Silacyclohexane compounds, preparation thereof, liquid crystal compositions comprising the same, and liquid crystal devices comprising the compositions

A silacyclohexane compound selected from the group consisting of compounds of the following formulas (I) and (II) ##STR133## wherein R represents a linear alkyl group having from 1 to 10 carbon atoms, a mono or difluoroalkyl group having from 1 to 10 carbon atoms, a branched alkyl group having from 3 to 8 carbon atoms, an alkoxyalkyl group having from 2 to 7 carbon atoms, or an alkenyl group having from 2 to 8 carbon atoms;

• one of ##STR134## represents a trans-1-sila-1,4-cyclohexylene group or trans-4-sila-1,4-cyclohexylene group in which the silicon atom at the 1 or 4 position has a substituent of H, F, Cl or CH.sub.3, and the other represents a trans-1,4-cyclohexylene group, or such a trans-1-sila-1,4-cyclohexylene group or trans-4-sila-1,4-cyclohexylene group as defined above, n is 0 or 1, L.sub.1 represents H or F, L.sub.2 represents H, F or Cl, and Z represents CN, F, Cl, CF.sub.3, CClF.sub.2, CHClF, OCF.sub.3, OClCF.sub.2, OCHF.sub.2, OCHClF, (O).sub.m CY=CX.sub.1 X.sub.2 wherein m is 0 or 1, Y and X.sub.1 independently represent H, F or Cl, X.sub.2 represents F or Cl, O(CH.sub.2).sub.r (CF.sub.2).sub.s X.sub.3 wherein r and s are respectively, 0, 1 or 2 provided that r+s is 2, 3 or 4, and X.sub.3 represents H, F or Cl, or R or OR wherein R is as defined above, and ##STR135## R, L.sub.1, L.sub.2, Z, ##STR136## are, respectively, as defined in the formula (I).