Synthesis, X-ray structure, and hydrolytic chemistry of the highly potent antiviral polyniobotungstate A-α-[Si2Nb6W18O77]8‒
Kim, Gyu-Shik; Zeng, Huadong; Rhule, Jeffrey T.; Weinstock, Ira A.; Hill, Craig L.; Chemical Communications  (1999) 1651–; doi:10.1039/a903983j

data_7110595
_publ_section_title
;
 Synthesis, X-ray structure, and hydrolytic chemistry of the highly potent
 antiviral polyniobotungstate A-\a-[Si2Nb6W18O77]8--
;
_journal_issue                   17
_journal_name_full               'Chemical Communications'
_journal_page_first              1651
_journal_paper_doi               10.1039/a903983j
_journal_year                    1999
_chemical_formula_moiety         '[(C4H9)4N]6H2[Si2Nb6W18O77].(C2H5)2O'
_chemical_formula_sum            'C100 H228 N6 Nb6 O78 Si2 W18'
_chemical_formula_weight         6685.81
_chemical_name_systematic
; 
 ? 
;
_space_group_IT_number           29
_symmetry_cell_setting           orthorhombic
_symmetry_space_group_name_Hall  'P 2c -2ac'
_symmetry_space_group_name_H-M   'P c a 21'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-97
_cell_angle_alpha                90.00
_cell_angle_beta                 90.00
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   29.4854(3)
_cell_length_b                   20.3867(3)
_cell_length_c                   28.42470(10)
_cell_measurement_reflns_used    258
_cell_measurement_temperature    293(2)
_cell_volume                     17086.4(3)
_computing_cell_refinement       'Siemens XSCANS'
_computing_data_collection       'Siemens XSCANS'
_computing_data_reduction        'Siemens SHELXTL'
_computing_molecular_graphics    'Siemens SHELXTL'
_computing_publication_material  'Siemens SHELXTL'
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 1990)'
_diffrn_ambient_temperature      293(2)
_diffrn_measured_fraction_theta_full 1.000
_diffrn_measured_fraction_theta_max 1.000
_diffrn_measurement_device_type  'Siemens SMART CCD'
_diffrn_measurement_method       '\w scans'
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0895
_diffrn_reflns_av_sigmaI/netI    0.1129
_diffrn_reflns_limit_h_max       35
_diffrn_reflns_limit_h_min       -35
_diffrn_reflns_limit_k_max       22
_diffrn_reflns_limit_k_min       -24
_diffrn_reflns_limit_l_max       30
_diffrn_reflns_limit_l_min       -33
_diffrn_reflns_number            87737
_diffrn_reflns_theta_full        25.00
_diffrn_reflns_theta_max         25.00
_diffrn_reflns_theta_min         1.00
_exptl_absorpt_coefficient_mu    12.540
_exptl_absorpt_correction_T_max  0.7876
_exptl_absorpt_correction_T_min  0.2549
_exptl_absorpt_correction_type   empirical
_exptl_crystal_colour            colorless
_exptl_crystal_density_diffrn    2.570
_exptl_crystal_description       needle
_exptl_crystal_F_000             12232
_exptl_crystal_size_max          0.15
_exptl_crystal_size_mid          0.10
_exptl_crystal_size_min          0.02
_refine_diff_density_max         2.317
_refine_diff_density_min         -1.366
_refine_diff_density_rms         0.277
_refine_ls_abs_structure_details 'Flack H D (1983), Acta Cryst. A39, 876-881'
_refine_ls_abs_structure_Flack   -0.008(6)
_refine_ls_extinction_coef       0.000016(2)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method     SHELXL
_refine_ls_goodness_of_fit_ref   0.988
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           fullcycle
_refine_ls_number_parameters     1348
_refine_ls_number_reflns         28106
_refine_ls_number_restraints     1
_refine_ls_restrained_S_all      0.988
_refine_ls_R_factor_all          0.0919
_refine_ls_R_factor_gt           0.0506
_refine_ls_shift/su_max          0.030
_refine_ls_shift/su_mean         0.002
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0463P)^2^+0.0000P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0941
_refine_ls_wR_factor_ref         0.1107
_reflns_number_gt                19664
_reflns_number_total             28106
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            903983jsup1.cif
_cod_data_source_block           hill19
_cod_original_sg_symbol_H-M      Pca2(1)
_cod_database_code               7110595