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. The bis(hexatriynyl) complexes (R2C(CH2PPh2)2)2Pt((CΞC)3H)2 (14; R = c, n‐Bu; e, p‐tolCH2) con­dense with the diiodide complexes R2C(CH2PPh2)2PtI2 (9a,c) in the presence of CuI (cat.) and excess HNEt2 to give the title macrocycles [(R2C(CH2PPh2)2)Pt(CΞC)3]4 (16c,e). The bis(triethylsilylpolyynyl) complexes (n‐Bu2C(CH2PPh2)2)Pt((CΞC)nSiEt3)2 (n = 2, 3) react with I2 at rt to give mainly the diiodide complex 9c and the coupling product Et3Si(CΞCCΞC)nSiEt3. Analogous reactions of the Pt4C24 macrocycle 16c also give 9c, but no sp 13C NMR signals or mass spectrometric Cxz+ ions (x = 24‐100) could be detected. It is proposed that some cyclo[24]car­bon is generated, but then rapidly converts to other forms of elemental carbon. 

In a seminal 1972 study, TESCxTES with x = 8, 12, 16, and 24 (TES = SiEt3) were presented as unisolable and thus only characterized by UV-visible spectroscopy. We find that TESC24TES is obtained from the reaction of trans-(C6F5)(p-tol3P)2Pt(C≡C)5SiEt3 and crude HC8TES under Hay oxidative cross coupling conditions. Hay oxidative homocouplings of HC4TES and crude HC8TES afford TESC8TES (83%) and TESC16TES (5%). A Cadiot-Chodkiewicz reaction of BrC4Br and HC4TES (2 equiv) yields TESC12TES (11%). All of these compounds are crystalline, and the crystal structures of TESC8TES and TESC16TES are determined. 

Reactions of trans‐(C6F5)(p‐tol3P)2Pt(C≡C)nSiEt3 (PtC2nSi; n = 5, 7, 9) and ex­cess PtCl in the presence of wet n‐Bu4N+ F– under Sonogashira‐type conditions (CuCl, base, other additives) afford the title compounds PtC10Pt, PtC14Pt, and PtC18­Pt in 42‐32% yields. A four‐fold substitution of the phosphine ligands in PtC10Pt by PEt3 affords Pt'C10Pt' (78%), and a Sonogashira reaction of Pt'C2H and Pt'Cl affords Pt'C2Pt' (68%). Certain sp chain extension reactions that lead to or employ the precursors PtC10Si, PtC12Si, PtC14Si, and PtC18Si sometimes give byproducts derived from C2 loss, and possible origins are discussed. 

CuI catalyzes reactions of cis -(R 2 C(CH 2 PPh 2 ) 2 )Pt(CCCCH) 2 and cis -(R 2 C(CH 2 PPh 2 ) 2 )PtI 2 in secondary amine solvents HNR’ 2 to give the title adducts [(R 2 C(CH 2 PPh 2 ) 2 )Pt(CCCC)] 4 ·(H 2 NR’ 2 + I − ) n (R/R’/ n = Me/Et/1, Me/((CH 2 CH 2 ) 2 O) 0.5 /3, Et/Et/1, Et/CH 2 CHCH 2 /1; 92–42%). Crystal structures of these or closely related species establish folded Pt 4 cores containing ammonium cation guests, with NH/ and NCH/CC hydrogen bonding. DOSY NMR experiments show that the host/guest relationship can be maintained in solution. 

Photolyses oftrans‐Fe(CO)₃(P((CH₂)_n)₃P) (n=10 (a), 12 (b), 14 (c), 16 (d), 18 (e)) in the presence of PMe₃provide the first economical and scalable route to macrobicyclic dibridgehead diphosphines P((CH₂)_n)₃P (1). These are isolated as mixtures ofin,in/out,outisomers that equilibrate with degeneratein,out/out,inisomers at 150 °C via pyramidal inversion at phosphorus. For the entire series, VT³¹P NMR data establish or boundK_eq, rates, and activation parameters for a variety of phenomena, many of which involve homeomorphic isomerizations, topological processes by which certain molecules can turn themselves inside out (e. g.,in,in⇌out,out). This provides the first detailed mapping of such trends in homologous series of aliphatic bicyclic compounds XE((CH₂)_n)₃EX with any type of bridgehead. Isomeric diborane adducts1 a,d ⋅ 2BH₃are also characterized. Crystal structures ofout,out‐1 aandin,in‐1 a ⋅ 2BH₃aid isomer assignments and reveal unusual cage conformations.

 

The diphosphine complexes cis - or trans -PtCl 2 (P((CH 2 ) n ) 3 P) ( n = b/12, c/14, d/16, e/18) are demetalated by MCX nucleophiles to give the title compounds (P((CH 2 ) n ) 3 )P (3b–e, 91–71%). These “empty cages” react with PdCl 2 or PtCl 2 sources to afford trans -MCl 2 (P((CH 2 ) n ) 3 P). Low temperature 31 P NMR spectra of 3b and c show two rapidly equilibrating species (3b, 86 : 14; 3c, 97 : 3), assigned based upon computational data to in , in (major) and out , out isomers. These interconvert by homeomorphic isomerizations, akin to turning articles of clothing inside out (3b/c: Δ H ‡ 7.3/8.2 kcal mol −1 , Δ S ‡ −19.4/−11.8 eu, minor to major). At 150 °C, 3b, c, e epimerize to (60–51) : (40–49) mixtures of ( in , in / out , out ) :  in , out isomers, which are separated via the bis(borane) adducts 3b, c, e·2BH 3 . The configurational stabilities of in , out -3b, c, e preclude phosphorus inversion in the interconversion of in , in and out , out isomers. Low temperature 31 P NMR spectra of in , out -3b, c reveal degenerate in , out / out , in homeomorphic isomerizations (Δ G ‡Tc 12.1, 8.5 kcal mol −1 ). When ( in , in / out , out )-3b, c, e are crystallized, out , out isomers are obtained, despite the preference for in , in isomers in solution. The lattice structures are analyzed, and the D 3 symmetry of out , out -3c enables a particularly favorable packing motif. Similarly, ( in , in / out , out )-3c, e·2BH 3 crystallize in out , out conformations, the former with a cycloalkane solvent guest inside. 

Reactions of trans-[[upper bond 1 start]Fe(CO)2(NO)(As((CH2)n)3As[upper bond 1 end])]+ BF4− (n = 10, 12, 14) and Bu4N+ Cl− afford the title compounds As((CH2)n)3As, which upon reaction (n = 14) with MCl2 (M = Pt, Ni), Rh(CO)(Cl), and Fe(CO)3 sources reconstitute cage like complexes trans-[upper bond 1 start]MLn(As((CH2)14)3A[upper bond 1 end]s). Reactions with H2O2 and BH3 give the corresponding arsine oxides and boranes. Crystal structures of metal-free species reveal out,out isomers, but cage complex formation is proposed to entail homeomorphic isomerization to in,in isomers with endo directed lone pairs.