B(C6F5)3 as C6F5 Transfer Agent in Zirconium Chemistry: Borole Sandwich and Borole-Bridged Triple-Decker Complexes

TJ Woodman, M Thornton-Pett, DL Hughes, M Bochmann

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Abstract

Treatment of Cp‘‘Zr(C6F5)(OEt2){?5-(3-RC4H3BC6F5)} (1H, R = H; 1Me, R = Me; Cp‘‘ = 1,3-C5H3(SiMe3)2) in toluene with nitriles R‘CN gives rise to the adducts Cp‘‘Zr(C6F5)(NCR‘){?5-(3-RC4H3BC6F5)} (2H, R = H, R‘ = Me; 3H, R = H, R‘ = tBu; 3Me, R = Me, R‘ = tBu) in high yields. The reaction of 1H and 1Me with a 4-fold excess of tert-butylisocyanide in toluene at -20 °C leads to the formation of Cp‘‘Zr(C6F5)(CNtBu)2{?5-(3-RC4H3BC6F5)} (4H, R = H; 4Me, R = Me), while warming to room temperature results in the insertion of one molecule of isocyanide into the zirconium-C6F5 bond to give the ?2-iminoacyl complexes Cp‘‘Zr{?2-(C6F5CNtBu)}(CNtBu){?5-(3-RC4H3BC6F5)} (5H, R = H; 5Me, R = Me). The structures of 3H and 5H were confirmed by X-ray diffraction. The reaction of the diene complexes CpRZr(?3-crotyl)(?4-butadiene) (6a, CpR = C5H4SiMe3; 6b, C5H4Me; 6c, Cp; 6d, Cp‘‘) with B(C6F5)3 in toluene solution at room temperature proceeds quantitatively with C-H activation, butene elimination, and C6F5 transfer to generate CpRZr(C6F5){?4-CH2CHCHCHB(C6F5)2} (7a-d). These boryldiene complexes are thermally unstable and smoothly rearrange to give the triple-decker complexes Zr2(CpR)2(C6F5)2{µ-?5:?5-C4H4BCH2-?3,?F-CHCHCHB(C6F5)3} (8a-d). The formation of these complexes involves the complete transfer of all three C6F5 substituents of one B(C6F5)3 molecule, as well as C-H activation and the loss of one C6F5 group as pentafluorobenzene. The triple-decker complexes feature a Zr2C4B core, a zwitterionic structure, and an unusually strong Zr-F donor interaction. On activation with methylalumoxane (MAO), 8a-d polymerize ethene.
Original languageEnglish
Pages (from-to)4080-4091
Number of pages12
JournalOrganometallics
Volume20
Issue number19
DOIs
Publication statusPublished - 10 Sep 2001

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