radical as defined above the cation m can itself be solvated or complexed to increase its solubility and or its reactivity for example if m is a proton the latter can be complexed with the help of a tertiary base having a strong nucleophilic character such as triethylamine dimethylaminopyridine 1 4 diazabicyclo 2 2 2 octane or in the form of a tertiobutyle radical that easily separates into a proton and ch 2 u2550 c ch 3 3 if m is a metallic ion the latter can be solvated by dialkylethers of oligo ethylene glycols or methylated oligo ethylenediamines alternately the cross linking agent a 2 y u2212 m can be formed in situ in the presence of a strong base for example an organometallic or a metallic dialkyl amine such as diisopropylamide lithium reacting on the leaving protons linked to the y radical in the following manner hn si ch 3 3 2 c 4 h 9 li u2192 c 4 h 10 lin si ch 3 3 2 ch 2 si ch 3 3 so 2 cf 3 2ch3mgclli u2192 2ch 4 mgcl 2 c si ch 3 3 so 2 cf 3 preferred organometallic cross linking agents include organo lithium organo magnesium or organo aluminium that are also a carbon source when y cr and amides and metallic nitrides as a nitrogen source when y n an advantage of the present invention is that the cross linking.