Olefin polymerization catalysts containing triquinane ligands
View Patent ↗A catalyst system useful for polymerizing olefins is disclosed. The catalyst system comprises an activator and an organometallic complex that incorporates a Group 3 to 10 transition metal and at least one chelating, dianionic triquinane ligand. The cis,syn,cis-triquinane framework is generated in three high-yield steps from inexpensive starting materials, and with heat and light as the only reagents. By modifying substituents on the triquinane ligand, polyolefin makers can control catalyst activity, comonomer incorporation, and polymer properties.
1. A method for preparing an organometallic complex useful for olefin polymerization, said method comprising:
(a) converting a pentacyclic diketone to a triquinane diene;
(b) doubly deprotonating the triquinane diene to produce a triquinane dianion; and
(c) reacting the dianion with a transition metal source to give an organometallic complex that incorporates a chelating, dianionic triquinane ligand.
2. The method of claim 1 wherein the pentacyclic diketone is produced by (a) reacting a cyclopentadiene and a p-benzoquinone to produce a Diels-Alder adduct; and (b) photolyzing the Diels-Alder adduct to effect a [2+2] cycloaddition reaction to give the pentacyclic diketone.
3. The method of claim 1 wherein step (a) is accomplished by first heating the pentacyclic diketone to cause a [2+2] cycloreversion reaction to give a cis,syn,cis-triquinane bis(enone), followed by conversion of the bis(enone) to the triquinane diene.
4. The method of claim 3 wherein the bis(enone) is converted to the triquinane diene by (a) reacting the bis(enone) with an arylhydrazine to produce an arylhydrazone; and (b) reducing the arylhydrazone to the diene by reacting it with an alkali metal cyanoborohydride or catecholborane.
5. The method of claim 3 wherein the bis(enone) is converted to the triquinane diene by reacting it with a trialkylhydrosilane in the presence of a Lewis acid.
6. The method of claim 1 wherein step (a) is accomplished by first converting the pentacyclic diketone to a pentacyclic hydrocarbon by reducing the carbonyl groups to methylene groups, and then heating the pentacyclic hydrocarbon to cause a [2+2] cycloreversion reaction to give the triquinane diene.
7. The method of claim 1 wherein the pentacyclic diketone is homologated by reacting it with diazomethane prior to conversion to the triquinane diene.
8. A method for preparing an organometallic complex useful for olefin polymerization, said method comprising:
(a) reacting a cyclopentadiene and a p-benzoquinone to produce a Diels-Alder adduct;
(b) photolyzing the Diels-Alder adduct to effect a [2+2] cycloaddition reaction to give a pentacyclic diketone;
(c) converting the pentacyclic diketone to a triquinane diene;
(d) doubly deprotonating the triquinane diene to produce a triquinane dianion; and
(e) reacting the dianion with a transition metal source to give an organometallic complex that incorporates a chelating, dianionic triquinane ligand.
9. The method of claim 8 wherein the Diels-Alder adduct is produced from cyclopentadiene and p-benzoquinone.