1,1-Diethynyl-1-stannacyclohexane (5) was prepd., and its reaction with triethylborane or 9-isobutyl-9-borabicyclo[3.3.1]nonane gave the corresponding spiro-Sn compds. 6 and 7 (shown as I) with a stannole fragment. The mol. structure of 7 was detd. by x-ray anal. (triclinic, space group P.hivin.1; a 835.2(7), b 1117.5(2), c 1165.6(2) pm; a 72.05(3), b 74.32(3), g 50.61(3) Deg). Treatment of 6 with trimethyltin ethoxide gave at 1st quant. the spiro-Sn compd. 8 with a 2-stannolene unit which rearranges upon heating into the spiro-Sn compd. 9 with a 3-stannolene unit. The reaction of 7 with trimethyltin butoxide gave quant. another tetracyclic compd. 10, analogous to 8. All compds. were characterized by 1H, 11B, 13C and 119Sn NMR data. Numerous coupling signs nJ(119Sn1H) and nJ(119Sn13C) and 2J(119Sn117Sn) were detd. by 2-dimensional 13C/1H and 119Sn/1H heteronuclear shift correlations. 7 Was studied by solid-state 13C and 119Sn CPMAS NMR. This revealed a 2nd cryst. phase in the bulk of the solid material, as confirmed by powder x-ray diffraction data. 119Sn CPMAS NMR spectra of 7 show resolved scalar 119Sn-11B coupling (3J(119Sn11B) = 68 +- 5 and 65 +- 5 Hz).