#------------------------------------------------------------------------------ #$Date: 2013-12-28 13:58:47 +0000 (Sat, 28 Dec 2013) $ #$Revision: 91933 $ #$URL: svn://www.crystallography.net/cod/cif/2/20/32/2203204.cif $ #------------------------------------------------------------------------------ # # This file is available in the Crystallography Open Database (COD), # http://www.crystallography.net/. The original data for this entry # were provided by IUCr Journals, http://journals.iucr.org/. # # The file may be used within the scientific community so long as # proper attribution is given to the journal article from which the # data were obtained. # data_2203204 loop_ _publ_author_name 'Ferguson, George' 'O'Leary, Brian J.' 'Spalding, Trevor R.' _publ_section_title ; The arsenic(V) compound PhAs(O)(OH)(OSiPh~3~) ; _journal_issue 2 _journal_name_full 'Acta Crystallographica Section E' _journal_page_first m222 _journal_page_last m224 _journal_volume 60 _journal_year 2004 _chemical_formula_iupac '[As (C6 H5) (C18 H15 O Si) O (O H)]' _chemical_formula_moiety 'C24 H21 As O3 Si' _chemical_formula_sum 'C24 H21 As O3 Si' _chemical_formula_weight 460.42 _chemical_name_systematic ; ; _space_group_IT_number 2 _symmetry_cell_setting triclinic _symmetry_space_group_name_Hall '-P 1' _symmetry_space_group_name_H-M 'P -1' _atom_sites_solution_hydrogens geom _atom_sites_solution_primary direct _atom_sites_solution_secondary difmap _cell_angle_alpha 89.948(6) _cell_angle_beta 74.391(9) _cell_angle_gamma 68.276(5) _cell_formula_units_Z 2 _cell_length_a 8.3350(9) _cell_length_b 9.8193(8) _cell_length_c 14.8736(14) _cell_measurement_reflns_used 25 _cell_measurement_temperature 294.0(10) _cell_measurement_theta_max 21.56 _cell_measurement_theta_min 14.57 _cell_volume 1082.51(19) _computing_cell_refinement 'SET4 and CELDIM (Enraf--Nonius, 1992)' _computing_data_collection 'CAD-4-PC Software (Enraf--Nonius, 1992)' _computing_data_reduction 'DATRD2 in NRCVAX94 (Gabe et al., 1989)' _computing_molecular_graphics 'ORTEPII (Johnson, 1976) and PLATON (Spek, 2003)' _computing_publication_material SHELXL97 _computing_structure_refinement 'SHELXL97 (Sheldrick, 1997) and WinGX (Farrugia 1997)' _computing_structure_solution 'NRCVAX94 via Patterson heavy-atom method' _diffrn_ambient_temperature 294.0(10) _diffrn_measured_fraction_theta_full 0.999 _diffrn_measured_fraction_theta_max 0.999 _diffrn_measurement_device 'Enraf--Nonius CAD-4' _diffrn_measurement_method \q/2\q _diffrn_radiation_monochromator graphite _diffrn_radiation_source 'X-ray tube' _diffrn_radiation_type 'Mo K\a' _diffrn_radiation_wavelength 0.71073 _diffrn_reflns_av_R_equivalents 0.000 _diffrn_reflns_av_sigmaI/netI 0.0511 _diffrn_reflns_limit_h_max 9 _diffrn_reflns_limit_h_min -10 _diffrn_reflns_limit_k_max 12 _diffrn_reflns_limit_k_min 0 _diffrn_reflns_limit_l_max 19 _diffrn_reflns_limit_l_min -18 _diffrn_reflns_number 4751 _diffrn_reflns_theta_full 27.05 _diffrn_reflns_theta_max 27.0 _diffrn_reflns_theta_min 2.2 _diffrn_standards_decay_% 0 _diffrn_standards_interval_time 120 _diffrn_standards_number 3 _exptl_absorpt_coefficient_mu 1.647 _exptl_absorpt_correction_T_max 0.702 _exptl_absorpt_correction_T_min 0.549 _exptl_absorpt_correction_type psi-scan _exptl_absorpt_process_details 'North et al., 1968)' _exptl_crystal_colour colorless _exptl_crystal_density_diffrn 1.413 _exptl_crystal_density_meas 'not measured' _exptl_crystal_description lath _exptl_crystal_F_000 472 _exptl_crystal_size_max 0.42 _exptl_crystal_size_mid 0.38 _exptl_crystal_size_min 0.22 _refine_diff_density_max 0.303 _refine_diff_density_min -0.319 _refine_ls_extinction_coef 0.0044(9) _refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^ _refine_ls_extinction_method SHELXL97 _refine_ls_goodness_of_fit_ref 1.012 _refine_ls_hydrogen_treatment constr _refine_ls_matrix_type full _refine_ls_number_parameters 264 _refine_ls_number_reflns 4751 _refine_ls_number_restraints 0 _refine_ls_restrained_S_all 1.012 _refine_ls_R_factor_all 0.0700 _refine_ls_R_factor_gt 0.0352 _refine_ls_shift/su_max 0.002 _refine_ls_shift/su_mean 0.000 _refine_ls_structure_factor_coef Fsqd _refine_ls_weighting_details 'calc w = 1/[\s^2^(Fo^2^)+(0.0386P)^2^+0.0624P] where P = (Fo^2^+2Fc^2^)/3' _refine_ls_weighting_scheme calc _refine_ls_wR_factor_gt 0.0733 _refine_ls_wR_factor_ref 0.0795 _reflns_number_gt 3281 _reflns_number_total 4751 _reflns_threshold_expression I>2\s(I) _[local]_cod_data_source_file lh6160.cif _[local]_cod_data_source_block V _cod_original_cell_volume 1082.51(18) _cod_database_code 2203204 loop_ _symmetry_equiv_pos_as_xyz 'x, y, z' '-x, -y, -z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv _atom_site_adp_type _atom_site_calc_flag _atom_site_refinement_flags _atom_site_occupancy _atom_site_type_symbol As1 0.39390(4) 0.67046(3) 0.418064(19) 0.04001(11) Uani d . 1 As Si1 0.61356(10) 0.74695(8) 0.22909(5) 0.03830(18) Uani d . 1 Si O1 0.4832(2) 0.7677(2) 0.33838(12) 0.0500(5) Uani d . 1 O O2 0.4793(3) 0.49333(19) 0.37839(14) 0.0611(6) Uani d . 1 O O3 0.4450(3) 0.7061(2) 0.51450(14) 0.0606(6) Uani d . 1 O H3 0.4583 0.6354 0.5452 0.091 Uiso calc R 1 H C11 0.1419(4) 0.7557(3) 0.43679(18) 0.0467(7) Uani d . 1 C C12 0.0386(5) 0.6913(4) 0.4950(2) 0.0766(10) Uani d . 1 C H12 0.0930 0.6096 0.5236 0.092 Uiso calc R 1 H C13 -0.1459(6) 0.7484(6) 0.5107(3) 0.0995(14) Uani d . 1 C H13 -0.2162 0.7048 0.5496 0.119 Uiso calc R 1 H C14 -0.2235(5) 0.8662(6) 0.4699(3) 0.0910(14) Uani d . 1 C H14 -0.3480 0.9038 0.4809 0.109 Uiso calc R 1 H C15 -0.1243(5) 0.9330(4) 0.4123(3) 0.0802(11) Uani d . 1 C H15 -0.1814 1.0155 0.3850 0.096 Uiso calc R 1 H C16 0.0619(4) 0.8775(4) 0.3945(2) 0.0631(8) Uani d . 1 C H16 0.1311 0.9215 0.3551 0.076 Uiso calc R 1 H C21 0.6663(3) 0.9156(3) 0.22219(17) 0.0387(6) Uani d . 1 C C22 0.5343(4) 1.0514(3) 0.26476(19) 0.0476(7) Uani d . 1 C H22 0.4182 1.0576 0.2952 0.057 Uiso calc R 1 H C23 0.5720(4) 1.1777(3) 0.2629(2) 0.0551(7) Uani d . 1 C H23 0.4819 1.2674 0.2923 0.066 Uiso calc R 1 H C24 0.7429(5) 1.1701(4) 0.2176(2) 0.0623(8) Uani d . 1 C H24 0.7690 1.2544 0.2170 0.075 Uiso calc R 1 H C25 0.8739(5) 1.0385(4) 0.1737(2) 0.0675(9) Uani d . 1 C H25 0.9889 1.0336 0.1423 0.081 Uiso calc R 1 H C26 0.8365(4) 0.9115(3) 0.1756(2) 0.0570(8) Uani d . 1 C H26 0.9269 0.8226 0.1452 0.068 Uiso calc R 1 H C31 0.4854(3) 0.7400(3) 0.14577(18) 0.0405(6) Uani d . 1 C C32 0.4058(4) 0.6368(3) 0.1486(2) 0.0541(7) Uani d . 1 C H32 0.4146 0.5719 0.1943 0.065 Uiso calc R 1 H C33 0.3148(4) 0.6287(4) 0.0854(2) 0.0618(8) Uani d . 1 C H33 0.2638 0.5585 0.0885 0.074 Uiso calc R 1 H C34 0.2993(4) 0.7237(4) 0.0183(2) 0.0613(8) Uani d . 1 C H34 0.2378 0.7180 -0.0243 0.074 Uiso calc R 1 H C35 0.3739(4) 0.8274(4) 0.0135(2) 0.0645(9) Uani d . 1 C H35 0.3633 0.8923 -0.0321 0.077 Uiso calc R 1 H C36 0.4653(4) 0.8348(3) 0.0773(2) 0.0554(8) Uani d . 1 C H36 0.5149 0.9060 0.0739 0.067 Uiso calc R 1 H C41 0.8222(4) 0.5768(3) 0.20707(18) 0.0435(6) Uani d . 1 C C42 0.9197(5) 0.5417(4) 0.2714(2) 0.0820(12) Uani d . 1 C H42 0.8781 0.6026 0.3275 0.098 Uiso calc R 1 H C43 1.0782(5) 0.4178(5) 0.2542(3) 0.1036(16) Uani d . 1 C H43 1.1418 0.3965 0.2985 0.124 Uiso calc R 1 H C44 1.1412(5) 0.3266(4) 0.1722(3) 0.0781(11) Uani d . 1 C H44 1.2466 0.2426 0.1610 0.094 Uiso calc R 1 H C45 1.0495(4) 0.3596(3) 0.1077(3) 0.0653(9) Uani d . 1 C H45 1.0925 0.2986 0.0515 0.078 Uiso calc R 1 H C46 0.8912(4) 0.4840(3) 0.1249(2) 0.0501(7) Uani d . 1 C H46 0.8300 0.5052 0.0795 0.060 Uiso calc R 1 H Cg1 -0.0419 0.81202 0.45320 0.01 Uiso dum . 0.0 C Cg2 0.70432 1.04413 0.21946 0.01 Uiso dum . 0.0 C Cg3 0.39075 0.73190 0.08148 0.01 Uiso dum . 0.0 C Cg4 0.98367 0.45108 0.18958 0.01 Uiso dum . 0.0 C loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_22 _atom_site_aniso_U_33 _atom_site_aniso_U_12 _atom_site_aniso_U_13 _atom_site_aniso_U_23 As1 0.04947(18) 0.03256(15) 0.03596(16) -0.01297(12) -0.01315(11) 0.00818(10) Si1 0.0401(4) 0.0340(4) 0.0385(4) -0.0130(3) -0.0094(3) 0.0063(3) O1 0.0541(12) 0.0406(10) 0.0449(11) -0.0159(9) -0.0012(9) 0.0097(8) O2 0.0915(16) 0.0311(10) 0.0551(12) -0.0127(10) -0.0279(11) 0.0005(9) O3 0.0908(16) 0.0523(12) 0.0535(12) -0.0320(12) -0.0377(12) 0.0119(10) C11 0.0451(16) 0.0540(17) 0.0395(15) -0.0186(14) -0.0106(12) 0.0018(13) C12 0.070(2) 0.089(3) 0.069(2) -0.036(2) -0.0086(18) 0.0189(19) C13 0.063(3) 0.140(4) 0.090(3) -0.045(3) -0.004(2) 0.012(3) C14 0.047(2) 0.133(4) 0.078(3) -0.022(2) -0.012(2) -0.028(3) C15 0.069(2) 0.084(3) 0.076(3) -0.004(2) -0.038(2) -0.009(2) C16 0.059(2) 0.069(2) 0.062(2) -0.0187(17) -0.0280(16) 0.0103(17) C21 0.0434(15) 0.0387(14) 0.0383(14) -0.0184(12) -0.0149(12) 0.0082(11) C22 0.0457(16) 0.0434(16) 0.0533(17) -0.0177(13) -0.0132(13) 0.0038(13) C23 0.064(2) 0.0389(16) 0.0612(19) -0.0172(14) -0.0204(16) 0.0018(13) C24 0.082(2) 0.055(2) 0.068(2) -0.0436(19) -0.0260(18) 0.0160(16) C25 0.061(2) 0.070(2) 0.076(2) -0.0389(19) -0.0066(17) 0.0144(18) C26 0.0478(18) 0.0532(18) 0.0619(19) -0.0204(15) -0.0017(15) 0.0006(15) C31 0.0398(15) 0.0369(14) 0.0425(14) -0.0138(12) -0.0098(12) 0.0030(11) C32 0.0605(19) 0.0512(17) 0.0589(19) -0.0292(15) -0.0195(15) 0.0159(14) C33 0.067(2) 0.064(2) 0.072(2) -0.0403(18) -0.0247(17) 0.0086(17) C34 0.057(2) 0.074(2) 0.062(2) -0.0303(17) -0.0242(16) 0.0016(17) C35 0.079(2) 0.074(2) 0.061(2) -0.0408(19) -0.0358(18) 0.0256(17) C36 0.065(2) 0.0569(18) 0.0625(19) -0.0372(16) -0.0282(16) 0.0201(15) C41 0.0442(15) 0.0388(14) 0.0436(15) -0.0144(12) -0.0088(12) 0.0093(12) C42 0.069(2) 0.092(3) 0.0486(19) 0.010(2) -0.0186(17) -0.0004(18) C43 0.069(3) 0.126(4) 0.069(3) 0.017(2) -0.024(2) 0.031(3) C44 0.054(2) 0.063(2) 0.083(3) 0.0033(17) -0.0016(19) 0.023(2) C45 0.054(2) 0.0478(18) 0.077(2) -0.0153(15) 0.0020(17) -0.0083(16) C46 0.0472(17) 0.0447(16) 0.0581(18) -0.0188(14) -0.0132(14) 0.0014(14) loop_ _atom_type_symbol _atom_type_description _atom_type_scat_dispersion_real _atom_type_scat_dispersion_imag _atom_type_scat_source C C 0.0033 0.0016 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' H H 0.0000 0.0000 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' As As 0.0499 2.0058 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' O O 0.0106 0.0060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' Si Si 0.0817 0.0704 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' loop_ _diffrn_standard_refln_index_h _diffrn_standard_refln_index_k _diffrn_standard_refln_index_l 2 0 -8 -3 4 -1 -2 3 -2 loop_ _geom_angle_atom_site_label_1 _geom_angle_atom_site_label_2 _geom_angle_atom_site_label_3 _geom_angle _geom_angle_publ_flag O2 As1 O3 114.05(10) y O2 As1 O1 110.76(10) y O3 As1 O1 103.12(10) y O2 As1 C11 111.69(12) y O3 As1 C11 110.74(12) y O1 As1 C11 105.85(11) y O1 Si1 C31 109.47(11) y O1 Si1 C21 103.41(11) y C31 Si1 C21 111.04(11) y O1 Si1 C41 110.96(11) y C31 Si1 C41 110.40(12) y C21 Si1 C41 111.37(12) y Si1 O1 As1 140.79(12) y As1 O3 H3 109.5 ? C12 C11 C16 120.4(3) ? C12 C11 As1 117.3(2) ? C16 C11 As1 122.3(2) ? C11 C12 C13 119.7(4) ? C11 C12 H12 120.1 ? C13 C12 H12 120.1 ? C14 C13 C12 120.0(4) ? C14 C13 H13 120.0 ? C12 C13 H13 120.0 ? C13 C14 C15 121.5(4) ? C13 C14 H14 119.2 ? C15 C14 H14 119.2 ? C14 C15 C16 119.9(4) ? C14 C15 H15 120.1 ? C16 C15 H15 120.1 ? C11 C16 C15 118.5(3) ? C11 C16 H16 120.8 ? C15 C16 H16 120.8 ? C26 C21 C22 117.5(2) ? C26 C21 Si1 122.0(2) ? C22 C21 Si1 120.4(2) ? C23 C22 C21 121.4(3) ? C23 C22 H22 119.3 ? C21 C22 H22 119.3 ? C24 C23 C22 119.9(3) ? C24 C23 H23 120.1 ? C22 C23 H23 120.1 ? C25 C24 C23 119.8(3) ? C25 C24 H24 120.1 ? C23 C24 H24 120.1 ? C24 C25 C26 120.4(3) ? C24 C25 H25 119.8 ? C26 C25 H25 119.8 ? C21 C26 C25 121.0(3) ? C21 C26 H26 119.5 ? C25 C26 H26 119.5 ? C36 C31 C32 116.4(3) ? C36 C31 Si1 122.1(2) ? C32 C31 Si1 121.5(2) ? C33 C32 C31 121.7(3) ? C33 C32 H32 119.2 ? C31 C32 H32 119.2 ? C34 C33 C32 120.0(3) ? C34 C33 H33 120.0 ? C32 C33 H33 120.0 ? C33 C34 C35 120.2(3) ? C33 C34 H34 119.9 ? C35 C34 H34 119.9 ? C34 C35 C36 119.3(3) ? C34 C35 H35 120.3 ? C36 C35 H35 120.3 ? C31 C36 C35 122.3(3) ? C31 C36 H36 118.9 ? C35 C36 H36 118.9 ? C46 C41 C42 116.8(3) ? C46 C41 Si1 122.1(2) ? C42 C41 Si1 121.1(2) ? C41 C42 C43 121.4(3) ? C41 C42 H42 119.3 ? C43 C42 H42 119.3 ? C44 C43 C42 120.2(3) ? C44 C43 H43 119.9 ? C42 C43 H43 119.9 ? C45 C44 C43 119.5(3) ? C45 C44 H44 120.2 ? C43 C44 H44 120.2 ? C44 C45 C46 120.2(3) ? C44 C45 H45 119.9 ? C46 C45 H45 119.9 ? C41 C46 C45 121.9(3) ? C41 C46 H46 119.1 ? C45 C46 H46 119.1 ? loop_ _geom_bond_atom_site_label_1 _geom_bond_atom_site_label_2 _geom_bond_distance _geom_bond_publ_flag As1 O1 1.7086(17) y As1 O2 1.6551(18) y As1 O3 1.6740(18) y As1 C11 1.891(3) y Si1 O1 1.6585(18) y Si1 C21 1.860(3) y Si1 C31 1.857(3) y Si1 C41 1.862(3) y O3 H3 0.82 ? C11 C12 1.374(4) ? C11 C16 1.380(4) ? C12 C13 1.379(5) ? C12 H12 0.93 ? C13 C14 1.335(6) ? C13 H13 0.93 ? C14 C15 1.366(6) ? C14 H14 0.93 ? C15 C16 1.389(5) ? C15 H15 0.93 ? C16 H16 0.93 ? C21 C26 1.387(4) ? C21 C22 1.389(4) ? C22 C23 1.386(4) ? C22 H22 0.93 ? C23 C24 1.376(4) ? C23 H23 0.93 ? C24 C25 1.365(4) ? C24 H24 0.93 ? C25 C26 1.392(4) ? C25 H25 0.93 ? C26 H26 0.93 ? C31 C36 1.380(4) ? C31 C32 1.397(4) ? C32 C33 1.375(4) ? C32 H32 0.93 ? C33 C34 1.365(4) ? C33 H33 0.93 ? C34 C35 1.369(4) ? C34 H34 0.93 ? C35 C36 1.384(4) ? C35 H35 0.93 ? C36 H36 0.93 ? C41 C46 1.375(4) ? C41 C42 1.380(4) ? C42 C43 1.385(5) ? C42 H42 0.93 ? C43 C44 1.369(5) ? C43 H43 0.93 ? C44 C45 1.349(5) ? C44 H44 0.93 ? C45 C46 1.387(4) ? C45 H45 0.93 ? C46 H46 0.93 ? loop_ _geom_hbond_atom_site_label_D _geom_hbond_atom_site_label_H _geom_hbond_atom_site_label_A _geom_hbond_site_symmetry_A _geom_hbond_distance_DH _geom_hbond_distance_HA _geom_hbond_distance_DA _geom_hbond_angle_DHA _geom_hbond_publ_flag O3 H3 O2 2_666 0.82 1.73 2.528(3) 164 y C15 H15 Cg2 1_455 0.93 2.85 3.536 132 y C24 H24 Cg4 1_565 0.93 3.04 3.932 160 y C33 H33 Cg4 1_455 0.93 2.96 3.784 149 y C35 H35 Cg2 2_675 0.93 3.01 3.824 147 y C42 H42 Cg1 1_655 0.93 3.14 3.946 146 y loop_ _geom_torsion_atom_site_label_1 _geom_torsion_atom_site_label_2 _geom_torsion_atom_site_label_3 _geom_torsion_atom_site_label_4 _geom_torsion C31 Si1 O1 As1 74.2(2) C21 Si1 O1 As1 -167.43(18) C41 Si1 O1 As1 -47.9(2) O2 As1 O1 Si1 8.1(2) O3 As1 O1 Si1 130.5(2) C11 As1 O1 Si1 -113.1(2) O2 As1 C11 C12 56.0(3) O3 As1 C11 C12 -72.3(3) O1 As1 C11 C12 176.6(2) O2 As1 C11 C16 -124.0(2) O3 As1 C11 C16 107.7(2) O1 As1 C11 C16 -3.4(3) C16 C11 C12 C13 0.4(5) As1 C11 C12 C13 -179.6(3) C11 C12 C13 C14 -0.4(6) C12 C13 C14 C15 0.0(7) C13 C14 C15 C16 0.5(6) C12 C11 C16 C15 0.0(5) As1 C11 C16 C15 -179.9(2) C14 C15 C16 C11 -0.5(5) O1 Si1 C21 C26 139.7(2) C31 Si1 C21 C26 -103.0(2) C41 Si1 C21 C26 20.5(3) O1 Si1 C21 C22 -39.9(2) C31 Si1 C21 C22 77.4(2) C41 Si1 C21 C22 -159.1(2) C26 C21 C22 C23 -1.6(4) Si1 C21 C22 C23 178.0(2) C21 C22 C23 C24 0.5(4) C22 C23 C24 C25 0.8(5) C23 C24 C25 C26 -0.9(5) C22 C21 C26 C25 1.4(4) Si1 C21 C26 C25 -178.2(2) C24 C25 C26 C21 -0.2(5) O1 Si1 C31 C36 124.7(2) C21 Si1 C31 C36 11.1(3) C41 Si1 C31 C36 -112.9(2) O1 Si1 C31 C32 -56.1(2) C21 Si1 C31 C32 -169.7(2) C41 Si1 C31 C32 66.3(3) C36 C31 C32 C33 1.0(4) Si1 C31 C32 C33 -178.3(2) C31 C32 C33 C34 -0.5(5) C32 C33 C34 C35 -0.1(5) C33 C34 C35 C36 0.1(5) C32 C31 C36 C35 -1.0(5) Si1 C31 C36 C35 178.3(3) C34 C35 C36 C31 0.5(5) O1 Si1 C41 C46 138.3(2) C31 Si1 C41 C46 16.7(3) C21 Si1 C41 C46 -107.1(2) O1 Si1 C41 C42 -44.8(3) C31 Si1 C41 C42 -166.3(3) C21 Si1 C41 C42 69.8(3) C46 C41 C42 C43 -0.8(5) Si1 C41 C42 C43 -177.9(3) C41 C42 C43 C44 -0.2(7) C42 C43 C44 C45 1.0(6) C43 C44 C45 C46 -0.8(5) C42 C41 C46 C45 1.1(4) Si1 C41 C46 C45 178.1(2) C44 C45 C46 C41 -0.3(5) _cod_database_fobs_code 2203204 _journal_paper_doi 10.1107/S1600536804001217