Hak-Chul Kang

Alcoholysis of Aluminum Alkyls Supported by Bulky Phenoxide Ligands: Synthesis, Characterization, and ε-Caprolactone Polymerization Activity of Two Dimeric Aluminum Isopropoxides

Reaction of trialkylaluminum Al2R6 (R = Me, Et) with 2,2′-methylenebis(6-tert-butyl-4-methylphenol) (mbmpH2) gives the dimeric mono(alkyl) complex [Al(mbmp)R]2 with bridging oxygen atoms. Reaction of [Al(mbmp)R]2 with one equiv. of 2-propanol results in the formation of the dimeric isopropoxide [Al(mbmp)(μ-OiPr)]2. Single-crystal X-ray analysis shows a C2h-symmetric structure with a planar Al2O2 core. Monomeric methylbis(2,6-di-tert-butyl-4-methylphenolato)aluminum, AlMe(OC6H2-2,6-tBu2-4-Me)2 (MAD), was found to react with one equiv. of 2-propanol to give a dimeric isopropoxide [AlMe(OC6H2-2,6-tBu2-4-Me)(μ-OiPr)]2 in which the bulky phenolate, instead of the methyl group, has been displaced. According to the single-crystal X-ray structure analysis, the molecule contains a similar Al2O2 core, but the two 2,6-di-tert-butyl-4-methylphenolato ligands are cis- and orthogonally arranged to each other. ϵ-Caprolactone is polymerized at 50 °C in toluene in a controlled manner by [Al(mbmp)(μ-OiPr)]2, to give poly(ϵ-caprolactone) with high molecular weights and narrow molecular weight distributions (Mw/Mn < 1.50). The low efficiency values (number of polymer chains initiated per aluminum atom) imply that [Al(mbmp)(μ-OiPr)]2 exists in a monomer–dimer equilibrium. The polymerization of ϵ-caprolactone by [AlMe(OC6H2-2,6-tBu2-4-Me)(μ-OiPr)]2 is faster, but somewhat less controlled.

Indenyl effect in d0-transition metal complexes: synthesis, molecular structure and lactone polymerization activity of [Ti(η5-C9H7)Cl2OMe)]

Abstract The titanium methoxo complex Ti(η 5 -C 9 H 7 )Cl 2 OMe), prepared from the trichloro complex Ti(η 5 -C 9 H 7 )Cl 3 , was found to polymerize ϵ-caprolactone with ring opening significantly more efficiently than analogous cyclopentadienyl derivatives. The crystal structure of Ti(η 5 -C 9 H 7 )Cl 2 OMe) was determined and shows a C s -symmetric piano-stool conformation with the strongly π-donating methoxo group trans to the six-membered ring.

Synthesis and structural characterization of titanium complexes containing a sulfinyl-bridged bis(phenolato) ligand

Abstract Titanium complexes containing the novel tridentate 2,2′-sulfinylbis(6-tert-butyl-4-methylphenoxo) ligand (sibmp) were synthesized and characterized. Treatment of titanium tetra-iso-propoxide with 2,2′-sulfinylbis(6-tert-4-methylphenol) (sibmpH2) in 1:1 molar ratio afforded red-orange, sparingly soluble di-iso-propoxo derivative [Ti(sibmp)(O-i-Pr)2]2·0.5 Et2O. The single-crystal structure analysis was performed and revealed a dimeric centrosymmetric structure with a planar Ti2O2 core. The titanium center is approximately octahedral with a SO function intramolecularly coordinated at the titanium center. Treatment of sibmpH2 with titanium tetra-iso-propoxide in 2:1 molar ratio gave yellow Ti(sibmp)2 with a C2-symmetric spirocyclic structure. The dark red dichloro complex [Ti(sibmp)Cl2] was prepared by reacting titanium tetrachloride with sibmpH2.

Aluminum complexes of sterically hindered tetradentate Schiff bases: Synthesis, structure, and reactivity toward ɛ-caprolactone

Abstract The sterically hindered Schiff bases tbmSalenH2 [tbmSalen = N,N′-1,2-ethylenebis(3-tert-butyl-5-methylsalicylideneimine)] and tbmSalcenH2 [tbmSalcen = N,N′-trans-1,2-cyclohexanediyl-bis(3-tert-butyl-5-methylsalicylideneimine)] afforded a series of aluminum complexes of the general formulae [Al(tbmSalen)X] and [Al(tbmSalcen)X] (X = Cl, Me, Et). The molecular structure of [Al(tbmSalcen)Cl] was determined by single-crystal X-ray structural analysis which revealed a five-coordinate aluminum center with a distorted square pyramidal geometry. The alkyl complexes were found to oligomerize ɛ-caprolactone.

Die Kristallstrukturen der silylierten Phosphanimine Me3SiNPPh3 und Me3SiNPPh2 - C2H4 - PPh2NSiMe3 / Crystal Structures of the Silylated Phosphanimines Me3SiNPPh3 und Me3SiNPPh2 - C2H4 - PPh2NSiMe3

The crystal structures of two silylated phosphanimines have been determined. Me3SiNPPh3: Space group P 1̃, Z = 2, structure refinement with 2907 observed unique reflections with Fo > 5 σ(Fo), R = 0.052. Lattice dimensions at 19 °C: a = 876.6(1), b = 1125.8(1), c = 1151.2(1) pm, α = 61.71(1)°, β = 88.08(1)°, γ = 87.18(1)°. The compound forms monomeric molecules with a SiNP bond angle of 140.2° and bond lengths PN of 154.2 pm and SiN of 168.6 pm which correspond with PN double and SiN single bonds. Me3SiNPPh2 - C2H4 -PPh2N SiMe3: Space group P31, Z = 3, structure refinement with 4251 independent reflections, R = 0.061 for 3587 reflections with I > 2σ(I). Lattice dimensions at - 80 °C: a = b = 1591.4(1), c = 1165.8(1) pm. The compound forms monomeric molecules with a c/s-conformation of the PNSiMe3 groups. Bond angles and bond lengths (average) are SiNP = 140.8°, PN = 153.8 pm, SiN = 165.6 pm.

Über die Reaktion von SbPh3 mit S3N2Cl2 Kristallstrukturen von [xxx] und [(Ph3SbCl2)2·S4N4]/ On the Reaction of SbPh3 with S3N2Cl2. Crystal Structures of [xxx] and [(Ph3SbCl2)2· S4N4]

Abstract Triphenylantimony reacts with S3N2Cl2 in dichloromethane solution to give yellow crystals of the cyclostibathiazene derivative [xxx], As a by-product orange single crystals of [(Ph3SbCl2)2·S4N4] were isolated, in which the molecular compounds Ph3SbCl2 and S4N4 only form van der Waals contacts with one another. Both compounds are characterized by crystal structure determinations. [xxx]: Space group P21/n, Z = 4; lattice dimensions at -80°C: a = 759.4(1), b = 1448.5(3); c = 1557.6(2) pm; β = 91.09(1)°, R = 0.026. The complex has a molecular structure in which the Sb atom is coordinate in a distorted trigonal-bipyramidal fashion with one phenyl group and one of the nitrogen atoms of the planar [xxx] ring in the apical positions. [(Ph3SbCL)2·S4N4]: Space group C2/c, Z = 8 ; lattice dimensions at -60°C: a = 1549.3(1), b = 1017.7(1), c = 2623.9(1) pm, β = 105.56(2)°, R = 0.050.

Ionische Phosphaniminato-Komplexe von Schwefel(IV) und Selen(IV ). Die Kristallstrukturen von [S(NPMe3)3]Cl · CH2Cl2, [S(N PPh3)3]S4N5 und [Se(NPMe3)3]Cl · C7H8 / Ionic Phosphorane Iminato Complexes of Sulfur(IV) and Selenium(IV). Crystal Structures of [S(NPMe3)3]Cl ·CH2Cl2, [S(NPPh3)3]S4N5 and [Se(NPMe3)3]Cl · C7H8

[S(NPMe3)3]Cl · CH2C12 and [S(NPPh3)3]S4N5 were prepared by the reaction of Me3SiNPMe3 or Me3SiNPPh3 with sulfur dichloride and S3N2Cl2, respectively, in CH2Cl2 solutions as colourless, moisture sensitive crystals. The corresponding selenium compound was prepared from SeCl4 and Me3SiNPMe3 in acetonitrile solution; it crystallizes from toluene solutions with one mole of toluene per formula unit. All complexes have been characterized by IR spectroscopy and by crystal structure determinations. [S(NPMe3)3]Cl-CH2Cl2: Space group Pna21, Z = 8 , 3930 observed unique reflections, R = 0.033. Lattice dimensions at -120 °C: a = 1200.9(1), b = 1020.2(1), c = 1790.5(1) pm. [S(NPPh3)3]S4N5: Space group P63, Z = 2, 2586 observed unique reflections, R = 0.054. Lattice dimensions at -100 °C: a = b = 1334.7(2), c = 1652.6(2) pm. [Se(NPMe3)3]Cl · C7H8: Space group C2/c, Z = 8 , 1475 observed unique reflections, R = 0.059. Lattice dimensions at -40 °C: a = 1853.6(8), b = 1159.2(4), c = 2053.2(4) pm. β = 101.92(3)°. All compounds contain cations [E(NPR3)3]+ (E = S, Se) with pyramidal structures. Bond lengths and bond angles are in average: S-N 162.5 pm, S-N-P 120.5° (R = Me), S-N 161.8 pm, S-N-P 119.2° (R = Ph), Se-N 177.8 pm, Se-N-P 120.3°.