Zirconium and Hafnium Complexes with (Allylsilyl)(η‐amidosilyl)‐η⁵‐cyclopentadienyl Ligands: Synthesis, Structure and Reactivity

Abstract

The disubstituted cyclopentadiene C5H4(SiMe2Cl)[SiMe2(CH2CH=CH2)] was isolated by reaction of the lithium salt [Li{C5H4SiMe2(CH2CH=CH2)}] with SiMe2Cl2. It was then treated with NH2tBu and LiNH(2,6‐Me2C6H3) to give the (aminosilyl)cyclopentadienes C5H4[SiMe2(CH2CH=CH2)][SiMe2(NHR)], which were further deprotonated to their dilithium salts [Li2{1‐SiMe2NR‐3‐SiMe2(CH2CH=CH2)C5H3}] (R = tBu, 2,6‐Me2C6H3). Reactions of the metal halides ZrCl4(THF)2 and HfCl4 with these dilithium salts, followed by alkylation of the resulting dichloro complexes, afforded the (η1‐amidosilyl)‐η5‐cyclopentadienyl complexes [M{η5‐C5H3(SiMe2‐η1‐NR)[SiMe2(CH2CH=CH2)]}X2] (R = tBu, 2,6‐Me2C6H3; X = Cl, Me, CH2Ph; M = Zr, Hf). Only the bis(iminoacyl) complexes [M{η5‐C5H3(SiMe2‐η1‐NtBu)[SiMe2(CH2CH=CH2)]}{η2‐CR=N(2,6‐Me2C6H3)}2] (M = Zr, Hf; R = Me, CH2Ph) could be isolated when the dialkylzirconium and ‐hafnium complexes were treated with CN(2,6‐Me2C6H3); these were slowly transformed into the C–C‐coupled diazametallacyclopentene compounds [M{η5‐C5H3(SiMe2‐η1‐NtBu)[SiMe2(CH2CH=CH2)]}{η1‐N(2,6‐Me2C6H3)‐CR=CR‐η1‐N(2,6‐Me2C6H3)}] (R = Me, CH2Ph, M = Zr; R = Me, M = Hf) when their toluene solutions were heated to 70 °C–80 °C for long periods (2–4 d). The structural characterisation of all of the new compounds is described and the molecular structure of the dimeric dichlorozirconocene [ZrCl(μ‐Cl){η5‐C5H3(SiMe2‐η1‐NtBu)[SiMe2(CH2CH=CH2)]}]2, was determined by X‐ray diffraction methods. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

[(Allylsilyl)(η-amidosilyl)-η5-cyclopentadienyl] Group 4 Metal Complexes: Synthesis, Reactivity, and Olefin Polymerization

“…Similar reactions were carried out by addition of 1 equiv of B(C 6 F 5 ) 3 to C 7 D 8 solutions of the dibenzyl complexes [M(η 5 -C 5 Me 4 SiMe 2 -η 1 -N t Bu)(CH 2 Ph) 2 ] (M = Zr, Hf) previously reported, using Teflon-valved NMR tubes, and monitored by 1 H, 13 C, and 19 F NMR spectroscopy. An immediate reaction occurred at 25 °C to give the new ionic species [M{η 5 -C 5 H 3 (SiMe 2 -η 1 -N t Bu)[SiMe 2 −CH 2 −CH(CH 2 Ph)-η 1 -CH 2 ]}] + [(CH 2 Ph)B(C 6 F 5 ) 3 ] - (M = Zr, 13 ; Hf, 14 ), which were characterized by NMR spectroscopy as compounds containing metallacyclic alkyl cations, analogous to the hafnocenium cation reported previously (see Scheme 5).…”

“…The method based on the reaction of the metal(IV) chlorides with the dilithium salt of the disilylated cyclopentadienyl ring was initially used to transfer this ligand in order to synthesize the zirconium and hafnium derivatives reported recently …”

“…Elemental analyses were performed on a Perkin-Elmer 240C microanalyzer. Compounds TiCl 3 (THF) 3 B(C 6 F 5 ) 3 , dilithium salts Li 2 {C 5 H 3 [1-SiMe 2 (NR)][3-SiMe 2 (CH 2 CHCH 2 )]} (R = t Bu; 2,6-Me 2 C 6 H 3 ), and complexes [M(η 5 -C 5 Me 4 SiMe 2 -η 1 -N t Bu)(CH 2 Ph) 2 ] (M = Zr, Hf) 18 were prepared by literature methods. TiCl 4 (Aldrich), MgClMe (Aldrich), and MgCl(CH 2 Ph) (Aldrich) were purchased from commercial sources and used without further purification.…”

μ2,η1-N-[(N,N-Dimethylamino)dimethylsilyl]-2,6-diisopropylanilido Metal (Li, Zr, Hf) Compounds and the Catalytic Behaviors of the IVB Compounds in Ethylene (Co)Polymerization

“…The molecular structure of dinuclear zirconium compound [Zr L Cl 2 (μ-Cl)] 2 ( 6 ) consists of a discrete centrosymmetric center (Figure ), with its bond lengths and angles collected in Table S7 of the Supporting Information. The association interactions between two zirconium atoms are four common bridging zirconium−chlorine bonds [2.5736(11)−2.6997(11) Å]. − Each zirconium unit is six-coordinated and possesses a distorted octahedral geometry. The benzylamido nitrogen atom and the bridging chloride ion occupy the axial sites N(1)−Zr−Cl(3) [158.54(9)°].…”

Synthesis and reactivity of imido niobium complexes containing the functionalized (dichloromethylsilyl)cyclopentadienyl ligand

“…We focused our research interest on studies related to cyclopentadienyl group 4-6 metal complexes supporting modified cyclopentadienyl rings [2][3][4][5][6][7][8][18][19][20][21][22][23][24], and reported the synthesis of silyl-g-amido cyclopentadienyl group 4 and 5 metal complexes using the related (chlorodimethylsilyl)cyclopentadienyl metal derivatives [2][3][4][5][6][7][8]24]. Hydrolysis of these compounds also led to the isolation of dinuclear derivatives with Si-O-Si bridges for Nb [8,21,25], Mo and W [24] and Si-O-M bridges for Nb [25] and group 4 metals [2,26,27].…”