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_4111590
_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            'C41 H91 Nb O3 Si3'
_chemical_formula_weight         821.33
_chemical_name_systematic
; 
 ? 
;
_space_group_IT_number           29
_symmetry_cell_setting           orthorhombic
_symmetry_space_group_name_Hall  'P 2c -2ac'
_symmetry_space_group_name_H-M   'P c a 21'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-97
_cell_angle_alpha                90.00
_cell_angle_beta                 90.00
_cell_angle_gamma                90.00
_cell_formula_units_Z            16
_cell_length_a                   24.8008(8)
_cell_length_b                   17.4613(5)
_cell_length_c                   45.1532(18)
_cell_measurement_temperature    173(2)
_cell_volume                     19553.8(11)
_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 0.926
_diffrn_measured_fraction_theta_max 0.926
_diffrn_measurement_device_type  'Bruker 1K CCD'
_diffrn_measurement_method       '0.3 deg. omega & phi 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  0.0683
_diffrn_reflns_av_sigmaI/netI    0.0631
_diffrn_reflns_limit_h_max       26
_diffrn_reflns_limit_h_min       -25
_diffrn_reflns_limit_k_max       18
_diffrn_reflns_limit_k_min       -15
_diffrn_reflns_limit_l_max       46
_diffrn_reflns_limit_l_min       -45
_diffrn_reflns_number            80231
_diffrn_reflns_theta_full        22.11
_diffrn_reflns_theta_max         22.11
_diffrn_reflns_theta_min         1.17
_exptl_absorpt_coefficient_mu    0.352
_exptl_absorpt_correction_T_max  0.9657
_exptl_absorpt_correction_T_min  0.9018
_exptl_absorpt_correction_type   SADABS
_exptl_crystal_colour            green
_exptl_crystal_density_diffrn    1.116
_exptl_crystal_description       block
_exptl_crystal_F_000             7200
_exptl_crystal_size_max          0.30
_exptl_crystal_size_mid          0.20
_exptl_crystal_size_min          0.10
_refine_diff_density_max         1.546
_refine_diff_density_min         -0.752
_refine_diff_density_rms         0.109
_refine_ls_abs_structure_details 'Flack H D (1983), Acta Cryst. A39, 876-881'
_refine_ls_abs_structure_Flack   0.27(7)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.058
_refine_ls_hydrogen_treatment    riding
_refine_ls_matrix_type           full
_refine_ls_number_parameters     1171
_refine_ls_number_reflns         20278
_refine_ls_number_restraints     9019
_refine_ls_restrained_S_all      1.322
_refine_ls_R_factor_all          0.1053
_refine_ls_R_factor_gt           0.0880
_refine_ls_shift/su_max          2.999
_refine_ls_shift/su_mean         0.152
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0894P)^2^+177.1745P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.2054
_refine_ls_wR_factor_ref         0.2182
_reflns_number_gt                16965
_reflns_number_total             20278
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            ja046180ksi20040706_120327.cif
_cod_data_source_block           asv610
_cod_database_code               4111590