Seven group 13/15 four-membered-ring compounds of the general type [R2ME-t-Bu-2](2) bearing the chromophoric substituents (R) vinyl, allyl, and benzyl have been synthesized by treatment of t-Bu2PLi or t-Bu2AsLi with the appropriate gallium or indium chloride, R2MCl (prepared in situ), in Et2O solution: 3 (R = vinyl, M = Ga, E = P); 4 (R = vinyl, M = In, E = P); 5 (R = allyl, M = In, E = P); 6 (R = allyl, M = Ga, E As); 7 (R = benzyl, M = In, E P); 8 (R = benzyl, M = Ga, E = As); 10 (R = vinyl, M = Ga, E = As). The partially substituted derivative [(vinyl)ClGaAs-t-Bu-2](2) (9) was prepared by a similar one-pot procedure. All eight new compounds were characterized by X-ray crystallography, NMR, and mass spectroscopy. Compounds 3-8 absorb light at relatively long wavelengths with cutoffs ranging from similar to 300 nm for the vinyl-substituted compounds to similar to 330 nm for the corresponding allyl- and benzyl-substituted derivatives.