Hd. Hornung et al., CH-PI INTERACTION IN BINUCLEAR ANTIMONY(V ) COMPLEXES WITH BRIDGING PHOSPHONATO LIGANDS, Silicon, germanium, tin and lead compounds, 20(3), 1997, pp. 157-167
The binuclear antimony(V) complexes Cl3Sb(O)[R-3((RO)-O-1)PO2](OR2)SbC
l3 with R-t = R-2 = CH3 and R-3 = C6H5 (1), (C6H5)(2)CH (2) and (C6H5C
)(3) (3) are prepared by reaction of the corresponding methoxophosphon
ic acids with antimony(V) chloride, water and methanol. 2 and 3 crysta
llize in the monoclinic space group P2(1)/c with a = 966.8, b = 1603.4
, c = 1794.8 pm, beta = 91.4 degrees, Z = 4 and with a = 988.0, b = 15
92.8, c = 1816.0 pm, beta = 91.7 degrees and 2 = 4 resp.. The molecule
s of 1 to 3 are formed from two octahedra sharing one edge with antimo
ny as central atoms. Oxygen atoms are links between the antimony atoms
which are bridged by the bidentate phosphonato ligands. The molecules
of 2 and 3 show a significant CH-pi interaction between the CH3 group
R-2 and a phenyl ring of the bridging phosphonato groups in the solid
state as well as in solution. In solution the phosphonato groups are
inverted rapidly and the R-2 groups undergo a slow intermolecular exch
ange. Two isomers can be detected by NMR spectroscopy.