Prediction of 195Pt NMR chemical shifts of dissolution products of H2[Pt(OH)6] in nitric acid solutions by DFT methods: how important are the counter‐ion effects? |
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| Authors: | Athanassios C Tsipis Ioannis N Karapetsas |
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| Institution: | Laboratory of Inorganic and General Chemistry, Department of Chemistry, University of Ioannina, Ioannina, Greece |
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| Abstract: | 195Pt NMR chemical shifts of octahedral Pt(IV) complexes with general formula Pt(NO3)n(OH)6 ? n]2?, Pt(NO3)n(OH2)6 ? n]4 ? n (n = 1–6), and Pt(NO3)6 ? n ? m(OH)m(OH2)n]?2 + n ? m formed by dissolution of platinic acid, H2Pt(OH)6], in aqueous nitric acid solutions are calculated employing density functional theory methods. Particularly, the gauge‐including atomic orbitals (GIAO)‐PBE0/segmented all‐electron relativistically contracted–zeroth‐order regular approximation (SARC–ZORA)(Pt) ∪ 6–31G(d,p)(E)/Polarizable Continuum Model computational protocol performs the best. Excellent second‐order polynomial plots of δcalcd(195Pt) versus δexptl(195Pt) chemical shifts and δcalcd(195Pt) versus the natural atomic charge QPt are obtained. Despite of neglecting relativistic and spin orbit effects the good agreement of the calculated δ 195Pt chemical shifts with experimental values is probably because of the fact that the contribution of relativistic and spin orbit effects to computed σiso 195Pt magnetic shielding of Pt(IV) coordination compounds is effectively cancelled in the computed δ 195Pt chemical shifts, because the relativistic corrections are expected to be similar in the complexes and the proper reference standard used. To probe the counter‐ion effects on the 195Pt NMR chemical shifts of the anionic Pt(NO3)n(OH)6 ? n]2? and cationic Pt(NO3)n(OH2)6 ? n]4 ? n (n = 0–3) complexes we calculated the 195Pt NMR chemical shifts of the neutral (PyH)2Pt(NO3)n(OH)6 ? n] (n = 1–6; PyH = pyridinium cation, C5H5NH+) and Pt(NO3)n(H2O)6 ? n](NO3)4 ? n (n = 0–3) complexes. Counter‐anion effects are very important for the accurate prediction of the 195Pt NMR chemical shifts of the cationic Pt(NO3)n(OH2)6 ? n]4 ? n complexes, while counter‐cation effects are less important for the anionic Pt(NO3)n(OH)6 ? n]2? complexes. The simple computational protocol is easily implemented even by synthetic chemists in platinum coordination chemistry that dispose limited software availability, or locally existing routines and knowhow. Copyright © 2016 John Wiley & Sons, Ltd. |
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| Keywords: | NMR 195Pt NMR DFT calculations prediction of 195Pt chemical shifts octahedral Pt(IV) complexes in nitric acid solution counter‐ion effects |
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