Synthesis, Structures, and Spectroscopy of the Metallostannylenes (η5-C5H5)(CO)3M−Sn−C6H3-2,6-Ar2 (M = Cr, Mo, W; Ar = C6H2-2,4,6-Me3, C6H2-2,4,6-Pri3)

The metallostannylene compounds (η 5 -C 5 H 5 )(CO) 3 MSnC 6 H 3 -2,6-Mes 2 (Mes = C 6 H 2 -2,4,6-Me 3; M = Cr ( 1 ), Mo ( 2 ), W ( 3 )), (η 5 -C 5 H 5 )(CO) 3 MSnC 6 H 3 -2,6-Trip 2 (Trip = C 6 H 2 -2,4,6-Pr i 3; M = Cr ( 4 ), Mo ( 5 ), W ( 6 )), and (η 5 -1,3-Bu t C 6 H 3 )MoSnC 6 H 2 -2,6-Trip 2 ( 7 ) were synthesized by the reaction of the appropriate aryltin(II) halide with the alkali-metal salt of the cyclopentadienylcarbonylmetalate. The compounds, which were isolated as purple ( 1 − 6 ) or turquoise ( 7 ) crystals, are monomeric with V-shaped two-coordinate geometries at tin. The tin−transition-metal bonds are slightly longer than the distances predicted from metallic and covalent radii or those observed in related tin(IV)−transition-metal species. The compounds were also characterized by IR and UV−vis spectroscopy as well as 1 H, 13 C, and 119 Sn NMR spectroscopy. The 119 Sn NMR spectra displayed singlet resonances whose chemical shifts were in the range 2116−2650 ppm. These shifts were consistent with the two-coordination at tin. With use of 119 Sn NMR and UV−visible spectroscopic data for 1 − 7, together with data for other two-coordinate tin(II) species, it was shown that there is a rough correlation between the 119 Sn NMR chemical shift and the wavelength of the n−p transition. This correlation underlines the importance of the paramagnetic shielding term in determining 119 Sn chemical shifts.