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_4111589
_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 H89 O3 Si3 Ta'
_chemical_formula_weight         883.33
_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   difmap
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-97
_cell_angle_alpha                90.00
_cell_angle_beta                 91.57(2)
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   13.115(7)
_cell_length_b                   20.965(8)
_cell_length_c                   17.257(6)
_cell_measurement_temperature    173(2)
_cell_volume                     4743(4)
_computing_cell_refinement       'Bruker SAINT'
_computing_data_collection       'Bruker SMART'
_computing_data_reduction        'Bruker SAINT'
_computing_molecular_graphics    'Bruker SHELXTL'
_computing_publication_material  'Bruker 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 0.990
_diffrn_measured_fraction_theta_max 0.990
_diffrn_measurement_device_type  'Bruker 1K CCD area detector'
_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  0.0625
_diffrn_reflns_av_sigmaI/netI    0.0503
_diffrn_reflns_limit_h_max       18
_diffrn_reflns_limit_h_min       -13
_diffrn_reflns_limit_k_max       29
_diffrn_reflns_limit_k_min       -29
_diffrn_reflns_limit_l_max       23
_diffrn_reflns_limit_l_min       -24
_diffrn_reflns_number            60972
_diffrn_reflns_theta_full        30.51
_diffrn_reflns_theta_max         30.51
_diffrn_reflns_theta_min         1.53
_exptl_absorpt_coefficient_mu    2.424
_exptl_absorpt_correction_T_max  0.7936
_exptl_absorpt_correction_T_min  0.4439
_exptl_absorpt_correction_type   SADABS
_exptl_crystal_colour            red
_exptl_crystal_density_diffrn    1.237
_exptl_crystal_density_meas      0
_exptl_crystal_description       irregular
_exptl_crystal_F_000             1872
_exptl_crystal_size_max          0.40
_exptl_crystal_size_mid          0.30
_exptl_crystal_size_min          0.10
_refine_diff_density_max         2.390
_refine_diff_density_min         -1.267
_refine_diff_density_rms         0.115
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.008
_refine_ls_hydrogen_treatment    isotropic
_refine_ls_matrix_type           full
_refine_ls_number_parameters     748
_refine_ls_number_reflns         14350
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.008
_refine_ls_R_factor_all          0.0608
_refine_ls_R_factor_gt           0.0344
_refine_ls_shift/su_max          3.493
_refine_ls_shift/su_mean         0.082
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0447P)^2^+1.7205P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0755
_refine_ls_wR_factor_ref         0.0862
_reflns_number_gt                10581
_reflns_number_total             14350
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            ja046180ksi20040706_120230.cif
_cod_data_source_block           kh1
_cod_original_cell_volume        4743(3)
_cod_database_code               4111589