Chapter 1 gives a brief introduction into carborane and metallacarborane chemistry and
provides a short review ofliterature relevant to the topic ofthe thesis.
Chapter 2 describes the syntheses of metallacarboranes starting from 1,12-diphenyl1,12-
carborane. This includes reduction and metallation at both room temperature and
low temperature (_42°C and -78°C). As a result of these reactions 4,1,6, 4,1,8, 4,1,10,
4,1,11 and 4,1,12 isomers of l,x-Ph2-4-(p-cymene)-4,I,x-c!oso-RuC2BlOHlO were
obtained, the 4,1,11 isomer being the first example of 13-vertex 4,1,11-MC2BlO and
4,1,8 being the first example of 4,1,8-RuC2BlO. This synthetic work together with some
related computational studies reveals the mechanism of reduction of 1,12-carborane
(involving the initial formation of 1,7 and 4,7 isomers of [x,y-Ph2-x,y-nido-C2BlOHlOt
and 3,7, 7,9 and 7,10 isomers by the subsequent rearrangement of 1,7 and 4,7) and
defines the role of phenyl substituents on the carborane cage (lowering the temperature
of isomerisation of reduced species). Experimental facts were in accord with the
calculated energies of the five nido dianionic isomers which increase in the order
7,9<7,10<4,7<3,7<1,7.
Chapter 3 describes similar work (reduction and metallation at room temperature and at
-78°C) starting from 1,2-diphenyl-l,2-carborane and 1,7-diphenyl-l,7-carborane. In the
former case experimental and computational results mainly coincide, although some
more work is required to explain the results of the room temperature reaction. The
interpretation of results obtained experimentally and those from computational studies
for 1,7-carborane is not so straightforward and more work is required in this area.
Chapter 4 focusses on the properties of the 13-vertex monometallacarboranes
synthesized. Study ofthe rearrangements of 13-vertex ruthenacarboraries 4,I,x-RuC2BlO
establish the 4,1,6 ~ 4,1,8 ~ 4,1,12 isomerization, previously reported for
cobaltacarboranes only. The 4,1,1O~4,1,12 pathway, known from literature for nonphenylated
compounds, was also established, as well as the 4,1, 11 ~ 4,1,8
isomerization. Putting together these experimental results and the calculated stabilities
of 4,I,x-RuC2BlO isomers allowed a mapping of these isomerisation pathways. Under
this scheme each individual isomerization step is explained as a move to the next lower
energy isomer accessible by a single TFR. Reduction-metallation and reduction-oxidation reactions of diphenylated 4,1,8- and 4,1,12-RuC1BlO are also described.
Comparison of these reactions with those starting from non-phenylated analogues
allowed the proposition that the presence of phenyl groups leads to the rearrangement
(at or below room temperature) of the reduced form of 4,1,8 to species analogous to
those formed at the reduction of 4,1,12 isomer. Thus it was shown that the reduction
and metallation of both phenylated 4,1,8 and 4,1,12 isomers led to the same 14-vertex
species (1,14,2,10 isomer). In the case of the 4,1,8 compound partial cage degradation
(removal of B5) occurred leading to the rare 12-vertex 8,1,2-RuC1B9 isomer on
oxidation and 13-vertex 4,5,1,6-RulC1B9 on metallation.
Chapter 5 (the synthetic work for this Chapter was carried out by MChem student Ross
McLellan under the supervision of the author) attempts to quantify the effect of Ph
group addition by the reduction and metallation of 1-phenyl-l, 12-carborane. It is shown
that in these reactions one Ph group has the same net effect as two Ph groups since the
reduction and metallation of I-Ph-1,12-closo-C2BlOHll at room temperature produces
the 4,1,6 isomer of the metallacarborane. It is also shown that reactions starting either
from 1-phenyl-I,12-carborane or 1-phenyl-1,2-carborane lead to the 4,1,6 isomer
having the Ph substituent located exclusively on the four-connected C1 rather than fiveconnected
C6.
Chapter 6 gives experimental details of all the reactions performed and also provides
spectroscopic and analytical data for all compounds synthesized.
In the 'Suggestions for Future Work' section the possible reactions which elaborate or
develop the ideas ofthis thesis are summarized.
Appendix 1 provides some details of the crystal structure determination of compounds
synthesized. Appendix 2 (provided on compact disk) gives the appropriate files in RTF
and CIF (or MOL2) format.
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