文摘
Recrystallization of [PdCl2([9]aneS2O)] ([9]aneS2O = 1-oxa-4,7-dithiacyclononane), 1, and [PtCl2([9]aneS2O)], 2, by diffusion of Et2O vapor into solutions of the complexes in MeNO2 yielded three phases of 1 and two phases of 2. The known phase of 1, herein designated 伪-1, was obtained under ambient conditions. A second phase, designated 尾-1, was initially also obtained by this method; however, following the advent of a third phase, 纬-1, all subsequent efforts over a period of a year to crystallize 尾-1 yielded either 纬-1, obtained by carrying out the recrystallization at elevated temperature, or 伪-1, commonly found throughout the study. This persistent absence of a phase which could initially be crystallized with ease led us to the conclusion that 尾-1 was an example of a 鈥渄isappearing polymorph鈥? The first phase obtained of 2, designated 伪-2, was obtained by recrystallization under ambient conditions and is isomorphous and isostructural with 伪-1. The second phase 尾-2 was obtained by slight elevation of the recrystallization temperature and was found to be isomorphous and isostructural with 尾-1. Subsequently, 尾-2 was used to seed the growth of the disappearing polymorph 尾-1. No third phase of 2 (纬-2) has been isolated thus far.