TY - JOUR

T1 - Ligation-Enhanced π-Hole···π Interactions Involving Isocyanides: Effect of π-Hole···π Noncovalent Bonding on Conformational Stabilization of Acyclic Diaminocarbene Ligands

AU - Михердов, Александр Сергеевич

AU - Кинжалов, Михаил Андреевич

AU - Новиков, Александр Сергеевич

AU - Боярский, Вадим Павлович

AU - Боярская, Ирина Алексеевна

AU - Авдонцева, Маргарита Сергеевна

AU - Кукушкин, Вадим Юрьевич

PY - 2018/5/24

Y1 - 2018/5/24

N2 - The reaction of cis-[PdCl 2(CNXyl) 2] (Xyl = 2,6-Me 2C 6H 3) with the aminoazoles [1H-imidazol-2-amine (1), 4H-1,2,4-triazol-3-amine (2), 1H-tetrazol-5-amine (3), 1H-benzimidazol-2-amine (4), 1-alkyl-1H-benzimidazol-2-amines, where alkyl = Me (5), Et (6)] in a 2:1 ratio in the presence of a base in CHCl 3 at RT proceeds regioselectively and leads to the binuclear diaminocarbene complexes [(ClPdCNXyl) 2{μ-C(N-azolyl)N(Xyl)C=NXyl}] (7-12; 73-91%). Compounds 7-12 were characterized by C, H, N elemental analyses, high-resolution ESI +-MS, Fourier transform infrared spectroscopy, 1D ( 1H, 13C) and 2D ( 1H, 1H-COSY, 1H, 1H-NOESY, 1H, 13C-HSQC, 1H, 13C-HMBC) NMR spectroscopies, and X-ray diffraction (XRDn). Inspection of the XRDn data and results of the Hirshfeld surface analysis suggest the presence in all six structures of intramolecular π-hole isocyanide···π arene interactions between the electrophilic C atom of the isocyanide moiety and the neighboring arene ring. These interactions also result in distortion of the Pd-C=N-Xyl fragment from the linearity. Results of density functional theory calculations [M06/MWB28 (Pd) and 6-31G∗ (other atoms) level of theory] for model structures of 7-9 followed by the topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method) reveal the presence of these weak interactions also in a CHCl 3 solution, and their calculated strength is 1.9-2.2 kcal/mol. The natural bond orbital analysis of 7-9 revealed that π(C-C)Xyl → π∗(C-N)isocyanide charge transfer (CT) takes place along with the intramolecular π-hole isocyanide···π arene interactions. The observed π(C-C) Xyl → π∗(C-N) isocyanide CT is due to ligation of the isocyanide to the metal center, whereas in the cases of the uncomplexed p-CNC 6H 4NC and CNXyl species, the effects of CT are negligible. Available CCDC data were processed from the perspective of isocyanide-involving π-hole···π interactions, disclosed the role of metal coordination in the π-hole donor ability of isocyanides, and verified the π-hole isocyanide···π arene interaction effect on the stabilization of the in-conformation in metal-bound acyclic diaminocarbenes.

AB - The reaction of cis-[PdCl 2(CNXyl) 2] (Xyl = 2,6-Me 2C 6H 3) with the aminoazoles [1H-imidazol-2-amine (1), 4H-1,2,4-triazol-3-amine (2), 1H-tetrazol-5-amine (3), 1H-benzimidazol-2-amine (4), 1-alkyl-1H-benzimidazol-2-amines, where alkyl = Me (5), Et (6)] in a 2:1 ratio in the presence of a base in CHCl 3 at RT proceeds regioselectively and leads to the binuclear diaminocarbene complexes [(ClPdCNXyl) 2{μ-C(N-azolyl)N(Xyl)C=NXyl}] (7-12; 73-91%). Compounds 7-12 were characterized by C, H, N elemental analyses, high-resolution ESI +-MS, Fourier transform infrared spectroscopy, 1D ( 1H, 13C) and 2D ( 1H, 1H-COSY, 1H, 1H-NOESY, 1H, 13C-HSQC, 1H, 13C-HMBC) NMR spectroscopies, and X-ray diffraction (XRDn). Inspection of the XRDn data and results of the Hirshfeld surface analysis suggest the presence in all six structures of intramolecular π-hole isocyanide···π arene interactions between the electrophilic C atom of the isocyanide moiety and the neighboring arene ring. These interactions also result in distortion of the Pd-C=N-Xyl fragment from the linearity. Results of density functional theory calculations [M06/MWB28 (Pd) and 6-31G∗ (other atoms) level of theory] for model structures of 7-9 followed by the topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method) reveal the presence of these weak interactions also in a CHCl 3 solution, and their calculated strength is 1.9-2.2 kcal/mol. The natural bond orbital analysis of 7-9 revealed that π(C-C)Xyl → π∗(C-N)isocyanide charge transfer (CT) takes place along with the intramolecular π-hole isocyanide···π arene interactions. The observed π(C-C) Xyl → π∗(C-N) isocyanide CT is due to ligation of the isocyanide to the metal center, whereas in the cases of the uncomplexed p-CNC 6H 4NC and CNXyl species, the effects of CT are negligible. Available CCDC data were processed from the perspective of isocyanide-involving π-hole···π interactions, disclosed the role of metal coordination in the π-hole donor ability of isocyanides, and verified the π-hole isocyanide···π arene interaction effect on the stabilization of the in-conformation in metal-bound acyclic diaminocarbenes.

UR - http://www.scopus.com/inward/record.url?scp=85048257672&partnerID=8YFLogxK

U2 - 10.1021/acs.inorgchem.8b01027

DO - 10.1021/acs.inorgchem.8b01027

M3 - Article

VL - 57

SP - 6722−6733

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 11

ER -