2-(3-pyridyl) propanenitrile derivatives

A compound of the formula

• wherein:
• Hal denotes a halogen atom;
• R denotes:
• a lower alkyl radical, optionally substituted with one or more substituents selected from the group consisting of halogen atoms, lower alkoxy radicals, lower alkylthio radicals and a radical
• (CH.sub.2).sub.x SiR.sub.1 R.sub.2 R.sub.3, wherein x is 0 or 1 and R.sub.1, R.sub.2 and R.sub.3, which may be identical or different, are lower alkyl, lower alkoxy, aryl or aralkyl;
• a 3- to 7-membered cycloalkyl radical selected from the group consisting of cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl, which is optionally substituted in the same manner as the lower alkyl radical;
• an aralkyl radical optionally substituted in the same manner as the lower alkyl radical;
• or
• a mono- or polyunsaturated lower alkenyl or alkynyl radical, optionally substituted in the same manner as the lower alkyl radical, with the proviso that there is no unsaturation at the alpha-position with respect to the carbon bearing the CN group;
• Z denotes a lower alkyl or lower alkoxy radical;
• and
• m denotes 0, 1 or 2, the groups Z being identical or different when m is 2.