Trapping of Terminal Platinapolyynes by Copper(I) Catalyzed Click Cycloadditions; Probes of Labile Intermediates in Syntheses of Complexes with Extended sp Carbon Chains, and Crystallographic Studies

The silylated hexatriynyl complex trans ‐(C 6 F 5 )( p ‐tol 3 P) 2 Pt(C≡C) 3 SiEt 3 ( PtC 6 TES ) is converted in situ to PtC 6 H (wet n ‐Bu 4 N + F − , THF) and cross coupled with the diyne H(C≡C) 2 SiEt 3 ( HC 4 TES ; CuCl/TMEDA, O 2 ) to give PtC 10 TES (71 %). This sequence is repeated twice to afford PtC 14 TES (65 %) and then PtC 18 TES (27 %). An analogous series of reactions starting with PtC 8 TES gives PtC 12 TES (60 %), then PtC 16 TES (43 %), and then PtC 20 TES (17 %). Similar cross couplings with H(C≡C) 2 Si( i ‐Pr) 3 ( HC 4 TIPS ) give PtC 12 TIPS (68 %), PtC 14 TIPS (68 %), and PtC 16 TIPS (34 %). The trialkylsilyl species (up to PtC 18 TES ) are converted to 3+2 “click” cycloadducts or 1,4‐disubstituted 1,2,3‐triazoles trans ‐(C 6 F 5 )( p ‐tol 3 P) 2 Pt(C≡C) n ‐1 C=CHN(CH 2 C 6 H 5 )N=N (29–92 % after workups). The most general procedure involves generating the terminal polyynes PtC x H (wet n ‐Bu 4 N + F − , THF) in the presence of benzyl azide in DMF and aqueous CuSO 4 /ascorbic acid. All of the preceding complexes are crystallographically characterized and the structural and spectroscopic properties analyzed as a function of chain length. Two pseudopolymorphs of PtC 20 TES are obtained, both of which feature molecules with parallel sp carbon chains in a pairwise head/tail packing motif with extensive sp/sp van der Waals contacts.