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Rhodium(I) and Iridium(I) Complexes of the Conformationally Rigid IBioxMe4 Ligand: Computational and Experimental Studies of Unusually Tilted NHC Coordination Geometries
| Content Provider | Semantic Scholar |
|---|---|
| Author | Luy, Jan-Niclas Hauser, Simone A. Chaplin, Adrian B. Tonner, Ralf |
| Copyright Year | 2016 |
| Abstract | Computational methods have been used to analyze distorted coordination geometries in a coherent range of known and new rhodium(I) and iridium(I) complexes containing bioxazoline-based NHC ligands (IBiox). Such distortions are readily placed in context of the literature through measurement of the Cnt(NHC)–CNCN– M angle (ΘNHC; Cnt = ring centroid). On the basis of restricted potential energy calculations using cis[M(IBioxMe4)(CO)2Cl] (M1, M = Rh, Ir), in plane (yawing) tilting of the NHC was found to incur significantly steeper energetic penalties than orthogonal out of plane (pitching) movement, which is characterized by noticeably flat potential energy surfaces. Energy Decomposition Analysis (EDA) of the ground state and pitched structures of M1 indicated only minor differences in bonding characteristics. In contrast, yawing of the NHC ligand is associated with significant increase in Pauli repulsion (i.e. sterics) and reduction in M→ NHC π−back donation, but counteracted by supplemental stabilising bonding interactions only possible due to closer proximity of the methyl substituents with the metal and ancillary ligands. Aided by this analysis, comparison to a range of carefully selected model systems and EDA, distorted coordination modes in trans[M(IBioxMe4)2Cl(COE)] (M2, M = Rh, Ir) and [M(IBioxMe4)3] (M3, M = Rh, Ir) have been rationalised. Steric interactions were identified as the major contributing factor and are associated with a high degree of NHC pitching. In the case of Rh3, weak agostic interactions also contribute to the distortions, particularly with respect to NHC yawing, and are notable for increasing the bond dissociation energy of the distorted ligands. Supplementing the computational analysis, an analogue of formally 14 VE Rh(I) Rh3 bearing the cyclohexylfunctionalised IBiox6 ligand ([Rh(IBiox6)3], Rh3-Cy) was prepared and found to exhibit an exceptionally distorted NHC ligand (ΘNHC = 155.7(2)°) in the solid-state. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://wrap.warwick.ac.uk/76666/1/WRAP_Chaplin_coordination_geometries.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
