Group 8 & 9 catalysts for the dehydropolymerisation of amine-boranes

Chapter 1: This introductory chapter covers topics that are necessary to understand
the research background upon which this thesis is built. These include fundamental
amine-borane and polyaminoborane chemical properties, the origin of catalytic routes
to polyaminoborane formation, the potential applications of polyaminoboranes, the
mechanisms of amine-borane dehydropolymerisation and the general concept of metal
ligand cooperative catalysis.
Chapter 2: In the second chapter, the activation and deactivation pathways of group 9
metal ligand cooperative amine-borane dehydropolymerisation catalysts are
investigated, primarily focussing on rhodium metal-ligand cooperative aminophosphine
complexes (such as Rh(iPr-PNHP)H2Cl) that have recently been reported by the Weller
group. The slow spontaneous dissociation of amine-boranes in solution is discussed
and its poisoning effect on amine-borane dehydropolymerisation catalysts, forming
borohydride complexes. This is related to the as-yet unsolved problem that the
substrate scope for previously reported amine-borane dehydropolymerisation catalysts
is limited primarily to the parent ammonia-borane and its N-methyl derivative.
Chapter 3: In this chapter the structure, mechanism and speciation are investigated
for amine-borane dehydropolymerisation catalysts based upon the previously reported
but broadly overlooked ruthenium aminophosphine precatalyst
Ru(iPr2PCH2CH2NH2)2Cl2. The highly unusual and reactive square-planar, d6 and low�spin precatalyst Ru(iPr2CH2CH2NH)2 is characterised and its electronic structure
discussed. Such precatalysts are shown to exhibit the highest-yet reported rate of
amine-borane dehydropolymerisation, and this rapid catalysis is utilised for the
synthesis of high molecular weight N-methyl polyaminoborane. ethyl and propyl
polyaminoboranes. Parts of this chapter are published as a communication in an
Angew. Chem. Int. Ed. article.
Chapter 4: This final discussion chapter covers the first report of selective N-ethyl and
N-propyl amine-borane catalytic dehydropolymerisation, forming the N-ethyl and N�propyl polyaminoboranes utilising the ruthenium catalyst discussed in chapter 3
(Ru(iPr2PCH2CH2NH2)2Cl2). The possible routes of catalyst deactivation when using
these amine-boranes as substrates is also discussed.
Chapter 5: Experimental data, figures, tables and methods.