Compounds of formula (I) and salts and solvates are provided: ##STR00001## wherein R.sup.2 is selected from phenyl substituted with n R.sup.1 groups, and pyridyl substituted with n R.sup.1 groups; n=0, 1 or 2; each R.sup.1 is independently selected from the group consisting of halo, C.sub.1-4alkyl, C.sub.1-4alkoxy, haloC.sub.1-4alkyl, haloC.sub.1-4alkoxy and cyano; R.sup.3 is selected from hydrogen and C.sub.1-2 alkyl; R.sup.4 is selected from the group consisting of ethyl, n-propyl, i-propyl, n-butyl, i-butyl and t-butyl; or R.sup.3 and R.sup.4 together with the nitrogen atom to which they are attached form a saturated 5- or 6-membered heterocyclic ring optionally substituted with one or more groups X; each X is independently selected from the group consisting of C.sub.1-4alkyl, and haloC.sub.1-4alkyl; R.sup.12 is selected from the group consisting of hydrogen, fluoro, chloro, bromo, methyl and methylthio; R.sup.13 is selected from hydrogen, chloro and trifluoromethyl; R.sup.14 is selected from hydrogen, trifluoromethyl and chloro; R.sup.15 is selected from hydrogen, chloro and trifluoromethyl; R.sup.16 is selected from hydrogen, methyl, fluoro and chloro; R.sup.12, R.sup.13, R.sup.14, R.sup.15 and R.sup.16 not all simultaneously being hydrogen.