Building Blocks for Molecular Polygons Based on Platinum Vertices and Polyynediyl Edges

Reactions of Cl2P(CH2)3PCl2 and p-MgBrC6H4X (X = a/OMe, b/OtBu, c/tBu, d/SiMe3) give the diphosphines (p-XC6H4)2P(CH2)3P(p-C6H4X)2 (1a–d; 47–66%). Additions of 1a,d to (COD)PtCl2 yield (CH2(CH2P(p-C6H4X)2)2)PtCl2 (2a,d; 62–88%), which upon reaction with butadiyne (2 equiv; HNEt2/cat. CuI) give (CH2(CH2P(p-C6H4X)2)2)Pt((C≡C)2H)2 (3a,d; 34–76%). Alternatively, 3a–d can be accessed from trans-(p-tol3P)2Pt((C≡C)2H)2 and 1a–d (30–87%). Reactions of (p-tol3P)2PtCl2 and H(C≡C)2SiR3 (2 equiv, HNEt2/cat. CuI; R = Me/Et/iPr) give trans-(p-tol3P)2Pt((C≡C)2SiR3)2 (77–95%), and subsequent additions of 1a,b,d yield the corresponding adducts (CH2(CH2P(p-C6H4X)2)2)Pt((C≡C)2SiR3)2 (R/X = Me/OMe, 5a; iPr/OMe, 6a; iPr/OtBu, 6b; iPr/SiMe3, 6d; 52–95%) and (for 5a) a luminescent diplatinum byproduct with trans Pt((C≡C)2SiMe3)2 units. 5a and 6b hydrolyze in the presence of F– to 3a,b (92–93%). Reaction of 2a and 3a (HNEt2/cat. CuI) affords the Pt4C16 polygon ([(CH2(CH2P(p-C6H4OMe)2)2)Pt(C≡C)2]4 as an H2NEt2+ Cl– adduct (66%). The 13C{1H} NMR spectra of 3a–d, 5a, and 6a,b,d feature complex AMXX′ (CPtPP′) spin systems, and simulations allow J values to be extracted. The crystal structures of 2a, 3a,b,d, 5a, and 6a are determined and analyzed.