2. Group 3 (scandium and yttrium)
1.Group 3 transition metals have +3 as their primary oxidation
state, attaining a d0 electron configuration by losing their three valence
s- and d-electrons.
2.While there are some theoretical studies
of other oxidation states in the literature [29]
3.experimental studies
are somewhat rarer. Early studies carried out by Corbett and his
group produced a few scandium(II) halides using scandium trihalide
as starting material in a sealed tantalum tube, reacting at a
very high temperature over 3–6 weeks [30].
4.Arguably, of more
interest is the scandium(I) complex reported by Nixon and coworkers
in 1996 [31].
5. The complex was synthesised by a process
called metal vapour synthesis, where co-condensation of electron
beam vaporised scandium with an excess of t
BuCP at 77 K gave the complex [{g5
-P3C2
t
Bu2}Sc]2(l-g6
:g6
-P3C3
t
Bu3) (Fig. 3). The
complex contains two scandium(I) centres, each sandwiched between
a P3C2
t
Bu2 and a P3C3
t
Bu3 ring, resulting in a triple-decker
structure.
6.Apart from being the first ever example of a complex carrying
formal scandium(I) centres, the authors also commented that the
very low electron count on the scandium centres was remarkable.
7.Before their successful synthesis of the complex, a 30/34 valence
electron rule was proposed to account for the stability of a tripledecker
complex, however, the scandium(I) centre only contains
an electron count of 22. Subsequently,
8.the group has continued
to publish papers reporting analogous complexes [32]. As well as
the +1 and +2 oxidation states, there are also studies into the zero
oxidation state of the Group 3 transition metals [33].