Formal coupling of two alkylidyne ligands on a metal center

Abstract
Reaction of the alkylidyne complexes [W(CR)Br(CO)3L] [2b (L = CO; R = C6H4‐OMe‐4), 2c (L = CO, R = C6H4‐NMe2‐4), 3a (L = PPh3; R = Ph), and 3c (L = PPh3; R = C6H4‐NMe2‐4)] with methyllithium in THF at ‐78°C affords the alkylidyne acyl tungsten complexes Li[W(CR)(COMe)Br(CO)3L] [4b (L = CO; R = C6H4‐OMe‐4), 4c (L = CO, R = C6H4‐NMe2‐4), 5a (L = PPh3; R = Ph), and 5c (L = PPh3; R = C6H4‐NMe2‐4)]. Reaction of complexes 4 and 5 with C2O2Br2 at ‐78°C‐0°C in CH2Cl2 followed by addition of PPh3 gives the alkyne complexes [WBr2(CO)(CH3C = CR)(PPh3)2] (6). The formation of the alkyne ligands in complexes 6 may be considered as the result of formal coupling of two alkylidyne ligands.

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