Lanthanum coordination polymers

Lanthanum dibenzyl complexes with triazanonane-silylamide, amidine and 1,3-diketiminate monoanionic ancillary ligands were also prepared by in situ peralkylation in the presence of the protonated ligand or by com-plexation (for 1,3-diketiminate) with lanthanum tribromide and subsequent alkylation. The coordination polymer [p-r 2 r 1-ArNC(Me)CHC(CH2)-NAr]2La[K(THF)4] n formed by H-abstraction from one of the diketimi-nate Me groups and a ligand redistribution.14... 

Various lanthanide halides (ScCb, YCI3, LaCb, Ndl3) react with K2[3-(C3Et3SiMe3-l)2SiMe2] to form an5 a-bis(aUyl) complexes. The lanthanum derivative has been stmcturally authenticated as a coordination polymer (14), in which aUyl anions interleave alternating lanthanum and potassium ions the latter display K- MeSi contacts of 2.79(3) and2.96(4) A. ... 

BERNSON A, LINDGREN J, HUANG w and FRECH R, Coordination and conformation in PEO, PEGM and PEG systems containing Uthium or lanthanum triflate . Polymer, 1995,36(23), 4471-4478... 

Structure Non-hydrated rare earth fluorides have two different crystal systems, a hexagonal system (lanthanum to terbium) and an orthorhombic system (dysprosium to lutetium, yttrium). In the crystal of LaFs, the central ion is nine coordinated by nine fluoride atoms. Each fluoride atom further connects with two lanthanum atoms through a [13-bridge to form an infinite polymer. 

Hydrates of rare earth chlorides also have two different crystal systems a triclinic system for lanthanum, cerium, and praseodymium, as well as a monoclinic system for neodymium to lutetium and yttrium. CeCl3-7H20, as an example of the former system, is different from the above infinite polymer as two cerium atoms are connected by two [i2-bridges to form a dimer. The formula for this dimer is [(H20)7Ce([i2-Cl)2Ce(H20)7]Cl4 as shown in Figure 1.18. Therefore, the coordination number of cerium is nine and the polyhedron takes on a destroyed mono-capped square antiprism configuration. 

Coordination centers studied include beryllium, lanthanum, cerium, titanium, zirconium, thorium, uranium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, aluminum, tin, and lead. Many nonmetallic elements have been incorporated into the bridging groups and side groups, so that, in all, some 30 elements have been included in polymers of the phosphinate type. Of most interest are some of the polymers with tetrahedral and octahedral centers. 

Lanthanide compounds such as yttrium and lanthanum alkoxides have been reported to yield high-molecular-mass polyesters under mild conditions. The yttrium alkoxide-initiated polymerization of CL proceeded rapidly at room temperature [27-29], while the use of bulky groups reduced the transesterification reaction such that polymers with a narrow molecular mass were obtained (Scheme 11.3). For example, the bulky phenoxide ligands of the yttrium or lanthanide catalyst were exchanged for the smaller alcohol (2-propanol), followed by coordination and insertion of the monomer (CL) [27]. 

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