Cover Feature: Multistimuli‐Responsive [3]Dioxaphosphaferrocenophanes with Orthogonal Switches (Chem. Eur. J. 61/2021)

Abstract

A retro‐style arcade machine needs an oxidant or a proton to be inserted to start playing and to switch the donating capabilities of novel phosphine ligands orthogonally and reversibly. Rh‐catalysed hydrosilylation showed that these triggers can influence either the rate of conversion and/or the product distribution. The Japanese kanji for “iron” highlights the ferrocene moiety in the ligands′ metal complexes. More information can be found in the Communication by F. Dielmann, F. Breher et al. (DOI: 10.1002/chem.202101969).

Tris(tetramethylguanidinyl)phosphine: The Simplest Non‐ionic Phosphorus Superbase and Strongly Donating Phosphine Ligand

“…The average P−N bond length of 1 (1.706 Å) is in the range of that of IV (1.701 Å) and longer than that of II (1.689 Å). [ 3 , 13 ] The same trend is observed for the pyramidalization of the phosphorus atom gauged by the sum of NPN angles ( 1 : 296.2°, II : 294.5°, IV : 307.1°).…”

“…We have previously shown that the exocyclic imine N atoms of type II and IV phosphines form stable coordination compounds with alkali metal salts, especially when lithium salts are involved and the imine N atoms are sterically accessible. [ 6 , 13 ] Since this property can make the isolation of superbases prohibitively difficult, we decided to avoid lithium bases in the synthesis of tris(tetramethylguanidinyl)phosphine ( 1 ), and adopted the synthetic procedure used for I and III by employing PCl(NMe 2 ) 2 as phosphorus precursor. [ 5 , 31 , 32 ] The electrophile PCl(NMe 2 ) 2 has a built‐in auxiliary base and is readily accessible by mixing PCl 3 and P(NMe 2 ) 3 in 1 : 2 ratio.…”

“…[4] The resulting very basic phosphines have shown the capacity to react with particularly inert small molecules, including CO 2 , SO 2 , N 2 O and SF 6 ,[ 6 , 7 , 8 ] and they have been successfully applied as ligands in coordination chemistry and catalysis. [ 2 , 4 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ] Prospective widespread application of superbasic phosphines as ligands, but more importantly as nucleophiles in stoichiometric reactions, will require synthetic protocols that enable their easy and scalable preparation from cheap starting materials. While imidazolin‐2‐ylidenaminophosphines (IAP) have the advantage that their steric and electronic properties can be varied over a wide range by modification of the imidazole backbone, their synthesis often involves several reaction steps.…”

“…While imidazolin‐2‐ylidenaminophosphines (IAP) have the advantage that their steric and electronic properties can be varied over a wide range by modification of the imidazole backbone, their synthesis often involves several reaction steps. [ 2 , 6 , 13 ]…”

“…This stands in marked contrast to the imidazolin‐2‐ylidenamino and pyridinylidenamino substituents, which both have negative substituent parameters and obey the additivity rule. [ 2 , 6 , 11 , 13 , 30 ] To shed light on these inconsistencies, we seized on Schmutzler's work and report herein on the synthesis and properties of the hitherto unknown phosphine P(tmg) 3 ( 1 ).…”