1204317-76-9Relevant academic research and scientific papers
Self-assembled tetranuclear palladium catalysts that produce high molecular weight linear polyethylene
Shen, Zhongliang,Jordan, Richard F.
, p. 52 - 53 (2010/03/25)
(Figure Presented) The phosphine-bis-arenesulfonate ligand PPh(2-SO 3Li-4-Me-Ph)2 (Li2[OPO]) coordinates as a K2-P,O chelator in Li[(Li-OPO)PdMe(Cl)] (2a) and (Li-OPO)PdMe(L) (L = pyridine (2b); MeOH (2d); 4-(5-nonyl)pyridine) (py, 3)). 2a reacts with AgPF6 to form {(Li-OPO)PdMe}n (2c). Photolysis of 2d yields {(OPO)Pd}2 (5) in which the [OPO]2- ligand coordinates as a K3-O,P,O pincer. 3 self-assembles into a tetramer in which four (Li-OPO)PdMe(py) units are linked by Li-O bonds that form a central Li4S4O12 cage. The Pd centers are equivalent but are spatially separated into two identical pairs. The Pd-Pd distance within each pair is 6.04 A. IR data (u(ArSO3 -) region) suggest that the solid state structures of 2a-c are similar to that of 3. 3 reacts with the cryptand Krypt211 to form [Li(Krypt211)][(OPO)PdMe(py)] (4). 3 is in equilibrium with a monomeric (Li-OPO)PdMe(py) species (3) in solution. 2a-c and 3 produce polyethylene (PE) with high molecular weight and a broad molecular weight distribution, characteristic of multisite catalysis. Under conditions where the tetrameric structure remains substantially intact, the PE contains a substantial high molecular weight fraction, while, under conditions where fragmentation is more extensive, the PE contains a large low molecular weight fraction. These results suggest that the tetrameric assembly gives rise to the high molecular weight polymer. In contrast, the monomeric complex 4, which contains a free pendant sulfonate group that can bind to Pd, oligomerizes ethylene to a Schultz-Flory distribution of C4-C18 oligomers.
