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Synthesis, Structural and Chemical Characterization of Unsaturated C 4 ‐ and C 10 ‐Bridged Group‐4 ansa ‐Metallocenes Obtained Through a Ring‐Closing Olefin Metathesis Reaction
Author(s) -
Hüerländer Doris,
Kleigrewe Nina,
Kehr Gerald,
Erker Gerhard,
Fröhlich Roland
Publication year - 2002
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200210)2002:10<2633::aid-ejic2633>3.0.co;2-4
Subject(s) - chemistry , cyclopentadienyl complex , metallocene , metathesis , double bond , zirconium , medicinal chemistry , salt metathesis reaction , olefin fiber , ethylene , catalysis , polymer chemistry , polymerization , organic chemistry , polymer
Bis[(5‐hexenyl)cyclopentadienyl]zirconium dichloride ( 3 ) underwent ring‐closure olefin metathesis with loss of ethylene when treated with 10 mol % of the [Cl 2 (PCy 3 ) 2 Ru=CHPh] catalyst in refluxing dichloromethane, to yield the large ansa ‐zirconocene complex [dec‐5‐ene‐1,10‐diylbis(η 5 ‐cyclopentadienyl)]ZrCl 2 ( trans ‐ 4 ). Characterization by NMR and by X‐ray diffraction revealed that the isolated complex contained a trans ‐C=C double bond inside the ansa bridge. Similarly, bis[(allyl)cyclopentadienyl]ZrCl 2 ( 7 ) gave the ansa ‐metallocene [but‐2‐ene‐1,4‐diylbis(η 5 ‐cyclopentadienyl)]zirconium dichloride ( cis ‐ 8 ) when treated with the same ruthenium metathesis catalysts (10 mol %) under similar conditions, except that a cis ‐C=C double bond was now found to be present (shown by NMR and X‐ray diffraction). The cis ‐ 8 complex was used as a homogeneous Ziegler−Natta catalyst for ethylene polymerization [after activation of the metallocene dichloride 8 with MAO (methylalumoxane) or treatment of the corresponding dimethylmetallocene complex 9 with B(C 6 F 5 ) 3 ]. Complex 8 was also converted into a mixture of ( s ‐ cis ‐ and s ‐ trans ‐η 4 ‐butadiene)‐ ansa ‐metallocene complexes ( s ‐ cis ‐ 15 / s ‐ trans ‐ 15 = 4:5) by treatment with (butadiene)magnesium. The C=C double bond of cis ‐ 8 could be hydroborated with 9‐BBN or with the H−B(C 6 F 5 ) 2 reagent. Li + [B(C 6 F 5 ) 4 − ] added to cis ‐ 8 to yield an interesting solid‐state chain structure in which the [Zr]Cl 2 unit and the o ‐/ m ‐F pairs of two −C 6 F 5 groups were found to be in contact with the central lithium cation in a distorted octahedral coordination environment (as shown by X‐ray diffraction). (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)