Amidometallate von Seltenerdelementen. Synthese und Kristallstrukturen von [Na(12-Krone-4)2][M{N(SiMe3)2}3(OSiMe3)] (M = Sm,Yb), [Na(THF)3Sm{N(SiMe3)2}3(C≡C–Ph)], [Na(THF)6][Lu2(μ-NH2)(μ-NSiMe3){N(SiMe3)2}4] sowie von [NaN(SiMe3)2(THF)]2. Anwendungen der Seltenerdkomplexe als Polymerisationskatalysatoren |
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| Authors: | M. Karl,G. Seybert,W. Massa,K. Harms,S. Agarwal,R. Maleika,W. Stelter,A. Greiner,W. Heitz,B. Neumü ller,K. Dehnicke |
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| Abstract: | Amido Metalates of Rare Earth Elements. Syntheses and Crystal Structures of [Na(12-crown-4)2][M{N(SiMe3)2}3(OSiMe3)] (M = Sm, Yb), [Na(THF)3Sm{N(SiMe3)2}3(C≡C–Ph)], [Na(THF)6][Lu2(μ-NH2)(μ-NSiMe3){N(SiMe3)2}4], and of [NaN(SiMe3)2(THF)]2. Applications of Rare Earth Metal Complexes as Polymerization Catalysts The amido silyloxy complexes [Na(12-crown-4)2][M{N(SiMe3)2}3(OSiMe3)] with M = Sm ( 1 a ), Eu ( 1 b ), Yb ( 1 c ), and Lu ( 1 d ) were obtained from the trisamides M[N(SiMe3)3]3 and NaOSiMe3 in n-hexane in the presence of 12-crown-4; they form yellow to orange-red crystals, of which 1 a and 1 c were characterized crystallographically. The complexes crystallize isotypically with one another in the monoclinic space group I2/a with eight formula units per unit cell. The metal atoms of the complex anions are tetrahedrally coordinated by the three nitrogen atoms of the N(SiMe3)2– ligands and by the oxygen atom of the OSiMe3– ligand. With 172.4° for 1 a and 179.3° for 1 c the bond angles M–O–Si are practically linear. With ethynylbenzene in the presence of NaN(SiMe3)2 in tetrahydrofuran the trisamides M[N(SiMe3)2]3 react under formation of the complexes [Na(THF)3M{N(SiMe3)2}3 · (C≡C–Ph)] with M = Ce ( 2 a ), Sm ( 2 b ), and Eu ( 2 c ), of which 2 b was characterized crystallographically (monoclinic, space group P21/n, Z = 4). 2 b forms an ion pair in which the terminal carbon atom of the C≡C–Ph– ligand is connected with the samarium atom of the Sm[N(SiMe3)2]3 group and the sodium ion is side-on connected with the acetylido group. According to the crystal structure determination (space group P212121, Z = 4) [Na(THF)6][Lu2(μ-NH2)(μ-NSiMe3) · {N(SiMe3)2}4] ( 3 ), which is formed as a by-product, consists of [Na(THF)6]+ ions and dimeric anions, in which the lutetium atoms are connected to form a planar Lu2N2 four-membered ring via a μ-NH2 bridge with average Lu–N distances of 227.2 pm and via a μ-NSiMe3 bridge of average Lu–N distances of 218.5 pm. According to the crystal structure determination (space group P 1, Z = 1) [NaN(SiMe3)2(THF)]2 ( 4 ) forms centrosymmetric dimeric molecules with Na–N distances of the Na2N2 four-membered ring of 239.9 pm and distances Na–O of the terminally bonded THF molecules which are 226.7 pm. The vinylic polymerization of methylmethacrylate (MMA) catalyzed by 1 c resulted in high molecular weight polymethylmethacrylate (PMMA) with moderate yields. The reaction of 1 a or 2 b with MMA did not give PMMA. Insoluble polynorbornene was obtained in low yields by reaction of norbornene/methylaluminoxane (MAO) with 1 a , 1 c , or 2 b . The ring opening polymerization of ϵ-caprolacton or δ-valerolacton catalyzed by 2 b resulted in corresponding polylactones in quantitative yields. |
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| Keywords: | Amido Complexes Rare Earth Elements Crystal Structures Catalytic Properties Catalysis Vinylic Polymerization Ring-opening polymerization |
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