The Conformations of 13-Vertex <i>ML</i><sub>2</sub>C<sub>2</sub>B<sub>10</sub> Metallacarboranes:  Experimental and Computational Studies Kelly J. Dalby David Ellis Stefan Erhardt Ruaraidh D. McIntosh Stuart A. Macgregor Karen Rae Georgina M. Rosair Volker Settels Alan J. Welch Bruce E. Hodson Thomas D. McGrath F. Gordon A. Stone 10.1021/ja067698m.s002 https://acs.figshare.com/articles/dataset/The_Conformations_of_13_Vertex_i_ML_i_sub_2_sub_C_sub_2_sub_B_sub_10_sub_Metallacarboranes_Experimental_and_Computational_Studies/3017566 The docosahedral metallacarboranes 4,4-(PMe<sub>2</sub>Ph)<sub>2</sub>-4,1,6-<i>closo</i>-PtC<sub>2</sub>B<sub>10</sub>H<sub>12</sub>, 4,4-(PMe<sub>2</sub>Ph)<sub>2</sub>-4,1,10-<i>closo</i>-PtC<sub>2</sub>B<sub>10</sub>H<sub>12</sub>, and [N(PPh<sub>3</sub>)<sub>2</sub>][4,4-cod-4,1,10-<i>closo</i>-RhC<sub>2</sub>B<sub>10</sub>H<sub>12</sub>] were prepared by reduction/metalation of either 1,2-<i>closo</i>-C<sub>2</sub>B<sub>10</sub>H<sub>12</sub> or 1,12-<i>closo</i>-C<sub>2</sub>B<sub>10</sub>H<sub>12</sub>. All three species were fully characterized, with a particular point of interest of the latter being the conformation of the {<i>ML</i><i><sub>2</sub></i>} fragment relative to the carborane ligand face. Comparison with conformations previously established for six other <i>ML</i><sub>2</sub>C<sub>2</sub>B<sub>10</sub> species of varying heteroatom patterns (4,1,2-<i>M</i>C<sub>2</sub>B<sub>10</sub>, 4,1,6-<i>M</i>C<sub>2</sub>B<sub>10</sub>, 4,1,10-<i>M</i>C<sub>2</sub>B<sub>10</sub>, and 4,1,12-<i>M</i>C<sub>2</sub>B<sub>10</sub>) reveals clear preferences. In all cases a qualitative understanding of these was afforded by simple MO arguments applied to the model heteroarene complexes [(PH<sub>3</sub>)<sub>2</sub>PtC<sub>2</sub>B<sub>4</sub>H<sub>6</sub>]<sup>2-</sup> and [(PH<sub>3</sub>)<sub>2</sub>PtCB<sub>5</sub>H<sub>6</sub>]<sup>3-</sup>. Moreover, DFT calculations on [(PH<sub>3</sub>)<sub>2</sub>PtC<sub>2</sub>B<sub>4</sub>H<sub>6</sub>]<sup>2-</sup> in its various isomeric forms approximately reproduced the observed conformations in the 4,1,2-, 4,1,6-, and 4,1,10-<i>M</i>C<sub>2</sub>B<sub>10</sub> species, although analogous calculations on [(PH<sub>3</sub>)<sub>2</sub>PtCB<sub>5</sub>H<sub>6</sub>]<sup>3-</sup> did not reproduce the conformation observed in the 4,1,12-<i>M</i>C<sub>2</sub>B<sub>10</sub> metallacarborane. DFT calculations on (PH<sub>3</sub>)<sub>2</sub>PtC<sub>2</sub>B<sub>10</sub>H<sub>12</sub> yielded good agreement with experimental conformations in all four isomeric cases. Apparent discrepancies between observed and computed Pt−C distances were probed by further refinement of the 4,1,2- model to 1,2-(CH<sub>2</sub>)<sub>3</sub>-4,4-(PMe<sub>3</sub>)<sub>2</sub>-4,1,2-<i>closo</i>-PtC<sub>2</sub>B<sub>10</sub>H<sub>10</sub>. This still has a more distorted structure than measured experimentally for 1,2-(CH<sub>2</sub>)<sub>3</sub>-4,4-(PMe<sub>2</sub>Ph)<sub>2</sub>-4,1,2-<i>closo</i>-PtC<sub>2</sub>B<sub>10</sub>H<sub>10</sub>, but the structural differences lie on a very shallow potential energy surface. For the model compound a henicosahedral transition state was located 8.3 kcal mol<sup>-1</sup> above the ground-state structure, consistent with the fluxionality of 1,2-(CH<sub>2</sub>)<sub>3</sub>-4,4-(PMe<sub>2</sub>Ph)<sub>2</sub>-4,1,2-<i>closo</i>-PtC<sub>2</sub>B<sub>10</sub>H<sub>10</sub> in solution. 2007-03-21 00:00:00 2B PH conformation MC henicosahedral transition state carborane ligand face CH 8.3 kcal mol MO ML 2C species DFT calculations model