Even the normal is abnormal: N-heterocyclic carbene C(2) binding to a phosphaalkene without breaking the P[double bond, length as m-dash]C π-bond.
Majhi, Paresh Kumar; Chow, Keith C. F.; Hsieh, Tom H. H.; Bowes, Eric G.; Schnakenburg, Gregor; Kennepohl, Pierre; Streubel, Rainer; Gates, Derek P.; Chemical communications (Cambridge, England) 52 (2016) 998–1001; doi:10.1039/c5cc08181e

data_7118346
_publ_section_title
;
 Even the normal is abnormal: N-heterocyclic carbene C(2) binding to a
 phosphaalkene without breaking the P[double bond, length as m-dash]C
 \p-bond.
;
_journal_issue                   5
_journal_name_full               'Chemical communications (Cambridge, England)'
_journal_page_first              998
_journal_page_last               1001
_journal_paper_doi               10.1039/c5cc08181e
_journal_volume                  52
_journal_year                    2016
_chemical_formula_moiety         '2(C27 H32 B N2 P), C4 H8 O'
_chemical_formula_sum            'C58 H72 B2 N4 O P2'
_chemical_formula_weight         924.75
_space_group_crystal_system      monoclinic
_space_group_IT_number           15
_space_group_name_Hall           '-C 2yc'
_space_group_name_H-M_alt        'C 1 2/c 1'
_symmetry_space_group_name_Hall  '-C 2yc'
_symmetry_space_group_name_H-M   'C 1 2/c 1'
_atom_sites_solution_hydrogens   mixed
_audit_creation_method           SHELXL-2013
_audit_update_record
;
2015-09-28 deposited with the CCDC.
2015-11-16 downloaded from the CCDC.
;
_cell_angle_alpha                90
_cell_angle_beta                 108.32(1)
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   25.984(2)
_cell_length_b                   9.734(1)
_cell_length_c                   21.550(2)
_cell_measurement_reflns_used    2990
_cell_measurement_temperature    123(2)
_cell_measurement_theta_max      27.49
_cell_measurement_theta_min      2.83
_cell_volume                     5174.3(9)
_computing_cell_refinement       'STOE X-AREA'
_computing_data_collection       'STOE X-AREA'
_computing_data_reduction        'STOE X-RED'
_computing_structure_refinement  'SHELXL-2013 (Sheldrick, 2013)'
_computing_structure_solution    'SHELXS-2013 (Sheldrick, 2013)'
_diffrn_ambient_temperature      123(2)
_diffrn_measured_fraction_theta_full 0.998
_diffrn_measured_fraction_theta_max 0.998
_diffrn_measurement_device_type  'STOE IPDS2T'
_diffrn_measurement_method       'fine slicing \f and \w scans'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_unetI/netI     0.3540
_diffrn_reflns_Laue_measured_fraction_full 0.998
_diffrn_reflns_Laue_measured_fraction_max 0.998
_diffrn_reflns_limit_h_max       31
_diffrn_reflns_limit_h_min       -31
_diffrn_reflns_limit_k_max       11
_diffrn_reflns_limit_k_min       -11
_diffrn_reflns_limit_l_max       25
_diffrn_reflns_limit_l_min       -21
_diffrn_reflns_number            33319
_diffrn_reflns_point_group_measured_fraction_full 0.998
_diffrn_reflns_point_group_measured_fraction_max 0.998
_diffrn_reflns_theta_full        25.242
_diffrn_reflns_theta_max         25.249
_diffrn_reflns_theta_min         2.960
_exptl_absorpt_coefficient_mu    0.128
_exptl_absorpt_correction_T_max  0.9124
_exptl_absorpt_correction_T_min  0.7027
_exptl_absorpt_correction_type   numerical
_exptl_absorpt_process_details   'STOE XRed (TwinAbs, V1.44)'
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.187
_exptl_crystal_description       plate
_exptl_crystal_F_000             1984
_exptl_crystal_size_max          0.15
_exptl_crystal_size_mid          0.09
_exptl_crystal_size_min          0.03
_refine_diff_density_max         0.468
_refine_diff_density_min         -0.322
_refine_diff_density_rms         0.061
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   0.754
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     340
_refine_ls_number_reflns         33319
_refine_ls_number_restraints     58
_refine_ls_restrained_S_all      0.755
_refine_ls_R_factor_all          0.2228
_refine_ls_R_factor_gt           0.0776
_refine_ls_shift/su_max          0.001
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
;
 w=1/[\s^2^(Fo^2^)+(0.0461P)^2^]
 where P=(Fo^2^+2Fc^2^)/3
;
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1453
_refine_ls_wR_factor_ref         0.1936
_reflns_Friedel_coverage         0.000
_reflns_number_gt                10263
_reflns_number_total             33319
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            c5cc08181e2.cif
_cod_data_source_block           2547
_cod_depositor_comments
;
The following automatic conversions were performed:

'_exptl_absorpt_correction_type' value 'Numerical' changed to
'numerical' according to
/usr/data/users/saulius/crontab/automatic-downloads/rss-feeds/RSC/lib/dictionaries/cif_core.dic
dictionary named 'cif_core.dic' version 2.4.2 from 2011-04-26.

Automatic conversion script
Id: cif_fix_values 4268 2015-11-12 08:31:59Z antanas 
;
_cod_original_cell_volume        5174.2(1)
_cod_database_code               7118346
_shelx_estimated_absorpt_t_min   0.981
_shelx_estimated_absorpt_t_max   0.996
_shelxl_version_number           2013-2
_shelx_res_checksum              34955