of cycloolefins. 2. Polymerization of cyclopentene by the catalyst system WCl6-tetraallylsilane between -20 and -78°C forms a polypentenamer with 94–99% cis-units. 3. We have studied the polymer-monomer equilibrium in the cis-polymerization of cyclopentene by the WC16- tetraallylsilane system and have determined some thermodynamic parameters for the process.

Role of carbene complexes in chain initiation and propagation of double-boot redistribution reactions

1. Catalytic decomposition of aliphatic diazo compound under the effect of tungsten chlorides leads to initiation of the chain process of opening of cycloolefins. 2. The possibility was shown on the example of the organotungsten compound (CH3)3SiCH2-WCl5 of using oxidation-reduction systems to generate carbene active centers at low temperatures. 3. Certain aspects of the chain stage of the double-bond redistribution process were examined in connection with the relative reactivity of carbene active centers.