THE ADDUCT FORMED BETWEEN DIMETHYLCADMIUM AND 2,2'-BIPYRIDYL, (2,2'-BIPYRIDYL)DIMETHYLCADMIUM(II) - CRYSTALLOGRAPHIC AND SPECTROSCOPIC STUDY

The reaction of dimethylcadmium with 2,2'-bipyridyl gives a 1:1 adduct (1). By heating 1, followed by trap to trap distillation of the evolved liquid, pure dimethylcadmium can be obtained. This process is more efficient than repeated vacuum distillation of crude dimethylcadmium obtained directly from a Grignard reaction. A sample of 1 was recrystallized by sublimation in vacuo to give yellow crystals whose structure has been determined. The crystals are orthorhombic and of space group Pbca with Z = 8, a = 15.710 (11) angstrom, b = 11.784 (12) angstrom, and c = 13.540 (10) angstrom. A total of 1038 reflections above background were collected on a diffractometer, and the structure was solved by the heavy-atom method. The cadmium atom is four-coordinate, being bound to two methyl groups [Cd-C(13) 2.172 (25) angstrom, Cd-C(14) 2.152 (22) angstrom] and two nitrogen atoms [Cd-N(1) 2.503 (13) angstrom, Cd-N(8) 2.535 (14) angstrom] from a chelating 2,2'-bipyridyl molecule. The C(13)-Cd-C(14) angle [148.4 (8)degrees] is larger than expected for an angle at a tetrahedral center, while a small ''bite'' angle [N(1)-Cd-N(8) 64.0 (5)degrees] is subtended by the ligand. The angle between the C(13)-Cd-C(14) and N(1)-Cd-N(8) planes is 79.0-degrees, and there are no inter- or intramolecular contacts that can be said to cause the deviation from the regular value of 90-degrees. Evidence for the existence of 1 not only as a solid but also as a vapor and in benzene and diethyl ether solutions was obtained from a spectroscopic study.