Giovanni Dozzi

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 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.

Synthesis and properties of poly(N-alkyliminoalanes) in tetrahydrofuran

Abstract A correspondence has been found between the conductimetric trends observed during the reaction of AlH3 with different primary amines and the structure of the resulting poly(N-aikyliminoalanes) (PIA). The conductivity measurements proved also to be effective in showing the formation of PIA having the same structural features from different synthetic methods as well as the interaction of PIA with AlH3.

SYNTHESIS OF N-ALKYLIMINOALANES IN TETRAHYDROFURAN

Abstract The synthesis of N-alkyliminoalanes in tetrahydrofuran (THF) has been performed in order to identify the nature of the possible intermediates of the final product poly(N-alkyliminoalanes) (PIA), starting from aluminium hydride and primary amines. The use of THF gives sufficient stability to intermediates, such as HAl(N-isoC 3 H 7 -AlH 2 ) 2 ·2THF, H 2 Al(N-isoC 3 H 7 )AlH 2 ·2THF, H 2 Al(N-isoC 3 H 7 )AlH 2 ·LiH·THF, Al(N-n-C 4 H 9 -AlH 2 ) 3 ·LiH·THF, which have been isolated and identified. The reactions between AlH 3 and primary amines have also been followed conductimetrically and a relationship between the conductimetric curves and composition of intermediates has been found.

Calcium alkoxyalanates : III. Reduction of organic functional groups by calcium tetrakis(alkoxy)alanates

Abstract Calcium tetrakis(alkoxy)alanates obtained from different alcohols reduce aldehydes, ketones, acids, esters, acid chlorides and anhydrides to alcohols in high yields. Good results are achieved in the reduction of amides to amines. The reductions of nitrile and oxime groups and dehalogenation reactions are more difficult. Selectivity is possible in the reduction of organic epoxides.

Calcium alkoxyalanates : II. Advances in the synthesis☆

Abstract Simple syntheses of calcium alkoxyalanates starting from NaAlH 4 , CaCl 2 and alcohols involving evolution of hydrogen and separation of sodium chloride are reported. More complex methods, which allow the preparation of calcium alkoxyllalanates without loss of hydride hydrogen from NaAlH 4 , CaCl 2 , NaOR and AlX 3 (X = OR, Cl) have also been developed.

The chemistry and stereochemistry of poly(N-alkyliminoalanes). XVII. The syntheses of poly(N-alkyliminoalanes) from dimethylamino- or methoxy-propylamines

Abstract 3-Dimethylamino-n-propylamine, 2-dimethylamino-isopropylamine and 3-methoxy-n-propylamine have been used to synthesize poly(N-alkyliminoalanes) (PIA) by different routes. These amines yielded PIA with open cage structures, in some cases even under the rather drastic conditions of direct synthesis from aluminum, amine and hydrogen. Reaction between LiAIH4 and mines gave open cage complexes with LiH.