Palladium, [
N
,
N
′‐1,2‐ethanediylidenebis[2,6‐dimethylbenzenamine‐κN]][(3,4‐
η
)‐2,5‐furandione] (
DMP
DAB–Pd–MAH)
Authors: Leitch David C. , Thomas Gilian T. 
Published: April 2024

image

[2721487‐84‐7]

C
22
H
22
N
2
O
3
Pd

(MW 468.85)

InChI =
1S/C18H20N2.C4H2O3.Pd/c1‐13‐7‐5‐8‐14(2)17(13)19‐11‐12‐20‐18‐15(3)9‐6‐10‐16(18)4;5‐3‐1‐2‐4(6)7‐3;/h5‐12H,1‐4H3;1‐2H;/b19‐11+,20‐12+;;

InChiKey =
WHOQNDZHEHSRKP‐GAMUHHASSA‐N

(palladium(0) compound used as a precursor to phosphine palladium(0) complexes,

1–5

and as a catalyst precursor for cross‐coupling reactions,

1,6

CH activation reactions,

7

and enantioselective allylation reactions

4,8

)

Alternative Names
: (1
E
,2
E
)‐
N
1,
N
2‐bis(2,6‐dimethylphenyl)ethane‐1,2‐diimine 2,5‐dihydrofuran‐2,5‐dione palladium, [κ

2

‐
N
,
N
′‐bis(2,6‐dimethylphenyl)ethan‐1,2‐diimine][
η
2
‐maleic anhydride]palladium(0).

Physical Data
: m.p. 121 °C (dec).

Solubility
: fully soluble (≥20 mg mL
−1
) in acetone, dichloromethane, tetrahydrofuran (THF), 2‐methyltetrahydrofuran (MeTHF); partially soluble in toluene (5 mg mL
−1
), ethyl acetate (2.5 mg mL
−1
); poorly soluble (≤2 mg mL
−1
) in pentane,
n
‐hexane,
n
‐heptane, diethyl ether,
tert
‐butylmethyl ether (TBME); insoluble in isopropanol (<1 mg mL
−1
); soluble but decomposes in acetonitrile, chloroform; poorly soluble and decomoposes in dimethylsulfoxide (DMSO),
N,N
‐dimethylformamide (DMF), methanol, ethanol; insoluble in water.

Form Supplied in
: red/purple crystalline solid.

Preparative Methods
: commercially available. There are two reported procedures

1

for preparing
DMP
DAB–Pd–MAH by reacting
N
,
N
′‐1,2‐ethanediylidenebis(2,6‐dimethylbenzenamine) (
DMP
DAB) and maleic anhydride (MAH)

9

with either Pd
2
dba
3
·CHCl
3

10

or “Pd(dba)
2
” (actually Pd
2
dba
3
·dba).

11

These palladium sources can be prepared from a variety of palladium(II) starting materials according to the method of Zalesskiy and Ananikov,

12

or purchased from commercial sources. Recystallization of crude “Pd(dba)
2
” is not required, since purification of
DMP
DAB–Pd–MAH removes residual dba and colloidal palladium(0) (see below).
N
,
N
′‐1,2‐ethanediylidenebis(2,6‐dimethylbenzenamine) (
DMP
DAB) is prepared from glyoxal (40% wt/wt solution in water) and 2,6‐dimethylaniline in methanol with

13

or without

14

formic acid as a catalyst.

Purification
: colloidal palladium(0) can be removed from
DMP
DAB–Pd–MAH by dissolving the solid in a minimum amount of acetone, dichloromethane, or THF, followed by filtration through a bed of Celite
™
and subsequent solvent removal from the filtrate. Uncoordinated
N
,
N
′‐1,2‐ethanediylidenebis(2,6‐dimethylbenzenamine) (
DMP
DAB), maleic anhydride, and/or residual dibenzylideneacetone (dba) from the synthesis can be removed by slurrying solid
DMP
DAB–Pd–MAH in TBME (∼30 mL g
−1
of solid), followed by filtration and washing with TBME.

Analysis of Reagent Purity
:
1
H NMR spectroscopic analysis is suitable for routine purity determination. In
d
6
‐acetone (solvent residual peak at 2.05 ppm),
DMP
DAB–Pd–MAH has diagnostic resonances at 8.55 ppm (s, 2
H
) for the N=CH–CH=N protons, 3.57 ppm (s, 2
H
) for the coordinated maleic anhydride, and 2.30 ppm (s, 12
H
) for the four Ar–CH
3
groups. Elemental analysis is also suitable for establishing bulk purity.

Handling, Storage, and Precautions
: solid
DMP
DAB–Pd–MAH is shelf‐stable when stored at room temperature in a closed container under ambient atmosphere.