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The Forgotten Nitroaromatic Phosphines as Weakly Donating P‐ligands: An N ‐Aryl ‐benzimidazolyl Series in RhCl(CO) Complexes
Author(s) -
Zhu Chongwei,
Gras Emmanuel,
Duhayon Carine,
Lacassin Francis,
Cui Xiuling,
Chauvin Remi
Publication year - 2017
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201701078
Subject(s) - chemistry , ligand (biochemistry) , aryl , benzimidazole , yield (engineering) , nitro , medicinal chemistry , stereochemistry , crystallography , organic chemistry , alkyl , receptor , materials science , biochemistry , metallurgy
The coordination chemistry of a priori weakly σ ‐donating nitroaromatic phosphines is addressed through a series of nitro‐substituted ( N ‐phenyl‐benzimidazol‐1‐yl)diphenylphosphines in Rh I complexes. From a set of seven such phosphines L=L xyz (′) ( x , y , z =0 or 1=number of NO 2 substituents at the 5, 6 and N‐Ph para positions, respectively), including the non‐nitrated parent L 000 and its dicationic N‐methyl counterpart L 000 ′, three LRhCl(COD) and seven L 2 RhCl(CO) complexes have been obtained in 72–95 % yield. Despite of a cis orientation of the L and CO ligands, the C=O IR stretching frequency ν CO varies in the expected sense, from 1967±1 cm −1 for L xy0 to 1978±1 cm −1 for L xy1 , and 2005 cm −1 for L 000 ′. The 103 Rh NMR chemical shift δ Rh varies from −288 ppm for L 000 to −316±1 ppm for L 10z or L 01z , and −436 ppm for L 000 ′. The ν CO and δ Rh probes thus reveal moderate but systematic variations, and act as “orthogonal” spectroscopic indicators of the presence of nitro groups on the N‐Ph group and the benzimidazole core, respectively. For the dicationic ligand L 000 ′, a tight electrostatic sandwiching of the Rh‐Cl bond by the benzimidazole moities is evidenced by X‐ray crystallography (RhCl δ − ⋅⋅⋅CN 2 + ≈3.01 Å). Along with the LRhCl(CO) complexes, dinuclear side‐products (μ‐CO)(RhClL) 2 were also obtained in low spectroscopic yield: for the dinitro ligand L=L 011 , a unique 1:6.7 clathrate structure, with dichloromethane as solvate, is also revealed by X‐ray crystallography.