Frontiers in the Crystallographic Characterization of Extended Conjugated Polyynes: New Structures of Diplatinum Adducts and a Literature Survey
Year: 2025
Type: article
Abstract: The crystal structures of the polyynes trans,trans‐(C6F5)(p‐tol3P)2Pt(C≡C)14Pt(Pp‐tol3)2(C6F5) (PtC28Pt) and trans,trans‐(C6F5)(Me3P)2Pt(C≡C)4Pt(PMe3)2(C6F5) (Pt*C8Pt*) are described. The former is available by a reported oxidative homocoupling and the latter by a fourfold Pp‐tol3/PMe3 substitution. The former represents the longest conjugated polyyne structurally characterized to date, and “near misses” involving higher homologs are detailed. The difference between the average C≡C and CC bond lengths (bond length alternation (BLA)) of PtC28Pt (1.217 and 1.338 Å;BLA(avg) 0.121 Å) is diminished relative to those of Pt*C8Pt* (1.240 and 1.370 Å; BLA(avg) 0.130 Å) or the Pp‐tol3 analog (1.231 and 1.358 Å; BLA(avg) 0.127 Å). Implications for the electronic structure of the sp carbon allotrope carbyne are discussed. In both new structures, all platinum–platinum vectors run parallel, but there are two distinct sets, offset by ≈14 and ≈5 sp carbon atoms, respectively. Within a set, the chains are well separated, but PtC28Pt exhibits 3.47 Å van der Waals contacts between sets. Considering all literature data, still higher polyynes are viewed as more challenging to crystallographically characterize, but not impossible.
Institution: Texas A&M University
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,960
OpenAlex ID: W4408798843