# Supplementary Material (ESI) for Chemical Communications # This journal is (c) The Royal Society of Chemistry 2009 data_global _journal_name_full Chem.Commun. _journal_coden_cambridge 0182 _journal_year ? _journal_volume ? _journal_page_first ? _publ_contact_author_name 'Piero Macchi' _publ_contact_author_email PIERO.MACCHI@UNIMI.IT loop_ _publ_author_name P.Macchi N.Casati A.Sironi data_oxhh50u _database_code_depnum_ccdc_archive 'CCDC 703783' _audit_creation_date 2008-09-26T13:40:15-00:00 _audit_creation_method 'WinGX routine CIF_UPDATE' #----------------------------------------------------------------------------# # CHEMICAL INFORMATION # #----------------------------------------------------------------------------# _chemical_name_systematic ; oxalic acid dihydrate ; _chemical_formula_sum 'C H3 O3' _chemical_formula_weight 63.03 #----------------------------------------------------------------------------# # UNIT CELL INFORMATION # #----------------------------------------------------------------------------# _symmetry_cell_setting ? _symmetry_space_group_name_H-M 'P 21/n' loop_ _symmetry_equiv_pos_as_xyz 'x, y, z' '-x+1/2, y+1/2, -z+1/2' '-x, -y, -z' 'x-1/2, -y-1/2, z-1/2' _cell_length_a 6.1169(8) _cell_length_b 3.6053(6) _cell_length_c 12.049(3) _cell_angle_alpha 90.00 _cell_angle_beta 106.303(12) _cell_angle_gamma 90.00 _cell_volume 255.05(8) _cell_formula_units_Z 4 _cell_measurement_temperature 295(2) _cell_measurement_reflns_used 785 _cell_measurement_theta_min 4.3 _cell_measurement_theta_max 20.8 #----------------------------------------------------------------------------# # CRYSTAL INFORMATION # #----------------------------------------------------------------------------# _exptl_crystal_preparation 'mounted in a diamond-anvil cell ' loop_ _exptl_crystal_id _exptl_crystal_description _exptl_crystal_colour _exptl_crystal_size_max _exptl_crystal_size_mid _exptl_crystal_size_min 1 prism colourless 0.11 0.10 0.09 2 prism colourless 0.11 0.09 0.08 _exptl_crystal_density_diffrn 1.642 _exptl_crystal_density_method 'not measured' _exptl_crystal_F_000 132 #----------------------------------------------------------------------------# # ABSORPTION CORRECTION # #----------------------------------------------------------------------------# _exptl_absorpt_coefficient_mu 0.174 _exptl_absorpt_correction_type empirical _exptl_absorpt_correction_T_min 0.8 _exptl_absorpt_correction_T_max 1.0 _exptl_absorpt_process_details ; DAC absorption corrected with Absorb 6.0 (gaussian) (R.J. Angel, J. Appl. Cryst. 2004, 37(3), 486) Crystal absorption corrected with SADABS (empirical) Area-Detector Absorption Correction, (Siemens Industrial Automation, Inc.: Madison, WI, 1996) ; _exptl_special_details ; two crystals mounted in the cell ; #----------------------------------------------------------------------------# # DATA COLLECTION # #----------------------------------------------------------------------------# _diffrn_ambient_temperature 295(2) _diffrn_ambient_pressure 100 _diffrn_ambient_environment 'collected in a diamond anvil cell' _diffrn_radiation_wavelength 0.71069 _diffrn_radiation_type MoK\a _diffrn_radiation_source 'fine-focus sealed tube' _diffrn_radiation_monochromator graphite _diffrn_measurement_device_type ? _diffrn_measurement_method ? _diffrn_detector_area_resol_mean ? _diffrn_standards_number ? _diffrn_standards_interval_count ? _diffrn_standards_interval_time ? _diffrn_standards_decay_% ? _diffrn_reflns_number 2802 _diffrn_reflns_av_R_equivalents 0.0756 _diffrn_reflns_av_sigmaI/netI 0.0381 _diffrn_reflns_limit_h_min -7 _diffrn_reflns_limit_h_max 7 _diffrn_reflns_limit_k_min -4 _diffrn_reflns_limit_k_max 4 _diffrn_reflns_limit_l_min -13 _diffrn_reflns_limit_l_max 12 _diffrn_reflns_theta_min 4.31 _diffrn_reflns_theta_max 25.05 _reflns_number_total 263 _reflns_number_gt 214 _reflns_threshold_expression >2sigma(I) #----------------------------------------------------------------------------# # COMPUTER PROGRAMS USED # #----------------------------------------------------------------------------# _computing_data_collection ? _computing_cell_refinement ? _computing_data_reduction ? _computing_structure_solution ? _computing_structure_refinement 'SHELXL-97 (Sheldrick, 1997)' _computing_molecular_graphics ? _computing_publication_material ? #----------------------------------------------------------------------------# # REFINEMENT INFORMATION # #----------------------------------------------------------------------------# _refine_special_details ; Refinement of F^2^ against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The threshold expression of F^2^ > 2sigma(F^2^) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^2^ are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. ; _refine_ls_structure_factor_coef Fsqd _refine_ls_matrix_type full _refine_ls_weighting_scheme calc _refine_ls_weighting_details 'calc w=1/[\s^2^(Fo^2^)+(0.0707P)^2^+0.0324P] where P=(Fo^2^+2Fc^2^)/3' _atom_sites_solution_primary direct _atom_sites_solution_secondary difmap _atom_sites_solution_hydrogens geom _refine_ls_hydrogen_treatment mixed _refine_ls_extinction_method none _refine_ls_extinction_coef ? _refine_ls_number_reflns 263 _refine_ls_number_parameters 43 _refine_ls_number_restraints 2 _refine_ls_R_factor_all 0.0707 _refine_ls_R_factor_gt 0.0555 _refine_ls_wR_factor_ref 0.1325 _refine_ls_wR_factor_gt 0.1257 _refine_ls_goodness_of_fit_ref 1.247 _refine_ls_restrained_S_all 1.241 _refine_ls_shift/su_max 0.000 _refine_ls_shift/su_mean 0.000 #----------------------------------------------------------------------------# # ATOMIC TYPES, COORDINATES AND THERMAL PARAMETERS # #----------------------------------------------------------------------------# 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' O O 0.0106 0.0060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' loop_ _atom_site_label _atom_site_type_symbol _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv _atom_site_adp_type _atom_site_occupancy _atom_site_symmetry_multiplicity _atom_site_calc_flag _atom_site_refinement_flags _atom_site_disorder_assembly _atom_site_disorder_group C1 C -0.0450(5) -0.0528(9) 0.0502(4) 0.0362(12) Uani 1 1 d . . . O1 O -0.2197(4) -0.2312(7) 0.0365(3) 0.0461(11) Uani 1 1 d . . . O2 O 0.0840(4) 0.0596(7) 0.1487(2) 0.0480(11) Uani 1 1 d . . . H21 H 0.0106 -0.0117 0.2138 0.072 Uiso 1 1 calc R . . O3 O -0.0485(4) -0.1141(7) 0.3194(3) 0.0478(11) Uani 1 1 d D . . H31 H 0.065(6) -0.155(12) 0.393(2) 0.072 Uiso 1 1 d D . . H32 H -0.133(7) 0.059(10) 0.354(4) 0.072 Uiso 1 1 d D . . loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_22 _atom_site_aniso_U_33 _atom_site_aniso_U_23 _atom_site_aniso_U_13 _atom_site_aniso_U_12 C1 0.037(3) 0.0371(17) 0.033(3) -0.0005(19) 0.007(3) -0.0017(16) O1 0.0434(18) 0.0603(16) 0.035(2) -0.0003(14) 0.0126(18) -0.0157(12) O2 0.0439(18) 0.0666(17) 0.031(2) -0.0031(15) 0.0064(19) -0.0138(12) O3 0.0411(18) 0.0689(17) 0.034(2) 0.0038(15) 0.0115(17) 0.0100(13) #----------------------------------------------------------------------------# # MOLECULAR GEOMETRY # #----------------------------------------------------------------------------# _geom_special_details ; All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. ; loop_ _geom_bond_atom_site_label_1 _geom_bond_atom_site_label_2 _geom_bond_distance _geom_bond_site_symmetry_2 _geom_bond_publ_flag C1 O1 1.218(4) . ? C1 O2 1.292(4) . ? C1 C1 1.512(8) 3 ? O2 H21 1.0400 . ? O3 H31 0.9760(11) . ? O3 H32 0.9719(11) . ? loop_ _geom_angle_atom_site_label_1 _geom_angle_atom_site_label_2 _geom_angle_atom_site_label_3 _geom_angle _geom_angle_site_symmetry_1 _geom_angle_site_symmetry_3 _geom_angle_publ_flag O1 C1 O2 125.3(4) . . ? O1 C1 C1 121.8(4) . 3 ? O2 C1 C1 112.9(3) . 3 ? C1 O2 H21 109.5 . . ? H31 O3 H32 92(4) . . ? _diffrn_measured_fraction_theta_max 0.575 _diffrn_reflns_theta_full 25.05 _diffrn_measured_fraction_theta_full 0.575 _refine_diff_density_max 0.157 _refine_diff_density_min -0.195 _refine_diff_density_rms 0.061 _chemical_name_common 'oxalic acid dihydrate' #END data_oxhh51u _database_code_depnum_ccdc_archive 'CCDC 703784' _audit_creation_date 2008-09-26T13:40:15-00:00 _audit_creation_method 'WinGX routine CIF_UPDATE' #----------------------------------------------------------------------------# # CHEMICAL INFORMATION # #----------------------------------------------------------------------------# _chemical_name_systematic ; oxalic acid dihydrate ; _chemical_formula_sum 'C H3 O3' _chemical_formula_weight 63.03 #----------------------------------------------------------------------------# # UNIT CELL INFORMATION # #----------------------------------------------------------------------------# _symmetry_cell_setting ? _symmetry_space_group_name_H-M 'P 21/n' loop_ _symmetry_equiv_pos_as_xyz 'x, y, z' '-x+1/2, y+1/2, -z+1/2' '-x, -y, -z' 'x-1/2, -y-1/2, z-1/2' _cell_length_a 5.983(5) _cell_length_b 3.331(5) _cell_length_c 11.833(5) _cell_angle_alpha 90.000(6) _cell_angle_beta 106.15(3) _cell_angle_gamma 90.000(5) _cell_volume 226.5(4) _cell_formula_units_Z 4 _cell_measurement_temperature 295(2) _cell_measurement_reflns_used 888 _cell_measurement_theta_min 4.4 _cell_measurement_theta_max 22.1 #----------------------------------------------------------------------------# # CRYSTAL INFORMATION # #----------------------------------------------------------------------------# _exptl_crystal_preparation 'mounted in a diamond-anvil cell ' loop_ _exptl_crystal_id _exptl_crystal_description _exptl_crystal_colour _exptl_crystal_size_max _exptl_crystal_size_mid _exptl_crystal_size_min 1 prism colourless 0.11 0.08 0.09 2 prism colourless 0.10 0.08 0.08 _exptl_crystal_density_diffrn 1.848 _exptl_crystal_density_method 'not measured' _exptl_crystal_F_000 132 #----------------------------------------------------------------------------# # ABSORPTION CORRECTION # #----------------------------------------------------------------------------# _exptl_absorpt_coefficient_mu 0.196 _exptl_absorpt_correction_type empirical _exptl_absorpt_correction_T_min 0.82 _exptl_absorpt_correction_T_max 1.0 _exptl_absorpt_process_details ; DAC absorption corrected with Absorb 6.0 (gaussian) (R.J. Angel, J. Appl. Cryst. 2004, 37(3), 486) Crystal absorption corrected with SADABS (empirical) Area-Detector Absorption Correction, (Siemens Industrial Automation, Inc.: Madison, WI, 1996) ; _exptl_special_details ; two crystals mounted in the cell ; #----------------------------------------------------------------------------# # DATA COLLECTION # #----------------------------------------------------------------------------# _diffrn_ambient_temperature 295(2) _diffrn_ambient_pressure 1600000 _diffrn_ambient_environment 'collected in a diamond anvil cell' _diffrn_radiation_wavelength 0.71069 _diffrn_radiation_type MoK\a _diffrn_radiation_source 'fine-focus sealed tube' _diffrn_radiation_monochromator graphite _diffrn_measurement_device_type ? _diffrn_measurement_method ? _diffrn_detector_area_resol_mean ? _diffrn_standards_number ? _diffrn_standards_interval_count ? _diffrn_standards_interval_time ? _diffrn_standards_decay_% ? _diffrn_reflns_number 2447 _diffrn_reflns_av_R_equivalents 0.0796 _diffrn_reflns_av_sigmaI/netI 0.0351 _diffrn_reflns_limit_h_min -6 _diffrn_reflns_limit_h_max 6 _diffrn_reflns_limit_k_min -3 _diffrn_reflns_limit_k_max 3 _diffrn_reflns_limit_l_min -11 _diffrn_reflns_limit_l_max 11 _diffrn_reflns_theta_min 4.40 _diffrn_reflns_theta_max 25.15 _reflns_number_total 218 _reflns_number_gt 185 _reflns_threshold_expression >2sigma(I) #----------------------------------------------------------------------------# # COMPUTER PROGRAMS USED # #----------------------------------------------------------------------------# _computing_data_collection ? _computing_cell_refinement ? _computing_data_reduction ? _computing_structure_solution ? _computing_structure_refinement 'SHELXL-97 (Sheldrick, 1997)' _computing_molecular_graphics ? _computing_publication_material ? #----------------------------------------------------------------------------# # REFINEMENT INFORMATION # #----------------------------------------------------------------------------# _refine_special_details ; Refinement of F^2^ against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The threshold expression of F^2^ > 2sigma(F^2^) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^2^ are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. ; _refine_ls_structure_factor_coef Fsqd _refine_ls_matrix_type full _refine_ls_weighting_scheme calc _refine_ls_weighting_details 'calc w=1/[\s^2^(Fo^2^)+(0.0585P)^2^+0.0532P] where P=(Fo^2^+2Fc^2^)/3' _atom_sites_solution_primary direct _atom_sites_solution_secondary difmap _atom_sites_solution_hydrogens geom _refine_ls_hydrogen_treatment mixed _refine_ls_extinction_method none _refine_ls_extinction_coef ? _refine_ls_number_reflns 218 _refine_ls_number_parameters 44 _refine_ls_number_restraints 2 _refine_ls_R_factor_all 0.0560 _refine_ls_R_factor_gt 0.0409 _refine_ls_wR_factor_ref 0.1043 _refine_ls_wR_factor_gt 0.0952 _refine_ls_goodness_of_fit_ref 1.200 _refine_ls_restrained_S_all 1.193 _refine_ls_shift/su_max 0.000 _refine_ls_shift/su_mean 0.000 #----------------------------------------------------------------------------# # ATOMIC TYPES, COORDINATES AND THERMAL PARAMETERS # #----------------------------------------------------------------------------# 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' O O 0.0106 0.0060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' loop_ _atom_site_label _atom_site_type_symbol _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv _atom_site_adp_type _atom_site_occupancy _atom_site_symmetry_multiplicity _atom_site_calc_flag _atom_site_refinement_flags _atom_site_disorder_assembly _atom_site_disorder_group C1 C -0.0454(5) -0.0553(8) 0.0518(4) 0.0269(18) Uani 1 1 d . . . O1 O -0.2296(3) -0.2375(6) 0.0360(3) 0.0320(14) Uani 1 1 d . . . O2 O 0.0883(4) 0.0546(6) 0.1512(3) 0.0321(13) Uani 1 1 d . . . H21 H 0.0163 -0.0381 0.2192 0.048 Uiso 1 1 calc R . . O3 O -0.0494(3) -0.1354(6) 0.3202(3) 0.0305(12) Uani 1 1 d D . . H31 H 0.071(5) -0.175(10) 0.3944(19) 0.046 Uiso 1 1 d D . . H32 H -0.131(5) 0.064(9) 0.354(3) 0.046 Uiso 1 1 d D . . loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_22 _atom_site_aniso_U_33 _atom_site_aniso_U_23 _atom_site_aniso_U_13 _atom_site_aniso_U_12 C1 0.025(2) 0.0188(14) 0.032(4) 0.0041(18) -0.001(3) -0.0018(13) O1 0.0283(14) 0.0376(12) 0.030(3) 0.0003(13) 0.0087(18) -0.0104(10) O2 0.0329(13) 0.0409(13) 0.022(3) 0.0016(12) 0.007(2) -0.0109(10) O3 0.0259(12) 0.0404(13) 0.026(3) 0.0000(13) 0.0081(17) 0.0059(9) #----------------------------------------------------------------------------# # MOLECULAR GEOMETRY # #----------------------------------------------------------------------------# _geom_special_details ; All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. ; loop_ _geom_bond_atom_site_label_1 _geom_bond_atom_site_label_2 _geom_bond_distance _geom_bond_site_symmetry_2 _geom_bond_publ_flag C1 O1 1.226(4) . ? C1 O2 1.278(4) . ? C1 C1 1.518(9) 3 ? O2 H21 1.0590 . ? O3 H31 0.9780(12) . ? O3 H32 0.9719(13) . ? loop_ _geom_angle_atom_site_label_1 _geom_angle_atom_site_label_2 _geom_angle_atom_site_label_3 _geom_angle _geom_angle_site_symmetry_1 _geom_angle_site_symmetry_3 _geom_angle_publ_flag O1 C1 O2 126.0(4) . . ? O1 C1 C1 120.4(4) . 3 ? O2 C1 C1 113.6(3) . 3 ? C1 O2 H21 109.5 . . ? H31 O3 H32 93(3) . . ? _diffrn_measured_fraction_theta_max 0.549 _diffrn_reflns_theta_full 25.15 _diffrn_measured_fraction_theta_full 0.549 _refine_diff_density_max 0.180 _refine_diff_density_min -0.208 _refine_diff_density_rms 0.051 _chemical_name_common 'oxalic acid dihydrate' #END data_oxhh52u _database_code_depnum_ccdc_archive 'CCDC 703785' _audit_creation_date 2008-09-26T13:40:15-00:00 _audit_creation_method 'WinGX routine CIF_UPDATE' #----------------------------------------------------------------------------# # CHEMICAL INFORMATION # #----------------------------------------------------------------------------# _chemical_name_systematic ; oxalic acid dihydrate ; _chemical_formula_sum 'C H3 O3' _chemical_formula_weight 63.03 #----------------------------------------------------------------------------# # UNIT CELL INFORMATION # #----------------------------------------------------------------------------# _symmetry_cell_setting ? _symmetry_space_group_name_H-M 'P 21/n' loop_ _symmetry_equiv_pos_as_xyz 'x, y, z' '-x+1/2, y+1/2, -z+1/2' '-x, -y, -z' 'x-1/2, -y-1/2, z-1/2' _cell_length_a 5.8093(7) _cell_length_b 3.1657(9) _cell_length_c 11.676(4) _cell_angle_alpha 90.00 _cell_angle_beta 106.01(4) _cell_angle_gamma 90.00 _cell_volume 206.39(10) _cell_formula_units_Z 4 _cell_measurement_temperature 295(2) _cell_measurement_reflns_used 985 _cell_measurement_theta_min 4.5 _cell_measurement_theta_max 23.1 #----------------------------------------------------------------------------# # CRYSTAL INFORMATION # #----------------------------------------------------------------------------# _exptl_crystal_preparation 'mounted in a diamond-anvil cell ' loop_ _exptl_crystal_id _exptl_crystal_description _exptl_crystal_colour _exptl_crystal_size_max _exptl_crystal_size_mid _exptl_crystal_size_min 1 prism colourless 0.11 0.08 0.09 2 prism colourless 0.10 0.08 0.08 _exptl_crystal_density_diffrn 2.029 _exptl_crystal_density_method 'not measured' _exptl_crystal_F_000 132 #----------------------------------------------------------------------------# # ABSORPTION CORRECTION # #----------------------------------------------------------------------------# _exptl_absorpt_coefficient_mu 0.215 _exptl_absorpt_correction_type empirical _exptl_absorpt_correction_T_min 0.84 _exptl_absorpt_correction_T_max 1.0 _exptl_absorpt_process_details ; DAC absorption corrected with Absorb 6.0 (gaussian) (R.J. Angel, J. Appl. Cryst. 2004, 37(3), 486) Crystal absorption corrected with SADABS (empirical) Area-Detector Absorption Correction, (Siemens Industrial Automation, Inc.: Madison, WI, 1996) ; _exptl_special_details ; two crystals mounted in the cell ; #----------------------------------------------------------------------------# # DATA COLLECTION # #----------------------------------------------------------------------------# _diffrn_ambient_temperature 295(2) _diffrn_ambient_pressure 3600000 _diffrn_ambient_environment 'collected in a diamond anvil cell' _diffrn_radiation_wavelength 0.71069 _diffrn_radiation_type MoK\a _diffrn_radiation_source 'fine-focus sealed tube' _diffrn_radiation_monochromator graphite _diffrn_measurement_device_type ? _diffrn_measurement_method ? _diffrn_detector_area_resol_mean ? _diffrn_standards_number ? _diffrn_standards_interval_count ? _diffrn_standards_interval_time ? _diffrn_standards_decay_% ? _diffrn_reflns_number 2220 _diffrn_reflns_av_R_equivalents 0.0654 _diffrn_reflns_av_sigmaI/netI 0.0352 _diffrn_reflns_limit_h_min -6 _diffrn_reflns_limit_h_max 6 _diffrn_reflns_limit_k_min -3 _diffrn_reflns_limit_k_max 3 _diffrn_reflns_limit_l_min -10 _diffrn_reflns_limit_l_max 10 _diffrn_reflns_theta_min 4.50 _diffrn_reflns_theta_max 25.03 _reflns_number_total 198 _reflns_number_gt 170 _reflns_threshold_expression >2sigma(I) #----------------------------------------------------------------------------# # COMPUTER PROGRAMS USED # #----------------------------------------------------------------------------# _computing_data_collection ? _computing_cell_refinement ? _computing_data_reduction ? _computing_structure_solution ? _computing_structure_refinement 'SHELXL-97 (Sheldrick, 1997)' _computing_molecular_graphics ? _computing_publication_material ? #----------------------------------------------------------------------------# # REFINEMENT INFORMATION # #----------------------------------------------------------------------------# _refine_special_details ; Refinement of F^2^ against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The threshold expression of F^2^ > 2sigma(F^2^) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^2^ are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. ; _refine_ls_structure_factor_coef Fsqd _refine_ls_matrix_type full _refine_ls_weighting_scheme calc _refine_ls_weighting_details 'calc w=1/[\s^2^(Fo^2^)+(0.0700P)^2^+0.0154P] where P=(Fo^2^+2Fc^2^)/3' _atom_sites_solution_primary direct _atom_sites_solution_secondary difmap _atom_sites_solution_hydrogens geom _refine_ls_hydrogen_treatment mixed _refine_ls_extinction_method none _refine_ls_extinction_coef ? _refine_ls_number_reflns 198 _refine_ls_number_parameters 43 _refine_ls_number_restraints 2 _refine_ls_R_factor_all 0.0479 _refine_ls_R_factor_gt 0.0387 _refine_ls_wR_factor_ref 0.0984 _refine_ls_wR_factor_gt 0.0928 _refine_ls_goodness_of_fit_ref 1.140 _refine_ls_restrained_S_all 1.133 _refine_ls_shift/su_max 0.000 _refine_ls_shift/su_mean 0.000 #----------------------------------------------------------------------------# # ATOMIC TYPES, COORDINATES AND THERMAL PARAMETERS # #----------------------------------------------------------------------------# 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' O O 0.0106 0.0060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' loop_ _atom_site_label _atom_site_type_symbol _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv _atom_site_adp_type _atom_site_occupancy _atom_site_symmetry_multiplicity _atom_site_calc_flag _atom_site_refinement_flags _atom_site_disorder_assembly _atom_site_disorder_group C1 C -0.0458(4) -0.0534(8) 0.0530(4) 0.0172(15) Uani 1 1 d . . . O1 O -0.2398(3) -0.2404(5) 0.0353(2) 0.0250(11) Uani 1 1 d . . . O2 O 0.0907(3) 0.0560(6) 0.1532(3) 0.0266(12) Uani 1 1 d . . . H21 H 0.0118 -0.0464 0.2248 0.040 Uiso 1 1 calc R . . O3 O -0.0497(3) -0.1461(6) 0.3231(2) 0.0240(11) Uani 1 1 d D . . H31 H 0.082(4) -0.178(10) 0.3960(18) 0.036 Uiso 1 1 d D . . H32 H -0.136(5) 0.037(10) 0.364(3) 0.036 Uiso 1 1 d D . . loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_22 _atom_site_aniso_U_33 _atom_site_aniso_U_23 _atom_site_aniso_U_13 _atom_site_aniso_U_12 C1 0.0201(19) 0.0171(14) 0.014(4) -0.0002(14) 0.004(2) 0.0008(10) O1 0.0189(12) 0.0294(10) 0.027(2) 0.0007(10) 0.0069(14) -0.0069(8) O2 0.0246(13) 0.0322(11) 0.022(3) 0.0011(11) 0.0044(17) -0.0057(8) O3 0.0211(12) 0.0302(11) 0.022(2) 0.0017(11) 0.0084(15) 0.0025(7) #----------------------------------------------------------------------------# # MOLECULAR GEOMETRY # #----------------------------------------------------------------------------# _geom_special_details ; All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. ; loop_ _geom_bond_atom_site_label_1 _geom_bond_atom_site_label_2 _geom_bond_distance _geom_bond_site_symmetry_2 _geom_bond_publ_flag C1 O1 1.239(3) . ? C1 O2 1.267(5) . ? C1 C1 1.514(8) 3 ? O2 H21 1.1060 . ? O3 H31 0.9789(12) . ? O3 H32 0.9730(11) . ? loop_ _geom_angle_atom_site_label_1 _geom_angle_atom_site_label_2 _geom_angle_atom_site_label_3 _geom_angle _geom_angle_site_symmetry_1 _geom_angle_site_symmetry_3 _geom_angle_publ_flag O1 C1 O2 126.4(4) . . ? O1 C1 C1 118.6(4) . 3 ? O2 C1 C1 115.0(3) . 3 ? C1 O2 H21 109.5 . . ? H31 O3 H32 91(3) . . ? _diffrn_measured_fraction_theta_max 0.545 _diffrn_reflns_theta_full 25.03 _diffrn_measured_fraction_theta_full 0.545 _refine_diff_density_max 0.162 _refine_diff_density_min -0.196 _refine_diff_density_rms 0.053 _chemical_name_common 'oxalic acid dihydrate' #END data_oxhh53u _database_code_depnum_ccdc_archive 'CCDC 703786' _audit_creation_date 2008-09-26T13:40:15-00:00 _audit_creation_method 'WinGX routine CIF_UPDATE' #----------------------------------------------------------------------------# # CHEMICAL INFORMATION # #----------------------------------------------------------------------------# _chemical_name_systematic ; oxalic acid dihydrate ; _chemical_formula_sum 'C H3 O3' _chemical_formula_weight 63.03 #----------------------------------------------------------------------------# # UNIT CELL INFORMATION # #----------------------------------------------------------------------------# _symmetry_cell_setting ? _symmetry_space_group_name_H-M 'P 21/n' loop_ _symmetry_equiv_pos_as_xyz 'x, y, z' '-x+1/2, y+1/2, -z+1/2' '-x, -y, -z' 'x-1/2, -y-1/2, z-1/2' _cell_length_a 5.744(3) _cell_length_b 3.098(4) _cell_length_c 11.630(4) _cell_angle_alpha 90.00 _cell_angle_beta 106.150(10) _cell_angle_gamma 90.00 _cell_volume 198.8(3) _cell_formula_units_Z 4 _cell_measurement_temperature 295(2) _cell_measurement_reflns_used 478 _cell_measurement_theta_min 4.6 _cell_measurement_theta_max 23.8 #----------------------------------------------------------------------------# # CRYSTAL INFORMATION # #----------------------------------------------------------------------------# _exptl_crystal_preparation 'mounted in a diamond-anvil cell ' _exptl_crystal_description prism _exptl_crystal_colour colourless _exptl_crystal_size_max 0.10 _exptl_crystal_size_mid 0.08 _exptl_crystal_size_min 0.08 _exptl_crystal_density_diffrn 2.106 _exptl_crystal_density_method 'not measured' _exptl_crystal_F_000 132 #----------------------------------------------------------------------------# # ABSORPTION CORRECTION # #----------------------------------------------------------------------------# _exptl_absorpt_coefficient_mu 0.223 _exptl_absorpt_correction_type empirical _exptl_absorpt_correction_T_min 0.78 _exptl_absorpt_correction_T_max 1.0 _exptl_absorpt_process_details ; DAC absorption corrected with Absorb 6.0 (gaussian) (R.J. Angel, J. Appl. Cryst. 2004, 37(3), 486) Crystal absorption corrected with SADABS (empirical) Area-Detector Absorption Correction, (Siemens Industrial Automation, Inc.: Madison, WI, 1996) ; _exptl_special_details ; ? ; #----------------------------------------------------------------------------# # DATA COLLECTION # #----------------------------------------------------------------------------# _diffrn_ambient_temperature 295(2) _diffrn_ambient_pressure 5300000 _diffrn_ambient_environment 'collected in a diamond anvil cell' _diffrn_radiation_wavelength 0.71069 _diffrn_radiation_type MoK\a _diffrn_radiation_source 'fine-focus sealed tube' _diffrn_radiation_monochromator graphite _diffrn_measurement_device_type ? _diffrn_measurement_method ? _diffrn_detector_area_resol_mean ? _diffrn_standards_number ? _diffrn_standards_interval_count ? _diffrn_standards_interval_time ? _diffrn_standards_decay_% ? _diffrn_reflns_number 1086 _diffrn_reflns_av_R_equivalents 0.0635 _diffrn_reflns_av_sigmaI/netI 0.0357 _diffrn_reflns_limit_h_min -4 _diffrn_reflns_limit_h_max 4 _diffrn_reflns_limit_k_min -3 _diffrn_reflns_limit_k_max 3 _diffrn_reflns_limit_l_min -10 _diffrn_reflns_limit_l_max 11 _diffrn_reflns_theta_min 4.55 _diffrn_reflns_theta_max 24.48 _reflns_number_total 113 _reflns_number_gt 93 _reflns_threshold_expression >2sigma(I) #----------------------------------------------------------------------------# # COMPUTER PROGRAMS USED # #----------------------------------------------------------------------------# _computing_data_collection ? _computing_cell_refinement ? _computing_data_reduction ? _computing_structure_solution ? _computing_structure_refinement 'SHELXL-97 (Sheldrick, 1997)' _computing_molecular_graphics ? _computing_publication_material ? #----------------------------------------------------------------------------# # REFINEMENT INFORMATION # #----------------------------------------------------------------------------# _refine_special_details ; Refinement of F^2^ against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The threshold expression of F^2^ > 2sigma(F^2^) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^2^ are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. ; _refine_ls_structure_factor_coef Fsqd _refine_ls_matrix_type full _refine_ls_weighting_scheme calc _refine_ls_weighting_details 'calc w=1/[\s^2^(Fo^2^)+(0.1168P)^2^+0.1331P] where P=(Fo^2^+2Fc^2^)/3' _atom_sites_solution_primary direct _atom_sites_solution_secondary difmap _atom_sites_solution_hydrogens geom _refine_ls_hydrogen_treatment mixed _refine_ls_extinction_method none _refine_ls_extinction_coef ? _refine_ls_number_reflns 113 _refine_ls_number_parameters 23 _refine_ls_number_restraints 2 _refine_ls_R_factor_all 0.0659 _refine_ls_R_factor_gt 0.0569 _refine_ls_wR_factor_ref 0.1624 _refine_ls_wR_factor_gt 0.1531 _refine_ls_goodness_of_fit_ref 1.130 _refine_ls_restrained_S_all 1.118 _refine_ls_shift/su_max 0.000 _refine_ls_shift/su_mean 0.000 #----------------------------------------------------------------------------# # ATOMIC TYPES, COORDINATES AND THERMAL PARAMETERS # #----------------------------------------------------------------------------# 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' O O 0.0106 0.0060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' loop_ _atom_site_label _atom_site_type_symbol _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv _atom_site_adp_type _atom_site_occupancy _atom_site_symmetry_multiplicity _atom_site_calc_flag _atom_site_refinement_flags _atom_site_disorder_assembly _atom_site_disorder_group C1 C -0.048(2) -0.0530(17) 0.0535(7) 0.0215(18) Uiso 1 1 d . . . O1 O -0.2491(19) -0.2406(12) 0.0362(6) 0.0285(17) Uiso 1 1 d . . . O2 O 0.0953(16) 0.0613(13) 0.1527(6) 0.0297(15) Uiso 1 1 d . . . H21 H -0.0007 -0.0506 0.2436 0.045 Uiso 1 1 calc R . . O3 O -0.0456(19) -0.1497(13) 0.3225(6) 0.0302(16) Uiso 1 1 d D . . H31 H 0.05(3) -0.15(2) 0.408(4) 0.045 Uiso 1 1 d D . . H32 H -0.157(10) 0.03(3) 0.358(6) 0.045 Uiso 1 1 d D . . #----------------------------------------------------------------------------# # MOLECULAR GEOMETRY # #----------------------------------------------------------------------------# _geom_special_details ; All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. ; loop_ _geom_bond_atom_site_label_1 _geom_bond_atom_site_label_2 _geom_bond_distance _geom_bond_site_symmetry_2 _geom_bond_publ_flag C1 O2 1.268(7) . ? C1 O1 1.257(16) . ? C1 C1 1.53(3) 3 ? O2 H21 1.3650 . ? O3 H31 0.9950(12) . ? O3 H32 1.0130(12) . ? loop_ _geom_angle_atom_site_label_1 _geom_angle_atom_site_label_2 _geom_angle_atom_site_label_3 _geom_angle _geom_angle_site_symmetry_1 _geom_angle_site_symmetry_3 _geom_angle_publ_flag O2 C1 O1 127.6(12) . . ? O2 C1 C1 112.9(13) . 3 ? O1 C1 C1 119.6(7) . 3 ? C1 O2 H21 109.5 . . ? H31 O3 H32 79(9) . . ? _diffrn_measured_fraction_theta_max 0.337 _diffrn_reflns_theta_full 24.48 _diffrn_measured_fraction_theta_full 0.337 _refine_diff_density_max 0.256 _refine_diff_density_min -0.285 _refine_diff_density_rms 0.071 _chemical_name_common 'oxalic acid dihydrate'