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Unprecedented Ring–Ring Interconversion of N,P,C‐Cage Ligands
Author(s) -
Villalba Franco José Manuel,
Schnakenburg Gregor,
Espinosa Ferao Arturo,
Streubel Rainer
Publication year - 2015
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.201405754
Subject(s) - phosphinidene , chemistry , ring (chemistry) , ligand (biochemistry) , stereochemistry , cage , covalent bond , phenylacetylene , electrophile , crystallography , biochemistry , receptor , mathematics , organic chemistry , combinatorics , catalysis
The novel N,P,C‐cage complexes 5 a – f and 6 a – f have been obtained by the reaction of the P ‐pentamethylcyclopentadienylphosphinidene complex 2 , generated thermally from 2 H ‐azaphosphirene complex 1 , with N ‐methyl‐ C ‐arylcarbaldimines 3 a – f . Li/Cl phosphinidenoid complex 8 reacted with 3 a , b to give N,P,C‐cage complexes 6 a , b , whereas with 3 c – f , complexes 6 c – f were obtained in negligible amounts only. Both types of ligand N,P,C‐cage structures 5 and 6 were found to be in an unprecedented equilibrium, with 5 a , f as the predominant species. Transient electrophilic terminal phosphinidene complexes 10 a – f serve as intermediates in both ligand interconversions ( 5 a , f ↔ 6 a , f ), as evidenced through trapping reactions with phenylacetylene and N ‐methyl‐ C ‐phenylcarbaldimine, thus leading to the novel N,P,C‐cage complexes 13 b and 15 . DFT calculations predicted a small difference in the relative energies of the two types of N,P,C‐cage ligands, and a remarkable stabilisation of the aminophosphinidene complex 10 as the common precursor, thereby providing an insight into this surprising 5‐ring–3‐ring interconversion. In depth analysis of intermediate 10 revealed the occurrence of both through‐bond (conventional inductive/mesomeric effects) and through‐space (non‐covalent interactions) mechanisms, which amount to 67.8 and 14.4 kcal mol −1 , respectively, and account for the remarkable stabilisation of this intermediate.