Mark Schormann

Monocyclopentadienyl phenoxy-imine and phenoxy-amine complexes of titanium and zirconium and their application as catalysts for 1-alkene polymerisation

Abstract Deprotonation of the phenol-imines 2-But-6-(RNCH)C6H3OH (R=2,4,6-Me3C6H2 (1a), C6F5 (1b), C6H11 (1c) and phenol-amines 2,4-But2-6-(R′NCH2)C6H2OH (R′=C4H8 (1d), C5H10 (1e)) with n-BuLi gives the corresponding lithium phenoxides. The reaction with MCl4 in THF solution leads to the bis(ligand) complexes {2-But-6-(RNCH)C6H3O}2MCl2 and {2,4-But2-6-(R′NCH2)C6H2O}2MCl2 (M=Ti: 2a, 2d, 2e, Zr: 3a, 3d and 3e). The cyclopentadienyl phenoxy-imine and -amine complexes Cp{2-But-6-(RNCH)C6H3O}MCl2 and Cp{2,4-But2-6-(R′NCH2)C6H2O}MCl2 (M=Ti: 4a–4e, Zr: 5a–5e) were prepared similarly through reaction with CpMCl3. The crystal and molecular structures of 2a, 3a, 4a and 4e have been determined. 2a and 3a are isostructural and exhibit a distorted octahedral geometry. 4a has a distorted square-pyramidal structure whereas 4e is essentially tetrahedral and the nitrogen does not coordinate. All new complexes are active for the polymerisation of ethene when activated with methyaluminoxane. 4b, 5a, 5d and 5e are active for the copolymerisation of ethene and 1-hexene and the oligomerisation of 1-hexene.

Gold(III) Olefin Complexes

Zeises salt gets company: 185 years after the report of the well-known platinum(II) ethylene compound, examples of isolable olefin complexes of its isoelectronic neighbor in the periodic table, gold(III), have been prepared (see picture). The complexes are very susceptible towards nucleophilic attack; there is also structural evidence for Au-Ag interactions. Copyright

Synthesis, structure and catalytic activity of new iminophenolato complexes of scandium and yttrium

The reaction of equimolar amounts of 2-(2,4,6-Me3C6H2N=CH)(6-But)C6H3OH (HL1) with M(CH2SiMe3)3(THF)3 (M=Sc or Y) under mild conditions gives M(CH2SiMe3)2(THF)(L1). The trigonal-bipyramidal structure of these dialkyls was confirmed crystallographically for M=Sc. Whereas the scandium complex is stable in solution at room temperature, the yttrium derivative slowly disproportionates to give Y(L1)3 which is also accessible from Y(CH2SiMe3)3(THF)3 and three HL1. The X-ray structure of Y(L1)3 indicates a chiral tris-chelate complex. While the reaction of the related ligand (2-CyN=CH)(6-But)C6H3OH (HL2, Cy=cyclohexyl) with Sc(CH2SiMe3)3(THF)3 gives the expected dialkyl Sc(CH2SiMe3)2(THF)(L2), the reaction with the yttrium analogue affords the six-coordinate monoalkyl product Y(CH2SiMe3)(THF)(L2)2. This product is stable in solution towards disproportionation. The reaction of Y[N(SiMe3)2]3 with (2-C6F5N=CH)(6-But)C6H3OH (HL3) affords Y{N(SiMe3)2}(L3)2 and Y(L3)3. Both complexes are seven-coordinate in the solid state due to Y•••F co-ordination to the C6F5 substituents. The scandium alkyl complexes are efficient catalysts for the ring-opening polymerisation of e-caprolactone.

Role of B(C 6 F 5 ) 3 in catalyst activation, anion formation, and as C 6 F 5 transfer agent* , **

The versatile reactivity of B(C6F5)3 in alkene polymerization reactions is summarized. Adduct formation with basic anions such as CN– and NH2– gives extremely weakly co- ordinating diborates, which are the basis of some of the most active polymerization catalysts known to date. By contrast, the reaction of B(C6F5)3 with zirconium half-sandwich complexes leads to extensive C6F5 transfer, including the surprising formation of borole-bridged triple decker complexes. Main group alkyls undergo such C6F5 exchange reactions very readily unless donor ligands are present. Borate salts of new three-coordinate zinc alkyl cations proved to be highly effective catalysts for the ring-opening polymerization of epoxides and lactones.

Preparation of bistrimethylsilylmethylniobiumtetrafluoride and the application of KHF2 and n-Bu4NHF2 as fluorinating reagents

Abstract BisTiCl3 (1), BisNbCl4 (2) and BisNbBr4 (3) were prepared by alkylation of NbCl5, NbBr5 and TiCl4 with Bis2Zn (4) (Bis=(SiMe3)2CH). Compounds 2 and 3 were obtained as solids in moderate yields and are sensitive to moisture and air. In addition, the corresponding fluoride derivative of 2, i.e. BisNbF4 (5) was prepared in moderate yield via chlorine–fluorine metathesis employing Me3SnF (6) as a fluorinating reagent. In another attempt Ti(Oi-Pr)4 was reacted with KHF2 to give the fluorine-containing titanium cluster μ3-fluoro-μ3-oxo-tris(μ-isopropoxy)-hexakis(isopropoxy)-tri-titanium (7). The fluorine-free tantalum cluster bis(μ3-oxo)-hexakis(μ-ethoxy)-octakis(μ-oxo)-tetradecakis(ethoxy)-octa-tantalum (8) was obtained from n-Bu4NHF2 and Ta(OEt)5. The identity of all new compounds was documented by analytical/spectroscopic (IR, 1H-, 29Si-, 19F-NMR, MS) data. The crystal structures of 2, 7 and 8 were determined by single crystal X-ray diffraction.

Synthesis, Characterization, and Reactivity of Lanthanide Complexes with Bulky Silylallyl Ligands

The synthesis of new lanthanide allyl complexes of enhanced stability and solubility in saturated hydrocarbons based on silyl-substituted allyl ligands is reported. Thus the potassium salt K(CH2CHCHSiMe3) ( 1 ) reacts with YCl3 in tetrahydrofuran to give the tris-allyl complex Y(CH2CHCHSiMe3)3 ( 2 ), while K(CH2CHCHSiMe2tBu) ( 3 ) affords Y(CH2CHCHSiMe2tBu)3(THF)1.5 ( 4 ). Slow re-crystallization of 4 from light petroleum in the presence of tert-butylcyanide led to multiple insertion to give the sec-amido complex Y{NHC(tBu)(CH)3SiMe2tBu}2{?2-NHC(tBu)CH=CHCH2SiMe2tBu)CH(CHCHSiMe2tBu)CtBuNH}(THF)·(CH3CH(Me)(CH2)2CH3) ( 5 ), which was crystallographically characterized. The reaction of ScCl3(THF)3 with two equivalents of Li{1,3-C3H3(SiMe3)2} in tetrahydrofuran gives the bis-allyl complex {1,3-C3H3(SiMe3)2}2Sc(µ-Cl)2Li(THF)2 ( 6 ), while the analogous reaction of K{1,3-C3H3(SiMe3)2} ( 7 ) with either LaCl3 or YCl3 in tetrahydrofuran affords the bis-allyl complexes MCl{1,3-C3H3(SiMe3)2}2(THF)x (8, M = La, x = 1; 9, M = Y, x = 0). An attempt to prepare the similar neodymium complex gave the mono-allyl complex NdI2{1,3-C3H3(SiMe3)2}(THF)1.25 ( 10 ). The reactions of 8 and 9 with triisobutyl aluminum in benzene-d6 show allyl exchange between lanthanide and aluminum. Complexes 8 , 9 , and 10 have been tested with a variety of activator systems as catalysts for the polymerization of 1,3-butadiene.

Synthesis and catalytic activity of three-coordinate zinc cations

Reaction between DADZnR2 and either B(C6F5)3 or ZnR2 and [DADH][B(C6F5)4] affords three-coordinate alkyl and amide zinc cations which are active for the ring opening polymerisation of epoxides and e-caprolactone [DAD = (MeCNC6H3Pri2-2,6)2].

(2-Di­methyl­amino­ethyl)­di­methyl­ammonium di­chloro­tri­methyl­stannate(IV)

The structure of the title compound, (C6H17N2)[SnCl2(CH3)2], shows an anion–cation contact via a hydrogen bond. The stannate anion is five-coordinate. There are two cations and two anions in the asymmetric unit.

Acetylacetonatodifluorooxometalates of vanadium and molybdenum: syntheses and crystal structures

[Et4N][HF2] reacted with VO(acac)2 and MoO2(acac)2 in acetonitrile at room temperature with elimination of Hacac to produce the metalates [Et4N][(acac)VOF2] 1 and [Et4N][(acac)MoO2F2] 2, respectively. These compounds are the first examples of fluorometalates of vanadium and molybdenum bearing the acetylacetonato group. The crystal structures have been determined.