Alkyl, alkylidene, and alkylidyne complexes of rhenium

Article abstract of DOI:10.1021/om00004a047

The reaction of Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)₂ with triflic acid, pentafluorophenol, HBF₄·OEt₂, or [H(OEt₂)₂]⁺[BAr^F₄] ^- (Ar^F = 3,5-C₆H₃(CF₃)₂) yields complexes of the general formula Re(C-t-Bu)(CH₂-t-Bu)₃X (X = OTf, OC₆F₅, BF₄, BAr^F₄) in 60-80% yield. Re(C-t-Bu)(CH₂-t-Bu)₃X reacts with coordinating ligands L (L = py, CH₃CN, CD₃OD, THF) to form neopentane and Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(L)_nX (n = 1-3). The reaction of Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(py)₂(OTf) with NaC₅H₅, NaL_OEt (L_OEt = [CpCo(PO(OEt)₂)₃], or NaHBpZ₃ in THF yields Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(η⁵-C₅H ₅), Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(L_OEt), or Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(HBpz₃), respectively, while the reaction between Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(py)₂(OTf) and 1,4,7-trithiacyclononane produces colorless [Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(η³-S₃C ₆H₁₂)]⁺[OTf]- in 96% yield. Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(L) (L = Cp, L_OEt) and [Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(η³-S₃C ₆H₁₂)]⁺[OTf]^- react with triflic acid to form Re(C-t-Bu)(CH-t-Bu)(L)(OTf) or [Re(C-t-Bu)(CH-t-Bu)(OTf)-(η³-S₃C₆H ₁₂)]⁺[OTf]^-, respectively. A similar reaction between Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(L_OEt) and [H(OEt₂)₂]⁺[BAr^F₄] ^- in ether produces [Re(C-t-Bu)(CH-t-Bu)(OEt₂)(L_OEt)]⁺[BAr ^F₄]^-. Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(py)₂(OTf) reacts with H₂C=CHR (R = OCH₂CH₃, C₆H₅) to yield neohexene and Re(C-t-Bu)(CHR)(CH₂-t-Bu)(py)₂(OTf) complexes. Re(C-t-Bu)(CH-t-Bu)-(CH₂-t-Bu)(py)₂(OTf) reacts with ethylene to form the unstable methylidene complex, Re(C-t-Bu)(CH₂)(CH₂-t-Bu)(py)₂(OTf), which can be trapped upon addition of bpy to yield red Re(C-t-Bu)(CH₂)(CH₂-t-Bu)(bpy)(OTf). Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(py)₂(OTf) reacts with excess ethylene to form colorless Re(C-t-Bu)[(CH₂)₃-t-Bu](C₂H ₄)(py)₂(OTf) in 85% yield. Re(C-t-Bu)(CH-t-Bu)(CH₂-t-Bu)(CH₃CN)(OTf) metathesizes 100 equiv of cis-2-pentene in less than 5 min, but the catalyst is not long-lived.