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)(3)Sm(N(SiMe3)(2)}(3)(C C-Ph)], [Na(THF)(6)][Lu-2(mu-NH2)(mu-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 tri samides M[N(SiMe3)(3)](3) and NaOSiMe3 in n-hexane in the presence of 12-cr own-4; they form yellow to orange-red crystals, of which la and Ic were cha racterized crystallographically. The complexes crystallize isotypically wit h one another in the monoclinic space group I2/a with eight formula units p er unit cell. The metal atoms of the complex anions are tetra-hedrally coor dinated by the three nitrogen atoms of the N(SiMe3)(2)(-) ligands and by th e oxygen atom of the OSiMe3- ligand. With 172.4 degrees for la and 179.3 de grees 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 w hich 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), wh ich is formed as a by-product, consists of [Na(THF)6](+) ions and dimeric a nions, in which the lutetium atoms are connected to form a planar Lu2N2 fou r-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. Accordin g 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 resu lted in high molecular weight polymethylmethacrylate (PMMA) with moderate y ields. The reaction of 1a or 2b with MMA did not give PMMA. Insoluble polyn orbornene was obtained in low yields by reaction of norbornene/methylalumin oxane (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.