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Cleavage of a P=P Double Bond Mediated by N‐Heterocyclic Carbenes
Author(s) -
Hayakawa Naoki,
Sadamori Kazuya,
Tsujimoto Shota,
Hatanaka Miho,
Wakabayashi Tomonari,
Matsuo Tsukasa
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201701201
Subject(s) - carbene , chemistry , steric effects , cleavage (geology) , bond cleavage , molecule , double bond , stereochemistry , medicinal chemistry , crystallography , catalysis , polymer chemistry , organic chemistry , materials science , fracture (geology) , composite material
The reaction of the bulky diphosphenes (Rind)P=P(Rind) ( 1 ; Rind=1,1,3,3,5,5,7,7‐octa‐R‐substituted s ‐hydrindacen‐4‐yl) with two molecules of N‐heterocyclic carbene (NHC; 1,3,4,5‐tetramethylimidazol‐2‐ylidene) resulted in the quantitative formation of the NHC‐bound phosphinidenes NHC→P(Rind) ( 2 ), along with the cleavage of the P=P double bond. The reaction times are dependent on the steric size of the Rind groups (11 days for 2 a (R=Et) and 2 h for 2 b (R=Et, Me) at room temperature). The mechanism for the double bond‐breaking is proposed to proceed via the formation of the NHC‐coordinated, highly polarized diphospehenes 3 as an intermediate. Approach of a second NHC to 3 induces P−P bond cleavage and P−C bond formation, which proceeds through a transition state with a large negative Gibbs energy change to afford the two molecules of 2 , thus being the rate‐determining step of the overall reaction with the activation barriers of 80.4 for 2 a and 29.1 kJ mol −1 for 2 b .