COCRYSTALLIZATION OF ORGANOMETALLIC CLUSTERS - HOMOMOLECULAR AND HETEROMOLECULAR CRYSTALS OF RU6C(CO)14(ETA(6)-C6H4ME2) AND RU6C(CO)11(ETA(6)-C6H4ME2)2

The molecular structure of Ru6C(CO)11(eta6-C6H4Me2)2 (2) has been esta blished by the single crystal X-ray diffraction method in its crystall ine form B. The species has also been found to cocrystallize with Ru6C (CO)14(eta6-C6H4Me2) (1), and the structure of the heteromolecular coc rystal C has been determined. A homomolecular crystal of 1 (crystal A) had been discovered previously. The mono- and bis(xylene) derivatives in their homo- and heteromolecular crystals have been compared in ter ms of molecular and crystal structure, intermolecular interlocking, an d packing potential energies. Crystal B, containing only molecules of type 2, is monoclinic, space group Pn, a = 10.242(3) angstrom, b = 14. 047(6) angstrom, c = 11.242(2) angstrom, beta = 106.15(2)-degrees, V = 1553.6(9) angstrom3, Z = 4. Cocrystal C, formed by 1 and 2, is tricli nic, space group P1BAR, a = 9.852(4) angstrom, b = 10.444(9) angstrom, c = 32.320(10) angstrom, alpha = 95.65(6)-degrees, beta = 92.03(4)-de grees, gamma = 115.29(4)-degrees, V = 2981(3) angstrom3, Z = 2 on each molecular unit. It has been shown that a precise relationship exists between the crystal structures of the homomolecular crystals A and B a nd that of the heteromolecular crystal C, the last being essentially f ormed by bimolecular layers similar to those present in the separate c rystals. The three crystal forms also compare strictly in terms of pac king efficiency and crystal cohesion.