Acid–Base Interaction between Transition‐Metal Hydrides: Dihydrogen Bonding and Dihydrogen Evolution

Abstract

Reaction of the acidic tungsten(II) hydride 2 with the nickel(II) pincer complex 1 in either THF or toluene after an initial dihydrogen bonding (DHB) interaction led to the formation of the Ni–W bimetallic species 3 (see picture). The first example of DHB between two metal hydrides with opposite polarity was analyzed by NMR and IR spectroscopy, X‐ray crystallography, and DFT calculations.

Heterobimetallic H2 Addition and Alkene/Alkane Elimination Reactions Related to the Mechanism of E-Selective Alkyne Semihydrogenation

“…Experimental evidence for M−H···H−M′ dihydrogen bonding in a related system has been reported, and the accompanying computational analysis indicated a dihydrogen bond strength of 1.7 kcal/mol in that system. 41 The reaction profile was also analyzed using computed bond orders, determined by calculation of Wiberg bond indices (WBIs) derived from natural bond orbital (NBO) calculations. The changes in WBI values across the reaction coordinate ( Figure 3) reinforce conclusions reached by analyzing bond distances.…”

Leveraging molecular metal–support interactions for H2 and N2 activation

“…In general, Ni tends to be both a poor π-back-donor and poor σ-acceptor toward H 2 ; thus, examples of H 2 reacting with Ni are uncommon [32,39,[46][47][48][49][50]. Classical H 2 oxidative addition at a single Ni center has not been reported to our knowledge, attesting to the poor π-back-donor ability of Ni.…”

Bifunctional activation of amine-boranes by the W/Pd bimetallic analogs of “frustrated Lewis pairs”

“…2 ) appeared to be very similar to those reported for the related Ni-containing complexes. 8,9,11 The larger steric volume of the Tp ligand leads to a different orientation of the [TpW(CO) 3 ] fragment: rotation around the Pd–O bond places terminal CO ligands on one side of the [(PCP)Pd] plane.…”

“…The ensemble of the reaction products ((PCP)PdH, LW(CO) 3 H and H 2 B NR 2 ) is only slightly higher in free energy than the starting adduct 5 (+1.0 kcal mol −1 ), and the reaction is still reversible. However, since H 2 evolution from the two hydrides ( k 1 , Scheme 3 ) 8,9,33 and the off-metal B N dimerization 34,35 are featured with a comparable barrier, the overall reaction of dehydrogenative DMAB coupling becomes irreversible.…”

“…Dihydrogen bonding (DHB, M–H δ − ⋯ δ + H–M′; M–H = (PCP)NiH, (PCP)PdH; M′–H = CpWH(CO) 3 ( 1a ); PCP = 2,6-C 6 H 3 (CH 2 P t Bu 2 ) 2 ) precedes the concerted proton and hydride transfer, 7 eventually yielding the bimetallic isocarbonyl bridging M/W bimetallic complex 4 ( Scheme 1 ). 8,9 Up to date, there are only a few examples of the attempted use of such systems in catalysis. CpMoH(CO) 3 has been used as a proton source in Rh-catalyzed hydroformylation.…”