1278-83-7Relevant academic research and scientific papers
1H and 13C NMR spectroscopic study of titanium(IV) species formed by activation of Cp2TiCl2 and [(Me4C5)SiMe2NtBu]TiCl2 with methylaluminoxane (MAO)
Bryliakov, Konstantin P.,Talsi, Evgenii P.,Bochmann, Manfred
, p. 149 - 152 (2008/10/09)
Using 13C and 1H NMR spectroscopy, the products of the reaction of Cp2TiCl2 with methylaluminoxane (MAO) at Al:Ti ratios of 5:1 to 300:1 have been identified as Cp2TiMeCl, Cp2TiMe2, [Cp2TiMe(μ-Cl)Cp2-TiCl]+[Me-MAO]- (II1), [Cp2TiMe(μ-Cl)Cp2TiMe]+[Me-MAO]- (II2), [Cp2TiMe(μ-Me)Cp2TiMe]+[Me-MAO]- (II3), the heterobinuclear ion pair [Cp2Ti(μ-Me)2AlMe2]+[Me-MAO] - (III), and a zwitterion-like intermediate, formulated as Cp2TiMe+←Me-Al-≡MAO (IV). In contrast, [(Me4C5)SiMe2NtBu]TiCl2/M AO gives only zwitterion-like, not heterobinuclear, species.
Activation of alkylidene-bridged heterobimetallic complexes toward electrophilic attack
Clift, Susan M.,Schwartz, Jeffrey
, p. C5-C8 (2007/10/02)
Treatment of alkylidene-bridged zirconium-aluminum species with HMPA renders the CAl bond of the alkylidene unit susceptible to electrophilic attack; in the absence of HMPA, the CZr bond is attacked.
Selectivity and reactivity in reactions of methylaryltitanium(IV) complexes with electrophiles
Puddephatt, Richard J.,Stalteri, Maria A.
, p. 1400 - 1405 (2008/10/08)
Methyl or phenyl for halogen-exchange reactions occur between [TiMe2(η-C5H5)2] or [TiPh2(η-C5H5)2] with [TiX2(η-C5H5)2], X = halogen, to give [TiXMe(η-C5H5)2] or [TiXPh(η-C5H5)2], respectively. The reactions are complicated by parallel decomposition of the methyl- or phenyltitanium complexes, which is catalyzed by [TiX2(η-C5H5)2] or [TiXR(η-C5H5)2]. In general, there is little difference in the rates of reaction of [TiMe2(η-C5H5)2] and [TiPh2(η-C5H5)2] toward the symmetrization reactions. These reagents also transfer a methyl group or phenyl group to platinum(II) or gold(III), but there are again side reactions. The complex [TiMePh(η-C5H5)2] reacts with electrophiles HCl, HOAc, HgCl2, and MeHgCl to give cleavage of both methyl- and phenyltitanium bonds with little selectivity. In cleavage of [TiMe(C6H4X)(η-C5H5) 2] there is a correlation of the selectivity for cleavage of the aryl group by electrophiles HCl or HgCl2 with the σ+ parameters of substituents X. A mechanism of reaction involving electron transfer from the complex to the electrophile followed by rapid cleavage is tentatively suggested.
Metallocene Derivatives of Early Transition Metals. Part 4. Chemistry of the Complexes and the X-Ray Structures of (M' = C or Si)
Jeffery, John,Lappert, Michael F.,Luong-Thi, N. Tuyet,Webb, Maurice,Atwood, Jerry L.,Hunter, William E.
, p. 1593 - 1605 (2007/10/02)
The metallocene(IV) halogeno-alkyls have been prepared either by interaction of the appropriate Grignard reagent and or from and Mg(CH2SnMe3)X (Cl-X exchange).Metallocene(IV) dialkyls (type (iv) R = CH2SnMe3 = R', M = Ti, Zr, of Hf; type (v) R = CH2SnMe3, R' = CH2SiMe3, M = Ti, Zr, or Hf; type (vi) R = CH2CMe3 = R', M = Ti or Zr; type (vii) R = CH2SnMe3; R' = CH2CMe3, CH2GeMe3, or Me; M = Ti; type (viii) R = CH2SiMe3, R' = CH2GeMe3, M = Ti; type (ix) R = CH(SiMe3)2; R' = Me, Et, Prn, CH2SiMe3, or Ph; M = Zr> have been synthesised by reaction of (a) with 2Mg(CH2SnMe3)X (X = Cl or Br) or (b) with LiR'.Also obtained are and H)2>, the latter from and Li or and successively Lit)3> and Li.The reaction of an equimolar portion of HCl in OEt2 and gives predominantly the products of CH2-SnMe3, rather than Ti-CH2, scission.By contrast, the dialkyls , containing one or two CH2SnMe3 ligands, give largely RH or R'H and ; the relative ability of R as a leaving group decreases in the sequence CH2SnMe3 > CH2CMe3 > CH2SiMe3 >= CH2GeMe3 > CH3, the distinctions being more marked for Ti than Zr of Hf.The dialkyds are generally stable when heated at 80 deg C in PhMe, except for the titanium complexes; (M' = Si or Ge) gives M'Me4 as the sole volatile product, with ti 110 (M' = Si) or 140 min (M' = Sn).Treatment of in C6H6 with CO under ambient conditions affords the appropriate ε2-acyl 2-COR)X> ; the formation of type (xi), rather than the isomer resulting from CO insertion into the less hindered Zr-Me bond, is noteworthy.A single-crystal X-ray diffraction study has been carried out on , with a = 9.142(4), b = 9.142(4). c = 23.326(9) Angstroem, β = 90 deg, and Z = 4.Crystals of (42) are monoclinic, space group P21/n, a = 13.745(6), b = 7.048(3), c = 22.057(9) Angstroem, β = 95.65(4) deg, and Z = 4.For complex (28), 487 reflections have been considered and the data refined to R = 0.029, R' = 0.032; for complex (42), 2688 independent reflections led to R = 0.029, R' = 0.033.The slightly larger steric requirement of the neopentyl ligand compared with -CH2SiMe3 manifests itself in a larger Zr-cyclopentadienyl approach but the Zr-CH2 bond length is indistinguishable, 2.51(2) Angstroem for (28) and 2.52(2) Angstroem for (42).
