Amphoteric Zinc(II) Hydride Cations [ZnH]⁺: Effect of a Bipyridyl Ligand

This is the authors' abstract. We don't add key points for this paper.

Terminal zinc hydride cations [(Me 2 bpy)ZnH(L)][BAr F 4 ] (Me 2 bpy = 6,6′-dimethyl-2,2′-dipyridyl; Ar F = 3,5-(CF 3 ) 2 C 6 H 3; L = THF, 1a; 4-(dimethylamino)pyridine, DMAP, 1b; pyridine, 1c; 4-(trifluoromethyl)pyridine, 1d ) show Zn–H distances in the expected range, as exemplified by single-crystal X-ray diffraction for the THF adduct 1a and the pyridine adduct 1c . With the exception of labile 1a, the ν(ZnH) stretching frequencies correlate with the electron donating character of the L ligand. The Zn–H bond shows amphoteric behavior. Reaction of 1a with ZnEt 2 gives the cationic ethyl complex [(Me 2 bpy)ZnEt(thf)][BAr F 4 ] ( 2a ), while it undergoes CO 2 insertion to form the cationic formato complex [(Me 2 bpy)Zn(OCHO)(thf)][BAr F 4 ] ( 3a ). Thermolysis of 3a at 80 °C gives the dinuclear metalation product 4a, which is also formed by photolysis of 1a . The Zn–H bond of 1a acts as a proton donor when treated with the N -heterocyclic carbene I t Bu (I t Bu = 1,3-di- tert -butylimidazol-2-ylidene), giving the imidazolium salt [I t BuH][BAr F 4 ], zinc metal, and Me 2 bpy. The deprotonation of the Zn–H bond in 1a occurs with ZnCp* 2 (Cp* = pentamethylcyclopentadienyl) to give the dizinc(I) cation [(Me 2 bpy)Zn–ZnCp*(thf)][BAr F 4 ] ( 6a ) and Cp*H. Reaction of 1a with Cp 2 MoH 2 (Cp = η 5 -cyclopentadienyl) leads to the heterobimetallic complex [(Me 2 bpy)Zn(μ-H)MoCp 2 ] + [BAr F 4 ] − ( 7 ) under H 2 elimination.