Valence Tautomerism for Quinone Complexes of Manganese: Members of the MnIV(N-N)(Cat)2-MnIII(N-N)(SQ)(Cat)-MnII(N-N)(SQ)2 Series

Valence Tautomerism in ao-Benzoquinone Adduct of a Tetraazamacrocycle Complex of Manganese

“…The average MnÀO distance of 1.87 agrees well with those in other metal(iii) catecholato derivatives. [7,8] Finally, the structural parameters of the coordinated benzoquinone are typical of a catecholato dianion; the CÀO and CÀC bond lengths are similar to those observed for other dtbcat derivatives. [1] The IR spectrum of 1 is virtually superimposable on those of the chromium, iron, and cobalt analogues, which can be unambiguously described as containing catecholato adducts of the trivalent metal ions.…”

“…The decrease between 280 and 120 K might be due both to interconversion between the Mn II Àsq and Mn III Àcat forms and to antiferromagnetic coupling between the paramagnetic metal ion and the radical ligand. [7,8,15] If the former were dominant, the interconversion process should be of the noncooperative type. The X-band EPR spectra of 1 and 2 at low temperatures show several features which may be due to impurities.…”

“…The reaction of [Be{N(SiMe 3 ) 2 } 2 ] [7] with two equivalents of HSPh in toluene in the presence of [18]crown-6 gave a thick, white suspension; addition of one equivalent of pyridine generated a homogenous solution, [8] from which 1 was obtained as colorless crystals, which were analyzed by single-crystal X-ray diffraction. The identity of 1 was also …”

Trigonal‐Prismatic vs. Octahedral Geometry for MnII Complexes with Innocent Didentate Ligands: A Subtle Difference as Shown by XRD and DFT on [Mn(acac)2(bpy)]

“…[2] In addition a limited, but growing number of examples of nondithiolene [M(didentate) 3 ] trigonal-prismatic compounds is known, for instance with buta-1,3-diene, methyl vinyl ketone or acetylacetonate as ligands. [3][4][5][6] A few mixed ligand trigonal-prismatic complexes of the form [M(didentate1) 2 (didentate2)] are known, for example the complexes with a diimine and two (substituted) catechol semiquinonates as ligands, [7][8][9] but they are definitely not as common as homoleptic tris(didentate) complexes. Most compounds mentioned above have either noninnocent ligands, or ligands that can easily participate in π-(back) bonding.…”

One Novel Cu(II)–Amino Acid Schiff Base Complex Derived from Salicylaldehyde and L-Serine: Identification of Unusual Monodentate 4,4′-Bipyridine

“…Keeping this in mind, we have tried to synthesise copper(II)-Schiff base complex with bridging 4,4 -bipyridine spacer and obtained one novel copper(II)-Schiff base complex where 4,4 -bipyridine functions as a monodentate ligand, which appears to be an unusual phenomenon [27,28]. In the present complex, one of the N -donor atoms of 4,4 -bipyridine is engaged in intermolecular hydrogen bonding with protonated carboxylate group without which an extended copper(II)-4,4 -bipyridine chain could have been envisioned.…”