Amido metalates of rare earth elements.: Syntheses and crystal structures of [Na(12-clown-4)2][M{N(SiMe3)2}3(OSiMe3)] (M = Sm, Yb), [Na(THF)3Sm(N(SiMe3)2}3(CC-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 (la), Eu (Ib), To (Ic), and Lu (Id) 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 la and Ic 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 tetra-hedrally coordinated by the three nitrogen atoms of the N(SiMe3)(2)(-) ligands and by the oxygen atom of the OSiMe3- ligand. With 172.4 degrees for la and 179.3 degrees for Ic 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)(3)M{N(SiMe3)(2)}(3).(C = C-Ph)] with M = Ce (2a), Sm (2b), and Eu (2c), of which 2b was characterized crystallographically (monoclinic, space group P2(1)/n, Z = 4). 2b 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 P2(1)2(1)2(1), Z = 4) [Na(THF)(6)] [Lu-2(mu-NH2) (mu-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 mu-NH2 bridge with average Lu-N distances of 227.2 pm and via a mu-NSiMe3 bridge of average Lu-N distances of 218.5 pm. According to the crystal structure determination (space group P (1) over bar, 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 Ic resulted in high molecular weight polymethylmethacrylate (PMMA) with moderate yields. The reaction of 1a or 2b with MMA did not give PMMA. Insoluble polynorbornene was obtained in low yields by reaction of norbornene/methylaluminoxane (MAO) with 1a, 1c, or 2b. The ring opening polymerization of epsilon-caprolacton or delta-valerolacton catalyzed by 2b resulted in corresponding polylactones in quantitative yields.