Synthesis, structure, and reactivity of sp carbon chains with bis(phosphine) pentafluorophenylplatinum endgroups:: Butadiynediyl (C4) through hexadecaoctaynediyl (C16) bridges, and beyond

The reaction of trans-[(C6F5)(p-tol(3)P)(2)PtCl] (PtCl) and butadiyne (cat. CuI, HNEt2) gives trans-[(C6F5) (p-tol(3)P)(2)Pt(CdropC)(2)H] (PtC4H, 81%), which reacts with excess HdropCSiEt(3) under Hay coupling conditions (O-2, cat. CuCl/TMEDA, acetone) to yield PtC6Si (53%). A solution of PtC6Si in acetone is treated with wet nBu(4)NF to generate PtC6H. The addition of ClSiMe3 (F- scavenger) and then excess HCdropCSiEt(3) under Hay conditions gives PtC8Si (39%). Hay homocouplings of PtC4H, PtC6H, and PtC8H (generated in situ analogously to PtC6H) yield PtC8Pt, PtC12Pt, and PtC16Pt (97-92%). Reactions Of PtC4H and PtC6H with PtCl (cat. CuCl, HNEt2) give PtC4Pt and PtC6Pt (69%, 34%). The attempted conversion of PtC8H to PtC10Si affords mainly PtC16Pt, with traces Of PtC20Pt and PtC24Pt. The complexes PtCxPt are exceedingly stable (dec pts 234 to 288degreesC), and Et3P displaces p-tol(3)P to give the corresponding compounds Pt'C8Pt' and Pt'C12Pt' (94-90%). The effect of carbon chain lengths upon IR nu(Cequivalent toC) patterns (progressively more bands), UV/Vis spectra (progressively red-shifted and more intense bands with epsilon>600000M(-1)cm(-1)), redox properties (progressively more difficult and less reversible oxidations), and NMR values are studied, and analyzed with respect to the polymeric sp carbon allotrope carbyne. The crystal structure of PtC12Pt shows a dramatic, unprecedented degree of chain bending, whereas the chains in PtC8Pt, Pt'C12Pt', and PtC16Pt are nearly linear.