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A series of group 4 metal complexes M(η5:η1:η1-C5Me4SiMe2NCH2CH2X)R2 (M = Ti; R = Me, CH2Ph; M = Zr, Hf; R = Me, Et, nPr, nBu, CH2Ph, CH2SiMe3, Ph) containing the tridentate-linked amido−tetramethylcyclopentadienyl ligand C5Me4SiMe2NCH2CH2X (X = OMe, NMe2) were synthesized by alkylation of the dichloro complexes M(η5:η1:η1-C5Me4SiMe2NCH2CH2X)Cl2. The complexes were characterized by 1H and 13C NMR spectroscopy, mass spectrometry, and elemental analysis. Nuclear Overhauser effect measurements of the dimethyl complexes show that, in solution, the side chains of the zirconium derivatives coordinate intramolecularly, in contrast to the titanium complexes. The crystal structures of the zirconium alkyls Zr(η5:η1:η1-C5Me4SiMe2NCH2CH2OMe)R2 (R = Me, Ph) were determined by X-ray diffraction studies. Both complexes adopt a trigonal-bipyramidal structure, with the five-membered ring and the methoxy group in the apical positions. Insertion of carbon monoxide into the hafnium dimethyl and di(n-butyl) complexes led to the η2-acyl derivatives Hf(η5:η1:η1-C5Me4SiMe2NCH2CH2OMe)(η2-COR)R (R = Me, nBu). Chloro mono(ethyl) complexes underwent insertion of tert-butyl isonitrile to give η2-iminoacyl derivatives M(η5:η1-C5Me4SiMe2NCH2CH2X){η2-C(NtBu)Et}Cl. The X-ray diffraction structure of the titanium complex Ti(η5:η1-C5Me4SiMe2NCH2CH2OMe){η2-C(NtBu)Et}Cl showed a square-pyramidal configuration with the imino nitrogen trans to the amido nitrogen. The zirconium dimethyl complexes Zr(η5:η1:η1-C5Me4SiMe2NCH2CH2X)Me2 reacted with B(C6F5)3 to form the contact ion pairs [Zr(η5:η1:η1-C5Me4SiMe2NCH2CH2X)Me]+[MeB(C6F5)3]-. Reaction between the titanium dibenzyl Ti(η5:η1-C5Me4SiMe2NCH2CH2X)(CH2Ph)2 and B(C6F5)3 resulted in the clean formation of the solvent-separated ion pair [Ti(η5:η1:η1-C5Me4SiMe2NCH2CH2X)(CH2Ph)]+[(PhCH2)B(C6F5)3]-. When activated with methylaluminoxane, the complexes Ti(η5:η1-C5Me4SiMe2NCH2CH2OMe)Cl2 and M(η5:η1:η1-C5Me4SiMe2NCH2CH2OMe)R2 (M = Zr, Hf; R = Me, nBu) are active in the polymerization of ethylene.

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Two new titanium complexes of the general type Ti(q5:q1-function of the temperature, indicating the presence of a n C5H4SiMe,NCH,CH2X)C12 (X = NMe,, OMe), containing a equilibrium between the tri-and bidentate bonding mode tridentate ligand, were prepared by reaction of Ti(q5-C5H4Si-of the ligand. A single-crystal X-ray structural analysis of Me2C1)CI3 with the lithium amide Li(NHCH2CH2X) (X = Ti(q5 :q1-C,H4SiMe2NCH,CI-I,0Me)C12 revealed that the NMe2, OMe). The 'H-NMR chemical shifts for the protons methoxy function is not intramolecularly coordinated in the of the ethylene link were found to vary considerably as a solid state.Functionalized cyclopentadienyl liganddl] allow the synthesis of a wide variety of transition metal complexes with novel coordination spheres, which may be used in the control of the catalytic behavior of the metal center. In the context of designing new metallocene catalysts for olefin polymerization, amido-functionalized cyclopentadienyl ligands in particular have been of considerable recent interest[*]. Not only do they allow variation of the ring substituents and the nature of the bridge, which constitute common tools for the manipulation of Brintzinger-type ansa-metallocenes, but modification of the amido substit~ent[~] is also possible. In order to modulate the Lewis acidic group-4 metal center, we are studying potentially tridentate ligands by introducing an additional donor is significantly broadened at low temperatures. Despite the presumably higher Lewis acidity of the titanium center compared with that of the tetramethyl analog Ti(q5:q '-CSMe4SiMe2NCH2CH2NMe2)-Cl,['l, the dimethylamino group is apparently not more strongly coordinated [8]. On the other hand, a single-crystal structure analysis revealed that the additional donor site is unambiguously interacting with the titanium center, although considerable disorder in the CH2CH2NMe2 chain precluded an accurate solution of the Figure 1. ORTEP diagram of the molecular structure of Ti(q5:q1-C5H4SiMe2NCH2CH20Me)CI2. Thermal ellipsoids are drawn at the 50% probability level R Results and DiscussionPreviously we noted that the reaction of the dilithium derivatives Li2(C5H4SiMe2NCH2CH2X) (X = NMe2, OMe) with TiC14(THF)2, or with TiC13(THF)3 followed by oxidation, unexpectedly led to the formation of the stable C2-symmetric bis(1igand) complexes of the type Ti( q5:q'-CsH4SiMezNCH2CH2X)2[S,7a] rather than to the mono(1igand) complexes Ti(q5:q'-C5H4Si-Me2NCH2CH2X)CI2. In contrast, Ti($ :q1-C5H4SiMe2NCH2-CH2NMe2)C12 could be obtained as orange crystals in good yield by the reaction of the easily prepared Ti(q5-C5H4SiMe2CI)C13[6] with 1.33 equivalents of Li(NHCH2CH2NMe2) in toluene, followed by work-up of the reaction mixture by filtering off LiCl and the ammonium salt [NH3CH2CH2NHMe2]CI2. 'H-, I3C-NMR-spectroscopic as well as mass-spcctral and analytical data confirm the structure o f a mono(1igand) complex. However, the nature of the additional bonding site remains undefined. Variable temperature IH-NMR spectra show a fairty strong shif...