TY - JOUR
T1 - Metallocene derivatives of early transition elements. Part 3. Synthesis, characterisation, conformation, and rotational barriers [for the Zr-C(sp3) bond] of the zirconium(IV) complexes [Zr(η-C5H4R)2{CH-(SiMe3) 2}Cl] and the crystal and ...
AU - Lappert, Michael F.
AU - Riley, Paul I.
AU - Yarrow, Paul I.W.
AU - Atwood, Jerry L.
AU - Hunter, William E.
AU - Zaworotko, Michael J.
PY - 1981
Y1 - 1981
N2 - full title: Metallocene derivatives of early transition elements. Part 3. Synthesis, characterisation, conformation, and rotational barriers [for the Zr-C(sp3) bond] of the zirconium(IV) complexes [Zr(η-C5H4R)2{CH-(SiMe3) 2}Cl] and the crystal and molecular structures of the t-butyl and trimethylsilyl complexes (R = CMe3 or SiMe3) The complexes [Zr(η-C5H4R)2{CH(SiMe3) 2}Cl] have been prepared from the appropriate metallocene dichloride (R = Me, Et, Pri, But, or SiMe3) and an equimolar portion of Li[CH(SiMe3)2] in diethyl ether. [The same method failed to yield the hafnium analogues (for R = H or SiMe3).] Except for R = Et, these are white or pale yellow sharp-melting crystalline solids which have been characterised by elemental analysis and i.r., 1H, and 13C n.m.r. spectra. Variable-temperature 1H n.m.r. spectra show that (i) at low temperature (coalescence temperature, Tc, -4 to 18 °C) the preferred conformation has diastereotopic pairs of SiMe3 [of CH(SiMe3)2] and η-C5H4R groups, and (ii) ΔG‡ for rotation about the Zr-C(sp3) bond is in the range 59.8 to 65.6 kJ mol-1 (R = SiMe3 > Et > But > Pri ≈ Me > H). The ring cyclopentadienyl 13C n.m.r. signals are each split into a doublet at -30 °C but are observed as three distinct sharp singlets at 60 °C. The compounds [Zr(η-C5H4R)2{CH(SiMe3) 2}Cl] (R = But or SiMe3) are isostructural, crystallising in the space group P21/n, with cell constants, for Z = 4, being a = 10.496(6), b = 15.250(8), c = 18.272(9) Å, β = 100.48(5)° for R = But, and a = 10.525(5), b = 15.320(7), c = 19.064(8) Å, β = 98.73(4)° for R = SiMe3. There is considerable strain within the substitued cyclopentadienyl ligands, as exemplified by the distinct spread in the range of Zr-C(π) distances and the significant deviation from the cyclopentadienyl plane of the-XMe3 moiety. The remainder of the molecule, however, does not seem to be influenced by any steric constraints with the Zr-Cl bonds, of 2.452(2) and 2.447(1) Å (for X = C and Si respectively), and the Zr-C(σ) bonds, of 2.324(8) and 2.327(3) Å, being within previously observed limits. The conformation in the crystal corresponds to that found by low-temperature n.m.r. spectroscopy.
AB - full title: Metallocene derivatives of early transition elements. Part 3. Synthesis, characterisation, conformation, and rotational barriers [for the Zr-C(sp3) bond] of the zirconium(IV) complexes [Zr(η-C5H4R)2{CH-(SiMe3) 2}Cl] and the crystal and molecular structures of the t-butyl and trimethylsilyl complexes (R = CMe3 or SiMe3) The complexes [Zr(η-C5H4R)2{CH(SiMe3) 2}Cl] have been prepared from the appropriate metallocene dichloride (R = Me, Et, Pri, But, or SiMe3) and an equimolar portion of Li[CH(SiMe3)2] in diethyl ether. [The same method failed to yield the hafnium analogues (for R = H or SiMe3).] Except for R = Et, these are white or pale yellow sharp-melting crystalline solids which have been characterised by elemental analysis and i.r., 1H, and 13C n.m.r. spectra. Variable-temperature 1H n.m.r. spectra show that (i) at low temperature (coalescence temperature, Tc, -4 to 18 °C) the preferred conformation has diastereotopic pairs of SiMe3 [of CH(SiMe3)2] and η-C5H4R groups, and (ii) ΔG‡ for rotation about the Zr-C(sp3) bond is in the range 59.8 to 65.6 kJ mol-1 (R = SiMe3 > Et > But > Pri ≈ Me > H). The ring cyclopentadienyl 13C n.m.r. signals are each split into a doublet at -30 °C but are observed as three distinct sharp singlets at 60 °C. The compounds [Zr(η-C5H4R)2{CH(SiMe3) 2}Cl] (R = But or SiMe3) are isostructural, crystallising in the space group P21/n, with cell constants, for Z = 4, being a = 10.496(6), b = 15.250(8), c = 18.272(9) Å, β = 100.48(5)° for R = But, and a = 10.525(5), b = 15.320(7), c = 19.064(8) Å, β = 98.73(4)° for R = SiMe3. There is considerable strain within the substitued cyclopentadienyl ligands, as exemplified by the distinct spread in the range of Zr-C(π) distances and the significant deviation from the cyclopentadienyl plane of the-XMe3 moiety. The remainder of the molecule, however, does not seem to be influenced by any steric constraints with the Zr-Cl bonds, of 2.452(2) and 2.447(1) Å (for X = C and Si respectively), and the Zr-C(σ) bonds, of 2.324(8) and 2.327(3) Å, being within previously observed limits. The conformation in the crystal corresponds to that found by low-temperature n.m.r. spectroscopy.
UR - http://www.scopus.com/inward/record.url?scp=51149221987&partnerID=8YFLogxK
U2 - 10.1039/DT9810000814
DO - 10.1039/DT9810000814
M3 - Article
AN - SCOPUS:51149221987
SN - 1472-7773
SP - 814
EP - 821
JO - Journal of the Chemical Society, Dalton Transactions
JF - Journal of the Chemical Society, Dalton Transactions
IS - 3
ER -