Supplementary Material (ESI) for Dalton Transactions
This journal is © The Royal Society of Chemistry 2004

data_global
_journal_name_full               'Dalton Trans.'

_journal_coden_Cambridge         0222

_publ_contact_author_name        'Prof David Rankin'
_publ_contact_author_address     
;
School of Chemistry
University of Edinburgh
West Mains Road
Edinburgh
EH9 3JJ
UNITED KINGDOM
;

_publ_contact_author_email       D.W.H.RANKIN@ED.AC.UK

_publ_section_title              
;
Molecular structure of
1,1,2,2-tetra-tert-butyldisilane: unusual structural motifs in
sterically crowded disilanes
;
loop_
_publ_author_name
'David Rankin'
'K. Hassler'
'Sarah L. Hinchley'
'Andrew Parkin'
'Heather E. Robertson'
;
G.Tekautz
;

data_sibu4b
_database_code_depnum_ccdc_archive 'CCDC 227310'

_audit_creation_method           SHELXL-97
_chemical_name_systematic        
;
?
;
_chemical_name_common            ?
_chemical_melting_point          ?
_chemical_formula_moiety         'tBu2 SiH SiH tBu2'
_chemical_formula_sum            'C16 H38 Si2'
_chemical_formula_weight         286.64

loop_
_atom_type_symbol
_atom_type_description
_atom_type_scat_dispersion_real
_atom_type_scat_dispersion_imag
_atom_type_scat_source
C C 0.0033 0.0016 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
H H 0.0000 0.0000 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'
Si Si 0.0817 0.0704 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'

_symmetry_cell_setting           Orthorhombic
_symmetry_space_group_name_H-M   Pnma

loop_
_symmetry_equiv_pos_as_xyz
'x, y, z'
'-x+1/2, -y, z+1/2'
'-x, y+1/2, -z'
'x+1/2, -y+1/2, -z+1/2'
'-x, -y, -z'
'x-1/2, y, -z-1/2'
'x, -y-1/2, z'
'-x-1/2, y-1/2, z-1/2'

_cell_length_a                   9.4428(8)
_cell_length_b                   12.8854(11)
_cell_length_c                   16.5058(13)
_cell_angle_alpha                90.00
_cell_angle_beta                 90.00
_cell_angle_gamma                90.00
_cell_volume                     2008.3(3)
_cell_formula_units_Z            4
_cell_measurement_temperature    150(2)
_cell_measurement_reflns_used    3023
_cell_measurement_theta_min      2.4
_cell_measurement_theta_max      26.5

_exptl_crystal_description       cylinder
_exptl_crystal_colour            Colourless
_exptl_crystal_size_max          1.00
_exptl_crystal_size_mid          0.30
_exptl_crystal_size_min          0.30
_exptl_crystal_density_meas      ?
_exptl_crystal_density_diffrn    0.948
_exptl_crystal_density_method    'not measured'
_exptl_crystal_F_000             648
_exptl_absorpt_coefficient_mu    0.165
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_correction_T_min  0.797
_exptl_absorpt_correction_T_max  1.000
_exptl_absorpt_process_details   sadabs

_exptl_special_details           
;
?
;

_diffrn_ambient_temperature      150(2)
_diffrn_radiation_wavelength     0.71073
_diffrn_radiation_type           MoK\a
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_monochromator  graphite
_diffrn_measurement_device_type  'Bruker SMART APEX CCD area detector'
_diffrn_measurement_method       'phi and omega scans'
_diffrn_detector_area_resol_mean ?
_diffrn_standards_number         0
_diffrn_standards_interval_count ?
_diffrn_standards_interval_time  ?
_diffrn_standards_decay_%        ?
_diffrn_reflns_number            10755
_diffrn_reflns_av_R_equivalents  0.0399
_diffrn_reflns_av_sigmaI/netI    0.0316
_diffrn_reflns_limit_h_min       -11
_diffrn_reflns_limit_h_max       11
_diffrn_reflns_limit_k_min       -12
_diffrn_reflns_limit_k_max       16
_diffrn_reflns_limit_l_min       -20
_diffrn_reflns_limit_l_max       20
_diffrn_reflns_theta_min         2.01
_diffrn_reflns_theta_max         26.39
_reflns_number_total             2141
_reflns_number_gt                1672
_reflns_threshold_expression     >2sigma(I)

_computing_data_collection       'Bruker SMART'
_computing_cell_refinement       'Bruker SMART'
_computing_data_reduction        'Bruker SHELXTL'
_computing_structure_solution    'SHELXTL '
_computing_structure_refinement  'SHELXTL '
_computing_molecular_graphics    'Bruker SHELXTL'
_computing_publication_material  'Bruker SHELXTL'

_refine_special_details          
;
Refinement of F^2^ against ALL reflections.  The weighted R-factor wR and
goodness of fit S are based on F^2^, conventional R-factors R are based
on F, with F set to zero for negative F^2^. The threshold expression of
F^2^ > 2sigma(F^2^) is used only for calculating R-factors(gt) etc. and is
not relevant to the choice of reflections for refinement.  R-factors based
on F^2^ are statistically about twice as large as those based on F, and R-
factors based on ALL data will be even larger.
;

_refine_ls_structure_factor_coef Fsqd
_refine_ls_matrix_type           full
_refine_ls_weighting_scheme      calc
_refine_ls_weighting_details     
'calc w=1/[\s^2^(Fo^2^)+(0.0719P)^2^+0.9764P] where P=(Fo^2^+2Fc^2^)/3'
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_atom_sites_solution_hydrogens   geometric/difmap
_refine_ls_hydrogen_treatment    'riding, rotating and restrained'
_refine_ls_extinction_method     none
_refine_ls_extinction_coef       0
_refine_ls_number_reflns         2141
_refine_ls_number_parameters     146
_refine_ls_number_restraints     25
_refine_ls_R_factor_all          0.0815
_refine_ls_R_factor_gt           0.0646
_refine_ls_wR_factor_ref         0.1616
_refine_ls_wR_factor_gt          0.1520
_refine_ls_goodness_of_fit_ref   1.079
_refine_ls_restrained_S_all      1.082
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000

loop_
_atom_site_label
_atom_site_type_symbol
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_U_iso_or_equiv
_atom_site_adp_type
_atom_site_occupancy
_atom_site_symmetry_multiplicity
_atom_site_calc_flag
_atom_site_refinement_flags
_atom_site_disorder_assembly
_atom_site_disorder_group
Si1 Si 0.27358(9) 0.2500 0.60955(5) 0.0443(3) Uani 1 2 d SD . .
H1 H 0.154(3) 0.2500 0.6600(17) 0.048(9) Uiso 1 2 d SD . .
C1 C 0.3690(3) 0.1242(2) 0.63847(15) 0.0583(7) Uani 1 1 d D A .
C1A C 0.2560(7) 0.0240(5) 0.6399(3) 0.0670(18) Uani 0.50 1 d PD A 1
H1A1 H 0.2106 0.0175 0.5867 0.100 Uiso 0.50 1 calc PR A 1
H1A2 H 0.1836 0.0359 0.6814 0.100 Uiso 0.50 1 calc PR A 1
H1A3 H 0.3078 -0.0399 0.6523 0.100 Uiso 0.50 1 calc PR A 1
C1B C 0.4878(8) 0.0851(6) 0.5852(5) 0.087(2) Uani 0.50 1 d PD A 1
H1B1 H 0.5276 0.0216 0.6086 0.130 Uiso 0.50 1 calc PR A 1
H1B2 H 0.5620 0.1381 0.5815 0.130 Uiso 0.50 1 calc PR A 1
H1B3 H 0.4510 0.0702 0.5309 0.130 Uiso 0.50 1 calc PR A 1
C1C C 0.4208(10) 0.1193(12) 0.7294(7) 0.077(3) Uani 0.50 1 d PD A 1
H1C1 H 0.3440 0.1419 0.7653 0.116 Uiso 0.50 1 calc PR A 1
H1C2 H 0.5027 0.1651 0.7365 0.116 Uiso 0.50 1 calc PR A 1
H1C3 H 0.4478 0.0479 0.7429 0.116 Uiso 0.50 1 calc PR A 1
C1A' C 0.3035(7) 0.0459(5) 0.5893(5) 0.0752(18) Uani 0.50 1 d PD A 2
H1A4 H 0.3491 -0.0211 0.5996 0.113 Uiso 0.50 1 calc PR A 2
H1A5 H 0.3141 0.0641 0.5320 0.113 Uiso 0.50 1 calc PR A 2
H1A6 H 0.2027 0.0413 0.6029 0.113 Uiso 0.50 1 calc PR A 2
C1B' C 0.5321(7) 0.1380(6) 0.6143(5) 0.0731(19) Uani 0.50 1 d PD A 2
H1B4 H 0.5815 0.0717 0.6211 0.110 Uiso 0.50 1 calc PR A 2
H1B5 H 0.5757 0.1904 0.6494 0.110 Uiso 0.50 1 calc PR A 2
H1B6 H 0.5389 0.1603 0.5577 0.110 Uiso 0.50 1 calc PR A 2
C1C' C 0.3616(10) 0.1148(10) 0.7267(6) 0.067(3) Uani 0.50 1 d PD A 2
H1C4 H 0.2622 0.1126 0.7437 0.100 Uiso 0.50 1 calc PR A 2
H1C5 H 0.4084 0.1747 0.7518 0.100 Uiso 0.50 1 calc PR A 2
H1C6 H 0.4093 0.0509 0.7438 0.100 Uiso 0.50 1 calc PR A 2
Si2 Si 0.17339(13) 0.21157(9) 0.47711(7) 0.0370(3) Uani 0.50 1 d PD B -1
H2 H 0.181(4) 0.1031(15) 0.462(2) 0.041(11) Uiso 0.50 1 d PD C -1
C2 C 0.2652(5) 0.2500 0.3825(2) 0.0736(13) Uani 1 2 d SD . .
C2A C 0.4269(5) 0.2500 0.3946(3) 0.0862(15) Uani 1 2 d SD B .
H2A1 H 0.4516 0.2968 0.4392 0.129 Uiso 0.50 1 calc PR . .
H2A2 H 0.4733 0.2736 0.3448 0.129 Uiso 0.50 1 calc PR . .
H2A3 H 0.4589 0.1796 0.4076 0.129 Uiso 0.50 1 calc PR . .
C2B C 0.2273(9) 0.1969(6) 0.3097(3) 0.094(2) Uani 0.50 1 d PD B -1
H2B1 H 0.1246 0.2013 0.3018 0.141 Uiso 0.50 1 calc PR B -1
H2B2 H 0.2555 0.1239 0.3138 0.141 Uiso 0.50 1 calc PR B -1
H2B3 H 0.2756 0.2292 0.2636 0.141 Uiso 0.50 1 calc PR B -1
C2C C 0.2212(7) 0.3776(5) 0.3626(4) 0.0781(19) Uani 0.50 1 d PD B -1
H2C1 H 0.2818 0.4043 0.3191 0.117 Uiso 0.50 1 calc PR B -1
H2C2 H 0.2349 0.4193 0.4116 0.117 Uiso 0.50 1 calc PR B -1
H2C3 H 0.1218 0.3815 0.3457 0.117 Uiso 0.50 1 calc PR B -1
C3 C -0.0271(4) 0.2500 0.4861(2) 0.0579(10) Uani 1 2 d SD . .
C3A C -0.1049(6) 0.2500 0.4040(3) 0.117(2) Uani 1 2 d SD B .
H3A1 H -0.0950 0.1818 0.3784 0.176 Uiso 0.50 1 calc PR . .
H3A2 H -0.0637 0.3032 0.3687 0.176 Uiso 0.50 1 calc PR . .
H3A3 H -0.2055 0.2651 0.4126 0.176 Uiso 0.50 1 calc PR . .
C3B C -0.0729(3) 0.1544(2) 0.5322(2) 0.0822(10) Uani 1 1 d D B .
H3B1 H -0.0301 0.1551 0.5863 0.123 Uiso 1 1 calc R . .
H3B2 H -0.0421 0.0922 0.5030 0.123 Uiso 1 1 calc R . .
H3B3 H -0.1763 0.1539 0.5373 0.123 Uiso 1 1 calc R . .

loop_
_atom_site_aniso_label
_atom_site_aniso_U_11
_atom_site_aniso_U_22
_atom_site_aniso_U_33
_atom_site_aniso_U_23
_atom_site_aniso_U_13
_atom_site_aniso_U_12
Si1 0.0305(4) 0.0732(7) 0.0291(4) 0.000 0.0003(3) 0.000
C1 0.0456(14) 0.0752(17) 0.0541(14) -0.0084(13) -0.0112(11) 0.0116(13)
C1A 0.089(5) 0.052(3) 0.060(4) 0.012(3) -0.029(3) -0.011(3)
C1B 0.073(5) 0.083(5) 0.104(6) 0.000(4) 0.011(4) 0.039(4)
C1C 0.075(7) 0.076(5) 0.080(5) 0.006(4) -0.034(5) 0.002(6)
C1A' 0.080(5) 0.045(3) 0.101(5) 0.000(3) -0.022(4) 0.013(3)
C1B' 0.049(4) 0.088(5) 0.082(5) 0.009(4) -0.003(3) 0.021(4)
C1C' 0.076(7) 0.065(5) 0.059(4) 0.029(3) -0.009(4) 0.003(5)
Si2 0.0425(7) 0.0398(5) 0.0287(5) 0.0021(4) -0.0015(5) -0.0054(5)
C2 0.066(3) 0.120(4) 0.0344(18) 0.000 0.0072(18) 0.000
C2A 0.070(3) 0.134(4) 0.055(2) 0.000 0.028(2) 0.000
C2B 0.131(6) 0.119(6) 0.032(3) -0.010(3) 0.017(3) -0.036(5)
C2C 0.086(4) 0.083(4) 0.065(4) 0.035(3) -0.003(3) -0.017(4)
C3 0.0371(18) 0.097(3) 0.0396(18) 0.000 -0.0116(14) 0.000
C3A 0.067(3) 0.225(7) 0.061(3) 0.000 -0.034(2) 0.000
C3B 0.0616(19) 0.075(2) 0.110(3) 0.0037(19) -0.0336(18) -0.0087(15)

_geom_special_details            
;
All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix.  The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry.  An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes.
;

loop_
_geom_bond_atom_site_label_1
_geom_bond_atom_site_label_2
_geom_bond_distance
_geom_bond_site_symmetry_2
_geom_bond_publ_flag
Si1 C1 1.915(3) 7_565 ?
Si1 C1 1.915(3) . ?
Si1 Si2 2.4329(14) . ?
Si1 Si2 2.4329(14) 7_565 ?
C1 C1A' 1.435(7) . ?
C1 C1C' 1.463(10) . ?
C1 C1B 1.512(7) . ?
C1 C1C 1.580(11) . ?
C1 C1B' 1.600(7) . ?
C1 C1A 1.675(7) . ?
Si2 C2 1.854(4) . ?
Si2 C3 1.963(4) . ?
C2 C2B 1.427(6) . ?
C2 C2B 1.427(6) 7_565 ?
C2 C2A 1.540(6) . ?
C2 C2C 1.727(7) 7_565 ?
C2 C2C 1.727(7) . ?
C2 Si2 1.854(4) 7_565 ?
C3 C3B 1.511(4) 7_565 ?
C3 C3B 1.511(4) . ?
C3 C3A 1.542(5) . ?
C3 Si2 1.963(4) 7_565 ?

loop_
_geom_angle_atom_site_label_1
_geom_angle_atom_site_label_2
_geom_angle_atom_site_label_3
_geom_angle
_geom_angle_site_symmetry_1
_geom_angle_site_symmetry_3
_geom_angle_publ_flag
C1 Si1 C1 115.63(17) 7_565 . ?
C1 Si1 Si2 125.40(8) 7_565 . ?
C1 Si1 Si2 103.58(8) . . ?
C1 Si1 Si2 103.58(8) 7_565 7_565 ?
C1 Si1 Si2 125.40(8) . 7_565 ?
Si2 Si1 Si2 23.49(5) . 7_565 ?
C1A' C1 C1C' 118.9(6) . . ?
C1A' C1 C1B 75.9(5) . . ?
C1C' C1 C1B 125.9(6) . . ?
C1A' C1 C1C 130.0(6) . . ?
C1C' C1 C1C 20.9(5) . . ?
C1B C1 C1C 108.0(5) . . ?
C1A' C1 C1B' 110.6(4) . . ?
C1C' C1 C1B' 107.6(5) . . ?
C1B C1 C1B' 34.7(3) . . ?
C1C C1 C1B' 86.8(5) . . ?
C1A' C1 C1A 36.0(3) . . ?
C1C' C1 C1A 83.8(5) . . ?
C1B C1 C1A 102.9(4) . . ?
C1C C1 C1A 98.8(5) . . ?
C1B' C1 C1A 134.5(4) . . ?
C1A' C1 Si1 104.6(3) . . ?
C1C' C1 Si1 107.2(5) . . ?
C1B C1 Si1 119.1(4) . . ?
C1C C1 Si1 114.6(6) . . ?
C1B' C1 Si1 107.3(3) . . ?
C1A C1 Si1 110.8(3) . . ?
C2 Si2 C3 116.61(16) . . ?
C2 Si2 Si1 121.38(13) . . ?
C3 Si2 Si1 104.81(10) . . ?
C2B C2 C2B 57.2(6) . 7_565 ?
C2B C2 C2A 111.0(4) . . ?
C2B C2 C2A 111.0(4) 7_565 . ?
C2B C2 C2C 47.4(3) . 7_565 ?
C2B C2 C2C 103.6(5) 7_565 7_565 ?
C2A C2 C2C 105.3(3) . 7_565 ?
C2B C2 C2C 103.6(5) . . ?
C2B C2 C2C 47.4(3) 7_565 . ?
C2A C2 C2C 105.3(3) . . ?
C2C C2 C2C 144.3(5) 7_565 . ?
C2B C2 Si2 136.0(4) . 7_565 ?
C2B C2 Si2 117.6(3) 7_565 7_565 ?
C2A C2 Si2 110.7(3) . 7_565 ?
C2C C2 Si2 107.6(3) 7_565 7_565 ?
C2C C2 Si2 78.1(3) . 7_565 ?
C2B C2 Si2 117.6(3) . . ?
C2B C2 Si2 136.0(4) 7_565 . ?
C2A C2 Si2 110.7(3) . . ?
C2C C2 Si2 78.1(3) 7_565 . ?
C2C C2 Si2 107.6(3) . . ?
Si2 C2 Si2 30.98(9) 7_565 . ?
C3B C3 C3B 109.2(4) 7_565 . ?
C3B C3 C3A 107.8(2) 7_565 . ?
C3B C3 C3A 107.8(2) . . ?
C3B C3 Si2 121.3(2) 7_565 . ?
C3B C3 Si2 96.25(18) . . ?
C3A C3 Si2 113.1(3) . . ?
C3B C3 Si2 96.25(18) 7_565 7_565 ?
C3B C3 Si2 121.3(2) . 7_565 ?
C3A C3 Si2 113.1(3) . 7_565 ?
Si2 C3 Si2 29.22(8) . 7_565 ?

loop_
_geom_torsion_atom_site_label_1
_geom_torsion_atom_site_label_2
_geom_torsion_atom_site_label_3
_geom_torsion_atom_site_label_4
_geom_torsion
_geom_torsion_site_symmetry_1
_geom_torsion_site_symmetry_2
_geom_torsion_site_symmetry_3
_geom_torsion_site_symmetry_4
_geom_torsion_publ_flag
H1 Si1 Si2 H2 -94.2(18) . . . . ?

_diffrn_measured_fraction_theta_max 0.999
_diffrn_reflns_theta_full        26.39
_diffrn_measured_fraction_theta_full 0.999
_refine_diff_density_max         0.309
_refine_diff_density_min         -0.285
_refine_diff_density_rms         0.049