Synthesis and Characterization of the Series of d⁰ Arene Complexes [Cp*MMe₂(η⁶-arene)][MeB(C₆F₅)₃] (M = Ti, Zr, Hf)

Abstract

Treatment of the neutral trimethyl compounds Cp*MMe 3 (M ) Ti, Zr, Hf) with the highly electrophilic borane B(C 6 F 5 ) 3 in methylene chloride in the presence of various arenes results in methyl carbanion abstraction and coordination of the arene to form complexes of the type [Cp*MMe 2 (η 6 -arene)][MeB(C 6 F 5 ) 3 ] (M ) Ti, Zr, Hf; arene ) benzene, toluene, m-and p-xylene, anisole, styrene, mesitylene). Indications of relative metal-arene affinities have been gleaned from a variety of low-temperature 1 H NMR experiments, and it seems that both steric and electronic factors play significant roles in determining stabilities. The crystal and molecular structures of [Cp*HfMe 2 (η 6 -toluene)][MeB(C 6 F 5 ) 3 ] have been determined; as anticipated, there are no significant contacts between anion and cation, and the latter assumes a bent-metallocene type of structure.

Kinetic and mechanistic aspects of metallocene polymerisation catalysts

“…In these more open systems solvent coordination becomes more important and may even outweigh anion coordination. For example, while Cp * TiMe 3 reacts with B(C 6 F 5 ) 3 in toluene to give 6, the zirconium and hafnium analogues form ionic toluene complexes 7 [39,40]. The crystal structures of the C 5 H 3 (SiMe 3 ) 2 and Cp * compounds confirm g 6 -toluene coordination and the absence of close contacts with the anion.…”

Alkylmono(cyclopentadienyl)titanium Complexes Containing the 2,2′‐Methylenebis(6‐tert‐butyl‐4‐methylphenoxido) Ligand – Studies on the Nature of the Catalytic Species Present in α‐Olefin Polymerisation Processes

“…After 1 h at room tempera- -fragment gives signals at δ = 0.84 and 0.91 ppm for derivatives 12 and 14, respectively, suggesting a certain interaction between the anionic and the cationic centres. [25][26][27][28][29] The signals of the methylene protons of the benzylborate anion [(PhCH 2 )B(C 6 F 5 ) 4 ] -appear at δ = 3.14 and 2.90 ppm for derivatives 13 and 15, respectively. It is not easy to establish a limit to determine the coordination or non-coordination of the anionic and cationic centres by analysing the methylene benzylborate anion resonances.…”

Arene Complexes of β‐Diketiminato Supported Organoscandium Cations: Mechanism of Arene Exchange and Alkyne Insertion in Solvent Separated Ion Pairs

“…hibit a high barrier to arene exchange, [29] like their d n counterparts. The facility with which compounds 1 undergo such exchange is a sign that the steric crowding about the metal center has reached a level that encourages ring slippage to the lower hapticity intermediates necessary to initiate the exchange process.…”