Ruthenium(II) Hydrido Complexes of 2,6-(Diphenylphosphinomethyl)pyridine

Abstract

A series of PNP−ruthenium(II) complexes Ru(OCOMe)2(PNP) (1), Ru(OCOMe)2(PNP)(PPh3) (2), the monohydrides RuHX(PNP)(PPh3) (X = OCOMe (3); X = Cl (4)), and dihydride RuH2(PNP)(PPh3) (5) (PNP = 2,6-bis(diphenylphosphinomethyl)pyridine) were synthesized and characterized by microanalysis as well as NMR, IR, and mass spectroscopies. The solution dynamics of complex 1 were studied by variable-temperature 1H and 31P{1H} NMR spectroscopies. The crystal structure of RuHCl(PNP)(PPh3) (4) was determined by X-ray crystallography, showing that the PNP ligand coordinates the Ru atom in a meridional mode. The hydrido complexes RuH(OCOMe)(PNP)(PPh3) (3) and RuH2(PNP)(PPh3) (5) undergo deuterium exchange reactions with CD3OD to give substitution of both the hydrides and PNP methylene protons by deuterium. The probable intermediates involved in these exchange processes are molecular dihydrogen complexes of Ru(II).

Effect of Hydrated Metal Salts on the Coordination Product of Cobalt(II) halide and PNP Type Ligand, 2,6-bis(di-tertbutylphosphinomethyl) pyridine

“…This causes the molecular geometry to be a mixture of distorted square pyramidal and trigonal bipyramidal. The nitrogen to cobalt bond lengths, 2.308(6) Å, 2.283(6) Å, and 2.042(10) Å in the complexes 1, 2, 3 respectively are comparable with the bond distances found in the similar complexes [9,21,22]. The average Co-P bond lengths 2.506(3) Å, 2.543(3) Å, 2.364(4) Å observed in (PNP)CoCl 2 (1), (PNP)CoBr 2 (2) and (PNP)Col 2 (3) respectively were significantly elongated than the common Co-P bond distance 2.25 Å [23].…”

Osmium‐Mediated CH and CC Bond Cleavage of a Phenolic Substrate: p‐Quinone Methide and Methylene Arenium Pincer Complexes

“…The structural changes accompanying the protonation of 2 into 5 b are similar to that observed when switching from QM1 to MA1. Indeed, in these closely related pairs the CH 2 ÀC i bond length increases from 1.453(7) in 2 to 1.490 (14) in 5 b, to be compared to 1.441(8) in QM1 and 1.452(6) in MA1. A similar tendency is observed for the C À O distance, which increases upon protonation from 1.254(7) in 2 to 1.341(13) in 5 b, while it rises from 1.239(6) in QM1 to 1.338(5) in MA1.…”

“…ORTEP view of 7·CHCl 3 with the thermal ellipsoids at 30 % of probability. (14) , respectively, in 7. Accordingly, the longer C14 À O1 distance of 1.341(13) (1.327(13) in 7) is indicative of less pronounced delocalization of the oxygen electrons into the delocalized cyclic system in 7 compared to 5 a.…”

“…The interatomic distances within the ring are characteristic of the methylene arenium structure. Namely, the average C i ÀC o (C11ÀC12 and C11ÀC16) bond length (1.457(15) ) is longer than the average C o ÀC m distance (1.368 (14) for C12ÀC13 and C15ÀC16) and C m ÀC p distance (1.438 (14) for C13ÀC14 and C14ÀC15). The longer C m À C p bond lengths originate from the delocalization of the oxygen electrons pairs, which decreases the double-bond character for the C m À C p bonds (Scheme 6).…”

“…Reversible insertion of the coordinated double-bond into the OsÀH bond [13] accounts for deuterium incorporation into the QM methylenic position, thus generating a transient s-bound cyclohexadienonyl intermediate (Scheme 2). The phosphinomethylenic protons in pincer complexes are known to undergo exchange processes with hydride moieties, [14] presumably through deprotonation to generate the ylide form.…”