The effects of
para
-substitution on the structural
and electronic properties of four series of two-coordinate
m
-terphenyl Group 12 complexes (R-Ar
#
)
2
M (M = Zn, Cd, Hg; R =
t
-Bu
1
–
3
, SiMe
3
4
–
6
,
Cl
7
–
9
, CF
3
10
–
12
, where R-Ar
#
= 2,6-{2,6-Xyl}
2
-4-R-C
6
H
2
and 2,6-Xyl = 2,6-Me
2
C
6
H
3
) have been investigated. X-ray crystallography
shows little structural variation across the series, with no significant
change in the C–M–C bond distances and angles. However,
considerable electronic differences are revealed by heteronuclear
nuclear magnetic resonance (NMR) spectroscopy; a linear correlation
is observed between the
113
Cd,
199
Hg, and
1
H (2,6-Xyl methyl protons) NMR chemical shifts of the
para
-substituted complexes and the Hammett constants for
the R-substituents. Specifically, an upfield shift in the NMR signal
is observed with increasingly electron-withdrawing R-substituents.
Density functional theory (DFT) calculations are employed to attempt
to rationalize these trends.