SYNTHESIS, CRYSTAL-STRUCTURES, AND VIBRAT IONAL-SPECTRA OF [(MO6X8(I)Y-6(A)](2-), X-I=CL, BR Y-A=NO3, NO2

By treatment of [(Mo6X8i)Y-6(a)](2-); X-i = Y-a = Cl, Br with AgNO3 or AgNO2 by strictly exclusion of oxygene in acetone the hexanitrato and hexanitrito cluster anions [(Mo6X8i)Y-6(a)](2-), Y-a = NO2, NO3 are f ormed. X-ray structure determinations of (Ph4As)(2)[(Mo6Cl8i)(NO3)(6)( a)]. 2 Me2CO (1) (monoclinic, space group P2(1)/n, a = 12.696(3), b = 21.526(1), c = 14.275(5) Angstrom, beta = 115.02(2)degrees, Z = 2), (n - Bu4N)(2)[(Mo6Br8i)(NO3)(6)(a)] . 2 CH2Cl2 (2) (monoclinic, space gro up P2(1)/n, a = 14.390(5), b = 11.216(5), c = 21.179(5) Angstrom, beta = 96.475(5)degrees, Z = 2) and (Ph4P)(2)[(Mo6Cl8i) (NO2)(6)(a)] (3) ( monoclinic, space group P2(1)/n, a = 11.823(5), b = 13.415(5), c = 19. 286(5) Angstrom, beta = 105.090(5)degrees, Z = 2) reveal the coordinat ion of the ligands via O atoms with (Mo-O)bond lengths of 2.11-2.13 An gstrom, and (MoON) angles of 122-131 degrees. The vibrational spectra of the nitrate compounds show the typical innerligand vibrations v(as) (NO2) (similar to 1500), v(s)(NO2) (similar to 1270) and v(NO) (simila r to 980 cm(-1)). The stretching vibrations v(N=O) at 1460-1490 cm(-1) and v(N-O) in the range of 950-1000 cm(-1) are characteristic for nit rito ligands coordinated via O atoms.