Electron‐Transfer Studies of trans ‐Platinum Bis(acetylide) Complexes

The complexes trans ‐[Pt(C≡CFc) 2 (PFc m n Bu 3– m ) 2 ] (Fc = ferrocenyl; m = 0, 9a ; m = 1, 9b ; m = 2, 9c ) were prepared by the reactions of PFc m n Bu 3– m ( m = 0, 3a ; m = 1, 3b ; m = 2, 3c ) with cis ‐[PtCl 2 (SEt 2 ) 2 ] ( 6 ) to form [PtCl 2 (PFc m n Bu 3– m ) 2 ] ( m = 0, 7a ; m = 1, 7b ; m = 2, 7c ), which on treatment with [CuC≡CFc] ( 8 ) produced 9a – 9c . The reactions of PFc m n Bu 3– m ( m = 1–3; m = 3, 3d ) with S 8 or Se gave (S=)PFc m n Bu 3– m ( m = 1, 4b ; m = 2, 4c ; m = 3, 4d ) and (Se=)PFc m n Bu 3– m ( m = 1, 5b ; m = 2, 5c ; m = 3, 5d ). Compounds 5d , 7b , 7c , 9b , and 9c were structurally characterized by single‐crystal X‐ray diffraction studies; a trans arrangement of the phosphine units at the Pt center is typical. The redox behavior of 3 , 4 , 7 , and 9 was investigated by cyclic and square‐wave voltammetry. The Fc units of 9a – 9c could be oxidized separately indicating electronic interactions between the Fc/Fc + groups of the FcC≡C units [Δ E°′ = 105 ( 9a ), 115 ( 9b ), 120 mV ( 9c )]. Cationic [ 9b ] + and [ 9c ] + exhibit weak intervalence charge‐transfer (IVCT) absorptions at $\tilde {\nu}$ = 6700 cm –1 .