Reaction of dimethylamine with 4,5-dichloro-4-cyclopenten-1,3-dione: X-ray diffraction structure and cyclic voltammetric data for ClC=C(NMe2)C(O)CH2C(O)

Dimethylamine reacts with 4,5-dichloro-4-cyclopenten-1,3-dione (1) to give the mono-substituted amine compound 4-dimethylamino-5-chloro-4-cyclopenten-1,3-dione (2) as the sole isolable product. Attempts to replace the remaining chlorine group in 2 by a second dimethylamine group have been unsuccessful. Compound 2 has been isolated and characterized in solution by IR and NMR (1H and 13C) spectroscopy, and the solid-state structure for ClC=C(NMe2)C(O)CH2C(O) has been determined by X-ray diffraction analysis. ClC=C(NMe2)C(O)CH2C(O) crystallizes in the triclinic space group P1, a = 7.2224(4) Å, b = 7.9008(6) Å, c = 8.3284(8) Å, α = 63.803(6)°, β = 67.401(6)°, γ = 87.889(5)°, V = 388.59(6) Å3, Z = 2, dcalc = 1.484 g·cm-3; R = 0.0422, Rw = 0.0450 for 1552 observed reflections with l > 3σ(l). The cyclic voltammetric behavior of ClC=C(NMe2)C(O)CH2C(O) has been explored at a platinum electrode in CH2Cl2 and THF, and the orbital composition of the HOMO and LUMO in 2 was established by extended Hückel molecular orbital calculations on the model compound ClC=C(NH2)C(O)CH2C(O). The cyclic voltammetry data of 2 is contrasted with the known diphosphine compound 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd; 3) and predictions concerning the ability of ClC=C(NMe2)C(O)CH2C(O) to function as an electron reservoir in organometallic compounds is discussed.