Protonation sites of organic bases with several nitrogen functions: crystal structures of salts of chlordiazepoxide, dihydralazine, and phenformin

Abstract

The crystal structures of 7-chloro-2-methylamino-5-phenyl-3H-1,4-benzodiazepine 4-oxide (chlordiazepoxide) hydrochloride (1), 1,4-dihydrazinophthalazine (dihydralazine) hydrosulphate trihydrate (2), and 1-(2-phenylethyl)biguanide (phenformin) hydrochloride (3) have been determined by X-ray diffraction. All have space group P2₁/c, and for (1): a= 13.120(5), b= 8.439(3), c= 15.070(6)Å, β= 107.81(3)°, Z= 4; for (2)a= 6.966(3), b= 11.099(4), c= 19.005(5)Å, β= 104.72(3)°, Z= 4; and for (3)a= 14.947(5), b= 9.396(3), c= 20.345(7)Å, β= 116.73(3), Z= 8. In (1) and (2) protonation occurs at a ring nitrogen atom, leading to amidinium systems. The second proton in (2) is attached to a terminal hydrazine nitrogen. The two independent cations in (3) have the same tautomeric form RHN·C(NH₂)NC(NH₂)₂. The structure of (1) was determined by direct methods, those of (2) and (3) by the heavy-atom method. The structures were refined to R 0.059, 0.076, and 0.082 for 2 967, 2 015, and 4 672 observed intensities.