Alkyne Metatheses in Transition Metal Coordination Spheres: Convenient Tungsten‐ and Molybdenum‐Catalyzed Syntheses of Novel Metallamacrocycles

Reactions of (CO)₅Re(Br), (η⁵‐C₅H₅)Ru(Cl)(PPh₃)₂, and Pt(μ‐Cl)(C₆F₅)(S(CH₂CH₂‐)₂)]₂ with the alkyne‐containing phosphine Ph₂P(CH₂)₆C≡CCH₃ give the bis(phosphine) complexes fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 5 ), (η⁵‐C₅H₅)Ru(Cl)(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 6 ), and trans‐(Cl)(C₆F₅)Pt(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 7 ). Alkyne metatheses with the catalyst (t‐BuO)₃W(≡C‐t‐Bu) (10–15 mol %, chlorobenzene, 80 °C) give the seventeen‐membered metallamacrocycles fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 8 ), (η⁵‐C₅H₅)Ru(Cl)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 9 ), and trans‐(Cl)(C₆F₅)Pt(PPh₂(CH₂)₆CC(CH₂)₆P Ph₂) ( 10 ). ³¹P NMR analyses show 90–75% conversions to 8 – 10 (59–47% isolated after chromatography). The identity of 8 was confirmed by a crystal structure, and 10 was hydrogenated over Pd/C to fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 12 , 87%), which was crystallographically characterized earlier. A catalyst derived from Mo(CO)₆/4‐chlorophenol effects a slower conversion of 7 to 10 at 140 °C. In the case of 5 , a mer, trans isomer of 8 is isolated ( 11 , 44%), as established by NMR and IR data. In 10 – 12 , the diphosphines span trans positions. These results, together with previous examples involving group VIII metallocenes, establish the wide viability of the title reaction.