Redox‐Active Ligand‐Assisted Two‐Electron Oxidative Addition to Gallium(II)

Abstract

The reaction of digallane (dpp-bian)Ga-Ga(dpp-bian) (2) (dpp-bian=1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with allyl chloride (AllCl) proceeded by a two-electron oxidative addition to afford paramagnetic complexes (dpp-bian)Ga(η -All)Cl (3) and (dpp-bian)(Cl)Ga-Ga(Cl)(dpp-bian) (4). Treatment of complex 4 with pyridine induced an intramolecular redox process, which resulted in the diamagnetic complex (dpp-bian)Ga(Py)Cl (5). In reaction with allyl bromide, complex 2 gave metal- and ligand-centered addition products (dpp-bian)Ga(η -All)Br (6) and (dpp-bian-All)(Br)Ga-Ga(Br)(dpp-bian-All) (7). The reaction of digallane 2 with Ph SnNCO afforded (dpp-bian)Ga(SnPh ) (8) and (dpp-bian)(NCO)Ga-Ga(NCO)(dpp-bian) (9). Treatment of GaCl with (dpp-bian)Na in diethyl ether resulted in the formation of (dpp-bian)GaCl (10). Diorganylgallium derivatives (dpp-bian)GaR (R=Ph, 11; tBu, 14; Me, 15; Bn, 16) and (dpp-bian)Ga(η -All)R (R=nBu, 12; Cp, 13) were synthesized from complexes 3, 10, Bn GaCl, or tBu GaCl by salt metathesis. The salt elimination reaction between (dpp-bian)GaI (17) and tBuLi was accompanied by reduction of both the metal and the dpp-bian ligand, which resulted in digallane 2 as the final product. Similarly, the reaction of complex 10 with MentMgCl (Ment=menthyl) proceeded with reduction of the dpp-bian ligand to give the diamagnetic complex [(dpp-bian)GaCl ][Mg Cl (THF) ] (18). Compounds 11, 12, 13, 15, and 16 were thermally robust, whereas compound 14 decomposed when heated at reflux in toluene to give complex (dpp-bian-tBu)GatBu (19). Both complexes 7 and 19 contain R-substituted dpp-bian ligand: in the former compound the allyl group was attached to the imino-carbon atom, whereas in complex 19, the tBu group was situated on the naphthalene ring. Crystal structures of complexes 3, 8, 9, 10, 13, 14, 18, and 19 were determined by single-crystal X-ray analysis. The presence of dpp-bian radical anions in 3, 6, 8, and 10-16 was determined by ESR spectroscopy.

Cycloaddition versus Cleavage of the C=S Bond of Isothiocyanates Promoted by Digallane Compounds with Noninnocent α‐Diimine Ligands

“…Molecular structures of these four products revealed retention of the Ga−Ga bond. The Ga−Ga bonds (2.41–2.42 Å) in these four‐coordinate species are comparable to those in the starting materials 1 and 2 (2.455(1), and 2.3598(3) Å, respectively) as well as in other known divalent gallium dimers ,. The lengths of the newly formed C−C bond in cycloadducts 3 , 4 , 8 , and 9 (1.56–1.60 Å) are noticeably elongated relative to an ordinary C−C bond (1.54 Å).…”

“…These processes are greatly facilitated by low‐valent main group metal centers with appropriate protecting ligands. α‐Diimine ligands proved to be successful in stabilizing a variety of low‐valent metal complexes, including group 13 metal–metal‐bonded compounds such as digallanes and dialumanes –. These complexes have shown promising reactivity towards various small molecules, such as alkynes, alkenes, disulfides, azobenzenes, phenazine, sulfur dioxide, and ketone derivatives .…”

Element‐Ligand Cooperativity with p‐Block Elements

“…The field of gallium‐ligand cooperativity (GaLC) was launched by Fedushkin and co‐workers in 2010 and is primarily governed by the dinuclear Ga(II) complex 62 (Figure a) . 62 was found to undergo GaLC double binding of alkynes, isocyanates, isothiocyanats and allyl bromide along with the conservation of the Ga–Ga single bond. Other unsaturated substrates like alkenes, nitriles, isocyanides, acetone, and α,β‐unsaturated esters showed no reaction .…”

1D Coordination Polymer Derived from Redox‐Active Digallane

“…More, these complexes can cleave reductively multiple bonds C−X (X=O, N, S) recruiting the electrons from the M−M bonds [15] and dpp‐bian ligand as well [16] . Owing to the redox behavior of the ligand the two‐electron oxidative addition at each metal center in [LM−ML] becomes possible [16c] . One may suggest that MOFs derived from [LM−ML] (L=dpp‐bian; M=Al, Ga) may disclose rich chemistry.…”