Alkyne metatheses in transition metal coordination spheres: Convenient tungsten- and molybdenum-catalyzed syntheses of novel metallamacrocycles

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.