Sterically Crowded Tin Acenaphthenes

The synthesis of crowded peri-5-bromo-6-(organostannyl)acenaphthenes is described. Reaction of 5,6-dibromoacenaphthene with 1 equiv of n-BuLi at −40 °C in diethyl ether followed by addition of the appropriate organotin reagent at 0 °C gave 5-bromo-6-(triphenylstannyl)acenaphthene (1), 5-bromo-6-(chlorodiphenylstannyl)acenaphthene (2), bis(6-bromoacenaphthen-5-yl)diphenylstannane (3), bis(6-bromoacenaphthen-5-yl)dibenzylstannane (4), bis(6-bromoacenaphthen-5-yl)dibutylstannane (6), and bis(6-bromoacenaphthen-5-yl)dichlorostannane (7) in low to medium yields (10–56%). 4 was converted into 5-iodo-6-bromoacenaphthene (5) by stirring overnight in the presence of a large excess of iodine. The new compounds were fully characterized spectroscopically. 119Sn NMR spectra suggest and interaction between the tin atoms and the neighboring peri halogen atoms. Single-crystal X-ray studies on 1–4 and 6–8 revealed Sn···X distances which are significantly less than the sum of the van der Waals radii, while DFT calculations...