Dimethylamino -diborane

The volatile compound /i-[(CH3)2N]B2H5 has been prepared by the gas-phase reaction of [(CH3)2NBH2]2 with diborane(6) at 80°,1 and by the reaction of Na[(CH3)2NBH3]2 or Li[N(CH3)2]3 with excess diborane(6) in diethyl ether solution. The method described here4 offers the advantages that diborane(6) is not used and that reactions are carried out with bench apparatus with a vacuum line employed only for final separation and purification. Basic vacuum-line techniques are outlined in reference 9. 

The apparatus shown in Fig. 6 is purged with nitrogen, and 1.18 g (20 mmol) of (CH3)2NH-BH3J is added to the flask this is followed by 

The vapor pressure of /i-[(CH3)2N]B2H5 obeys the relationship log P = 2158.56/T + 1.75 log T - 0.008061T + 7.518831 (101 torr at 0°). The gas-phase infrared spectrum has been reported in detail.5 The compound is a useful intermediate in the synthesis of other boron nitrogen compounds, including those containing NBNB6 and PBNB7 chains, and Na[(CH3)2-N(BH3)2].8 The compound can be stored at 25° for months in sealed, evacuated Pyrex tubes. It is soluble in ethers and aromatic hydrocarbons, but is attacked by protic solvents. 

Shriver, The Manipulation of Air-Sensitive Compounds, McGraw-Hill Book Company, New York, 1969. 

TRIHYDRIDO(TRIMETHYLAMINE)ALUMINUM AND (DIETHYLAMINO)HYDRIDOALUMINUM COMPLEXES 

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Reaction of l,2-dichloro-l,2-bis(dimethylamino)diborane(4) with N-dilithio bis- or tris(amino)borane derivatives resulted in several derivatives of the system named in the heading, according to the following equation ... 

Tetra(dimethylamino)diborane(4) was treated with o-phenylene isothio-cyanato-boronate, to give an interesting reaction which involve not only disproportionation but also cleavage of the B-B bond giving compounds 51 and 52. In addition a third product, 2-(l,3,2-benzodioxaborolo)-l,3,2-benzodioxaborole 12, was isolated and compared with those previously reported elsewhere58 (Scheme 10). 

The compound bis-/i-(dimethylamino)-diborane(6), [(CH3)2NBH2]2, has been prepared by the pyrolysis of dimethylamine-borane, (CH3)2NH BH3,1-3 and by a novel iodination-deprotonation of (CH3)2NH BH3,4 The gas-phase pyrolysis described here is the simplest and most convenient method for the preparation of small samples, since no solvent is involved and separation problems are thus minimized. The basic vacuum-line techniques necessary for this synthesis are outlined in reference 7. 

Neopentanediol (0.093 mol), 100 ml diethyl ether and tetrakis(dimethylamino)diborane were mixed, cooled with an ice bath, and 76 ml 2.46 M anhydrous hydrogen chloride (0.187 mol) in ether added. The mixture came to ambient temperature and stirred overnight. The solution was filtered, the solvent evaporated and the product isolated in 23% yield. Residue precipitate was extracted twice with 200 ml benzene increasing the overall yield to 74%. The solid was re-crystallized in benzene/light petroleum and had a mp = 161-162°C. H-NMR data supplied. 

Reactions of this type are somewhat less satisfactory for preparation of mixed diboron derivatives containing boron-carbon bonds. Thus, while tetrakis(dimethylamino)diborane(4) is readily hydrolyzed to tetrahydroxy-diborane(4) in aqueous acid, l,2-bis(dimethylamino)-l,2-diethylborane(4) reacts with formation of hydrogen and cleavage of the boron-boron bond 14). Reaction of the dibutyl analog with a twofold excess of water gave the dimethylamine adduct of the boroxole... 

Organoboron heterocycles containing the boron-boron bond have also been prepared by the reaction of A -lithio derivatives of alkylbis(alkylamino)-boranes with l,2-dichloro-l,2-bis (dimethylamino)diborane(4) 74) ... 

Diorganobis(dimethylamino)diborane(4) derivatives react with carbon dioxide or carbon disulfide in petroleum ether to form the products of insertion into the boron-nitrogen bond (1) ... 

There are relatively few examples of formation of boron-carbon bonds in compounds containing preformed boron-boron fragments. The preparation of dibutylbis(dimethylamino)diborane(4) by alkyl-amino exchange has been noted (77). 

At the other extreme, the most stable derivatives of the B2X4 type appear to be the tetrakis(dialkylamino) compounds. Thus, tetrakis(dimethylamino)-diborane(4) is stable at its boiling point of 206° C 17). The compound decomposes at 300° C to form bis(dimethylamino)borane and involatile residues containing B—C bonds. It is reported that tetra(A -methylanilino)-borane(4) is pyrolyzed at 300° C by a different mechanism to yield N-methylaniline 18). 

Thermal decomposition of l,2-dibutyl-l,2-bis (dimethylamino)diborane-(4) at 200°-230°C was found by Noth and Fritz to yield 1-butene and butyl-(dimethylamino)borane, the reaction postulated being... 

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