Palladium alkyl complexes with a formazanate ligand: synthesis, structure and reactivity

Abstract

Palladium(ii) complexes with a bidentate, anionic formazanate ligand are described. Attempts to prepare mono(formazanate) palladium alkyl complexes often leads to the homoleptic bis(formazanate) complex, which shows rich electrochemistry due to the redox-active nature of the ligands. Performing salt metathesis between the precursor [Pd(COD)(CH3)Cl] and the potassium salt of the ligand in the presence of tetrabutylammonium chloride yields a square planar mono(formazanate) palladate complex through coordination of chloride anion. Ligand exchange allows binding of unsaturated molecules and evaluation of the reactivity of the Pd-CH3 fragment. Using this approach, insertion reactions of CO, isocyanide and methyl acrylate into the Pd-CH3 bond are demonstrated.

Formazanate Complexes of Bis-Cyclometalated Iridium

“…To better visualize the geometric differences between the "open" and "closed" forms, the bottom stick diagrams show bond lengths of 2d and 1cʹ in Å, with esd values in parentheses. 16,25,26,28,49,50,58 The different chelating modes of formazanates, however, impact the bond distances within the formazanate core critically. For both cases of 1cʹ and 2cʹ, which include the "closed" form of the formazanate, full π delocalization within the formazanate is indicated.…”

“…As shown in Table 1 and Figure 1, the binding mode of the formazanate ("open" vs. "closed") has little influence on the Ir-N (formazanate) bond distances, which range between 2.103( 7) and 2.210(5) Å and are significantly longer than those in other formazanate chelate complexes (1.809-2.090 Å). 16,25,26,28,49,50,58 The different chelating modes of formazanates, however, impact the bond distances within the formazanate core critically. For both cases of 1cʹ and 2cʹ, which include the "closed" form of the formazanate, full π delocalization within the formazanate is indicated.…”

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

“…The synthesis of organometallic mono(formazanate) palladium complexes with a Pd-Me bond was described by the groups of Otten and Milani (Scheme 16). 47 Salt metathesis between potassium formazanate and the palladium precursor (COD)Pd(CH 3 )Cl in THF was unsuccessful due to the poor stability of the putative three-coordinate complex (formazanate)Pd(CH 3 ). From these reactions, the corresponding homoleptic bis(formazanate) palladium complex was invariably obtained (a closely related compound was described previously by Siedle).…”