Recent advances in boron-nitrogen chemistry - II

The chemistry of dimethylaminopolyboranes Bn(NMe )nX2 (n = 3, =-= C1, Br) has been investigated. Nucleophil ic 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 perpendi- cular arrangement of the BNMe2 units. The scope of the chemistry of amino iminoboranes has been expanded by the synthesis of molecules containing two RN f B units. Reactions of amino iminoboranes with boron hydrides lead to hydroboration products in the case of BH .thf or BgH7.thf while a boron-boron bond is formed in the re- action wit; B10H14. While Bn(NMe2) C12 compounds exclusively chloroborate tmpB = NCMe3 no such reaction is olserved employing F~~(CO)~SZB~(NM~ ~)C~. This is due to then*-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 '2% B = PRO compounds. However, if the l one pair at the P atom is engaged in bonding with a M(CO)5 group (M = Cry W) allenic type complexes R N = B = PR'(M(CO)5) con- taining two coordinated boron and a BP double bod (1.741) result.