Search

Molybdenum dioxide (Mo2) synthesized through thermal decomposition of the [MoO2(i-C3H7NHO)2] complex and containing a nanosized fraction has been studied by MALDI-TOF. The composition of clusters of lower nonstoichiometric molybdenum oxide cations in the gas phase has been determined, and theoretical calculations of the thermodynamic stability and structure of the isomers of the most symmetric structures have been performed. Molecular orbitals of the cationic and neutral clusters Mo5O8 and Mo5O9 have been examined, and the aromaticity of the Mo-Mo bonds in metallacycles has been demonstrated.

The products resulting from the reaction of TiF4 with Ph2P(O)(CH2)2C(O)Me (L') in CH2Cl2 have been studied by 19F{1H} and 31P{1H} NMR spectroscopy. At a twofold excess of L', solution contains cis-TiF4(L')2 (>90%), trans-TiF4(L')2, and fac-[TiF3L3']+, where L' is coordinated via the P=O group, as well as the dimer [(Ti2F7L'2)2]+, where L' is coordinated through the P=O and C=O groups. An equimolar solution contains dimeric and polynuclear complexes containing moieties with three terminal cis fluorine ions, while the other coordination sites are occupied by the P=O groups and F– bridges. At a twofold excess of TiF4, ligand L' coordinates via the P=O and C=O groups and behaves as a bridge along with F– ions. Thermodynamic stability of the structures of the TiF4L'2 isomers and the structure of [(µ-F)(µ-L')2(TiF3)2]+ has been calculated.

The crystal structure of TiF4[(Ph2P(O)CH2CH2C(O)NMe2)] chelate (I) was studied by X-ray crystallography, which revealed four crystallographically independent complex molecules of similar structure (1–4). It was found that the molecules are only slightly different in the bond lengths between the coordinated atoms and the central titanium ion and considerably different in the geometry of the seven-membered TiOPCCCO chelate ring. The geometry of the chelate rings was found to be almost identical in each pair of complexes 1, 2 (A) and 3, 4 (B), and a conclusion was drawn on the presence of two conformational isomers (A and B) of the chelate complex. Quantum chemical calculations of the relative thermodynamic stability of molecules 1–4 were performed, and their geometry optimization led to one theoretical structure. The comparison of the chelate ring geometry in the theoretical structure and in conformers A and B revealed that the conformation of the theoretical chelate ring coincides with that of conformer A.

The composition and structure of the products of the reaction of titanium tetrafluoride with Ph2P(O)(CH2)2C(O)NМе2 (L), the simplest representative of diphenyl[2-(N,N-dialkylcarbamoyl)ethyl]phosphine oxides, in a СН2Сl2 have been studied by 19F and 31P NMR. It has been shown for the first time that functionalized phosphine oxides form stable seven-membered chelate heterocycles on complexes of d° transition metals. On the basis of NMR data, previously unknown conformational isomerism of the seven-membered TiOPCCCO heterocycle in solution has been proposed. A simple and rather efficient method of synthesis of the ligand (L) from commercially available reagents has been developed.

The reaction of TiF4 with a twofold excess of Ph2P(O)CH2C(O)Me (L) (one of the simplest and, very likely, most practically interesting representatives of a new class of organophosphorus ligands—diorganylphosphorylalkanones) in CH2Cl2 has been studied.