Adventures in Crystallization. Crystalline Salts Containing One, Two, or Even Three Chemically Distinct Cations Obtained from Solutions of [(Cyclohexyl Isocyanide)₄Rh^I]⁺

By judicious selection of crystallization conditions, it has been possible to obtain the salts of a common building block, [(RNC)4RhI]+, in single-crystal form suitable for X-ray diffraction. Salts that contain a single type of cation include deep green [(C6H11NC)12RhI3](SbF6)3, deep green [(C6H11NC)12RhI3](AsF6)3, and straw yellow [(C6H11NC)8RhII2Cl2](BF4)2 (in addition to the previously isolated trimeric deep green [(i-PrNC)12RhI3]Cl3·4.5H2O, monomeric, [(C6H11NC)4 RhI](BPh4), and [(i-PrNC)4RhI](BPh4) (both yellow), and red, dimeric [(C6H11NC)8RhI2]Cl2·0.5C6H6·2H2O). Ordered crystals of [(C6H11NC)12RhI3](SbF6)3 contain linear Rh3 units, while those of [(C6H11NC)12RhI3](AsF6)3 show disorder which is consistent with the presence of linear or bent Rh3 units. The formation of green [(C6H11NC)12RhV/III3Cl2][(C6H11NC)12RhI3]Cl6, and brown [(C6H11NC)12RhV/III3Cl2][(C6H11NC)8RhI2][(C6H11NC)4RhI]Cl6·16H2O·3C6H6 along with unidentified red-brown cubes from an air-exposed solution of [(C6H11NC)4RhI]Cl is reported. As their formulas indicate, green [(C6H11NC)12RhV/III3Cl2][(C6H11NC)12RhI3]Cl6, and brown [(C6H11NC)12RhV/III3Cl2][(C6H11NC)8RhI2][(C6H11NC)8RhI]Cl6·16H2O·3C6H6 contain two or three chemically distinct cations, respectively, but again are built from a common precursor, [(C6H11NC)4RhI]+.