Alessandro Mazzei

The chemistry and the stereochemistry of poly(N-alkyl-iminoalanes) : I. Synthesis and physicochemical characterization of poly(N-alkyliminoalanes)☆

Abstract The structural features of poly( N -alkyliminoalanes) (PIA) and their dependence on the method of preparation as well as on the amine have been investigated. Different PIA have been synthesized from ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl and cyclohexylamine, and have been characterized by X-ray diffraction, mass spectrometry, 1 H and 13 C NMR. In general all the results agree with the formation of oligomers of-HAlNR-units, with three dimensional structures made up by four and six membered rings. In particular a cage structure has been found for (HAlN- iso -C 3 H 7 ) 6 by X-ray diffraction on a single crystal.

A contribution to the organometallic chemistry of uranium: tetra(allyl)uranium

Abstract The synthesis of tetra-allyl Uranium obtained from UCl4 and C3H5 Mg Br, is reported. The isolated crystalline dark-red complex is not thermally stable above −20°C and burns spontaneously in the air. Its infrared spectra could be reasonably in agreement with π-bonded allylic groups. Thermal decomposition and cleavage with H2O gave the expected hydrocarbon products.

Hydrogenation catalysts from aluminium hydride derivatives and transition metal compounds

Abstract New homogeneous catalysts based on aluminum hydride derivatives and transition metal compounds for the hydrogenation of unsaturated hydrocarbon substrates are described. A feature of these catalysts is their high activity under very mild experimental conditions. Some aspects of the activity of aluminum hydrides cocatalysts are discussed, with particular reference to their molecular structure and to the hydridic hydrogen/transition metal atomic ratio.

The chemistry and the stereochemistry of poly(N-alkyliminoalanes) : VI. A novel synthesis of poly(N-alkyliminoalanes) by reaction of alkali metal alanates with primary amines

Abstract A novel synthesis of poly(N-alkyliminoalanes) (PIA) is reported. This involves the reaction in hydrocarbon solvents of LiAlH4 or NaAlH4 with primary amines having a nitrogen with α- or β- secondary carbon atoms or with tertbutylamine. Complexes of iminoalanes with alkali metal hydrides are obtained from linear amines. The same reaction carried out in polar solvents always gives complexes of PIA with LiH or NaH and the solvent. This new synthesis is simpler and convenient for producing soluble and well characterized PIA, some of which are not obtainable by other methods.

The chemistry and the stereochemistry of poly(N-alkyliminoalanes) : XIV. Some advances in the synthesis of mixed poly(N-alkylimino) derivatives of aluminum and alkaline-earth metals☆

Abstract Crystalline mixed imino derivatives of aluminum and calcium, [(t-C 4 H 9 NAlH) 3 (t-C 4 H 9 NCa · 3THF)] or magnesium [(t-C 4 H 9 AlH) 3 (t-C 4 H 9 NMg · THF)] were obtained by the reaction of a mixture of Ca(AlH 4 ) 2 — or Mg(AlH 4 ) 2 —tetrahydrofuranate and AlH 3 · N(CH 3 ) 3 with t-C 4 H 9 NH 2 . The molecular structures of these compounds have been fully characterized by X-ray analysis of single crystals. A mixed imino derivative of composition [(t-C 4 H 9 NAlH) 3 (t-C 4 H 9 NMg · 3THF)] was also obtained by direct synthesis from aluminum, magnesium and t-C 4 H 9 NH 2 in tetrahydrofuran under hydrogen pressure.

The chemistry and the stereochemistry of poly(N-alkyliminoalanes) : VII. The chlorination of poly(N-alkyliminoalanes)☆

Abstract Reactions of poly( N -alkyliminoalanes) (PIA) such as (HAlN-t-Bu) 4 , (HAlN-i-Pr) 4 , (HAlN-i-Pr) 6 and (HAlN-n-Pr) 8 with HCl, HgCl 2 and TiCl 4 have been investigated. Two reaction paths are observed which involve either the simple substitution of hydridic hydrogens with chlorine or the same reaction accompanied by the cleavage of AlN bonds with subsequent rearrangement of the molecular structure of the PIA. In both cases the reaction depends on the chlorination agent and the molecular features of the poly( N -alkyliminoalanes). Poly( N -alkyliminoalanes) have been obtained with partial and complete chlorination that include (ClAlN-t-Bu) 4 , (ClAlN-iPr) 4 , (ClAlN-i-Pr) 6 , which were separated as crystalline products and fully characterized.

The chemistry and stereochemistry of poly(N-alkyliminoalanes) : VIII. The direct synthesis of poly(N-alkyliminoalanes)

Abstract Poly( N -alkyliminoalanes) have been synthesized directly from aluminum and primary amines under hydrogen pressure. In particular, hexamers (HAINR) 6 were obtained from iso-C 3 H 7 NH 2 , sec-C 4 H 9 NH 2 and cyclohexylamine, octamers (HA1NR) 8 from n-C 3 H 7 NH 2 , and a mixture of oligomers from C 2 H 5 NH 2 and n-C 4 H 9 NH 2 . Tetramer (HA1NR) 4 has been isolated from a mixture of various imino derivatives, starting from tert-C 4 H 9 NH 2 . The reaction was induced by an activator. A number of activators have been screened for the synthesis of (HAIN-iso-C 3 H 7 ) 6 , with the result that Na and NaAlH 4 have been formed to be the most active. The mechanism of the reaction is discussed; aluminum amides [Al(NH-isoC 3 H 7 ) 3 ] 2 and (iso-C 3 H 7 NH-AlN-iso-C 3 H 7 ) 4 are intermediates in the synthesis of (HAIN-iso-C 3 H 7 ) 6 .

Mixed imino derivatives of aluminum and alkaline earth metals

Summary The reactions of Ca(AlH 4 ) 2 and Mg(AlH 4 ) 2 with primary amines or organic nitriles have been investigated. For amine (or nitrile)/alanate ratios of 3/1, mixed polyimino compounds containing AlH-NR- and -Ca-NR- (or -Mg-NR-) units are formed, whereas for lower molar ratios definite compounds cannot be isolated, except in the reaction of Ca(AlH 4 ) 2 with aniline, from which crystals of calcium N -phenyliminodialane have been obtained.

Metalation of alkyl aryl sulfones: qualitative and quantitative product determination

Abstract The metalation of methyl phenyl sulfone (I) and methyl naphthyl sulfone (II) was investigated under a variety of conditions. The product species were determined qualitatively and quantitatively after characterization with some electrophilic agents. After the primary metalation at the methyl position, species of various metalation degrees were prsent simultaneously, including the 1,1,1-trimetalated derivatives. With high LiR/sulfone ratios, in addition to the products of the primary metalation, compounds arising from metalation of the aromatic ring were formed as well as those from reduction, cleavage, etc.

Reactions Between AIRCl2 and Ti (OR)4 and Activity in Diolefin Polymerization

Abstract Through the use of a Ti(OR′)4-AlRCl2 catalyst system, high 1,4-cis isoprene polymers and crystalline 1,4-trans polybutadiene are obtained. Neither monomer is polymerized at a Al/Ti mole ratio of less than 4. The maximum activity and stereospecificity for isoprene is observed at Al/Ti = 4. For 1,4-trans butadiene polymers the activity increases progressively with increasing Al/Ti ratio. The investigations carried out on this catalyst system show that at a AI/Ti mole ratio of 4 the formation of crystalline β-TiCl3 takes place, while at lower ratios insoluble chloro-alkoxide derivatives of TiIII with different compositions separate. Soluble complexes containing aluminium and titanium are initially formed before precipitation occurs. Chemical data and investigations by IR and NMR spectroscopy indicate exchange reactions between Al-Cl, Al-R, and Ti-OR groups, together with reduction of the transition metal. A reaction mechanism and a hypothesis on the nature of the active catalyst are given.