Multinuclear Palladium Olefin Polymerization Catalysts Based on Self-Assembled Zinc Phosphonate Cages

The phosphine-phosphonate-sulfonate proligand HP+(4-Bu-t-Ph)(2-PO3H2-5-Me-Ph)(2-SO3--5-Me-Ph) (H-3[OP-P-SO], 1-H-3) was investigated as a building block for the self-assembly of multinuclear Pd compounds based on zinc phosphonate scaffolds. 1-H-3 reacts with Zn(OAc)(2)center dot 2H(2)O to afford {Zn[1-H]}(4), which adopts a Zn4P4O8 ring structure in which the Zn centers are linked by mu(2)-kappa(1),kappa(1)-bridging (aryl)PO3H- ligands. {Zn[1-H]}(4) reacts with (TMEDA)PdMe2 and pyridine to generate {[(kappa(2) -OP-P-SO)PdMe(py)]-[Zn(TMEDA)]}(2) (2), in which two [(kappa(2)-OP-P-SO)PdMe(py)](2-) units are linked through a Zn2P2O4 ring. The sequential reaction of CH3OH-free {Zn[1-H]}(4) with (COD)PdMe2 and 4-Bu-t-py generates {[kappa(2)-(Zn-OP-P-SO)]PdMe(4-Bu-t-py)}(4) (4- (4-Bu-t-py)), in which four [(kappa(2)-OP-P-SO)PdMe(4-Bu-t-py)](2-) units are arranged on the periphery of a double-four-ring (D4R) Zn-4 P4O12 cage. Analogous 4-L species were generated by the reaction of {Zn[1-H]}(4), (COD)PdMe2, and other pyridine ligands. 4-py reacts with CH3OH to form a trimeric cluster 3-py, which adopts a cage structure based on Zn3P3O6 and Pd3O3 rings. In the presence of B(C6F5)(3) to sequester the pyridine ligands, 4-(4-B-t-py) and 3-py polymerize ethylene at 80 degrees C to linear polyethylene with high molecular weight (up to M-w = 1 X 10(6) Da).