It is shown that a combination of Schwesinger's phosphazene base concept and the idea of the disubstituted 1,8-naphthalene spacer, first introduced by Alder in paradigmatic 1,8-bis(dimethylamino)naphthalene (DMAN), yields a new superbase, HMPN, which represents the up to date most basic representative of this class of "proton sponges", as evidenced by the theoretically estimated proton affinity PA = 274 kcal/mol and the measured pK(BH+) (MeCN) 29.9 +/- 0.2. HMPN is by nearly 12 orders of magnitude more basic than Alder's classical 1,8-bis(dimethylamino)naphthalene (DMAN). The title compound, HMPN, is prepared and fully characterized. The spatial structure of HMPN and its conjugate acid is determined by X-ray technique and theoretical DFT calculations. It is found that monoprotonated HMPN has an unsymmetrical intramolecular hydrogen bridge (IHB). This cooperative proton chelating effect renders the bisphosphazene more basic than Schwesinger's set of "monodentate" P1 phosphazene bases. The density functional calculations are in good accordance with the experimental results, providing some complementary information. They conclusively show that the high basicity of HMPN is a consequence of the high energy content of the base in its initial neutral state and the intramolecular hydrogen bonding in the resulting conjugate acid with contributions to proton affinity of 14.1 and 9.5 kcal/mol, respectively.

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A tale of two modes: An end‐on copper superoxo complex was identified in a combined experimental and theoretical study. Theory clearly discloses the presence of an end‐on complex (see picture, O red, Cu pink, N green) with a minute isotopic resonance Raman splitting below experimental resolution. The results cast doubts on the uncritical use of 16O,18O isotopic‐labeling Raman experiments to discriminate end‐on from side‐on bonding modes in M(O2) complexes.

1,8-bis(dimethylethyleneguanidino)naphthalene (DMEGN), the second example of a peralkyl guanidine "proton sponge" based on the 1,8-naphthalene backbone, was prepared and fully characterized. The crystal structure analysis of monoprotonated DMEGN reveals an unsymmetrical intramolecular hydrogen bridge. A decrease in the basicity with respect to the noncyclic parent 1,8-bis(tetramethylguanidino)naphthalene was found. Nevertheless, a new proton sponge provides a new crossbar in the ladder of highly basic neutral organic compounds. A detailed theoretical study of DMEGN and related cyclic guanidines explains this surprising experimental result. Homodesmotic reactions reveal that the intramolecular hydrogen bond contributes effectively 10 kcal/mol to proton affinity of DMEGN.

Keywords: Ligand design / N ligands / Tripodal ligands / Coordination chemistry / Manganese / Iron / Zinc / MolybdenumThe synthesis of the novel tripod ligand N[CH 2 CH 2 N= C(NMe 2 ) 2 ] 3 , based on the tris(2-ethylamino)amine (tren) backbone and having a set of three superbasic tetramethylguanidine (TMG) donor atoms instead of the primary amine functionalities, is described. This ligand has been prepared by treating tren with the Vilsmeyer salt [(Me 2 N) 2 CCl]Cl in

The coordination chemistry of copper(I) and copper(II) ions with novel tripodal peralkylguanidine derivatives of the tris(2-aminoethyl)amine (tren) backbone TMG(3)tren (tetramethylguanidino-tren) N[CH(2)CH(2)N=C(NMe(2))(2)](3) (1) and cyclic DMPG(3)tren (dimethylpropyleneguanidino-tren) N[CH(2)CH(2)N=C[NMe(CH(2))(3)NMe]](3) (2) is reported. These sterically demanding ligands form complexes of constraint trigonal geometry. Their superbasic character with estimated pK(BH)+ values 6 orders of magnitude higher than that of the known Me(6)tren and their softer N-donor character compared to tert-amine ligands stabilize cationic mononuclear Cu(I) and Cu(II) ions by delocalization of charge into the guanidine functionalities. The crystal structures and spectroscopic features of two cationic copper(I) complexes with an uncommon trigonal-pyramidal [N(4)Cu](+) coordination sphere and a sterically protected open coordination site and of two cationic copper(II) complexes with the characteristic trigonal-bipyramidal coordination geometry [N(4)CuCl](+) and [N(5)Cu](2+) are reported.

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Side on oder end on? Ein End‐on‐Kupfersuperoxokomplex wurde durch eine kombinierte experimentelle und theoretische Untersuchung nachgewiesen. Die theoretischen Daten belegen eine End‐on‐Koordination (siehe Bild) mit einer kleinen isotopenabhängigen Bandenaufspaltung unterhalb der experimentellen Auflösung. Diese Ergebnisse lassen bezweifeln, dass Resonanz‐Raman‐Ergebnisse für 16O18O‐Isotopenmarkierungen ohne weiteres zur Unterscheidung von End‐on‐ und Side‐on‐M(O2)‐Komplexen geeignet sind.