Alkali Metal and Zinc Complexes of a Bridging 2,5-Diamino-1,4-Benzoquinonediimine Ligand

Abstract

Two alkali metal complexes of a bridging 2,5-diamino-1,4-benzoquinonediimine ligand (dipp-dabqdiH(2)), [(thf)(2)Li(μ-dipp-dabqdi)Li(thf)(2)] (1) and [(dme)(1.5)Na(μ-dipp-dabqdi)Na(dme)(1.5)](n) (2, dme = 1,2-dimethoxyethane), have been synthesized by the reaction of dipp-dabqdiH(2) with Li(n)Bu or sodium metal. In addition, treatment of 1,2,4,5-tetrakis(2,6-diisopropylamino)benzene (dipp-tabH(4)) with potassium metal in dme afforded the complex [(dme)(2)K(μ-dipp-tabH(2))K(dme)(2)] (3). X-ray crystal diffraction analyses revealed that complexes 1 and 3 have dinuclear structures, while the sodium complex 2 aggregates to a one-dimensional polymer through bridging dme ligands. With increasing ion radius, the coordination number of the alkali metal (Li, Na, and K) increases from four to five to six, while the coordination geometry changes from distorted tetrahedral to square pyramidal and further to octahedral in 1, 2, and 3, respectively. The salt metathesis reactions of 1 and 2 with anhydrous ZnCl(2) yielded the ion-contacted zinc complexes [(thf)(3)Li(μ-Cl)ClZn(μ-dipp-dabqdi)ZnCl(μ-Cl)Li(thf)(3)] (4), [(dme)(2)Li(μ-Cl)ClZn(μ-dippdabqdi)ZnCl(μ-Cl)Li(dme)(2)] (5), and [(dme)(2)Na(μ-Cl)(2)Zn(μ-dipp-dabqdi)Zn(μ-Cl)(2)Na(dme)(2)] (6), respectively. The ligand exists as the dianionic form in compounds 1-6 upon double deprotonation, and a complete electronic delocalization (except for 3) of the quinonoid π-system is observed between the metal centers over the two N═C-C═C-N halves of the ligand. The electronic structures of the complexes were studied by density functional theory (DFT) computations.

An orthorhombic polymorph ofN1,N4-diphenyl-3,6-bis(phenylimino)cyclohexa-1,4-diene-1,4-diamine

“…Comment N 1 ,N 4 -Diphenyl-3,6-bis(phenylimino)cyclohexa-1,4-diene-1,4-diamine (I) was synthesized as early as in 1875 (Kimish, 1875) and called azophenine. Recently derivatives of I were prepared and these molecular structures were reported (Siri & Braunstein, 2000;Khramov et al, 2006;Boydston et al, 2006;Huang et al, 2008;Su et al, 2012). Previously, we reported the molecular structure of I in triclinic P-1 space group, which is obtained from an oxidation reaction of aniline in the presence of [V IV (O)(η 2 -ox)(H 2 O) 3 ] (ox 2-= oxalate) in a mixture of EtOH and H 2 O (Ohno et al, 2014).…”

“…For the triclinic polymorph of the title compound, see: Ohno et al (2014). For related structures, see: Siri & Braunstein (2000); Khramov et al (2006); Boydston et al (2006); Huang et al (2008); Su et al (2012). A calculation using Gaussian98 indicates that the triclinic form of the title compound is more stable, see: Frisch et al (2001).…”

N1,N4-Diphenyl-3,6-bis(phenylimino)cyclohexa-1,4-diene-1,4-diamine

“…For general background to the title compound, see: Kimish (1875); Rall et al (1998); Frantz et al (2004); Siri et al (2005); Taquet et al (2006); Schweinfurth et al (2013); Jeon et al (2013). For related structures, see: Hughes & Saunders (1956); Merchant et al (1984); Siri & Braunstein (2000); Wenderski et al (2004); Khramov et al (2006); Boydston et al (2006); Huang et al, (2008); Su et al (2012).…”

“…The molecular structures of the derivatives except I have been investigated (Boydston et al, 2006;Khramov et al, 2006;Huang et al, 2008). This class of compounds forms various metal complexes (Rall et al, 1998;Siri & Braunstein, 2000;Frantz et al, 2004;Siri et al, 2005;Su et al, 2012), some of which exhibit novel properties (Taquet et al, 2006;Schweinfurth et al, 2013), e.g. one-electron reduced dinuclear Fe complex with I behaves as a single molecule magnet with the strongest exchange coupling (Jeon et al, 2013).…”

Synthesis and structural characterization of LiI, ZnII, CdII, and HgII complexes containing a fluorinated β-diketiminate ligand

“…Although the β-diketonato (B) [2] and β-enaminoketonato (C) [3][4] ligands are the traditionally popular chelating systems, the isoelectronic β-diketiminato ligands have recently gained dramatically increasing attention, due to the ease variation of R groups on the nitrogen, which may be hydrogen, alkyl, aryl, or silyl groups [5][6] . In the past decade, the use of β-diketiminates as supporting ligands was extensively studied, and a wide range of main group element [7][8][9][10][11] , transition metal [12][13][14][15][16] and lanthanide complexes [17][18] containing this type of ligands have been reported. Importantly, a good number of these metal complexes have proven to serve as effective catalysts for olefin polymerization [19] , silane dehydropolymerization [20] , olefin hydrosilylation [21] , lactide polymerization [22] , Suzuki coupling [23] , hydroamination [24] , and other transformations.…”