Recent advances in boron—nitrogen chemistry—ii

Abstract

The chemistry of dimethylaminopolyboranes Bn(NMeo)nX2 (n= 3, 4,6, X' ‘= Cl, Br) has been investigated. Nucleophilic substitution of the halides by NHR, OR, SR and R groups is readily achieved as well as by di-functional nucleophiles which give access to boron rich heterocycles. The characteristic feature of all these new compounds is the almost perpendicular arrangement of the BNMe2 units. The scope of the chemistry of amino iminoboranes has been expanded by the synthesis of molecules containing two RN = B units. Reactions of amino iminoboranes with boron hydrides lead to hydroboration products in the case of BH3-thf or B3H7.thf while a boron-boron bond is formed in the reaction with B10h14. While Bn(NMe2)nCl2 compounds exclusively chloroborate tmpB =NCMe3 no such reaction is observed employing Fe2(CO)5S2B2(NMe2)Cl. This is due to the nido-structure of this compound. Its reaction with LiNMe2 converts it into Fe2(C0)6S2(BNMe2)2 cage containing a diboron unit. The R2N group cannot yet electronically stabilize R2N - B = PR1 compounds. However, if the lone pair at the P atom is engaged in bonding with a M(CO)5 group (M = Cr, W) allenic type complexes R2N = B = PR1(M(CO)5) containing two coordinated boron and a BP double bona (1.74a) result. © 1991, IUPAC