Three-Fold Intramolecular Ring Closing Alkene Metatheses of Square Planar Complexes with cis Phosphorus Donor Ligands P(X(CH₂)_mCH═CH₂)₃ (X = −, m = 5–10; X = O, m = 3–5): Syntheses, Structures, and Thermal Properties of Macrocyclic Dibridgehead Diphosphorus Complexes

Abstract

Reactions of cis-PtCl(P((CH) CH═CH)) and Grubbs' first generation catalyst and then hydrogenations afford cis- PtCl(P((CH) ) P) ( cis-2; n = 2 m + 2 = 12 (b), 14 (c), 16 (d), 18 (e), 20 (f), 22 (g); 6-40%), derived from 3-fold interligand metatheses. The phosphite complexes cis-PtCl(P(O(CH) CH═CH)) are similarly converted to cis- PtCl(P(O(CH) O) P) ( cis-5; n* = 8 (a), 10 (b), 12 (c), 10-20%). The substitution products cis- PtPh(P((CH) ) P) ( cis-6c,d) and cis- PtI(P(O(CH)O) P) are prepared using PhZn and NaI, respectively. Crystal structures of cis-2c,d,f, cis-5a,b, and cis-6c show one methylene bridge that roughly lies in the platinum coordination plane and two that are perpendicular. The thermal behavior of the complexes is examined. When the bridges are sufficiently long, they rapidly exchange via an unusual "triple jump rope" motion over the PtX moieties. NMR data establish Δ H, Δ S, and Δ G/Δ G values of 7.8 kcal/mol, -27.9 eu, and 16.1/18.8 kcal/mol for cis-2d, and a Δ G of ≥19.6 kcal/mol for the shorter bridged cis-2c. While cis-2c,g gradually convert to trans-2c,g at 150-185 °C in haloarenes, trans-2c,g give little reaction under analogous conditions, establishing the stability order trans > cis. Similar metathesis/hydrogenation sequences with octahedral complexes containing two cis phosphine ligands, fac-ReX(CO)(P((CH)CH═CH)) (X = Cl, Br), give fac- ReX(CO)( P(CH) CH)((CH))( P(CH) CH) (19-50%), which are derived from a combination of interligand and intraligand metathesis. The relative stabilities of cis/ trans and other types of isomers are probed by combinations of molecular dynamics and DFT calculations.

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

“…Two signals of each set exhibited phosphorus coupling. The overall pattern was quite similar to those shown by metal complexes with cis or trans coordinating diphosphine ligands of the formula ( 6 ) [ 6 – 7 12 – 13 35 ]. This suggested the diphosphine diborane structure 6 ·2BH 3 (see Scheme 2 ), which is derived from one metathesis involving alkenyl moieties on different phosphorus atoms, and two metatheses of alkenyl moieties on identical phosphorus atoms.…”

Syntheses, Structures, and Thermal Properties of Gyroscope-like Complexes Consisting of PtCl2 Rotators Encased in Macrocyclic Dibridgehead Diphosphines P((CH2)n)3P with Extended Methylene Chains (n = 20/22/30) and Isomers Thereof

“…However, except for a few octahedral systems with certain values of n , , it is always a minor pathway. Density functional theory (DFT) calculations (gas phase) suggest that trans - 2 is more stable than trans - 2′ for n < 16, but trans - 2′ is more stable for n ≥ 20. , …”

“…We have sought to fully explore the topological space associated with the preceding compounds, as well as the free diphosphine ligands, and have systematically targeted various types of stereoisomers that may be isolable. , One of these, trans - 2″ in Scheme , is also derived from three-fold interligand alkene metathesis, but two of the methylene chains “cross”, unlike the disposition in trans - 2 . A di metallic adduct of a bridgehead diphosphine and a free dibridgehead diphosphine dioxide with crossed methylene chains have in fact been isolated. , …”

Bulky Selenium Ligand Stabilized Trans‐Palladium Dichloride Complexes as Catalyst for Silver‐Free Decarboxylative Coupling of Coumarin‐3‐Carboxylic Acids

“…To substantiate our claim, we compare the activation energy of current rotational process with literature. The activation energies ranging from 0.8 kcal/mol to 16.1 kcal/mol are reported depending on the bulky nature of the stator units [5f,6] …”