What can NMR spectroscopy of selenoureas and phosphinidenes teach us about the π-accepting abilities of N-heterocyclic carbenes?
Vummaleti, Sai V. C.; Nelson, David J.; Poater, Albert; Gómez-Suárez, Adrián; Cordes, David B.; Slawin, Alexandra M. Z.; Nolan, Steven P.; Cavallo, Luigi; Chem. Sci. 6 (2015) 1895–; doi:10.1039/C4SC03264K

data_1518501
_publ_section_title
;
 What can NMR spectroscopy of selenoureas and phosphinidenes teach us
 about the \p-accepting abilities of N-heterocyclic carbenes?
;
_journal_issue                   3
_journal_name_full               'Chem. Sci.'
_journal_page_first              1895
_journal_paper_doi               10.1039/C4SC03264K
_journal_volume                  6
_journal_year                    2015
_chemical_absolute_configuration ad
_chemical_formula_moiety         'C23 H32 N2 Se'
_chemical_formula_sum            'C23 H32 N2 Se'
_chemical_formula_weight         415.48
_chemical_name_systematic        '[Se(IAd)]'
_space_group_crystal_system      orthorhombic
_space_group_IT_number           33
_space_group_name_Hall           'P 2c -2n'
_space_group_name_H-M_alt        'P n a 21'
_symmetry_space_group_name_Hall  'P 2c -2n'
_symmetry_space_group_name_H-M   'P n a 21'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_update_record
;
2014-09-17 deposited with the CCDC.
2015-01-02 downloaded from the CCDC.
;
_cell_angle_alpha                90.0000
_cell_angle_beta                 90.0000
_cell_angle_gamma                90.0000
_cell_formula_units_Z            4
_cell_length_a                   23.300(2)
_cell_length_b                   7.0807(7)
_cell_length_c                   11.6415(13)
_cell_measurement_reflns_used    6161
_cell_measurement_temperature    173
_cell_measurement_theta_max      25.35
_cell_measurement_theta_min      1.75
_cell_volume                     1920.6(3)
_computing_cell_refinement       'CrystalClear-SM Expert 2.1 b29'
_computing_data_collection       'CrystalClear-SM Expert 2.1 b29 (Rigaku, 2013)'
_computing_data_reduction        'CrystalClear-SM Expert 2.1 b29'
_computing_molecular_graphics    'CrystalStructure 4.1'
_computing_publication_material  'CrystalStructure 4.1 (Rigaku, 2014)'
_computing_structure_refinement  'SHELXL2013 (Sheldrick, 2008)'
_computing_structure_solution    'DIRDIF99-PATTY (Gould, et al., 1999)'
_diffrn_ambient_temperature      173
_diffrn_detector_area_resol_mean 5.811
_diffrn_measured_fraction_theta_full 1.000
_diffrn_measured_fraction_theta_max 1.000
_diffrn_measurement_device_type  'Rigaku XtaLAB P200'
_diffrn_measurement_method       \w
_diffrn_radiation_type           'Mo K\a'
_diffrn_radiation_wavelength     0.71075
_diffrn_reflns_av_R_equivalents  0.0402
_diffrn_reflns_Laue_measured_fraction_full 1.000
_diffrn_reflns_Laue_measured_fraction_max 1.000
_diffrn_reflns_limit_h_max       28
_diffrn_reflns_limit_h_min       -28
_diffrn_reflns_limit_k_max       8
_diffrn_reflns_limit_k_min       -8
_diffrn_reflns_limit_l_max       14
_diffrn_reflns_limit_l_min       -13
_diffrn_reflns_number            22163
_diffrn_reflns_point_group_measured_fraction_full 0.999
_diffrn_reflns_point_group_measured_fraction_max 0.998
_diffrn_reflns_theta_full        25.242
_diffrn_reflns_theta_max         25.381
_diffrn_reflns_theta_min         1.748
_diffrn_standards_number         0
_exptl_absorpt_coefficient_mu    1.965
_exptl_absorpt_correction_T_max  0.906
_exptl_absorpt_correction_T_min  0.746
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'REQAB (Rigaku, 1998)'
_exptl_crystal_colour            colorless
_exptl_crystal_density_diffrn    1.437
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       prism
_exptl_crystal_F_000             872.00
_exptl_crystal_recrystallization_method
'Re-crystallisation from solvent: DCM, pentane'
_exptl_crystal_size_max          0.120
_exptl_crystal_size_mid          0.050
_exptl_crystal_size_min          0.050
_refine_diff_density_max         1.05
_refine_diff_density_min         -0.15
_refine_ls_abs_structure_details
;
 Flack x determined using 1490 quotients [(I+)-(I-)]/[(I+)+(I-)]
 (Parsons and Flack (2004), Acta Cryst. A60, s61).
;
_refine_ls_abs_structure_Flack   0.007(4)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.015
_refine_ls_hydrogen_treatment    constr
_refine_ls_number_parameters     235
_refine_ls_number_reflns         3522
_refine_ls_number_restraints     1
_refine_ls_R_factor_all          0.0257
_refine_ls_R_factor_gt           0.0238
_refine_ls_shift/su_max          0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w = 1/[\s^2^(Fo^2^)+(0.0357P)^2^+0.0000P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0562
_refine_ls_wR_factor_ref         0.0568
_reflns_number_gt                3326
_reflns_number_total             3522
_reflns_threshold_expression     F^2^>2.0\s(F^2^)
_cod_data_source_file            c4sc03264k2.cif
_cod_data_source_block           '[Se(IAd)]'
_cod_depositor_comments
'Adding full bibliography for 1518501--1518512.cif.'
_cod_database_code               1518501
_shelx_res_checksum              30547