Methyleneamino derivatives of some metals and metalloids

Abstract

This thesis describes the preparation and properties of some methyleneamino derivatives of boron, magnesium and aluminium. The structural implications of their I.R. and (L^) H n.m.r. spectra are discussed. As a background to the work, the characteristics of such compounds are discussed and a survey of methyleneamino derivatives of metals and metalloids is presented. Bis (di-t-butylmethyleneamino) fluoroborane. ((^t) Bu (_2) C: N) (_2) BF, was prepared from borom trifluoride and di-t-butylmethyleneminolithium and used to synthesise and three compounds ((^t) Bu (_2) C: N) (_3) B, (^t) Bu (_2) C: NBF (_2) and ((^t) Bu (_2) C: N) (_2) BH. Several compounds in which boron is in a heterocyclic ring system, (^t) Bu (_2) c: NB (^X) – (^Y) – (_Y) – (_X) and two alkyl (di-t-butylmethyleneminolithium) boranes, (^t) Bu (_2) C: NB (^t) Bu (_2) and ((^t) Bu (_2) C: N) (_2) BMe, have been prepared. The I.r and (^1) H n.m.r spectra of these new di-t-butylmethyleneminolithium, ((^t) Bu (_2) C: N) (_n) BX (_3-n), are consistent with there c=n=b skeletons being linear as appropriate for significant n → b dative N-bonding. The new methyleneaminomagnesium compounds are of the following formula types: [R (_2) c: nmGx], [(R (_2) C: N) (_2) Mg] (_n), R (_2) C: NMgBr. 2THF, LiMg (N: CPh (_2)) (_3) OEt (_2)) (_4). The associated species (n usually = 2) are believed to co-ordinate via bridging methyleneamino groups. The I.R spectra of compounds containing terminal methyleneamino groups are consistent with the C.N.Mg units being effectively linear. The preparation of the tris (di-t-butylmethyleneminolithium) alane, ((^t) Bu (_2) C: N) (_3) Al, from aluminium hydride and di-t-butylmethyleneminolithium has been shown to be more reliable than the reaction between aluminium trichloride and iminolithium. Similar reactions o prepare mono and bis (imino) akanes were less successful, and only once could a bis (imino) alane be isolated as a trimethylamine adduct, ((^t) Bu (_2) C: N) (_2) AlH. NNMe (_3). The I.R and (^l) H n.m.r. spectra of these two compounds indicate that their c=n=Al units are effectively linear, as appropriate for N → Al dative N- Bonding. Preliminary studies of reactions between several methylaluminium compounds and di-t-butylmethyleneminolithium or its lithio derivative have been made. The preparation and properties of di-t-butylmethyleneminolithium, (^t) Bu (_2) C: NNMe (_2), are discussed boron compounds and tetramethylguanidine or its lithio derivative are described in Appendix 2. The experimental techniques used in this research are described in Appendix 3.