Reactions of ReOCl
2(OEt)(PPh
3)
2 with terminal alkynols produced rhenium oxo ylide complexes with the vinyl double bond located outside the ring system. Reactions of ReOCl
2(OEt)(PPh
3)
2 with internal alkynols also produced rhenium oxo ylide complexes but with the vinyl double bond located inside the ring system. DFT calculations show that, for reactions involving terminal alkynols, the C
β attacked products are thermodynamically more stable compared with the C
α attacked products, the reverse is true for reactions involving internal alkynols. Rhenium oxo vinyl complexes from the reactions involving internal alkynes can be oxidized in air to give paramagnetic Re(=CR(CPPh
3)CH
2CH
2O)OCl
3 complexes (R = Me and Ph) together with triphenylphosphine oxide.
Treatment of rhenacyclobutadiene (CO)
4Re(=C(Ph)C(CO
2Et)=C(OEt)) with 1-ethoxyehtyne in acetonitrile produced the rhenabenzene (CO)
4Re(=C(Ph)C(CO
2Et)=C(OEt)CH=C(OEt)). Rhenacyclobutadiene (CO)
4Re(=C(1-Naph)C(CO
2Et)=C(OEt)) reacted with 1-ethoxyehtyne in acetonitrile to give rhenabenzenes (CO)
4Re(=C(1-Naph)C(CO
2Et)=C(OEt)CH=C(OEt)) and (CO)
4Re(=C(OEt)CH=C(1-Naph)C(CO
2Et)=C(OEt)). Treatment of NaRe(CO)
5 with (4-Py)C≡CCO
2Et followed by ethylation afforded rhenacyclobutadiene (CO)
4Re(=C(4-Py)C(CO
2Et)=C(OEt)). Rhenacyclobutadiene (CO)
4Re(=C(4-Py)C(CO
2Et)=C(OEt)) reacted with 1-ethoxyethyne in acetonitrile to give rhenabenzenes (CO)
4Re(=C(4-Py)C(CO
2Et)=C(OEt)CH=C(OEt)) and (CO)
4Re(=C(OEt)CH=C(4-Py)C(CO
2Et)=C(OEt)). Reaction of NaRe(CO)
5 with (9-Anc)C≡CCO
2Et followed by ethylation produced the rhenacyclobutadiene (CO)
4Re(=C(CO
2Et)C(9-Anc)=C(OEt)) as a rearranged product. Reaction of NaRe(CO)
5 with PhC≡C(CO)Ph and EtOC≡C(CO
2Et) followed by ethylation gave the rhenafurane complexes (CO)
4Re(=C(Ph)CH=CPhO) and (CO)
4Re(=C(OEt)CH=C(OEt)O) respectively.
Reaction of NaRe(CO)
5 with (9-Phena)C≡CCO
2Et followed by ethylation allows the isolation of rhenacyclobutadiene (CO)
4Re(=C(9-Phena)C(CO
2Et)=C(OEt)) and sometimes rhenafuran (CO)
4Re(=C(9-Phena)CH=C(OEt)O) complex. Rhenacyclobutadiene (CO)
4Re(=C(9-Phena)C(CO
2Et)=C(OEt)) reacted with 1-ethoxyethyne in acetonitrile to give rhenabenzene (CO)
4Re(=C(9-Phena)C(CO
2Et)=C(OEt)CH=C(OEt)). Interestingly, treatment of NaRe(CO)
5 with benzyne followed by ethylation allows the isolation of rhenacyclobutadiene derivative (CO)
4Re(=C(OEt)C(CH)
4=C).
Treatment of CpW(CO)
3SnPh
3 with ortho-((RC≡C)LiC
6H
4) (R = TMS and Ph) followed by methylation with Me
3OBF
4 gave tungsten carbene-acetylene complexes Cp(CO)
2(SnPh
3)W(=C(OMe)C
6H
4(C≡CR)) and tungstalactone complexes Cp(CO)
2(SnPh
3)W(=C(O)C(CH)
4CC=CHR). Treatment of tungsten carbene-acetylene complex Cp(CO)
2(SnPh
3)W(=C(OMe)C
6H
4(C≡CR)) with iodine produced Cp(CO)
2lW(=C(OMe)C
6H
4(C≡CR)). Reaction of tungstalactone Cp(CO)
2(SnPh
3)W(=C(O)C(CH)
4CC=CH(Ph)) with HCl in ether led to the cleavage of Sn-Ph bond to give Cp(CO)
2(SnCl
2Ph)W(=C(O)C(CH)
4CC=CH(Ph)).
The reaction energies of the rearrangement of metallabenzenes of third row early transition metals and second row late transition metals to the corresponding Cp complexes have been evaluated by density functional theory calculations. Two aspects have been investigated: effect of ligands and the effect of substituents on the metallabenzene ring.
The reaction energies of the rearrangement reactions of metallabenzynes to give carbene complexes have been studied by density functional theory calculations. A preliminary study has been carried out to prepare metallabenzynes using metal vinylidene carbonyl precursors. Reaction of CpRe(CO)
2(THF) with ortho-(HC≡C)(Br)C
6H
4 in warm THF led to the isolation of Cp(CO)
2Re(η
2-acetylene) complex and dinuclear carbene complex Cp(CO)
2Re(=C(Cp(CO)
2Re)CH(C
6H
4Br)). Treatment of CpRe(CO)
2(THF) with ortho-(HC≡C)C(Ph)=C(Br)Ph in warm THF led to the isolation of dirhenium carbene complexes Cp(CO)
2Re(=C(Cp(CO)
2Re)CHC(Ph)=C(H)Ph) and Cp(CO)
2Re(Cp(CO)
2Re)C=CHC(Ph)=C(H)Ph.
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