X-ray Crystallographic Studies of the Products of Oxidative Additions of Iodine to Cyclic Trinuclear Gold(I) Complexes: Directional Effects for Au−I···I−Au Interactions

The crystal structures of cyclic trinuclear organogold compounds,
Au3In(CH3NCOCH3)3
(n = 2, 4, 6) reveal
that pairs of iodine atoms are added successively to each of the gold
atoms in the triangular complexes. Deep
red needles of
Au3I6(CH3NCOCH3)3·CH2Cl2
crystallize in the monoclinic space group
P21/c, with a =
14.762(4) Å, b = 8.723(3) Å, c =
22.278(6) Å, and β = 91.58(2)° at 123 K with
Z = 4. Refinement of 6591 reflections
and 164 parameters yielded R = 0.055. The structure
consists of columns of the molecular units united by weak
iodine···iodine interactions which range in length from
3.636(2) to 3.716(2) Å. Within the molecular unit,
all
iodine···iodine distances are well beyond the sum of their
van der Waals radii and fall in the range from
3.965(2)
to 4.211(2) Å. The gold coordination is significantly
distorted from planarity with I−Au−I angles of ca.
163°.
In
Au3I6(CH3NCOCH3)3
the intermolecular I···I interactions are significantly shorter
than the intramolecular
I···I contacts. Red parallelepipeds of the tetraiodo
complex,
Au2I4Au(CH3NCOCH3)3,
crystallize in the triclinic
space group P1̄, with a = 7.404(2)
Å, b = 9.278(2) Å, c = 16.331(3)
Å, α = 80.77(3)°, β = 78.68(3)°, and
γ
= 81.85(3)° at 123 K with Z = 2. Refinement
of 4963 reflections and 124 parameters yielded R = 0.048.
No
noteworthy intermolecular contacts are present in this compound.
Orange-red hexagonal plates of the diiodo
complex,
AuI2Au2(CH3NCOCH3)3,
crystallize in the monoclinic space group
P21/c, with a =
9.309(4) Å, b =
13.597(4) Å, c = 14.899(5) Å, and β =
101.26(3)° at 123 K with Z = 4. Refinement of
4133 reflections and 121
parameters yielded R = 0.064. This structure consists
of discrete molecular units displaying no noteworthy
inter-
or intramolecular contacts.