Thermodynamics, Kinetics, and Mechanism of (silox)3M(olefin) to (silox)3M(alkylidene) Rearrangements (silox =tBu3SiO; M = Nb, Ta)
Kurt F. Hirsekorn; Adam S. Veige; Michael P. Marshak; Yelena Koldobskaya; Peter T. Wolczanski; Thomas R. Cundari; Emil B. Lobkovsky; Journal of the American Chemical Society 127 (2005) 4809–4830; doi:10.1021/ja046180k

data_4111588
_publ_section_title
;
 Thermodynamics, Kinetics, and Mechanism of (silox)3M(olefin) to
 (silox)3M(alkylidene) Rearrangements (silox =tBu3SiO; M = Nb, Ta)
;
_journal_name_full               'Journal of the American Chemical Society'
_journal_page_first              4809
_journal_page_last               4830
_journal_paper_doi               10.1021/ja046180k
_journal_volume                  127
_journal_year                    2005
_chemical_formula_sum            'C40 H83 O3 Si3 Ta'
_chemical_formula_weight         877.28
_chemical_name_systematic
; 
 ? 
;
_space_group_IT_number           14
_symmetry_cell_setting           monoclinic
_symmetry_space_group_name_Hall  '-P 2yn'
_symmetry_space_group_name_H-M   'P 1 21/n 1'
_atom_sites_solution_hydrogens   mixed
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-97
_cell_angle_alpha                90.00
_cell_angle_beta                 93.297(2)
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   13.3980(5)
_cell_length_b                   17.3954(5)
_cell_length_c                   20.4727(6)
_cell_measurement_temperature    173(2)
_cell_volume                     4763.5(3)
_computing_cell_refinement       SAINT+
_computing_data_collection       SMART
_computing_data_reduction        SAINT+
_computing_molecular_graphics    SHELXTL
_computing_publication_material  SHELXTL
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 1990)'
_diffrn_ambient_temperature      173(2)
_diffrn_measured_fraction_theta_full 0.999
_diffrn_measured_fraction_theta_max 0.999
_diffrn_measurement_device_type  'Bruker 1K CCD'
_diffrn_measurement_method       '0.3 deg. omega 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  0.0457
_diffrn_reflns_av_sigmaI/netI    0.0370
_diffrn_reflns_limit_h_max       13
_diffrn_reflns_limit_h_min       -17
_diffrn_reflns_limit_k_max       22
_diffrn_reflns_limit_k_min       -23
_diffrn_reflns_limit_l_max       27
_diffrn_reflns_limit_l_min       -27
_diffrn_reflns_number            52843
_diffrn_reflns_theta_full        28.28
_diffrn_reflns_theta_max         28.28
_diffrn_reflns_theta_min         1.54
_exptl_absorpt_coefficient_mu    2.413
_exptl_absorpt_correction_T_max  0.6439
_exptl_absorpt_correction_T_min  0.4453
_exptl_absorpt_correction_type   SADABS
_exptl_crystal_colour            colorless
_exptl_crystal_density_diffrn    1.223
_exptl_crystal_description       block
_exptl_crystal_F_000             1848
_exptl_crystal_size_max          0.40
_exptl_crystal_size_mid          0.20
_exptl_crystal_size_min          0.20
_refine_diff_density_max         1.440
_refine_diff_density_min         -1.011
_refine_diff_density_rms         0.104
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.072
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     492
_refine_ls_number_reflns         11815
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.072
_refine_ls_R_factor_all          0.0524
_refine_ls_R_factor_gt           0.0336
_refine_ls_shift/su_max          1.432
_refine_ls_shift/su_mean         0.063
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0359P)^2^+5.5312P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0741
_refine_ls_wR_factor_ref         0.0807
_reflns_number_gt                9250
_reflns_number_total             11815
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            ja046180ksi20040706_120155.cif
_cod_data_source_block           asv673
_cod_database_code               4111588