An unexpected insertion of acetone into the silicon-carbon terminus of an sp carbon chain: syntheses and structures of model monoplatinum hexatriynyl and octatetraynyl complexes

The sequential treatment of trans-(C6F5)(p- tol3P)2PtC=CC=CC=CSiEt3 (2, acetone solution) with n-Bu4N+F- in wet THF (to generate a PtC=CC=CC=CH complex), ClSiMe3 (fluoride ion scavenger), excess HC=CSiEt3, excess O2, and CuCl/TMEDA (0.20-0.25 equiv in acetone; Hay cross-coupling conditions) gives trans-(C6F5)(p-tol3P)2PtC=CC=CC=CC=CSiEt3 (4, 30%), as previously reported. When an analogous reaction is conducted with SiMe4 in place of ClSiMe3, the side-product trans-(C6F5)(p- tol3P)2PtC=CC=CC=CC(Me)2OSiEt3 is obtained (ca 28%), the structure of which is established crystallographically. For comparison, crystal structures of three related complexes, 4, 2, and trans-(p-tol)(Ph3P)2PtC=CC=CC=CSiEt3, are determined.