sp Carbon chains surrounded by sp3 carbon double helices: wire-like Pt(CC)nPt moieties that are spanned by two α,ω-diphosphines that bear heteroatoms or alkyl substituents

Abstract

Reactions of trans-(C₆F₅)L₂PtCl (2, L = Ph₂P(CH₂)₄O(CH₂)₂CHCH₂; 6, L = Ph₂P(CH₂)₂C(CH₃)₂(CH₂)₃CHCH₂) and H(CC)₂H (HNEt₂, cat. CuI) give trans-(C₆F₅)L₂Pt(CC)₂H (3, 7; 86–97%). Oxidative homocouplings (O₂, cat. CuCl/TMEDA, acetone) yield trans,trans-(C₆F₅)L₂Pt(CC)₄PtL₂(C₆F₅) (4, 8; 75–86%). Reactions with Grubbs’ catalyst, followed by hydrogenation, give mainly trans,trans-(C₆F₅)(Ph₂P(CH₂)₄O(CH₂)₆O(CH₂)₄PPh₂)Pt(CC)₄Pt(Ph₂P(CH₂)₄O(CH₂)₆O(CH₂)₄PPh₂)(C₆F₅) (5), with termini-spanning diphosphines, and trans,trans-(C₆F₅)(Ph₂P(CH₂)₂C(CH₃)₂(CH₂)₈C(CH₃)₂(CH₂)₂PPh₂)Pt(CC)₄Pt(Ph₂P(CH₂)₂C(CH₃)₂(CH₂)₈C(CH₃)₂(CH₂)₂PPh₂)(C₆F₅) (9), with trans-spanning diphosphines, respectively. Reactions of trans,trans-(C₆F₅)(p-tol₃P)₂Pt(CC)₄Pt(Pp-tol₃)₂(C₆F₅) with Ph₂P(CH₂)₂C(CH₃)₂(CH₂)₈C(CH₃)₂(CH₂)₂PPh₂ and p-tol₂P(CH₂)₃(CF₂)₈(CH₂)₃Pp-tol₂ give 10 (70%), the isomer of 9 with termini-spanning diphosphines, and the analogous adduct of the fluorinated diphosphine. However, the latter oligomerizes upon attempted workup. The crystal structure of 5 shows that the sp³ chains adopt a chiral double-helical conformation about the sp chain, with the endgroups defining a 164.1° angle. Additional conformational properties of the preceding complexes are analyzed in detail, and dynamic properties are probed by low temperature NMR experiments.