Synthesis of 1,3,5-triaza-7-phosphaadamantane (PTA) and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) complexes and the development of chromium salen catalysts for the copolymerization of CO2 and epoxides

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Title: Synthesis of 1,3,5-triaza-7-phosphaadamantane (PTA) and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) complexes and the development of chromium salen catalysts for the copolymerization of CO2 and epoxides
Author: Ortiz, Cesar Gabriel
Abstract: Two main areas are considered in this manuscript . The first describes the synthesis of group 10 metal complexes incorporating the water -soluble 1 ,3 ,5 -triaza -7 -phosphaadamantane (PTA ) ligand and the second deals with the preparation of Cr (salen )X catalysts for the copolymerization of CO2 and epoxides . In the first topic , the synthesis of nickel (II ) and palladium (II ) salicylaldiminato complexes incorporating PTA has been achieved employing two preparative routes . Upon reacting the original ethylene polymerization catalyst developed by Grubbs and coworkers (Organometallics , 1998 , 17 , 3149 ) , (salicylaldiminato )Ni (Ph )PPh3 , with PTA using a homogeneous methanol /toluene solvent system resulted in the formation of the PTA analogs in good yields . Alternatively , complexes of this type may be synthesized via a direct approach utilizing (TMEDA )M (CH3 )2 (M = Ni , Pd ) , the corresponding salicylaldimine , and PTA . Polymerization reactions were attempted using the nickel -PTA complexes in a biphasic toluene /water mixture in an effort to initiate ethylene polymerization by trapping the dissociated phosphine ligand in the water layer , thereby , eliminating the need for a phosphine scavenger . Unfortunately , because of the strong binding ability of the small , donating phosphine (PTA ) as compared to PPh3 , dissociation did not occur at a temperature where the complexes are not subjected to decomposition . Additionally , the unexplored PTA derivative , 3 ,7 -diacetyl -1 ,3 ,7 -triaza -5 -phosphabicyclo[3 .3 .1]nonane (DAPTA ) , prepared by the literature procedure , was fully characterized by NMR and X -ray analysis . DAPTA is found be similar to its parent (PTA ) in coordination mode and binding strength , as supported by its representative group 6 and group 10 complexes The second main topic involves the copolymerization of CO2 and epoxides (i .e . , cyclohexene oxide (CHO ) ) for the formation of polycarbonate using Cr (salen )X (X = Br , OPh ) catalysts with one equivalent of PR3 as the co -catalyst . The use of these catalysts and cocatalysts results in the most active chromium -based catalytic systems to date . The . hr -1highest activities observed are on the order of 109 mol CHO consumed . mol Cr -1 using PCy3 as the co -catalyst , and is clearly seen in the in situ monitoring of copolymer formation . An advantage of these systems involves the lack of cyclic carbonate production and high CO2 incorporation ( >99 % ) within the polymer .
URI: http : / /hdl .handle .net /1969 .1 /359
Date: 2004-09-30

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Synthesis of 1,3,5-triaza-7-phosphaadamantane (PTA) and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) complexes and the development of chromium salen catalysts for the copolymerization of CO2 and epoxides. Available electronically from http : / /hdl .handle .net /1969 .1 /359 .

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