Process for the preparation of a polyolefin

1. A process for the polymerization of at least one aliphatic C 2-20 or aromatic C 4-20 hydrocarbyl mono- or multiolefin in the presence of a catalyst and a boron comprising co-catalyst, wherein the catalyst comprises a composition of an organometallic reagent, a spectator ligand (SH) and optionally at least one equivalent of a hydrocarbylating agent, and the organometallic reagent is represented by ML j X p , wherein

M is a metal from group 3-11, or the lanthanide series,

X is a monoanionic ligand bonded to M,

L is a neutral ligand bonded to M,

j represents an integer denoting the number of neutral ligands L, and

p is the valence of the metal M and

the spectator ligand is an imine ligand, or the HA adduct thereof, wherein HA represents an acid, of which H represents its proton and A its conjugate base.

2. A process for the polymerization of at least one aliphatic C 2-20 or aromatic C 4-20 hydrocarbyl mono- or multiolefin in the presence of a catalyst and a boron comprising co-catalyst, wherein the catalyst comprises a composition of an organometallic reagent, a spectator ligand (SH) and optionally at least one equivalent of a hydrocarbylating agent, and the organometallic reagent is represented by ML j X p , wherein

M is a metal from group 3-11, or the lanthanide series,

X is a monoanionic ligand bonded to M,

L is a neutral ligand bonded to M,

j represents an integer denoting the number of neutral ligands L, and

p is the valence of the metal M,

and the spectator ligand is represented by:

(HA 1 ) q -Z n -(A 2 H) r ,

wherein

A 1 and A 2 are cyclopentadienyl comprising ligands,

q and r represent an integer denoting the number of Cp ligands with q+r=1 or 2, optionally linked by n parallel bridging groups Z, A 1 , A 2 separately, or bonded via Z together forming a bidentate diacidic spectator ligand, and

n is 1, 2 or 3.

3. A process for the polymerization of at least one aliphatic C 2-20 or aromatic C 4-20 hydrocarbyl mono- or multiolefin in the presence of a catalyst and a boron comprising co-catalyst, wherein the catalyst comprises a composition of an organometallic reagent, a spectator ligand (SH) end optionally at least one equivalent of a hydrocarbylating agent, and the organometallic reagent is represented by ML j X p , wherein

M is a metal from group 3-11, or the lanthanide series,

X is a monoanionic ligand bonded to M,

L is a neutral ligand bonded to M,

j represents an integer denoting the number of neutral ligands L, and

p is the valence of the metal M

and the spectator ligand is a ligand according to the formula:

HA 1 -Z-D(H) b ,

in which

A 1 is a delocalized η 5 bonding cyclopentadienyl comprising ligand,

Z is a moiety comprising boron, or a member of Group 14, and optionally also sulfur or oxygen, said moiety having up to 20 non-hydrogen atoms, and optionally A 1 and Z together form a fused ring system,

D is a Lewis basic ligand bonded to Z, comprising a group 15 or 16 atoms and having up to 20 non-hydrogen atoms, or optionally D and Z together form a fused ring system and

b=0 or 1.

4. A process for the polymerization of at least one aliphatic C 2-20 or aromatic C 4-20 hydrocarbyl mono- or multiolefin in the presence of a catalyst and a boron comprising co-catalyst, wherein the catalyst comprises a composition of an organometallic reagent a spectator ligand (SH) and optionally at least one equivalent of a hydrocarbylating agent, and the organometallic reagent is represented by ML j X p , wherein

M is a metal from group 3-11, or the lanthanide series,

X is a monoanionic ligand bonded to M,

L is a neutral ligand bonded to M,

j represents an integer denoting the number of neutral ligands L, and

p is the valence of the metal M and

the spectator ligand is represented by:

Y(−R-DR′ n ) q ,

in which

Y represents a (substituted) cyclopentadienyl, (substituted) indenyl, (substituted) fluorenyl, (substituted) heterocyclopentadienyl, (substituted) heteroindenyl, (substituted) heterofluorenyl, or an imine group,

R is an optional bridging group between the Y moiety and the DR′ n ,

D is a hetero atom selected from group 15 or 16,

R′ is an optional substituent,

n is the number of R′ groups bonded to D and is 1 or 2, and

q is an integer >1.

5. A process for the polymerization of at least one aliphatic C 2-20 or aromatic C 4-20 hydrocarbyl mono- or multiolefin in the presence of a catalyst and a boron comprising co-catalyst, wherein the catalyst comprises a composition of an organometallic reagent, a spectator ligand (SH) and optionally at least one equivalent of a hydrocarbylating agent, and the organometallic reagent is represented by ML j X p , wherein

M is a metal from group 3-11, or the lanthanide series,

X is a monoanionic ligand bonded to M,

L is a neutral ligand bonded to M,

j represents an integer denoting the number of neutral ligands L, and

p is the valence of the metal M

and the ligand is represented by

R-D Z-D n R

wherein

Z is a bridging group, between two donor atom containing groups (D),

D is a group comprising a hetero atom chosen from group 15 or 16,

n is 0, 1, 2 or 3, and

R is a substituent and wherein the metal is a metal from Group 7-11.

6. The process according to any of claims 1 to 5 , wherein the hydrocarbylating agent comprises a metal or a metalloid chosen from group 1, 2, 11, 12, 13 or 14.

7. The process according to claim 6 , wherein the hydrocarbylating agent comprises Li, Mg, Zn, or Al.

8. The process according to claim 7 , wherein the hydrocarbylating agent is a C 1 -C 20 trihydrocarbyl aluminum or aluminoxane.

9. The process according to any of claims 1 to 5 , carried out the presence of a base other than the hydrocarbylating agent.

10. The process according to claim 1 , wherein the organometallic reagent comprises a group 4 metal and a cyclopentadienyl-comprising ligand.

11. The process according to claim 2 or 3 , wherein the metal is a group 4 or group 5 metal, or a metal selected from the lanthanide series.

12. The process according to claim 4 , wherein the metal is a group 4 metal with a valency of 3.