Neutron
Diffraction Studies of a Four-Coordinated
Hydride in Near Square-Planar Geometry
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Abstract
The
structure of a nanospheric polyhydrido copper cluster, [Cu<sub>20</sub>(H)<sub>11</sub>{S<sub>2</sub>P(O<sup><i>i</i></sup>Pr)<sub>2</sub>}<sub>9</sub>], was determined by single-crystal neutron diffraction.
The Cu<sub>20</sub> cluster consists of an elongated triangular orthobicupola
constructed from 18 Cu atoms that encapsulate a [Cu<sub>2</sub>H<sub>5</sub>]<sup>3–</sup> ion with an exceptionally short Cu–Cu
distance. The 11 hydrides in the cluster display three different coordination
modes to the Cu atoms: six μ<sub>3</sub>-hydrides in a pyramidal
geometry, two μ<sub>4</sub>-hydrides in a tetrahedral cavity,
and three μ<sub>4</sub>-hydrides in an unprecedented near square-planar
geometry. The neutron data set was collected for 7 days on a small
crystal with dimensions of 0.20 mm × 0.50 mm × 0.65 mm using
the Spallation Neutron Source TOPAZ single-crystal time-of-flight
Laue diffractometer at Oak Ridge National Laboratory. The final <i>R</i>-factor was 8.63% for 16,014 reflections