Hemilabile and Bimetallic Coordination in Rh and Ir Complexes of NCN Pincer Ligands
dataset
posted on 2014-10-06, 00:00 authored by Giulia Mancano, Michael
J. Page, Mohan Bhadbhade, Barbara A. MesserleTwo new pincer ligands have been
developed that contain a central
N-heterocyclic carbene (NHC) moiety linked to two pendant pyrazole
groups by either a methylene (NCN<sup>me</sup>) or ethylene (NCN<sup>et</sup>) chain. The coordination of these two ligands to rhodium
and iridium resulted in a variety of binding modes. Tridentate coordination
of the ligands was observed in the complexes [Rh(NCN<sup>me</sup>)(COD)]BPh<sub>4</sub> (<b>8</b>), [Ir(NCN<sup>me</sup>)(COD)]BPh<sub>4</sub> (<b>10</b>), [Rh(NCN<sup>et</sup>)(CO)<sub>2</sub>]BPh<sub>4</sub> (<b>13</b>), and [Ir(NCN<sup>me</sup>)(CO)<sub>2</sub>]BPh<sub>4</sub> (<b>14</b>), and monodentate NHC coordination
was observed for [Ir(NCN<sup>me</sup>)<sub>2</sub>(COD)]BPh<sub>4</sub> (<b>11</b>) and [Ir(NCN<sup>et</sup>)<sub>2</sub>(COD)]BPh<sub>4</sub> (<b>12</b>). Both tridentate and bidentate coordination
modes were characterized for [Rh(NCN<sup>et</sup>)(COD)]BPh<sub>4</sub> (<b>9</b>) in the solution and solid state, respectively,
while an unusual bridging mode was observed for the bimetallic complex
[Rh(μ-NCN<sup>me</sup>)(CO)]<sub>2</sub>(BPh<sub>4</sub>)<sub>2</sub> (<b>15</b>). The impact of this diverse coordination
chemistry on the efficiency of the complexes as catalysts for the
addition of NH, OH, and SiH bonds to alkynes was explored.
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