Metal–Metal Interactions in Dinuclear (triphos)Cobalt Complexes Exhibiting Mixed Valency

Abstract

The spectroscopic and electrochemical properties of a series of dinuclear mixed‐valence complexes containing two (triphos)Co units are reported: [(triphos)Co(L)Co(triphos)]+ (L = C6O4X2; × = H, Cl, Br, I, Me: 2a–e+; L = C14H4O4Me2: 4+). Complexes 2a–e+ are bridged by tetraoxybenzene ligands and exhibit very strong metal–metal interaction leading to delocalized class‐III behaviour while in 4+ the extended tetraoxoanthracence bridging ligand leads to a partial electron localization. Additionally, the different oxidation behaviour of the parent dicationic complexes 1a–e2+ and 32+ have been investigated and are explained on the basis of a qualitative MO model.

Radical ligand-containing single-molecule magnets

“…Efforts to generate benzosemiquinonoid-containing transition metal complexes with a nuclearity of greater than one have resulted in numerous dinuclear compounds, including those containing metal centers bridged by derivatives of 2,5-dihydroxy-1,4-benzoquinonoids [172][173][174][175][176][177][178][179][180][181][182][183][184][185][186][187][188][189], bis(pyrazolyl)benzoquinonoids [190][191][192][193], bis(phosphine)benzoquinonoids [194,195], bis(amino) benzoquinonoids [196][197][198][199][200][201][202], and bis(amino)diiminobenzoquinonoids [86,[203][204][205][206]. Indeed, the radical form of these ligands has shown enhanced magnetic coupling compared to their non-radical redox isomers [174,180,182].…”

Oxidation führt zu Reduktion – redoxinduzierter Elektronentransfer (RIET)

“…Die Monokationen [(triphos)Co( 1 R )Co(triphos)] + ( 12 + ; R=H, Cl, Br, I, Me) werden durch Reduktion von 12 2+ mit Cobaltocen gebildet16 und zersetzen sich bei Verlust von Solvensmolekülen aufgrund ihrer Sauerstoffempfindlichkeit. Glücklicherweise gelang es aber, durch Umsetzung von (triphos)CoCl mit H 2 ‐ 1 Cl in THF das Produkt [(triphos)Co III ( 1 Cl 4− )Co II (triphos)] 2 [CoCl 4 ] ([ 12 + ] 2 [CoCl 4 ]) zu gewinnen und seine Kristallstruktur aufzuklären 16. Sämtliche monoreduzierten monokationischen Komplexe zeigen EPR‐Spektren mit g ≈ 2.11 bei 298 K ( g =2.10 bei 100 K).…”