ИСТИНА

To study the structure of and intra-anionic interactions in the titled anion 1, MP2 and DFT (B97-1, B3LYP, B98, PBE, and PBE1KCIS) calculations were explored. For copper either all electron triple-zeta (TZ) basis set or an energy consistent scalar relativistic 19 electron basis set and small-core SDD pseudopotential (RS basis) were used. TZ, Dunning's cc-pVTZ or Pople’s 6-311++G(d,p) (P) basis sets for C and H were applied. Diphenylcuprate(I) anion 2 was studied for the comparison. RIMP2/TZ and B97-1/PRS (PRS is P basis for C and H atoms and RS basis for Cu) optimizations yield coplanar (D2h), twisted (D2), and perpendicular (D2d) conformers of 1. RI-MP2/TZ optimization results in twisted 1 with the twist angle θ of 31.1° between phenyl rings which is close to that of 26.0° in X-ray measured {(CuMes2)‾[Cu(dppe)2]+}1 (dppe=1,2-bis(diphenylphosphino)ethane). B97-1/PRS leads to D2 conformer with θ = 47.7°, whereas the rest DFT methods result in D2h and D2d conformers only. Also D2h and D2d conformers are only predicted for 2 by all calculations. The results obtained show that B97-1 functional underestimates dispersion interactions between ortho-methyl groups of 1 as well as other interactions influencing the twist angle between aromatic rings in this anion. B3LYP, B98, PBE, and PBE1KCIS functionals are completely not able describe properly these interactions. Barrier to rotation of phenyl rings in 1 through D2h transition state was found to exceed that in 2, evidencing repulsion interactions between ortho-methyl groups in 1. Quantum theory of atoms in molecules (QTAIM) and natural bond orbital analysis (NBO) were used for analysis of interactions in the target anions. NBO analysis reveals sufficiently strong C-H∙∙∙Cu intra-anionic hydrogen bonding interactions in all conformers of 1 and weaker second order orbital interactions between C-H bonds of ortho-methyl groups in D2 and D2h conformers. On the other hand, QTAIM predicts bond paths between hydrogen atoms in the last two conformers only evidencing H∙∙∙H bonding interactions.2 A rigorous QTAIM and NBO analyses were performed to establish how the θ magnitude affects a relation of attractive and repulsive interactions between ortho-methyl groups in 1. 1 Leoni, P.; Pasquali, M.; Ghilardi, C. A. J. Chem. Soc. Chem. Commun. 1983, 240. 2 Matta, C. F.; Hernández-Trujillo, J.; Tang, T.-H.; Bader, R. F. W. Chem. Eur. J. 2003, 9, 1940.