Catalytic composition and its preparation and use for preparing polymers from ethylenically unsaturated monomers

A catalytic composition comprising at least one cationic metal-pair complex, wherein:

• said cationic metal-pair complex comprises at least one metal atom pair, said pair comprising a first metal atom, M1, and a second metal atom, M2;
• said first metal atom and said second metal atom of said pair have a through-space internuclear distance of at least 1.5 Angstroms and no more than 20 Angstroms;
• and
• said cationic metal-pair complex is a complex according to formula I,
• wherein:
• M1 represents a first metal atom selected from iron, cobalt, ruthenium, rhodium, chromium, and manganese;
• L1 represents a set of first ligands;
• L2 represents a set of second ligands;
• L3 represents a set of third ligands;
• R1 represents a set of first anionic hydrocarbyl containing radicals;
• R2 represents a set of second anionic hydrocarbyl containing radicals;
• S1 represents a set of first labile ligands;
• S2 represents a set of second labile ligands;
• A1–A8 each represent a set of coordination bonds;
• WCA represents a weakly coordinating anion;
• a, b, h, k, m, and p are each selected from 0 and 1;
• α, β, and c each equal 1;
• d, r, and t are each selected from 0, 1, 2, 3, and 4;
• f is selected from 1, 2, 3, 4, and 5;
• 1≦m+p≦2;
• the sum d+f+r+t=5;
• and
• sum e+g+s+u=4, 5, or 6;
• and
• wherein:
• when the sum e+g+s+u=4,
• M2 represents a second metal atom selected from nickel, palladium, copper, iron, cobalt, rhodium, chromium, and manganese;
• e, s, and u are each selected from 0, 1, 2, and 3;
• g is selected from 1, 2, 3, and 4;
• 0≦d+e≦6;
• 1≦r+s≦6;
• 0≦t+u≦6;
• and 2≦f+g≦8;
• when the sum e+g+s+u=5,
• M2 represents a second metal atom selected from iron, cobalt, ruthenium, rhodium, chromium, and manganese;
• e, s, and u are each selected from 0, 1, 2, 3, and 4;
• g is selected from 1, 2, 3, 4, and 5;
• 0≦d+e≦7;
• 1≦r+s≦7;
• 0≦t+u≦7;
• and 2f+g≦9;
• or
• when the sum e+g+s+u=6,
• M2 represents a second metal atom selected from copper, iron, cobalt, ruthenium, rhodium, chromium, and manganese;
• e, s, and u are each selected from 0, 1, 2, 3, 4, and 5;
• g is selected from 1, 2, 3, 4, 5, and 6;
• 0≦d+e≦8;
• 1≦r+s≦8;
• 0≦t+u≦8;
• and 2≦f+g≦10.