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Odd-electron bonds have unique electronic structures and are often encountered as transiently stable, homonuclear species. In this study, a pair of copper complexes supported by Group 13 metalloligands, M[N(( o -C 6 H 4 )NCH 2 P i Pr 2 ) 3 ] (M = Al or Ga), featuring two-center/one-electron (2c/1e) σ-bonds were synthesized by one-electron reduction of the corresponding Cu( i ) ⇢ M(III) counterparts. The copper bimetallic complexes were investigated by X-ray diffraction, cyclic voltammetry, electron paramagnetic spectroscopy, and density functional theory calculations. The combined experimental and theoretical data corroborate that the unpaired spin is delocalized across Cu, M, and ancillary atoms, and the singly occupied molecular orbital (SOMO) corresponds to a σ-(Cu–M) bond involving the Cu 4p z and M n s/ n p z atomic orbitals. Collectively, the data suggest the covalent nature of these interactions, which represent the first examples of odd-electron σ-bonds for the heavier Group 13 elements Al and Ga. 

Completing a series of nickel-group 13 complexes, a coordinatively unsaturated nickel-boron complex and its derivatives with a H 2 , N 2 , or hydride ligand were synthesized and characterized. The toggling “on” of a Ni(0)–B( iii ) inverse-dative bond enabled the stabilization of a nickel-bound anionic hydride with a remarkably low thermodynamic hydricity of kcal mol −1 in THF. The flexible topology of the boron metalloligand confers both favorable hydrogen binding affinity and strong hydride donicity, albeit at the cost of high H 2 basicity during deprotonation to form the hydride. 

A tin-supported iron catalyst produces 5.9 turnovers of NH 3 from N 2 , using [Ph 2 NH 2 ]OTf as the acid and CoCp 2 * as the reductant. Two redox states of the Fe(N 2 ) adduct and an Fe silyldiazenido complex were characterized using X-ray crystallography along with NMR and Mössbauer spectroscopies. Density functional theory calculations reveal that the charge on the Sn center correlates strongly with both the polarization of the N 2 moiety and the charge on the distal N atom.