U. Kolb et al., HETEROCYCLIC-SYSTEMS CONTAINING TIN(IV) .10. CONTROL OF 3-CENTER INTERACTIONS X...SN-HAL IN STANNOCANES BY HALIDE TYPE, Inorganic chemistry, 33(20), 1994, pp. 4522-4530
The stannocanes Cl-2/Br-2/I-2-Sn(SCH2CH2)(2)X OL = NMe, O, S) have bee
n synthesized from SnHal(4) and (HSCH2CH2)(2)X. Assigned vibrational (
IR and Raman) and NMR data (C-13,and Sn-119) and, for X = O and S, cry
stal structure determinations are given. All nine compounds comprise m
olecules in which the tin atom approaches a trigonal-bipyramidal penta
coordination with 2xS and Hal(eq) as equatorial ligands and with X and
Hal, as axial ligands. The latter two bonds are described by means of
a three-center, four-electron interaction X Sn-Hal for which a qualit
ative MO description in terms of frontier orbitals is given. A ''path'
' from a tetrahedron to a trigonal bipyramid is controlled by four ele
ctronic factors (donor strength of X, electronegativity of Hal(ax), lo
ne pair interaction of Hal(ax), type of equatorial ligands) and one st
eric factor (geometrical flexibility of X). These influences are discu
ssed with respect to the structural and spectroscopic data (Pauling-ty
pe bond orders BO(X Sn) and BO(Sn-Hal), geometrical goodness of the tr
igonal bipyramids, force constants f(Sn-Hal), and Sn-119-NMR chemical
shifts) of the nine compounds and are compared with the data of five a
nalogous series taken from the literature. Regarding the influence of
Hal(ax), the factors ''electronegativity'' and ''lone pair interaction
'' are counteractive and cancel each other, between bromine and iodine
. The donor strength of X in the nine compounds decreases in the follo
wing orders: NMe > S greater than or equal to O in the solid state and
NMe > O > S in solution.