Syntheses of Tungsten Imido Cyclohexylidene Complexes Using Perfluoro-t-butanol or Hexafluoro-t-butanol as Acids.

ABSTRACT

The fluorinated alcohols, (CF3)3COH (RF9OH) and (CF3)2MeCOH (RF6OH), react with W(NR)2Cy2 (Cy = Cyclohexyl; R = 2,6-diisopropylphenyl or 1-adamantyl) in C6D6 at 55°C to give cyclohexylidene complexes.  Traditional routes to terminal alkylidene complexes (neopentylidene or neophylidene) have used either triflic acid or HCl (rarely), but relatively weak fluorinated acids are sufficient and active bisalkoxide catalysts are therefore prepared directly.  An ahydrogen abstraction reaction to give a cyclohexylidene complex from a biscyclohexyl appears to be as facile as ahydrogen abstraction to give a neopentylidene or neophylidene ligand, but isomerization of a cyclohexene formed through b hydrogen abstraction is also a possibility.  The ORF9 ligands can be replaced readily with dimethylpyrrolide (Me2Pyr) or other more basic alkoxides.  Single crystal X-ray studies were carried out on W(NAr)2Cy2, W(NAr)(ORF9)2(C6H10)(ArNH2), W(NAr)(ORF6)2(C6H10)(ArNH2), W(NAd)(ORF9)2(C6H10)(AdNH2), W(NAr)(O-i-PrF6)3Cy, and W(NAd)(h1-Me2Pyr)2(C6H10) (C6H10 = cyclohexylidene).