Robust iridium pincer complexes as a new framework for single-crystal to single-crystal transformations in solid-state organometallic chemistry Matthew Gyton, Simon B. Duckett and Andrew S. Weller University of York, UK Considerable advances have been made over the past decade in Solid-State Organometallic Chemistry (SMOM); this is best illustrated by the facile isolation and solid-state stability of the σ-alkane complex [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(norbornane)][BAr F 4 ] through the solid/gas hydrogenation of [Rh(Cy 2 PCH 2 CH 2 PCy 2 ) (norbornadiene)][BAr F 4 ]. 1 Critical to the stability of this complex in the solid state is the octahedral packing of the tetraarylborate [BAr F 4 ] anions that provides a rigid crystalline framework around the cationic metal centre that stabilises the weak metal-alkane interaction with supporting non-covalent interactions. This approach has allowed the extension of the series with wider bite-angle phosphines (Cy 2 P(CH 2 ) n PCy 2 , n = 3-5) afford similar polyhedral packing of the anion around the cation and similar stabilizing non-covalent interactions. 2 Recent efforts have focused on the extension of these solid/gas SMOM methods of synthesis to more varied ligand frameworks and metal centres beyond this now well-established chelating diphosphine manifold. Initial investigations have targeted complexes such as [Ir(PONOP iPr )(propene)][BAr F 4 ], in which the crystalline solid-state microenvironment gates reactivity by preventing propene insertion into an iridum hydride, which directly contrasts with observed solution phase behaviour. 3 This study seeks to extend this approach further through the use of a solid-state stable but solution-state dynamic and highly reactive complex [IrHMe(PONOP tBu )] [BAr F 4 ]. This pincer ligand framework provides cations of sufficient stability to afford facile, sequential transformations as single-crystalline materials. Discussion will focus on the solid/gas single-crystal transformations under thermal conditions and investigations into the differences in dynamics observed in the solid state.
Figure 1. The solid/gas reaction of [IrHMe(PONOP tBu )][BAr F
4 ] with: i) dihydrogen affording single crystalline [Ir(H) 2 (PONOP tBu )]
[BAr F 4 ] and subsequently ii) carbon monoxide to afford single crystalline [Ir(CO)(PONOP tBu )][BAr F 4 ]. References 1. S. D. Pike, F. M. Chadwick, N. H. Rees, M. P. Scott, A. S. Weller, T. Krämer and S. A. Macgregor, J. Am. Chem. Soc. , 2015, 137 , 820–833. 2. A. J. Martínez-Martínez, B. E. Tegner, A. I. McKay, A. J. Bukvic, N. H. Rees, G. J. Tizzard, S. J. Coles, M. R. Warren, S. A. Macgregor and A. S. Weller, J. Am. Chem. Soc. , 2018, 140 , 14958–14970. 3. C. G. Royle, L. Sotorrios, M. R. Gyton, C. N. Brodie, A. L. Burnage, S. K. Furfari, A. Marini, M. R. Warren, S. A. Macgregor and A. S. Weller, Organometallics , 2022, 41 , 3270–3280.
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