Nobuko Kanehisa

Catalytic activity of allyl-, azaallyl- and diaza-pentadienyllanthanide complexes for polymerization of methyl methacrylate ☆

Abstract A variety of allylic, aza-allylic and 1,5-diazapentadienyllanthanide compounds were synthesized and their polymerization catalysis toward methyl methacrylate were examined. Divalent Sm[1,3-bis(trimethylsilyl)propenyl] 2 (THF) 2 1 and Sm(1,3-diphenylpropenyl) 2 (THF) 2 2 were synthesized by the reaction of potassium 1,3-bis(trimethylsilyl)propenide or potassium 1,3-diphenylpropenide with SmI 2 . The aza-allyllanthanide compound was synthesized by the reaction of 2-pyridylbenzyllithium with SmCl 3 followed by the reaction with LiCH(SiMe 3 ) 2 to give (2-pyridylbenzyl) 2 SmCH(SiMe 3 ) 2 3 . 1,5-Diazapentadienyllanthanide was prepared by the reaction of K[(C 5 H 4 N) 2 CPh] with YbBr 2 to give Yb[(C 5 H 4 N) 2 CPh] 2 (THF) 2 4 , which crystalizes monoclinic, space group C 2/ C (No. 15), with a =35.19(1), b =13.613(3), c =26.552(7) A, β =133.77(1)°, and Z =8. Preparations of divalent samarium and ytterbium complexes with bis(2-pyridylphenylmethyl)dimethylsilane ligand ( 6 and 7 ) were carried out by the reaction of dipotassium salt of bis(2-pyridylphenylmethyl)dimethylsilane with SmI 2 or YbBr 2 . By using the resulting compounds 1 , 2 , 3 , 4 , 6 and 7 as initiator, we have examined their catalytic activities for the polymerization of methyl methacrylate and found that compounds 6 and 7 are effective to give high molecular weight isotactic polymers.

Reaction courses for formation of early transition metal phenoxides

Abstract The 1 : 1 and 1 : 2 reactions of TiCl4 with Me3SiO-2,6-(CH3)2C6H3 produced TiCl3[O-2,6-(CH3)2C6H3]2(THF)2 (1) and TiCl2[O-2,6-(CH3)2C6H3]2(THF)2 (2), respectively, bearing six-coordinated geometry around Ti. The compound 2 assumes the cis-geometry regarding the two phenoxy groups and THF is coordinated in the trans position of the phenoxy groups. Similarly, the 1 : 1 and 1 : 2 reactions of NbCl5 with the trimethylsilyl phenyl ether provided NbCl4[O-2,6-(CH3)2C6H3]2(THF) (7) and NbCl3[O-2,6-(CH3)2C6H3]2(THF) (8), respectively, with octahedron structure. The THF molecule again locates in the trans position of a phenoxy group in both cases and the two phenoxy groups of 8 locate in the cis position. Tungsten mono-phenoxide, WCl5[O-2,6-(CH3)2C6H3]2 (12), also has octahedron structure. In cases of tungsten bis-phenoxides, WCl4[O-2,6-(CH3)2C6H3]2 (13) and WCl4[O-2,6-(i-C3H7)C6H3]2 (14), the former has trans structure while the latter has cis structure regarding the phenoxy groups. A unique square pyramidal geometry has been observed in the tetrakis(phenoxy) tungsten, WCl[O-2,6(CH3)2C6H3]4 (16).

A simplest isolable monocyclic thiepin. Synthesis, structure, and thermal stability of 2,7-di-tert-butylthiepin

Abstract As an example of a simplest isolable monocyclic thiepin, 2,7-di-tert-butylthiepin (2) has been synthesized from 2,6-di-tert-butylthiopyrylium salt, and the thermal properties together with the X-ray crystal structure of (2) have been examined.

A new convenient preparation of monocyclooctatetraenyl-lanthanide complexes from metallic lanthanides and oxidants

Abstract Treatment of lanthanide metals with cyclooctatetraene in the presence of an equimolar amount of iodine afforded cyclooctatetraenyl-iodolanthanide(III) complexes, LnI(η 8 -cot)(thf) n . (cot = cyclooctatetraenyl; 1a : Ln  La, n = 3; 1b : Ln  Ce, n = 3; 1c : Ln  Pr, n = 3; 1d : Ln  Nd, n = 2; 1e : Ln  Sm, n = 1), in modest yields. Bromo and chloro-bridged dinuclear complexes of samarium, [Sm(μ-X)(cot)(thf)] 2 ( 2 : X  Br; 3 : X  Cl), are also prepared by the reaction of samarium metal with cyclooctatetraene in the presence of 1,2-dibromoethane or Ph 3 PCl 2 , respectively. The reaction of metallic samarium with cyclooctatetraene and diaryl disulfide or diphenyl diselenide in THF afforded cyclooctatetraenyl-thiolate or -selenolate complexes of samarium(III), [Sm(μ-EAr)(η 8 -cot)(thf) n ] 2 ( 4a : EAr  SPh, n = 2; 4b : SC 6 H 2 Me 3 -2,4,6, n = 2; 4c : SC 6 H 2 i Pr 3 -2,4,6, n = 1; 5 : SePh, n = 2). The dimeric structure of 5 was revealed by X-ray. crystallography [monoclinic, space group P 2 1 / n with a = 8.500(5), b = 21.805(6), c = 12.042(5) A, β = 105.98(4)°, V = 2145(1) A 3 , Z = 2, R = 0.055 for 2061 reflections with I > 3σ-( I ) and 235 parameters].A samarium (II) complex, [Sm(η 8 -cot)(thf)] n , ( 6 ), was also obtained by the direct reaction of samarium metal with cyclooctatetraene in THF with a catalytic amount of iodine. Reaction of 6 with iodine and diphenyl disulfide afforded 1e and 4a , respectively.

FERROMAGNETIC BEHAVIOR OF A TETRAFLUOROTETRACYANOQUINODIMETHANIDE SALT AT ROOM TEMPERATURE

Abstract Recrystallization of N(CH 3 ) 4 + · TCNQF 4 −. in the presence of TCNQF 4 from acetonitrile/ether gave a crystal of { N(CH 3 ) 4 + · TCNQF 4 −. }· 1 2 ( TCNQF 4 ) , which very interestingly exhibited ferromagnetism at temperature. This organic ferromagnet has characteristics of very small saturation moment (1.03 × 10 −3 μ B /molecule) and coercive field (≈ 25 Oe). The origin of this ferromagnetism could be attributed to a unique crystal structure of the radical anion salt: the TCNQF 4 /TCNQF 4 −. and N(CH 3 ) 4 + ion layers are alternately stacked and in the TCNQF 4 /TCNQF 4 −. layer each pair of two TCNQF 4 −. molecules is arranged in a completely perpendicular manner to each of one TCNQF 4 molecule.

1:2 TCNQ/TCNQ−. mixed salts exhibiting ferromagnetic behavior at room temperature

Abstract Ferromagnetic behavior at room temperature was observed in the tetramethylammonium (NMe + 4 ) and cesium (Cs + ) salts of tetracyanoquinodimethane (TCNQ) and its radical anion (TCNQ −. ) in a molecular ratio of 1:2. The saturation magnetizations and coercive forces are 0.79 emu/mol and ≈300 Oe for ( NMe + 4 · TCNQ −. ) · 1 2 TCNQ , and 1.46 emu/mol and ≈100 Oe for ( Cs +. · TCNQ −. ) · 1 2 TCNQ , respectively. In contrast, the 1:1 TCNQ/TCNQ −. mixed tetraethylammonium (NEt 4 + salt, (NEt 4 + ·TCNQ − ·)·TCNQ, exhibited no ferromagnetic behavior at room temperature nor at lower temperatures.

High polymerization of methyl methacrylate with organonickel/MMAO systems

A series of nickel complexes, including Ni(acac)2, (C5H5)Ni(η3-allyl), and [NiMe4Li2(THF)2]2, that were activated with modified methylaluminoxane (MMAO) exhibited high catalytic activity for the polymerization of methyl methacrylate (MMA) but showed no catalytic activity for the polymerization of ethylene and 1-olefins. The resulting polymers exhibited rather broad molecular weight distributions and low syndiotacticities. In contrast to these initiators, the metallocene complexes (C5H5)2Ni, (C5Me5)2Ni, (Ind)2Ni, and (Me3SiC5H4)2Ni provided narrower molecular weight distributions at 60 °C when these initiator were activated with MMAO. Half-metallocene complexes such as (C5H5)NiCl(PPh3), (C5Me5)NiCl(PPh3), and (Ind)NiCl(PPh3) produced poly(methyl methacrylate) (PMMA) with much narrower molecular weight distributions when the polymerization was carried out at 0 °C. Ni[1,3-(CF3)2-acac]2 generated PMMA with high syndiotacticity. The NiR(acac)(PPh3) complexes (R = Me or Et) revealed high selectivity in the polymerization of isoprene that produced 1,2-/3,4-polymer at 0 °C exclusively, whereas the polymerization at 60 °C resulted in the formation of cis-1,4-rich polymers. The polymerization of ethylene with Ni(1,3-tBu2-acac)2 and Ni[1,3-(CF3)2-acac]2 generated oligo-ethylene with moderate catalytic activity, whereas the reaction of ethylene with Ni(acac)2/MMAO produced high molecular weight polyethylene.

Monocyclooctatetraenyl(thiolato)samarium(III) complexes from the reaction of metallic samarium with cyclooctatetraene and diaryldisulfide: crystal structures of [Sm(µ-SPh)(C8H8)(thf)2]2 and [{Sm[µ-S(2,4,6-triisopropylphenyl)(C8H8)(thf)}2]

Metallic samarium reacts directly with Cyclooctatetraene in the presence of diaryldisulfide to give cyclooctatetraenyl(thiolato)samarium(III) complexes, {Sm(µ-SAr)(C8H8)(thf)n]2(thf = tetrahydrofuran)(1, Ar = C6H5, n= 2; 2, Ar = 2,4,6-Me3-C6H2, n= 2; 3, Ar = 2,4,6-(Pri)3-C6H2, n= 1), the structures of which are confirmed by single crystal X-ray analyses of 1 and 3, while Yb reacts with diphenyldisulfide in thf to afford [Yb(SPh)2(thf)]n.

Formation of lanthanoid(II) and lanthanoid(III) thiolate complexes derived from metals and organic disulfides: crystal structures of [{Ln(SAr)(µ-SAr)(thf)3}2](Ln = Sm, Eu), [Sm(SAr)3(py)2(thf)] and [Yb(SAr)3(py)3](Ar = 2,4,6-triisopropylphenyl; py = pyridine)

Reaction of metallic samarium, europium and ytterbium with bis(2,4,6-triisopropylphenyl) disulfide gave selectively LnII thiolate complexes, [{Ln(SAr)(µ-SAr)(thf)3}2] Ln = Sm 1; Ln = Eu 2 and [Yb(SAr)2(py)4]3, as well as LnIII thiolate complexes, [Ln(SAr)3(py)n(thf)3–n]: Ln = Sm, n= 3 4a; Ln = Sm, n= 2 4b; Ln = Yb, n= 3 5, (Ar = 2,4,6-trisopropylphenyl) depending on the stoichiometry of the lanthanoid and the disulfide; the molecular structures of 1, 2, 4b and 5 were determined by X-ray crystallography.

Synthesis of 2,6-dialkoxylphenyllanthanoid complexes and their polymerization catalysis

Abstract The 1:1–2:1 reaction of [2,6-( i PrO) 2 C 6 H 3 ]Li with anhydrous SmCl 3 in THF gave [2,6-( i PrO) 2 C 6 H 3 ] 3 Sm 1 exclusively, while the 3:1 reaction gave [2,6-( i PrO) 2 C 6 H 3 ] 4 SmLi 2 as major product, which crystallizes in the monoclinic space group C 2/ c (No. 15) with a =47.52(1) A, b =11.680(9) A, c =18.862(9) A, β =112.19(3)°, V =9694(8) A 3 , Z =8, R =0.077 and R w =0.074. In a similar manner, [2,6-( i PrO) 2 C 6 H 3 ] 3 La was obtained by reacting with LaCl 3 (THF) 2 . The 2:1 reaction of [2,6-( i PrO) 2 C 6 H 3 ]Li with YbCl 3 gave [2,6-( i PrO) 2 C 6 H 3 ] 2 YbCl, which produces [2,6-( i PrO) 2 C 6 H 3 ] 2 Yb[CH(SiMe 3 ) 2 ] 2 Li 4 by reaction with (SiMe 3 ) 2 CHLi. Polymerizations of ϵ -caprolactone and alkyl isocyanates were examined using the resulting complexes.