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A representative of the new class of organophosphorus ligands, viz., o,o"-dimethylene(tri-p-cresyl) bicyclophosphite (BCP), was studied as a promoter of Rh(acac)(CO)2 in hydrogenation and hydroformylation. BCP enhances the activity and stability of the catalyst much more strongly than analogous organophosphorus ligands used previously (triphenylphosphine, triphenyl phosphite, and etriolphosphite). A reason for this behavior of BCP was studied using NMR spectroscopy, quantum-chemical calculations, and molecular simulation. The high sensitivity of the 1H NMR signals of the methylene groups of BCP toward complexation appears due to the high density of the highest occupied and lowest unoccupied MO of protons of the CH2 groups, especially those directed toward the P atom. The 1H and 31P NMR spectra indicate the formation of hydrides of two types (HRh(BCP)3 and HRh(BCP)4) directly upon the addition of BCP in amounts exceeding that corresponding to the BCP/Rh = 2 ratio to a solution of Rh((acac)(CO)2. The most probable source of the hydride ion is the BCP molecule itself, namely, the bridging CH2 groups. The molecular mechanics simulation showed that in the [Rh(BCP)3]+ complexes the aromatic rings of BCP formed two molecular cavities. These cavities can alternatively open and close, thus providing flexible screening of the catalytic site. This explains the unusual behavior of the Rh complexes with BCP in hydrogenation and hydroformylation.

The data of temperature-programmed desorption of ammonia from the surface of oxide systems and IR spectroscopy were used to demonstrate that the strength of the surface acid sites in titanium oxides prepared by the alkoxo method and modified by aluminum decreases with respect to that in nonmodified titanium oxide. Modification of titanium oxide with P3+ ions from ethriol phosphite almost completely suppresses the acid properties. Modified oxides are able to chemisorb water. XANES data suggest that modification of titanium oxide with phosphorus ions increases the electron density on the titanium atoms and, correspondingly, the basicity of the materials.

The redox properties of heterogenized RhI, RhII, and RhIII complexes with different, particularly organophosphorus, ligands were studied by cyclic voltammetry (CVA). The support is a carbon-paste electrode based on a fibrous-carbon material and activated carbon. The electrochemical reduction of RhIII produces Rh metal, which further catalyzes hydrogen evolution. After the reduction of water-soluble binuclear RhII complexes, the CVA curves exhibit peaks of electrocatalytic hydrogen evolution and irreversible RhI→RhII oxidation. The RhII complexes with organophosphorus ligands are characterized only by the peak of RhI→RhII oxidation. After reduction, the RhI complexes behave as a pseudo-reverse Rh0/RhI pair. The electron-donating properties of the ligand determine the reversibility of the system. The degree of structurization of the carbon matrix and the presence of phosphorus(v) atoms in it affect the electrochemical activity of the RhII and RhI complexes.

The reactivities of cyclophosphite precursors in alkoxo syntheses involving titanium(iv) tetra(n-butoxide) were studied by 31P NMR and IR spectroscopy. 2-Diethylamido-4-methyl-1,3,2-dioxaphosphinane and 4-ethyl-2,6,7-trioxaphosphabicyclo[2.2.2]octane in benzene are inert toward Ti(OBu)4. Gelation is accompanied by hydrolysis 2-diethylamido-4-methyl-1,3,2-dioxaphosphinane to give the corresponding hydrophosphoryl compound, while 4-ethyl-2,6,7-trioxaphosphabicyclo[2.2.2]octane remains intact during gelation.

The influence of the nature of the organophosphorus ligand and the P/Rh molar ratio on the catalytic properties of rhodium carbonyl complexes in hydroformylation of 2-butenes was studied. The difference between phosphine and phosphite ligands during the formation of highly selective catalytic complexes was found. It was supposed that a decrease in the selectivity with respect to 2-methylbutanal is due to the isomerization of olefins under conditions of a decrease in the competitive capability of CO for coordination sites (the high P/Rh ratio, a decrease in the total pressure of the synthesis-gas).

Complete transligation of (AcO)4Rh2 with 4-ethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane was conducted in the solid phase on λ-Al2O3. The reduction of Rh11 to RhI on λ-Al2O3 at 130°C under the actionof the above-mentioned bicyclic phosphite is accompanied by the oxidation of the acetate anion to the acetoxyl radical. The oxidation products were detected by IR and ESR spectroscopy. 2,6-Di-tert-butyl-4-methylphenol was used as a “spin trap” to identify stable secondary radical cations.

It was demonstrated that the catalyst system based on acacRh(CO)2 and polyorgano-siloxanes exhibits high activity and stability in hydroformylation of 1-hexene. The effects of the nature of the oligomer, the ratio of oligomers, and the oligomer: rhodium ratio in the polymer on the synthesis and catalytic properties of the system were studied.