networks seen, the main factor holding the anions together is the
can be in determining the overall structure, as well as their
utility in structural design. Amongst these interactions was a rare
Au ◊ ◊ ◊ Au interaction.
presence of several Au ◊ ◊ ◊ Au interactions. In both salts, chains of
-
10
10
I
III
[
Au(CN)
2
] anions are generated via well-known d –d aurophilic
-
interactions. In the case of 4, the Au(III)-containing [AuBr
unit incorporates itself into the [Au(CN)
Au ◊ ◊ ◊ Br interactions. With 5, however, the unusual Au ◊ ◊ ◊ Au
2
(CN)
2
]
In previous examples, proximity of the Au centres was enforced
or encouraged either through a ligand framework or electrostatics.
Here, such an interaction is found in 5 in the absence of strong
supporting factors.
Finally, these building blocks provide opportunities to target
new types of coordination polymers with increased structural
dimensionality with the assistance of weak Au ◊ ◊ ◊ Au, Au ◊ ◊ ◊ X and
X ◊ ◊ ◊ X interactions, an avenue which we are currently exploring.
-
2
]
network through
I
I
III
I
I
interaction is also seen. In the case of Au ◊ ◊ ◊ Au interactions,
theoretical studies (supported by experimental observations) have
correlated the ancillary ligands on the Au(I) centre to the
27,63,64
strength of the interaction.
Such studies suggest that softer,
more polarizable ligands lead to an increased tendency to form
I
III
aurophilic interactions, hence the Au ◊ ◊ ◊ Au interactions are only
seen with the softest of ligands here (X = I).
Acknowledgements
A noteworthy structural feature of 4 and 5 is the relative
-
orientation of the cyano groups in pairs of [Au(CN)
2
]
units.
The authors thank NSERC of Canada and Natural Resources
Canada (JSO) for financial support.
Whereas in 4 the trans-cyano groups of interacting Au(I) centres
are parallel to each other, they are staggered in 5. This reflects
I
I
that such Au ◊ ◊ ◊ Au interactions are rotationally flexible, with a
2
very small energy difference between conformations. The cyano
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I
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1
350 | Dalton Trans., 2012, 41, 1345–1351
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