Rhenium η
2-vinyl and η
4-diene complexes are rare. We have successfully synthesized a series of aromatic bis-η
2-vinyl complexes Re(η
2-C(Ar)CH(PPh
3))
2Cl
3 bearing two staggered phosphonium-rhenacyclopropene rings by treating ReCl
3(PPh
3)
2NCMe with terminal alkynes HC≡CAr (Ar = Ph, 4-diphenyl, 2-triflorotoluene, 4-(9H-carbazol-9-yl)phenyl). In addition, treating the ReCl
3(PPh
3)
2NCMe with 2-ethynylbenzaldehyde gave the mono-η
2-vinyl complex bearing a rhena-2-benzopyrylium ring. These bis-η
2-vinyl complexes can undergo tail-to-tail oxidative coupling reactions to give the corresponding rhenium η
4-diene complexes Re(η
4-(C(Ar)=CH(PPh
3)
2)Cl
4.
A new series of rhenium carbyne complexes Re(L
xX
y)(PMePh
2)
3-xCl
2-y(≡ CCH
2Ph) bearing pincer, phenolate, and thiophenolate ligands for alkyne metathesis stud...[
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Rhenium η
2-vinyl and η
4-diene complexes are rare. We have successfully synthesized a series of aromatic bis-η
2-vinyl complexes Re(η
2-C(Ar)CH(PPh
3))
2Cl
3 bearing two staggered phosphonium-rhenacyclopropene rings by treating ReCl
3(PPh
3)
2NCMe with terminal alkynes HC≡CAr (Ar = Ph, 4-diphenyl, 2-triflorotoluene, 4-(9H-carbazol-9-yl)phenyl). In addition, treating the ReCl
3(PPh
3)
2NCMe with 2-ethynylbenzaldehyde gave the mono-η
2-vinyl complex bearing a rhena-2-benzopyrylium ring. These bis-η
2-vinyl complexes can undergo tail-to-tail oxidative coupling reactions to give the corresponding rhenium η
4-diene complexes Re(η
4-(C(Ar)=CH(PPh
3)
2)Cl
4.
A new series of rhenium carbyne complexes Re(L
xX
y)(PMePh
2)
3-xCl
2-y(≡ CCH
2Ph) bearing pincer, phenolate, and thiophenolate ligands for alkyne metathesis studies were synthesized. Ligands include 2-{(2-diphenylphosphinophenyl)iminomethyl}phenolate (PNO, x = 2, y = 1), 2-{(2-hydroxyphenyl)iminomethyl}phenolate (ONO, x = 1, y = 2), bis-(2-hydroxyphenyl)phenylphosphine (PO
2, x = 1, y = 2), bis-(2-hydroxyphenyl)thioester (SO
2, x = 1, y = 2), (3,5-di-tert-butyl-2-hydroxyphenyl)phenylphosphine (T
4PO
2, x = 1, y = 2) bis-(2-hydrothiophenyl)phenylphosphine (PS
2, x = 1, y = 2), (2-hydrothiophenyl)diphenylphosphine ((PS)
2, x = 2, y = 2), and bis-(2-hydrothiophenyl)thioester (S
3, x = 1, y = 2). Their activities in stoichiometric alkyne metathesis were examined with MeC≡CPh. All complexes bearing phenolate, and thiophenolate ligands showed observable activity. However, thermodynamically favoured dimerization occurred as a major side reaction in competing with metathesis for carbyne complexes 5.4, 5.7, and 5.9 bearing PS
2, PS, and S
3 ligands respectively. Rhenium carbyne complexes 5.1 and 5.2 bearing PO
2 and SO
2 ligands respectively only showed activity at high activation in stoichiometric alkyne metathesis and pyridine substitution reactions, while analogous reactions of the complex 5.3 with T
4PO
2 can proceed at a lower temperature. The complex 5.1 can undergo the stoichiometric alkyne metathesis reaction with the terminal alkyne PhC≡CH. Catalytic homometathesis of MeC≡CPh proceeded to about 20% of conversion under the condition of 5 mol% of the best-performed complex 5.3 and 2.5 mol % of phosphine scavenger [(p-cymene)RuCl
2]
2 after 4 days of heating at 100°C.
The cationic rhenium carbyne complexes [ReCl
2(PPh
2Me)
3(≡CCH
2PPh
2Me)]Cl (6.8) can be synthesized from the reactions of ReCl
3(PMePh
2)
3 with TMSC≡CH and PMePh
2 via rearrangement of a transient η
2-vinyl complex generated from the on-site phosphine attack on the coordinated alkyne. Analogues complexes [ReCl
2(PPh
3)
2(NCMe)(≡CCH
2PPh
3)]X (X = [ReCl
5(PPh
3)] (6.10), BF
4 (6.11)) can also be prepared from the reactions of ReCl
3(PPh
3)
2NCMe, PPh
3, and TMSC≡ CH, with or without the presence of AgBF
4. A (hydroxyphenyl)diphenylphosphine (PO) and pyridine substituted complex 6.12 was also successfully synthesized and isolated. The cationic carbyne complexes 6.8, 6.10, 6.11, and 6.12 have all been examined for their activity in stoichiometric alkyne metathesis reactions with MeC≡CPh and only the complex 6.8 was found to be reactive. Unexpectedly, the conjugated rhenium carbyne dimer [Cl
2(PPh
2Me)
3Re≡CHC=CHC≡ReCl
2(PPh
2Me)
3] (6.14) was isolated from the light-exposed complex 6.8 (in Hexane/DCM). Synthesis of rhenium carbyne complexes from an α-diazoalkyl complexes were also attempted, but with limited success.
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