Free radical polymerisation process

A Co II chelate of the following formula I:

• ##STR6## wherein each group X, independently in each ring and in different rings, is a substituent selected from alkyl of 1 to 14 carbon atoms and cycloalkyl of 6 to 14 carbon atoms;
• n, independently in each ring, is 0 to 5 provided that in at least one ring, n is 1 to 5;
• Z, independently on each boron atom, is selected F, Cl, Br, OH, alkoxy of 1 to 12 carbon atoms, aryloxy of 6 to 12 carbon atoms, alkyl of 1 to 12 carbon atoms, and aryl of 6 to 12 carbon atoms;
• or two Z groups taken together provide on one or both boron atoms a group --O--(Q)--O-- where Q is a divalent aryl or alicyclic linking group or an alkylene linking group, or two Z groups taken together on one or both boron atoms provide a 1,5-cyclooctanediyl linking group;
• or being a Co III analogue of said Co II chelate of formula I in which the Co atom is additionally covalently bonded, in a direction at right angles to the macrocyclic chelate ring system, to H, halide or other anion, or a homolytically dissociable organic group;
• and wherein optionally at least one further ligand is coordinated to the Co II or Co III atom, being a ligand(s) which does not alter the Co valency state.

Process for the production of a Co II chelate of formula I in which each Z is F, which comprises a) reacting a benzene-substituted benzil dioxime, which substitution corresponds with the desired substitution in the finished product, with cobalt acetate using diethyl ether as solvent and under an atmosphere of deoxygenated nitrogen ensuring that the reaction temperature does not exceed 5.degree. C.,

• b) introducing boron trifluoride etherate dropwise to the reaction mixture, ensuring that the reaction temperature does not exceed 5.degree. C.,
• c) warming the mixture to 40.degree. C. and holding at this temperature to ensure reaction,
• d) cooling the reaction temperature to 0.degree. C.,
• e) adding a base,
• f) stirring for a further period and then adding methanol,
• g) isolating the product by filtration, water wash, and then methanol wash, thereby to yield the Co-chelate as the dimethanol complex.