Syntheses, Structures, and Characterization of Nickel(II) Stibines: Steric and Electronic Rationale for Metal...

Reactions of the homoleptic and heteroleptic antimony ligands Sb ⁱPr₃, Sb ⁱPr₂Ph, SbMe₂Ph, and SbMePh₂ with NiI₂ generate rare Ni^II stibine complexes in either square planar or trigonal bipyramidal (TBP) geometries, depending on the steric size of the ligands. Tolman electronic parameters were calculated (DFT) for each antimony ligand to provide a tabulated resource for the relative strengths of simple antimony ligands. The electronic absorbance spectra of the square planar complexes exhibit characteristic bands [λ_max ≈ 560 nm (17 900 cm^-1), ε ≈ 4330 M^-1 cm^-1] at lower energies compared to the reported phosphine complexes, indicating the weak donor strength of the stibine ligands and resultant low-energy ligand field d→ d transitions. The square planar complex Ni(I)₂(Sb ⁱPr₃)₂ reacts with CO to form the TBP complex Ni(I)₂(Sb ⁱPr₃)₂(CO). Lastly, the complexes were investigated for nickel metal deposition on Si|Cu(100 nm) substrates. The complexes with the strongest donating ligand, Sb ⁱPr₃, deposited the purest layer of NiCu alloy according to the balanced reaction Ni(I)₂(Sb^{III i}Pr₃)₂ → Ni⁰ + Sb^V( ⁱPr₃)I₂; the iodinated Sb^V byproduct was unambiguously detected in the supernatant by ¹H NMR and mass spectrometry. Complexes with weaker ligands (poor I₂ acceptors/scavengers) resulted undesired deposition of iodine and CuI on the surface. This work thus serves as a guide for the design and synthesis of 3 d metal complexes with neutral, heavy main-group donors that are useful for metal deposition applications.