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Sterically Constrained Bicyclic Phosphines: A Class of Fascinating Compounds Suitable for Application in Small Molecule Activation and Coordination Chemistry
Author(s) -
Brand Alexander,
Uhl Werner
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201803331
Subject(s) - steric effects , chemistry , bicyclic molecule , coordination complex , molecule , class (philosophy) , small molecule , stereochemistry , organic chemistry , combinatorial chemistry , philosophy , biochemistry , epistemology , metal
Abstract Bicyclic phosphines with two annulated, electronically unsaturated five‐membered heterocycles are available through facile routes. In most cases, their phosphorus atoms are bound to heteroatoms such as oxygen or nitrogen (PN 3 or PN 2 O), whereas homoleptic coordination by three sp 2 ‐hybridized carbon atoms has been reported only recently. Steric strain causes unique reactivity. Oxidative addition of halogens, N−H or O−H bonds have afforded phosphoranes as valuable materials for secondary processes. Ring opening was identified as an important step for the understanding of these reactions and has been observed experimentally with a diphosphorus‐based ring system. A PH 2 derivative has been considered as a model system for small molecule activation, and hydrogen transfer to a diazo compound was observed experimentally. Several of these phosphines are excellent ligands for the coordination of transition‐metal atoms. The very bulky PC 3 compound has a basicity similar to that of PPh 3 and may allow the synthesis of complexes with unusually low coordination numbers at the metal atoms. These phosphines found recently renewed interest as promising reagents in various secondary transformations such as the activation of σ‐bonds or in coordination chemistry.