A process for polymerizing polar compounds which have a C.dbd.C double bond in the alpha-position to a carbonyl or nitrile group, which comprises polymerizing the polar compounds in the presence of initiators selected from the group consisting of organo-metallic compounds of silicon, germanium and tin with nucleophilic or electrophilic catalysts at temperatures in the range of from -100.degree. C. to +100.degree. C., in which the organo-metallic compounds are selected from the group consisting of
- (a) cyclic silazanes,
- (b) polymeric silazanes which contain at least three silazanyl units of the formula ##STR7## in which R is selected from the group consisting of alkyl, cycloalkyl, alkenyl, aryl, alkaryl, and aralkyl radicals, and the remaining valences of the Si atoms are saturated by radicals represented by R or are linked to NH groups of another units of formula (2) per molecule,
- (c) cyclic siloxanes,
- (d) polymeric siloxanes which contain at least three siloxanyl units of the formula ##STR8## in which R is selected from the group consisting of alkyl, cycloalkyl, alkenyl, aryl, alkaryl and aralkyl radicals and the remaining valences of the Si atoms are saturated by R radicals or are linked to an oxygen atom of another siloxane unit of formula (3) or a unit of the formula ##STR9## per molecule, where R is selected from the group consisting of alkyl, cycloalkyl, alkenyl, aryl, alkaryl, and aralkyl radicals,
- (e) silanes of the formula
- R.sub.4-n SiX.sub.n ( 1)
- where R is selected from the group consisting of alkyl, cycloalkyl, alkenyl, aryl, alkaryl and aralkyl radicals, X is selected from the group consisting of radicals of the formulas ##STR10## where R' is selected from the group consisting of H atoms and R radicals, R" is selected from the group consisting of radicals of the formulas --COOR, --COR and an oxygen atom in which the unsatisfied valence is satisfied by another silyl group, R"' is selected from the group consisting of radicals of the formulas --OR, --OCOR, --NHCOR, --CONHR, --NHCOOR, NHR, and an oxygen atom in which the unsatisfied valence is satisfied by another silyl group, n is 1 or 2 and m is 0, 1, 2 or 3,
- (f) silanes having at least three silyl groups per molecule of the formula
- R.sup.V O[Si(OR.sup.V).sub.2 ].sub.x [Si(R.sup.IV)(OR.sup.V)].sub.y [Si(R.sup.IV).sub.2 ].sub.z OR.sup.V ( 5')
- wherein R.sup.IV is selected from the group consisting of H atoms, alkyl, cycloalkyl, alkenyl, aryl, aralkyl and alkaryl radicals which may be substituted by radicals selected from the group consisting of fluorine, chlorine, alkoxy and acyloxy group, R.sup.V is selected from the group consisting of alkyl, cycloalkyl, aryl, aralkyl, alkaryl and alkenyl radicals with the proviso that the oxygen atoms must be bonded to an sp.sup.3 -hybridized carbon atom of the alkenyl radical, x, y and z have values of from 0 to 500 and the sum of x+y+z must be at least 2 with the proviso that at least one hydrocarbyloxy group is bonded to each silicon atom,
- (g) siloxanes having units of the formula ##STR11## in which R.sup.IV is selected from the group consisting of H atoms, alkyl, cycloalkyl, alkenyl, aryl, aralkyl and alkaryl radicals which may be substituted by radicals selected from the group consisting of fluorine, chlorine, alkoxy and acyloxy groups, R.sup.V is selected from the group consisting of alkyl, cycloalkyl, aryl, aralkyl, alkaryl and alkenyl radicals, with the proviso that the oxygen atom must be bonded to an sp.sup.3 -hybridized carbon atom of the alkenyl radical, c is 0, 1, 2 or 3, with an average of from 0.1 to 2.5, e is 0, 1, 2 or 3, with an average of from 0.1 to 2.5, and the sum of c+e is at most 3 per unit with the proviso that at least one hydrocarbyloxy group is bonded to each silicon atom,
- (h) compound of the formula
- R.sup.IV.sub.4-p M(OR.sup.V).sub.p ( 4)
- where M is selected from the group consisting of Ge and Sn R.sup.IV is selected from the group consisting of H atoms, alkyl, cycloalkyl, alkenyl, aryl, aralkyl and alkaryl radicals which may be substituted by radicals selected from the group consisting of fluorine, chlorine, alkoxy and acyloxy groups, R.sup.V is selected from group consisting of alkyl, cyclalkyl, aryl, aralkyl, alkaryl and alkenyl radicals with the proviso that the oxygen atoms must be bonded to an sp.sup.3 -hydribrized carbon atom of the alkenyl radical, p is 1, 2 or 3, with the proviso that at least one hydrocarbyloxy group is bonded to each M,
- (i) compounds of the formula
- R.sup.V O[M(OR.sup.V).sub.2 ].sub.x [M(R.sup.IV)(OR.sup.V)].sub.y [M(R.sup.IV).sub.2 ].sub.z OR.sup. ( 5)
- where M is selected from the group consisting of Ge and Sn, R.sup.IV is selected from the group consisting of H atoms, alkyl, cycloalkyl, alkenyl, aryl, aralkyl and alkaryl radicals which may be substituted by radicals selected from the group consisting of fluorine, chlorine, alkoxy and acyloxy groups, R.sup.V is selected from the group consisting of alkyl, cycloalkyl, aryl, aralkyl, alkaryl and alkenyl radicals with the proviso that the oxygen atoms must be bonded to an sp.sup.3 -hybridized carbon atom of the alkenyl radical, x, y and z each have values of from 0 to 500, with the proviso that the sum of x+y+z must be at least 2 with the proviso that at least one hydrocarbyloxy group is bonded to each M,
- (j) germanium compounds which correspond to the siloxanes of formula (6) and
- (k) stannoxane compounds which correspond to the siloxanes of formula (6)