430 MAKOTO INOUE A N D GOJI KODAMA
Inorycinic Chemistry CONTRIBUlIOS F R O M THE D E P A R T M E N T O F CHEMISTRY, KAGURAZAKA, S H I N J U K U , TOKYO, JAPAN
TOKYO COLLEGE OF SCIENCE,
The Preparation and Some Properties of Dihydridobis(monomethy1amine)and Dihydridobis(dimethylamine)boron(III) Tetrahydridoborate(1II)l BY hlXKOTO I S O U E
ASD
GOJI KODXMA
Receined April 3, 1967 Tetrahydridoboratc(II1) salts of H2B(CHaSH%):!+and H2B [ (CHa)&H]z+ cations were prepared by metathetical reactioiis between the chlorides of the cations and NaBH4 and by direct reactions between diborane and the amines. T h e pure B H 4 salts are stable, white solids in vacuo a t room tetnperature (mp 48" for [ H ~ B ( C H ~ S H Q ) ~and ]BH 57" ~ for [H2B{( C H I ) ~ N H } ~ ] BH4). T h e ligand monomethylamine in the H ~ B ( C H I S H ~ion ) ~ +can be replaced b y ammonia or dimethylamine, and the ligand dimethylamine in the H2B [ (CH3)2NH]2+ ion can be replaced by ammonia or monomethylamine. Spontaneous direct conversion of these BHI- salts t o the corresponding amine boranes was not observed. On the basis of observed stability of these salts, the process determining the formation of the unsymmetrical and symmetrical cleavage products of diborane was considered.
Shore, Hickam, and C o d e s 2 found, by means of BI1 nmr techniques, that both unsymmetrical and symmetrical cleavage products of diborane [;.e., [H2B(amine)%]BH4and amine-BH3, respectively], were formed when diborane reacted with excess monomethylamine or dimethylamine a t low temperatures. Beachley3 reported that the reaction of diborane with monomethylamine yielded a liquid product and demonstrated that the liquid could be represented as an Recently i t was reionic salt [ H ~ B ( C H ~ N H Q ) ~ ] B H~. ported4 that the salts [H2B(NH&]BH4and [H2B(CH3NH&]BHa could be prepared indirectly from NH3BH3 and CH3XHzBH3, respectively, and a mechanistic argument was presented to rationalize the cleavage pattern of diborane. When this work was initiated i t too had as its objective elucidation of the nature of the reactions between diborane and mono- or dimethylamine. Salts containing unusually stable cations of the form H2B (amine)2+ have been r e p ~ r t e d . ~Pure , ~ BH4salts of these cations have not, however, been described in the literature except for the salts of H2B(NH&+ and H2B(CH3NH2)z+ cations. Isolation and characterization of the BH4- salts of the cations HpB(CH3NH&+ and H2B[(CH&NH]p+ are described herein. Results and Discussion Preparation of BHa- Salts by Metathesis.(1) Tetrahydridoborate(III), BH4-, salts of the dihydrido(1) Based in part on a n M S . Thesis submitted by M. Inoue t o the Graduate School of the Tokyo College of Science, Feb 1965, Presented in pal-t a t the 18th annual meeting of the Chemical Society of Japan, April 1965, Paper N o . 6307. ( 2 ) S.G. Shore, C. W. Hickam, Jr., and D. Cowles, J . A m . Chem. Soc., 87, 2755 (1965). (3) 0. T. Beachley, 1noi.g. Chem., 4, 1823 (1966). (4) S. G. Shore and C. L. Hall, J . A m . Chem. Soc., 8 8 , 5346 (1966). ( 5 ) (a) H. Noth and H. Beyer, Angew. Chem., 71, 383 (1959); H . Xoth and H. J. Vetter, Bev., 97, 110 (1964); (b) H. X a t h and H. Beyer, i b i d . , 93, 1078 (1960); H. Noth, Anpew. Chena., 72, 638 (1960). (6) H. C. Miller, N. E. Miller and E. L. Muetterties, J . A m . Chem. Soc., 8 6 , 3885 (1963); N. E. Miller and E. L. Muetterties, ibid., 86, 1033 (1964); N. E. Miller, B. L. Chamberland, and E. L. Muetterties, Inoug. Chem., 3, 1064 (1964). (7) (a) D. I
