Influence of phosphine (pincer) ligands on the transition metal hydrides reactivity

Hard to Handle: Extremely Labile Hydrido Nickel(II) Complexes of Cyclometalated C∧N∧N and N∧C∧N Ligands

“…In several of the previous reports on nickel hydrido complexes mention was made of qualitatively similar lability, yielding darkened dispersions of elemental nickel and the protonated ligand. ,,,,,− Notwithstanding their substantial lability, however, the entire complex series in Chart was isolated and crystallized. While the lability of [Ni­(Phbpy)­H] with cis -configured anionic ligands is unsurprising, the rapid decay of trans -configured [Ni­(PyPhPy)­H] at −80 °C precluded isolation and even detailed spectroscopic analysis.…”

“…Organometallic nickel­(II) hydrido complexes have gained enormous interest in recent years due to their role as catalysts or as important intermediates in organometallic processes such as C–H functionalizations, − hydroarylation C–C coupling reactions and related, ,,− the oligomerization of ethene to α-olefins, ,,− (de)­hydrogenation reactions, ,,,− photo- or electrolytical dihydrogen evolution or oxidation, ,,− including the [FeNi] depending hydrogenases. ,,, Ni­(II) hydrido complexes are frequently formed in C–H activation through oxidative addition steps using a Ni(0) species, − ,, or through X – → H – ligand exchange (X = halides or pseudohalides), ,,− and the reactivity of such species has been studied in model complexes. − ,− Despite their vital role in dihydrogen turnover and C–H activation, however, synthetic access to and bulk isolation of Ni­(II) hydrido species are still hampered by their intrinsic lability. Only scant examples of Ni­(II) hydrido complexes have been structurally characterized. ,,,,,…”

The Dichotomy of Mn–H Bond Cleavage and Kinetic Hydricity of Tricarbonyl Manganese Hydride Complexes

“…The acidity and hydricity of the M−H bond can be quantified in terms of p ΔG°H-, respectively [14][15][16]. The quantitative scale of kinetic hydricity (kH-) has b veloped for group 6−7 metal hydrides in the pioneering work of Bullock [11].…”

“…The acidity and hydricity of 1-4 have not been evaluated before thi therefore, the entire set of these complexes could be used to create the scale thermodynamic/kinetic hydricity by evaluating the impact of the ligand. The acidity and hydricity of the M-H bond can be quantified in terms of pK a and ∆G • H− , respectively [14][15][16]. The quantitative scale of kinetic hydricity (k H− ) has been developed for group 6-7 metal hydrides in the pioneering work of Bullock [11].…”

Catalytic dehydrocoupling of methylamine borane using Yamashita's [Ir(PBP)] boryl complex – characterisation of a novel highly fluxional Ir tetrahydride

“…Late transition metal pincer oligohydride complexes are nowadays a well-established class of organometallic complexes that can be used for a variety of stoichiometric and catalytic transformations. [1][2][3] These species are further known to be important intermediates in a wide range of catalytic processes involving the transfer of hydrides, protons, and dihydrogen. A detailed study of these complexes is therefore of fundamental and practical importance.…”