81476-73-5Relevant articles and documents
MECHANISMS OF STEREOCHEMICAL CONTROL IN PROPYLENE POLYMERIZATIONS WITH SOLUBLE GROUP 4B METALLOCENE/METHYLALUMOXANE CATALYSTS.
Ewen
, p. 6355 - 6364 (1984)
The soluble bis(cyclopentadienyl)bis(phenyl)titanium/methylalumoxane catalyst system produces isotactic polypropylene with a novel stereoblock microstructure consistent with a chain-end stereochemical control mechanism. Chiral catalysts derived from the racemic enantiomers of ethylene-bridged indenyl derivatives are the first metallocene catalysts to form isotactic polypropylene with the conventional structure predicted by an enantiomorphic-site stereochemical control model. The meso achiral form of the ethylene-bridged titanium indenyl diastereomers and zirconocene derivatives produce polypropylene with an ideally atactic structure. Differing regiospecificities during cis addition with soluble Ti and V chain-end controlled stereospecific systems result in Ti being isotactic specific and V being syndiotactic specific.
Selective halodemethylation reactions of metallocene dimethyls with triphenylmethyl chloride and benzyl bromide
Hawrelak, Eric J.,Deck, Paul A.
, p. 9 - 11 (2008/10/09)
NMR-scale reactions of several group 4 metallocene dimethyls with either trityl chloride or benzyl bromide gave the corresponding L2M(Me)X complexes selectively. Five reactions, including syntheses of Cp2-Zr(Me)Cl and Ind2Zr(Me)Cl, were conducted on a preparative scale to afford useful isolated yields of L2M-(Me)Cl complexes.
Reactions of (η5-C5H5)(η5-C5Me5)ZrX (X = Cl, Me) complexes with carbon monoxide and the isocyanide 2,6-Me2C6H3NC. Crystal structure of (η5-C5H5)(η5C5Me5)Zr2-C(N-2,6-Me2C6H3)Si(SiMe3)3>Cl
Elsner, Frederick H.,Tilley, T. Don,Rheingold, Arnold L.,Geib, Steven J.
, p. 169 - 184 (2007/10/02)
The new tris(trimethylsilyl)silylzirconium derivative (η5-C5H5)(η5-C5Me5)ZrCl (1) is prepared by reaction of (Η5-C5H5)(η5-C5Me5)ZrCl2 with (THF)3LiSi(SiMe3)3.Mixed alkyl/silyl complex (η5-C5H5)(η5-C5Me5)ZrMe (2) is obtained after treatment of 1 with MeMgBr.Reactions of compounds 1 and 2 with carbon monoxide and 2,6-Me2C6H3NC are described.Carbon monoxide inserts cleanly into the Zr-Si bond of 1, giving the η2-silaacyl (η5-C5H5)(η5-C5Me5)Zr2-COSi(SiMe3)3>Cl (3).The reaction of 2 with CO proceeds via the intermediate (η5-C5H5)(η5-C5Me5)Zr2-COSi(SiMe3)3>Me (4) to the enolate hydride (η5-C5H5)(η5-C5Me5)ZrH (5).A mechanism for this rearrangement is proposed.This chemistry contrasts with that previously observed for (η5-C5H5)2ZrMe, which reacts with CO to cleanly give the stable acyl (η5-C5H5)2Zr(η2-COMe).Methyl iodide and compound 5 react to give the iodide (η5-C5H5)(η5-C5Me5)ZrI (6) and methane.The reaction of 5 with 2 equivalents of HCl provides a new synthetic route to an acysilane MeCOSi(SiMe3)3.Reactions of 1 and 2 with the isocyanide 2,6-Me2C6H3NC give the insertion products (η5-C5H5)(η5-C5Me5)Zr2-C(N-2,6-Me2C6H3)Si(SiMe3)3>Cl (7) and (η5-C5H5)(η5-C5Me5)Zr2-C(N-2,6-Me2C6H3)-Me>Si(SiMe3)3 (8), respectively.Steric crowding in these compounds is evidenced by restricted rotation about the N-C(xylyl) bonds.An X-ray crystal structure of 7 has been determined.Crystals of 7 are monoclinic, P21/c, with a 18.276(6) Angstroem, b 9.993(3) Angstroem, c 21.550(5) Angstroem, β 106.25(3) deg; V 3779(2) Angstroem3, Z = 4, RF 6.63percent RwF 6.48percent.