Two compounds containing a Sn(II) atom supported by a
bidentate
biscarborane ligand have been synthesized via salt metathesis. The
synthetic procedures for (bc)Sn·THF (bc= 1,1′ (ortho-carborane) (1) and K2[(bc)Sn]2(2) involved the reaction of K2[bc] with SnCl2in either a THF solution (1) or in a benzene/dichloromethane
solvent mixture (2). Using the same solvent conditions
as those used for2but using a shorter reaction time
gave a dibiscarboranyl ethene (3). The products were
characterized by1H,13C,11B,119Sn NMR, UV–vis, and IR spectroscopy, and by X-ray
crystallography. The diffraction data for1and2show that the Sn atom has a trigonal pyramid environment
and is constrained by thebcligand in a planar five-membered
C4Sn heterocycle. The119Sn NMR spectrum of1displays a triplet of triplets pattern signal, which is
unexpected given the absence of a Sn–H signal in the1H NMR, IR spectrum, and X-ray crystallographic data. However, a comparison
with other organotin compounds featuring a Sn atom bonded to carboranes
reveal similar multiplets in their119Sn NMR spectra, likely
arising from long-range nuclear spin–spin coupling between
the carboranyl11B and119Sn nuclei. Compound3displays structural and spectroscopic characteristics typical
of conjugated alkenes.