Chemistry Reference
In-Depth Information
Other hexaphenylethane molecules with structures determined by X-ray include
50
, which is restricted
from forming a head-to-tail dimer by the bulky substituents, with a central C-C bond length of 1.67(3) A.
19e
A different type of hexaphenylethane derivative is typified by
51
, which had already been already prepared
in 1933 for R
hydrogen,
19f
=
and has the central bond constrained by its intramolecular character. The
MeO) was measured as 1.670(3) A,
19g
central C-C bond of
51
(R
=
and related examples with similar
intramolecular constriction have bond lengths that are even longer.
19h,i
R
R
t-
Bu
Bu-
t
t-
Bu
Bu-
t
R
Bu-
t
t-
Bu
R
Bu-
t
t-
Bu
t-
Bu
Bu-
t
t-
Bu
Bu-
t
50
51
A variety of triarylmethyl radicals
52
with electron donating substituents were prepared by reduction
of the corresponding carbocations using cyclic voltametry (Table 1.2), including the ferrocenyl substituted
radical
53
(Equation 1.17).
20a
These showed strong downward shifts in the reduction potentials due to
the strongly electron donating substituents, and reversible redox behavior was even observed in aqueous
solution.
Ar
2
Ph
+
Ph
C
Ar
C
•
Ar
1
C
•
Ar
1
Ar
1
Fe
(1.17)
Fe
52
53
The bis(diphenylpentafulvene) iron complex
54
was also prepared, for which the structure was considered
as either the bis(radical)
54a
or the bis(fulvene)
54b
.
20b
The fact that the X-ray and calculated structure
(Figure 1.1) showed the exocyclic groups on the same side of the molecule was taken as favoring the
Table1.2
Triarylmethylradicals
52
studiedbycyclicvoltammetry
Ar
1'
Ar
2
Ar
2,4,6-(MeO)
3
C
6
H
2
2,4,6-(MeO)
3
C
6
H
2
2,4,6-(MeO)
3
C
6
H
2
2,4,6-(MeO)
3
C
6
H
2
2,6-(MeO)
2
C
6
H
3
2,6-(MeO)
2
C
6
H
3
2,6-(MeO)
2
C
6
H
3
2,6-(MeO)
2
C
6
H
3
2,6-(MeO)
2
C
6
H
3
4-MeOC
6
H
4
2,6-(MeO)
2
C
6
H
3
2,6-(MeO)
2
C
6
H
3
2-MeOC
6
H
4
2,6-(MeO)
2
C
6
H
3
2,6-(MeO)
2
C
6
H
3
Ph
2,6-(MeO)
2
C
6
H
3
2,6-(MeO)
2
C
6
H
3
Ferrocenyl
Ph
2,6-(MeO)
2
C
6
H
3
Ferrocenyl
2,6-(MeO)
2
C
6
H
3
H
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