Gravar-mail: (1R,2R,5R,6R,9S,10S,13S,14S)-1,6,7,8,9,14,15,16,17,17-Decachloro­penta­cyclo­[12.2.1.1(6,9).0(2,13).0(5,10)]octa­deca-7,15-diene