Reactions of (η⁵-C₅Me₅)ZrF₃, (η⁵-C₅Me₄Et)ZrF₃, (η⁵-C₅Me₅)₂ZrF₂, (η⁵-C₅Me₅)HfF₃, and (η⁵-C₅Me₅)TaF₄ with AlMe₃. Structure of the First Hafnium−Aluminum−Carbon Cluster

Abstract

The reaction of Cp*ZrF3 (1) (Cp* = η5-C5Me5) and AlMe3 resulted in the formation of cis-{[Cp*ZrMe(μ2-F)][(μ2-F)2AlMe2]}2 (6) and [(Cp*Zr)3Al6Me8(μ3-CH2)2(μ4-CH)4(μ3-CH)] (7), respectively. Analogously, (η5-C5Me4Et)ZrF3 (3) reacts with AlMe3 in a molar ratio of 1:5 with methane elimination to give the Zr3Al6C7 cluster of composition {[(η5-C5Me4Et)Zr]3Al6Me8(μ3-CH2)2(μ4-CH)4(μ3-CH)} (8), which has been characterized by elemental analysis and 1H NMR and mass spectrometry. Reaction of 2 equiv of AlMe3 with Cp*2ZrF2 (2) leads quantitatively to Cp*2ZrMe2 (12). Reaction of Cp*HfF3 (4) with AlMe3 in an equimolar ratio gives {[Cp*HfMe (μ2-F)][(μ2-F)2AlMe2]}2 (9) stereospecifically as its cis isomer in high yield. 9 crystallizes in the space group P21/c with four molecules in the elemental cell (Z = 16). From the reaction of 1 equiv of Cp*HfF3 (4) with 3 equiv of AlMe3, Cp*HfMe3 (10) can be obtained in a yield of 85%. As a byproduct of this reaction the Hf3Al6C7 cluster [(Cp*Hf)3Al6Me8(μ3-CH2)2(μ4-CH)4(μ3-CH)] (11) can be isolated in a yield of 5%. The characterization of 11 by single-crystal X-ray diffraction and 1H, 13C NMR and mass spectroscopic data will be discussed. Cp*TaF4 (5) reacts with a 5-fold excess of AlMe3, leading quantitatively to Cp*TaMe4 (13) without further decomposition via C−H activation processes.