Ligand “Brackets” for Ga–Ga Bond

The reactivity of digallane (dpp-Bian)­Ga–Ga­(dpp-Bian) (<b>1</b>) (dpp-Bian = 1,2-bis­[(2,6-diisopropylphenyl)­imino]­acenaphthene) toward acenaphthenequinone (AcQ), sulfur dioxide, and azobenzene was investigated. The reaction of <b>1</b> with AcQ in 1:1 molar ratio proceeds via two-electron reduction of AcQ to give (dpp-Bian)­Ga­(μ₂-AcQ)­Ga­(dpp-Bian) (<b>2</b>), in which diolate [AcQ]^2– acts as “bracket” for the Ga–Ga bond. The interaction of <b>1</b> with AcQ in 1:2 molar ratio proceeds with an oxidation of the both dpp-Bian ligands as well as of the Ga–Ga bond to give (dpp-Bian)­Ga­(μ₂-AcQ)₂Ga­(dpp-Bian) (<b>3</b>). At 330 K in toluene complex <b>2</b> decomposes to give compounds <b>3</b> and <b>1</b>. The reaction of complex <b>2</b> with atmospheric oxygen results in oxidation of a Ga–Ga bond and affords (dpp-Bian)­Ga­(μ₂-AcQ)­(μ₂-O)­Ga­(dpp-Bian) (<b>4</b>). The reaction of digallane <b>1</b> with SO₂ produces, depending on the ratio (1:2 or 1:4), dithionites (dpp-Bian)­Ga­(μ₂-O₂S–SO₂)­Ga­(dpp-Bian) (<b>5</b>) and (dpp-Bian)­Ga­(μ₂-O₂S–SO₂)₂Ga­(dpp-Bian) (<b>6</b>). In compound <b>5</b> the Ga–Ga bond is preserved and supported by dithionite dianionic bracket. In compound <b>6</b> the gallium centers are bridged by two dithionite ligands. Both <b>5</b> and <b>6</b> consist of dpp-Bian radical anionic ligands. Four-electron reduction of azobenzene with 1 mol equiv of digallane <b>1</b> leads to complex (dpp-Bian)­Ga­(μ₂-NPh)₂Ga­(dpp-Bian) (<b>7</b>). Paramagnetic compounds <b>2</b>–<b>7</b> were characterized by electron spin resonance spectroscopy, and their molecular structures were established by single-crystal X-ray analysis. Magnetic behavior of compounds <b>2</b>, <b>5</b>, and <b>6</b> was investigated by superconducting quantum interference device technique in the range of 2–295 K