Stereochemical structure determination of p-cymene Ru(II) complexes containing the PPh2Py ligand with 2-D NOESY and HMQC NMR experiments

Synthesis and characterisation of new pyrazole–phosphinite ligands and their ruthenium(II) arene complexes

“…The Ru(II) atom is g 6 -bonded to a p-cymene ring, to L 2 in a j 2 -P,N coordination mode and to a Cl atom. The Ru-Cl bond length of 2.407(1) Å was consistent with those reported in the literature [35]. The Ru-C(p-cymene) bond lengths average 2.242(4) Å and the Ru-C * distance is of 1.745(5) Å (C * = centroid ring).…”

“…The proton spectrum of complex 4 exhibited the CH p-cymene signals as three signals: two doublets at 5.42 (1H) and 4.93 (1H) ppm (J H,H = 5.8 Hz), and a multiplet at 4.72 (2H) ppm. The appearance of separated signals for CH p-cymene hydrogens was consistent with a C 1 symmetry of the complex, which was expected for a [(g 6 -arene)RuL 1 L 2 L 3 ] complex core [7,35,36]. In addition, the bulk of the pyrazole-phosphinite L 2 chelated ligand seems to prevent a free rotation of the p-cymene ligand around the arene-Ru axis.…”

“…This spectrum also displays the p-cymene CH protons as two doublets at 5.20 and 5.10 ppm ( 3 J H,H = 6.6 Hz). The presence of one (broad) or two signals corresponding to CH p-cymene hydrogens in the 1 H NMR spectra of 1 and 2 is consistent with a C s symmetry of complexes and with a free rotation of the arene ligand [35,36]. The proton NMR spectrum of complex 3 displays the CH 2 H 2 resonances of L 2 ligand as two broad signals at 4.21 and 4.10 ppm and the C 6 H 6 protons as a singlet at 5.34 ppm (6H).…”

“…In addition, the bulk of the pyrazole-phosphinite L 2 chelated ligand seems to prevent a free rotation of the p-cymene ligand around the arene-Ru axis. This phenomenon is common in [(g 6 -arene)RuCl(L-L)] + (L-L = neutral bidentate ligand) complexes [35,36]. With reference to complex 5, the C 6 H 6 proton signal is observed at 5.78 ppm as a singlet (6H).…”

A modular design of metal catalysts for the transfer hydrogenation of aromatic ketones

“…Analysis by 1 H NMR reveals this compound to be diamagnetic, exhibiting signals corresponding to the aromatic rings at 7.93–7.42 ppm. Another set of signals consisting of two doublets centred at 5.27 and 5.10 ppm is due to the presence of the aromatic protons in the p ‐cymene group (the presence of one (broad) or two signals corresponding to CH p ‐cymene protons in the 1 H NMR spectrum, consistent with a Cs symmetry of complex and with free rotation of the arene ligand) . Furthermore, in the 13 C NMR spectrum of 2 , J (31P‐13C) coupling constants of the carbons of the phenyl rings were observed, which are consistent with the literature values .…”