Search

Multiple C−H bond activation occurs upon reaction of phosphinimide complexes of the form Cp‘(R3PN)TiMe2 (Cp‘ = Cp, indenyl; R = i-Pr, Cy, Ph) with excess AlMe3, affording the carbide complexes Cp‘Ti(μ2-Me)(μ2-NPR3)(μ4-C)(AlMe2)3 or in some cases [CpTi(μ2-Me)(μ2-NPR3)(μ5-C)(AlMe2)3·(AlMe3)]. These species contain four- and five-coordinate carbide centers. VT-NMR studies established that such species exist in equilibrium. The four-coordinate carbide complexes retain Lewis acidity at a planar three-coordinate Al center, as evidenced by the reaction with diethyl ether, THF, or PMe3. This affords species of the form [CpTi(μ2-Me)(μ2-NPR3)(μ4-C)(AlMe2)2(AlMe2(L))] (L = Et2O, THF, PMe3). The Lewis acidity is also evidenced in the reaction of the carbide complexes with CpTi(NPR3)Me2. In this case, labeling studies affirm methyl group exchange processes. The analogous reactions of Cp(R3PN)Ti(CH2SiMe3)2 or Cp*(R3PN)TiMe2 with AlMe3 afforded CpTi(μ2-Me)(μ2-NPR3)(μ3-CSiMe3)(AlMe2)2 and Cp*Ti(μ2-Me)(μ2-NPR3)(μ3-CH)(AlM...

The phosphinimide complexes (t-Bu3PN)TiCl3 (1) and (t-Bu3PN)2TiCl2 (4) are readily prepared in high yields from the stoichiometric reaction of t-Bu3PNSiMe3 and TiCl4, while (t-Bu3PN)3TiCl (11) is readily obtained from the reaction of t-Bu3PNLi and TiCl4. The analogous 1:1 or 2:1 reactions of ZrCl4 and t-Bu3PNLi afford mixtures of products, although in the 3:1 stoichiometric ratio (t-Bu3PN)3ZrCl (12) is isolable. These complexes are readily alkylated with a variety of reagents to give (t-Bu3PN)TiMe3 (2), (t-Bu3PN)Ti(CH2Ph)3 (3), (t-Bu3PN)2TiMe2 (5), (t-Bu3PN)2Ti(η3-C3H5)2 (6), (t-Bu3PN)2Ti(CH2Ph)2 (7), (t-Bu3PN)2TiPh2 (8), (t-Bu3PN)2Ti(η5-Cp)Cl (9), (t-Bu3PN)2Ti(η5-Cp)Me (10), (t-Bu3PN)3TiMe (13), (t-Bu3PN)3TiPh (14), (t-Bu3PN)3ZrMe (15), (t-Bu3PN)3Zr(CH2Ph) (16), and (t-Bu3PN)3Zr(η5-Cp) (17). Subsequent reactions of some of these alkyl derivatives with [PhNMe2H][B(C6F5)4], [Ph3C][B(C6F5)4], or B(C6F5)3 are investigated. A number of zwitterionic and cationic species complexes have been characterized. These...

The compounds CpTiCl 2 (OC 6 H 3 - i -Pr 2 ) ( 1 ), CpTiCl(OC 6 H 3 - i- Pr 2 ) 2 ( 2 ), CpTi(R)(OC 6 H 3 - i -Pr 2 ) 2 (R= t -Bu 3 , s -Bu 4 , n -Bu 5 , Me 6 ) have been prepared and characterized. Compounds 1 or 2 in the presence of 500 equivalents of methylaluminoxane (MAO) act as catalyst precursors for ethylene polymerization. While the catalysts derived from the monocyclopentadienyl complexes are much less active that the metallocenes, there is a clear enhancement in the activity of about 40% as a result of the inclusion of a second aryloxide ligand. Reactions of 1 with AlMe 3 revealed stepwise formation of CpTi(Me)Cl(OC 6 H 3 - i -Pr 2 ) 7 and CpTi(Me) 2 (OC 6 H 3 - i -Pr 2 ) 8 , while subsequent addition of AlMe 3 afforded complete conversion to 8 , with formation of the aluminum species [AlMe 2 (OC 6 H 3 - i -Pr 2 )] n 9 . In contrast, the catecholate complex CpTi(O 2 C 6 H 4 )Cl 10 reacts with AlMe 3 yielding the paramagnetic species [CpTi(O 2 (C 6 H 4 ))·AlClMe 2 ] 2 11 . Incorporation of aryloxide ligands in modified metallocenes was readily accomplished with the preparation of Cp 2 ZrCl(OC 6 H 3 - i -Pr 2 ) 12 , Cp 2 ZrCl(OC 6 H 5 ) 13 , Cp 2 ZrMe(OC 6 H 5 ) 14 and Cp 2 TiCl(OC 6 H 3 - i -Pr 2 ) 15 . In combination with MAO, 12 , 14 and 15 effect the polymerization of ethylene with an 11% increase in activity over the parent metallocenedichlorides. The implications of the increased activity are considered. Crystallographic data are reported for 2 , 3 , 6 , 9 , 11 , 12 and 13 .

The diphosphines m-C6H4(CH2Pt-Bu2)21 and m-C6H4(CH2PCy2)22 were prepared and oxidized with Me3SiN3 to m-C6H4(CH2(t-Bu2)PNSiMe3)23 and m-C6H4(CH2(Cy2)PNSiMe3)24, and subsequently converted to m-C6H4(CH2(t-Bu)2PNH)25 and m-C6H4(CH2(Cy)2PNH)26. Reaction of 5 and 6 with Ti(NMe2)4 afforded the yellow compounds m-C6H4(CH2(t-Bu)2PN)2Ti(NMe2)27 and m-C6H4(CH2(Cy)2PN)2Ti(NMe2)28, and the low abundance by-product m-C6H4(CH2(t-Bu)2PN)2TiBr(NMe2) 9. In a similar manner, the species m-C6H4(CH2(t-Bu)2PN)2Zr(NEt2)210 was prepared from Zr(NEt2)4. Compounds 8, 9 and 10 were converted to C6H4(CH2(t-Bu)2PN)2TiBr211, m-C6H4(CH2(Cy)2PN)2TiCl213 and C6H4(CH2(t-Bu)2PN)2ZrCl214via reaction with Me3SiX (X = Br, Cl). Alternatively, m-C6H4(CH2(t-Bu)2PN)2TiCl212 and 13 were prepared in low yield from reaction of 3 or 4 with TiCl4. Alkylation of 11 with MeMgBr and PhCH2MgBr proceeded to give m-C6H4(CH2(t-Bu)2PN)2TiMe215 and m-C6H4(CH2(t-Bu)2PN)2Ti(CH2Ph)216, respectively. The species (m-C6H4(CH2(t-Bu)2PN)2)2Zr 17 was prepared from Zr(CH2Ph)4. These synthetic routes are described and the implications for applications in olefin polymerization catalysis are considered. X-Ray structural data for compounds 1, 3, 4, 5, 8, 9 and 16 are reported.