Zwitterionic Metallocycles
View Patent ↗A new class of zwitterionic metallocycles is disclosed. A positively charged Group 4-10 transition metal is chelated to two heteroatoms and one of the heteroatoms has a substituent bearing a negative charge. We have found that substitution in this position stabilizes the zwitterion form of the metallocycle. The zwitterionic metallocycle is useful for olefin polymerizations.
1. A zwitterionic metallocycle comprising a Group 4-10 transition metal chelated to two heteroatoms independently selected from the group consisting of P, N, O, and S wherein the two heteroatoms are each attached to a linking group to form a metallocycle and wherein one of the heteroatoms has a substituent bearing a full or partial negative charge on atom selected from the group consisting of B, Al, Sn and Sb and wherein said atom is directly bonded to the heteroatom and the transition metal has a full or partial positive charge.
2. A zwitterionic metallocycle of general formula:
wherein M is a Group 4-10 transition metal bearing a full or partial positive charge, G is a linking group to form a metallocycle and comprises two substituted or unsubstituted sp 2 carbon atoms to form a 5-membered metallocycle; each X is independently selected from the group consisting of P, N, O and S, each R 2 is independently selected from the group consisting of C 1 –C 30 hydrocarbyl, m is 0, 1 or 2, n is 0 or 1, R 1 contains an atom bearing a full or partial negative charge selected from the group consisting of B, Al, Sn and Sb, L is independently selected from the group consisting of halide, alkoxy, siloxy, alkylamino, and C 1 –C 30 hydrocarbyl and y satisfies the valence of M.
3. The zwitterionic metallocycle of claim 2 wherein X is N and R 1 contains an atom bearing a full or partial negative charge selected from the group consisting of B and Al.
4. The zwitterionic metallocycle of claim 2 having the general formula:
wherein each R 3 is independently selected from the group consisting of H and C 1 –C 30 hydrocarbyl and m is 0 or 1.
5. The zwitterionic metallocycle of claim 2 having the general formula:
wherein each R 3 is independently selected from the group consisting of H and C 1 –C 30 hydrocarbyl.
6. An olefin polymerization process comprising contacting an olefin with a zwitterionic metallocycle comprising a Group 4-10 transition metal chelated to two heteroatoms independently selected from the group consisting of P, N, O, and S wherein the two heteroatoms are each attached to a linking group to form a metallocycle, and wherein one of the heteroatoms has a substituent bearing a full or partial negative charge on an atom from the group consisting of B, Al, Sn and Sb and wherein said atom is directly bonded to the heteroatom and the transition metal bears full or partial positive charge.
7. The olefin polymerization process of claim 6 wherein the olefin is selected from the group consisting of ethylene, propylene, 1-butene, 1-hexene, 1-octene and mixtures thereof.
8. The olefin polymerization process of claim 6 wherein the olefin is copolymerized with a polar comonomer.
9. The olefin polymerization process of claim 8 wherein the olefin is ethylene and the polar comonomer is selected from the group consisting of carbon monoxide, vinyl silanes, vinyl acetates, acrylates and maleic anhydride.
10. The olefin polymerization process of claim 6 wherein the zwitterionic metallocycle is supported.
11. A slurry olefin polymerization process of claim 6 .
12. A gas-phase olefin polymerization process of claim 6 .