7-Substituted dinaphtho[2,1-b;l',2-d]-siloles 2 and -germoles 3, involving the first isolated example of optically active group 14 dinaphthoheteroles, have been prepared from 2,2'-dibromo-1,1'-binaphthyl (DBBN) via 2,2'-dilithio-1,1'-binaphthyl intermediate. They are fluxional in the NMR time scale at elevated temperatures, and the energy barriers (DeltaG(+/-)) for racemization arising from the flipping of the two naphthalene rings are estimated to be 76-77 +/-2 kJ mol(-1) for siloles 2b-d and 80 +/-2 kJ mol(-1) for germole 3b. The half-life (t(1/2)) for racemization of the optically active silole (R)-2b prepared from optically active (R)-DBBN by the same procedure is determined to be 7.2 h in benzene at 19 degreesC. (C) 2001 Elsevier Science Ltd. All rights reserved.