Alkyne Metatheses in Transition Metal Coordination Spheres: Convenient Tungsten‐ and Molybdenum‐Catalyzed Syntheses of Novel Metallamacrocycles
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Reactions of (CO)5Re(Br), (η5-C5H 5) Ru(Cl)(PPh3)2, and [Pt(μ-Cl)(C 6F5)(S(CH2CH2-)2)] 2 with the alkyne-containing phosphine Ph2P(CH 2)6 C≡CCH3 give the bis(phosphine) complexes fac-(CO)3Re(Br)(Ph2P(CH2) 6C≡CCH3)2 (5), (η5-C 5H5) Ru(Cl)(Ph2P(CH2) 6C≡CCH3)2 (6), and trans-(Cl) (C 6F5)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)(Ph 2P(CH2)6C≡C(CH2) 6PPh2) (8), η5-C5H 5)Ru(Cl)(Ph2P(CH2)6C≡C(CH 2)6PPh2) (9), and trans-(Cl)(C 6F5)Pt(PPh2(CH2)6C≡ C(CH2)6PPh2) (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)6PPh2) (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.
author list (cited authors)
Bauer, E. B., Hampel, F., & Gladysz, J. A.