Shape-selective binding of nitriles to the inorganic cavitand, V 12O 324−

Abstract

The benzonitrile guest-host complex [C 6H 5CN ⊂V 12O 24 4−)] has been prepared by thermal dehydration of H 2V 10O 28 4− in C 6H 5CN. Single crystal X-ray structural analysis of its solvated tetraphenylphosphoniumsalt 1 2 {(V 12O 32)[P(C 6H 5) 4] 4-(C 6H 5CN) 6} [ b = 19.392(9), b =11.679(4), c = 30.881(15), β = 107.78(4), P2/c-C 2h 4 (No. 13)] revealed the presence of P(C 6H 5) 4 + cations, C 6H 5CN molecules of solvation, and discrete [C 6H 5CN⊂(V 12O 32 4−)] ions in which an benzonitrile molecule is located in the center of a V 12O 32 4− cavitand. The V 12O 32 4− ion binds CH 3CN in preference to C 6H 5CN in C 6H 5NO 2 with K eq =10±3 for the equation CH 3CN + [C 6H 5CN⊂(V 12O 32 4−)] =C 6H 5CN + [CH 3CNc(V 12O 32 4−)]. According to computer modeling studies, van der Waals forces can account for the gross structural features of [CH 3CN⊂(V 12O 32 4−)] and [C 6H 5CN⊂(V 12O 32 4−)], but metal-ligand interactions are responsible for preventing a close approach of the guest molecules to the interior walls of the host cavity.