Stable, crystalline boron complexes with mono-, di- and trianionic formazanate ligands

Abstract

Redox-active formazanate ligands are emerging as tunable electron-reservoirs in coordination chemistry. Here we show that boron diphenyl complexes with formazanate ligands, despite their (formal) negative charge, can be further reduced by up to two electrons. A combined crystallographic, spectroscopic and computational study establishes that formazanate ligands are stable in mono-, di- and trianionic form.

Dinuclear Complexes of Flexidentate Pyridine‐Substituted Formazanate Ligands

“…[1][2][3] Formazanates have garnered considerable attention in coordination chemistry due to their ligand-based redox processes, which may facilitate multielectron redox transformations, [4] bond activations [5] and excited-state charge separation. [6] Av ariety of formazanate complexes of many main-group metals [7][8][9][10][11][12][13][14][15][16] andf irst-and second-row transition metals [17][18][19][20][21][22][23] have been described.T hese studies demonstrate the versatile coordination chemistry of formazanate ligandsa nd provides ignificant insight into the opticala nd redox properties of these compounds.S ome coppercomplexesc an also mediate oxygen activation, [24,25] certain cobalt and iron complexes exhibit unique magnetic characteristics, [17,26] and boronc omplexes in many cases feature not only the tunable redoxp roperties but also visible to nearinfrared photoluminescence, [9][10][11][12][13] finding applicationsa sc ellimaging agents [27,28] and electrochemiluminescence emitters. [10] Our group has expanded the coordination chemistry of formazanatest ot hird-row transition metals with as eries of hetero-leptic cyclometalated platinumc omplexes and bis-cyclometalated iridium complexes, [29][30][31] and accessed homoleptic azo-iminate platinum complexes and azo-1,2,3-triazolide iridium complexesv ia hydrogenative cleavage or [3+ +2]...…”

Formazanate coordination compounds: synthesis, reactivity, and applications

“…67 BPh 2 formazanate 76 was generated by refluxing BPh 3 with the appropriate formazan in toluene (Scheme 28a). 90 The radical anion 76 À and dianion 76 2À were subsequently generated by treatment with 1 equiv. of CoCp* 2 and 2 equiv.…”

Group 13 Complexes of Chelating N2O2n− Ligands as Hybrid Molecular Materials

“…In addition to many of the properties highlighted above, group 13 complexes of ligands derived from formazans offer rich redox chemistry . Boron and aluminum complexes of N 2 O 2 3− formazanate ligands are relatively straightforward to synthesize, and have been used as electrochemiluminescence (ECL) emitters and as precursors to redox‐active BN heterocycles …”

“…In addition to many of the properties highlighteda bove, group 13 complexes of ligandsd erived from formazans offer rich redox chemistry. [50][51][52][53] Boron and aluminum complexes of N 2 O 2 3À formazanate ligands are relativelys traightforward to synthesize, and have been used as electrochemiluminescence (ECL) emitters [17] anda sp recursorst or edox-active BN heterocycles. [16] Formazan 20 can be synthesized in as ingle step from cyanoacetic acid and two equivalents of the aryldiazoniums alt prepared from 2-aminophenol, under basic conditions.…”