Rare Au···H Interactions in Gold(I) Complexes of Bulky Phosphines Derived from 2,6-Dibenzhydryl-4-methylphenyl Core

Gold (I) complexes of sterically demanding phosphines derived from 2, 6-dibenzhydryl-4-methylphenyl core viz: 2, 6-dibenzhydryl-N, N-bis ( (diphenylphosphane) -methyl) -4-methylaniline (1), (2, 6-dibenzhydryl-4-methylphenyl) -diphenylphosphane (2), N- (2, 6-dibenzhydryl-4-methylphenyl) -1, 1-diphenylphosphanamine (3), and (2, 6-dibenzhydryl-4-methylphenoxy) -diphenylphosphane (4) are described. The reaction of 1 with 2 equiv of AuCl (SMe2) in dichloromethane yielded AuCl2Ar*N (CH2PPh2) 2 (5), which on further treatment with 2 equiv of AgSbF6 and 1 equiv of 1 produced 12-membered dimeric complex Au2μ- (Ar*N (CH2PPh2) 2) 2 (SbF6) 2 (6). A similar reaction of 5 with AgSbF6 in CH3CN afforded Au (NCCH3) 2Ar*N (CH2PPh2) 2 (SbF6) 2 (7). Equimolar reactions of bulky phosphines 2, 3, and 4 with AuCl (SMe2) resulted in AuCl (PPh2Ar*) (8), AuCl (PPh2NHAr*) (9), and AuCl (PPh2OAr*) (10). Complexes 9 and 10 on treatment with AgSbF6 in CH3CN produced the cationic complexes Au (NCCH3) (PPh2NHAr*) (SbF6) (11) and Au (NCCH3) (PPh2OAr*) (SbF6) (12), respectively. The molecular structure of complex 6 revealed the presence of a strong intramolecular aurophilic interaction with a Au···Au distance of 2. 9720 (4) Å. Careful analysis of molecular structure of 5 revealed the presence of rare Au···H-C (sp3) interactions between the gold (I) atom and one of the methylene protons of -NCH2PPh2 groups. The solution 1H NMR signals of the methylene protons of 5 showed a considerable downfield shift (∼1 ppm) compared to that of the free ligand indicating their interactions (Au···H) with the Au atom. Complexes 8 and 10 also showed Au···H interactions in their molecular structures. The existence of the Au···H interaction was studied by variable temperature 1H NMR data in the case of complex 5 and further evinced by the QTAIM analysis in complexes 5, 8, and 10.