Sn-X bond distances

For [Sn Xs] species having a basic trigonal pyramidal geometry, 5 values correlate with the Sn-X bond distance. 

Some bond distances and energies of Sn-X bonds are given in Table 2. 

Table 6. Bond distances Sn—X (pm) of molecules SnX2 and SnX4 in the gas phase...

The C=C harmonic vibrational frequency is calculated at 1671 cm-1 in free ethylene and is infrared (IR) forbidden. Its IR intensity is therefore expected to remain low in the vinyl series of compounds. The C=C stretch energy is calculated to be 1687 cm-1 in propene and then decline to 1629 4 cm-1 for X = Si - Pb. As in the equilibrium bond distance, there is also a very small counter-trend change in the vibrational frequency going from X = Sn to X = Pb that indicates a slight strengthening of the C=C bond. 

The compound 35 possesses exo- and air-stereochemistry of the methyl and the benzoate groups based on the nuclear Overhauser effect (NOE) data. Based on the C-N distance (r), the Woodward parameter (h) and the sum at the N-atom (SN) value from X-ray data, N-l is in a pyramidal environment. N-3 is on maximum resonance with the Jt-framework of the adjacent C=0 group. This is reflected in a shorter C(2)-N(3) bond (1.375(2) A, compared to the C(2)-N(l) bond distance [1.438(2)A]. JZN values are as follows N-3 = 359.99°, and ]N-1 =311.74° and, = 0,601 A. The X-ray crystallographic data support some of the conclusions derived from AMI calculations, viz. N-l and N-3 atoms are in chemically distinct environments and form C-N bonds of different strengths. This would have implications on the... 

We shall now consider some properties of M—X bonds (M = Ge, Sn, Pb) in comparison with Si—X and C—X. As the atomic number of M increases, these bond distances d (Table 2) become longer. It is caused by the increase in the covalent radius of the group 14 element as its atomic number rises. The d values of the Me3M—Me and Me3M—MMe3 bonds coincide to within 0.05 A with the sum of covalent radii of the atoms forming this bond. The Si—Cl bond distances in SiCLt are 0.15 A shorter than the sum of covalent radii of Si and Cl atoms. As the atomic number of M increases, the difference between the experimental d values in MCLj molecules and the expected ones (based on the sum of the... 

FIGURE 70. Calculated transition states at MP2 of the 1,2-migration of silyl, germyl and stannyl substituents of radicals H3E-CH2X to H3EX-CH2 (X = CH2, NH, O E = Si, Ge, Sn). Bond distances are in A, angles in deg. The calculated activation energies (kcal mol 1) at QCISD//MP2 refer to the forward reaction ( A E1 i ) and the reverse reaction (A E ), respectively. Reproduced by permission of The Royal Society of Chemistry from Reference 190... 

The reduction of bivalent aryltin chloride by sodium anthracenide in THF gave a new way to a bulky distannylanion in the form of a stable very close ion-pair (equation 54)71. The X-ray crystal structure reveals a normal Sn-Sn distance (2.81 A) in the distannylanion and a Sn—Na bond length of 3.24 A. 

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