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Formal nickelate(−I) complexes bearing Group 13 metalloligands (M=Al and Ga) were isolated. These 17 e⁻complexes were synthesized by one‐electron reduction of the corresponding Ni⁰→M^IIIprecursors, and were investigated by single‐crystal X‐ray diffraction, EPR spectroscopy, and quantum chemical calculations. Collectively, the experimental and computational data support: 1) the strengthening of the Ni−M bond upon one‐electron reduction, and 2) the delocalization of the unpaired spin across the Ni and M atoms. An intriguing electronic configuration is revealed where three valence electrons occupy two σ‐type bonding interactions: Ni(3d)²→M and σ‐(Ni−M)¹. The latter is an unusual Ni−M σ‐bonding molecular orbital that comprises primarily the Ni 4p_zand M np_z/ns atomic orbitals.

 

Understanding H 2 binding and activation is important in the context of designing transition metal catalysts for many processes, including hydrogenation and the interconversion of H 2 with protons and electrons. This work reports the first thermodynamic and kinetic H 2 binding studies for an isostructural series of first-row metal complexes: NiML, where M = Al ( 1 ), Ga ( 2 ), and In ( 3 ), and L = [N( o -(NCH 2 P i Pr 2 )C 6 H 4 ) 3 ] 3− . Thermodynamic free energies (Δ G °) and free energies of activation (Δ G ‡ ) for binding equilibria were obtained via variable-temperature 31 P NMR studies and lineshape analysis. The supporting metal exerts a large influence on the thermodynamic favorability of both H 2 and N 2 binding to Ni, with Δ G ° values for H 2 binding found to span nearly the entire range of previous reports. The non-classical H 2 adduct, (η 2 -H 2 )NiInL ( 3 -H 2 ), was structurally characterized by single-crystal neutron diffraction—the first such study for a Ni(η 2 -H 2 ) complex or any d 10 M(η 2 -H 2 ) complex. UV-Vis studies and TD-DFT calculations identified specific electronic structure perturbations of the supporting metal which poise NiML complexes for small-molecule binding. ETS-NOCV calculations indicate that H 2 binding primarily occurs via H–H σ-donation to the Ni 4p z -based LUMO, which is proposed to become energetically accessible as the Ni(0)→M( iii ) dative interaction increases for the larger M( iii ) ions. Linear free-energy relationships are discussed, with the activation barrier for H 2 binding (Δ G ‡ ) found to decrease proportionally for more thermodynamically favorable equilibria. The Δ G ° values for H 2 and N 2 binding to NiML complexes were also found to be more exergonic for the larger M( iii ) ions. 

We present three heterobimetallic complexes containing an isostructural nickel center and a lutetium ion in varying coordination environments. The bidentate iPr2PCH2NHPh and nonadentate (iPr2PCH2NHAr)3tacn ligands were used to prepare the Lu metalloligands, Lu( i Pr 2 PCH 2 NPh) 3 ( 1 ) and Lu{( i Pr 2 PCH 2 NAr) 3 tacn} ( 2 ), respectively. Reaction of Ni(COD) 2 (where COD is 1,5-cyclooctadiene) and 1 afforded NiLu( i Pr 2 PCH 2 NPh) 3 ( 3 ), with a Lu coordination number (CN) of 4 and a Ni–Lu distance, d (Ni–Lu), of 2.4644(2) Å. Complex 3 can further bind THF to form 3-THF , increasing both the Lu CN to 5 and d (Ni–Lu) to 2.5989(4) Å. On the other hand, incorporation of Ni(0) into 2 provides NiLu{( i Pr 2 PCH 2 NAr) 3 tacn} ( 4 ), in which the Lu coordination environment is more saturated (CN = 6), and the d (Ni–Lu) is substantially elongated at 2.9771(5) Å. Cyclic voltammetry of the three Ni–Lu complexes shows an overall ∼410 mV shift in the Ni(0/I) redox couple, suggesting tunability of the Ni electronics across the series. Computational studies reveal polarized bonding interactions between the Ni 3d z2 (major) and the Lu 5d z2 (minor) orbitals, where the percentage of Lu character increases in the order: 4 (6.0% Lu 5d z2 ) < 3-THF (8.5%) < 3 (9.3%). All three Ni–Lu complexes bind H 2 at low temperatures (−30 to −80 °C) and are competent catalysts for styrene hydrogenation. Complex 3 outperforms 4 with a four-fold faster rate. Additionally, adding increasing THF equivalents to 3 , which would favor build-up of 3-THF , decreases the rate. We propose that altering the coordination sphere of the Lu support can influence the resulting properties and catalytic activity of the active Ni(0) metal center.