Interplay between Metal[pi] Interactions and Hydrogen Bonds: Some Unusual Synergetic Effects of Coinage Metals and Substituents

• Published in: Chemphyschem Vol. 14; no. 14; p. 3341
• Main Authors: Gao, Meng, Yang, Xin, Cheng, Jianbo, Li, Qingzhong, Li, Wenzuo, Loffredo, Robert E
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 07.10.2013
• Subjects: Hydrogen bonds; Metals
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201300558

The ternary systems of C2H4 (C2H2 or C6H6)-MCN-HF (M=Cu, Ag, Au) and the respective binary systems were investigated to study the interplay between metalπ interactions and hydrogen bonds. The metalπ interactions in C2H4-MCN become stronger with the irregular order Ag<Cu<Au, while the hydrogen bonds in MCN-HF become weaker following the same order. The metalπ interactions are weakened as the H atoms in the π system are replaced with electron-withdrawing groups and enhanced by electron-donating groups. Type 1 of these ternary systems, in which MCN acts as Lewis base and acid simultaneously, is more stable than type 2, in which C2H4 acts as a double Lewis base. Negative cooperativity is present in type 2 ternary systems with a weakening of the metalπ interactions and the hydrogen bonds. Positive cooperativity is found in type 1 ternary systems with an enhancement of the metalπ interactions and the hydrogen bonds, except for C2(CN)4-AuCN-HF-1. The weaker metalπ interaction in C6H6-AuCN has a greater enhancing effect on the hydrogen bond in AuCN-HF than those in C2H4-AuCN and C2H2-AuCN. These synergetic effects were analyzed with the natural bond orbital and energy decomposition. [PUBLICATION ABSTRACT]