We have developed a convenient route to make new rhenium carbyne complexes. Treatment of [Re(dppm)₃]I with terminal alkynes in the presence of hydroiodic acid give [Re(≡CCH₂R)I(dppm)₂]I. When alknyols are used, rhenium vinyl carbyne [Re(≡CCH=CR¹R²)I(dppm)₂]I can be formed. Without hydroiodic acid, rhenium vinylidene complexes Re(=C=CHR)I(dppm)₂ can be produced. The conversions of rhenium carbynes into vinylidenes and allenylidenes are achieved through deprotonation.

The reactivity of [Re(≡CCH=CPh₂)I(dppm)₂]I (31a) is reported. Reaction of 31a with sulphur results in [Re(≡CCH=CPh₂)I(dppm)(SPPh₂CH₂PPh₂)]I. Replacement of a dppm ligand occurs in the reaction between 31a and PMe₃ which lead to the formation of Re(≡CCH=CPh₂)I₂(dppm)(PMe₃). [Re(≡CCH=CPh₂)X(dppm)₂]I (X = F or Cl) were forme...[ Read more ]

We have developed a convenient route to make new rhenium carbyne complexes. Treatment of [Re(dppm)₃]I with terminal alkynes in the presence of hydroiodic acid give [Re(≡CCH₂R)I(dppm)₂]I. When alknyols are used, rhenium vinyl carbyne [Re(≡CCH=CR¹R²)I(dppm)₂]I can be formed. Without hydroiodic acid, rhenium vinylidene complexes Re(=C=CHR)I(dppm)₂ can be produced. The conversions of rhenium carbynes into vinylidenes and allenylidenes are achieved through deprotonation.

The reactivity of [Re(≡CCH=CPh₂)I(dppm)₂]I (31a) is reported. Reaction of 31a with sulphur results in [Re(≡CCH=CPh₂)I(dppm)(SPPh₂CH₂PPh₂)]I. Replacement of a dppm ligand occurs in the reaction between 31a and PMe₃ which lead to the formation of Re(≡CCH=CPh₂)I₂(dppm)(PMe₃). [Re(≡CCH=CPh₂)X(dppm)₂]I (X = F or Cl) were formed by the reactions of 31a with AgBF₄ and 1,2-dichloroethane respectively. Re(η²H₃B-CH₂CH=CPh₂)(dppm)₂ can be produced by the reduction 31a with NaBH₄.

ReOX₃(PPh₃)₂ (X = Br or Cl) were found to be efficient catalysts in catalyzing degradation of lignin model compounds by C-C bond cleavage. These model compounds include ArCH(OH)CH(OAr’)(CR¹R²OH) (Ar = 3,4-dimethoxyphenyl; Ar’ = 2-methoxyphenyl) and 1,3-diols. For example, the model compound ArCH(OH)CH(OAr’)(CH₂OH) (veratrylglycerol-β-guaiacyl ether) was degraded into enol ethers ArCHCH(OAr’), p-guaiacol, (4-methoxyphenyl)acetaldehyde and formaldehyde. The catalytic properties of ReOX₃(SMe₂)(OPPh₃) (X = Cl, Br or I) and Re₂O₇ for disproportionation reactions of allylic alcohols and Meyer-Schuster rearrangement of propargylic alcohols were explored.