New air-stable zinc complexes formed from cyanoacrylate- and methylenemalonate-based [N2O2]-ligands and their role as catalysts in epoxide-CO2 coupling

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New air-stable zinc complexes formed from

cyanoacrylate- and methylenemalonate-based

[N₂O₂]-ligands and their role as catalysts in

epoxide–CO₂coupling†

Cite this: Catal. Sci. Technol., 2014,

4, 1658

*

M. A. Fuchs, C. Altesleben, S. C. Staudt, O. Walter, T. A. Zevaco and E. Dinjus

The synthesis of a range of zinc complexes based on ligands displaying an N₂O₂-framework with

cyanoacrylate and/or malonate functionality is presented. Some complexes could be examined via X-ray

diffraction on single crystals, giving interesting insights into the structures of these zinc compounds,

some of them building coordination polymers. The zinc complexes are highly active in the catalytic

conversion of propylene oxide with CO₂to afford propylene carbonate. The study of this class of

complexes leads to reactivity trends showing that ligands with aromatic diamino linkers and malonate

fragments display the highest catalytic activity under mild conditions.

Received 30th January 2014,

Accepted 5th March 2014

DOI: 10.1039/c4cy00125g

www.rsc.org/catalysis

and environmentally friendly systems. To have a chance to

compete with the known systems, a “good” catalyst should

Introduction

During the last two decades, the catalytic formation of ali-

phatic polycarbonates (aPC) and cyclic carbonates (CC) from

CO₂and epoxides has been a growing area, attracting increas-

ingly the focus of both academia and industry.¹This is partly

due to the fact that using an epoxide, an intrinsic reactive

substrate, and having on the other hand a limited number of

final products can possibly provide a rich chemistry and good

outcomes in a short period of time. Both organic carbonates,

CC and aPC, (Scheme 1) are actually useful products found

in some industrial applications: the monomers, for example,

are used as polar, non-toxic solvents or electrolytes in lithium

ion cells,²whereas the copolymers find applications as com-

plements to the more common aromatic polycarbonates and

as starting materials for specialty materials (e.g. PPC as sacri-

ficial binders in the ceramic industry a.k.a. “evaporative cast-

ing patterns”³or as telechelic polymers in the formation of

“environmentally friendly” polyurethanes⁴).

display a highly versatile and rather straightforward synthesis

(the lower the number of synthetic/purification steps the better

it is), should be highly selective and, considering the rising

energy costs, should be also active under mild conditions.⁵We

have already reported the successful use of iron and aluminium

Scheme 1 Possible products of the reaction of carbon dioxide with

epoxides.

An increasing number of catalytic systems, homogeneous

as well as heterogeneous, have been reported for the coupling

of epoxides with CO₂in the literature. Fig. 1 undeniably

shows this trend as well as the related number of publica-

tions and reviews released.

Although the “market” seems to be saturated with promis-

ing catalytic systems, there is still a big demand for cheap

Karlsruhe Institute of Technology, Institute for Catalysis Research and Technology

(IKFT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen,

Germany. E-mail: thomas.zevaco@kit.edu; Fax: +49 721 608 22244

† CCDC 974318–974322. For crystallographic data in CIF or other electronic

format see DOI: 10.1039/c4cy00125g

Fig. 1 Publication trend dealing with organic carbonates from CO₂

and epoxides.

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complexes in the coupling of CO₂with epoxides, the catalysts

involving simple N₂O₂-ligands displaying cyanoacrylate and

malonate functionalities.^6,7Considering the preponderant role

of some zinc catalysts in the formation of organic carbonates

and especially polycarbonates,⁸we concentrated afterwards on

the related N₂O₂–zinc complexes and could isolate a new, easy-

to-handle Zn–N₂O₂complex that is revealed to be highly active

in the coupling of CO₂and epoxides.⁹We report here on the

related zinc-derivatives presenting N₂O₂ligand systems with

aminoacrylate and/or aminomalonate moieties in the backbone

as well as different diamino-linkers, with a.o. substituted 1,2-

phenylenediamine linkers. Among the 19 zinc complexes, it

was possible to structurally characterize five of them via X-ray

diffraction on single crystals. This range of zinc complexes was

particularly tested in the coupling of CO₂with PO to evaluate

the influence of the ligand structure on the catalytic activity and

connect the results to the first Zn-complex of this row.⁹Most of

the complexes were revealed to be highly active in the formation

of PC, in some cases, under mild reaction conditions.

Scheme

2

General synthetic ways to the iminoacrylate and

amidomalonate ligands and formation of the zinc complexes.

Results and discussion

Synthesis

The N₂O₂-chelating ligands used to form the catalysts are

known since the 1940s,¹⁰obtained from the reaction of a

diamine linker with diethyl ethoxymethylenemalonate or

ethyl 2-cyano-3-ethoxyacrylate under liberation of ethanol.

These two starting compounds are commercially available

and relatively cheap esters principally obtained via the reac-

tion of triethyl orthoformate with the related esters.¹¹

This class of ligands was thoroughly studied by the group

of E.-G. Jäger¹²and B. Weber¹³as interesting model com-

plexes of specific enzymes or as building blocks of larger sys-

tems with promising magnetic properties. The synthesis of

the symmetrically substituted ligands (R₁R₂CN or CO₂Et)

is straightforward, giving the ligands in high yields

(Scheme 2). The asymmetrically substituted ligands are

obtained in a two-step procedure with isolation of a “mono-

substituted” N₂O-ligand that further reacts with a second

ester to give the sought after asymmetric ligand. These N₂O-

ligands have actually also great potential and their complexes

will be reported elsewhere. The reaction works particularly

well with 1,2-phenylenediamine linkers whereas only a small

range of non-aromatic diamine-linkers leads to N₂O₂-ligands

in reasonable yields (Scheme 3 for overview). Further reaction

of the ligands with organometallic zinc precursors is

undemanding and realized in anhydrous tetrahydrofuran as

the solvent (Scheme 2). Once the ligand was dissolved in the

solvent, diethyl zinc dissolved in hexane was added drop-wise

to yield under liberation of ethane the zinc complex almost

quantitatively. Interestingly, the solubility of the complexes

based on ligands with nitrile moieties is lower than that of

the related malonato derivatives, with the formation of

nitrile-bridged structures (vide infra) being apparently respon-

sible for the easy and rapid separation of the complexes from

the reaction mixture.

Scheme 3 N₂O₂ligands used in this study and their nomenclature; for

the zinc complexes' nomenclature: Zn[ligand number], e.g. Zn[8b].

Crystallography

Single crystals suitable for crystal structure analysis could be

only isolated with complexes based on symmetric ligands:

nitrilo Zn[1a] (see ref. 9), Zn[2a] and Zn[3a] and malonato

ligands Zn[1b], Zn[2b] and Zn[3b]. Crystallization was

performed using concentrated DMSO solutions to yield after

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Table 1 Crystal data and structure refinement details of complexes

Zn[2a] and Zn[3a] (more detail in Experimental)

a couple of days at room temperature well-formed yellowish

rhombuses (crystallographic data of the structures have been

deposited at the Cambridge Crystallographic Database Cen-

tre; supplementary publication no. CCDC complex Zn[2a]:

974320, Zn[3a]: 974319, Zn[1b]: 974318, Zn[2b]: 974321 and

Zn[3b]: 974322). Structural investigation revealed clearly two

different types of structure: on the one hand, the malonate-

based ligands yielded monomeric structures with zinc being

either pentacoordinated (tetragonal pyramidal with H₂O or

DMSO as the apical neutral ligand) or hexacoordinated

(distorted octahedral geometry with two axial DMSO). On the

other hand, the cyanoacrylate-based ligands led to coordina-

tion polymers comparable to “metal–organic frameworks”

displaying zinc atoms octahedrally coordinated with the nitrile

groups of one ligand coordinating to the next neighbouring

zinc complex, occupying the next axial position. A similar

behaviour has been reported for related iminoacrylate zinc

complexes by M. Kröger et al.¹⁴The alternating coordination

pattern leads to characteristic zig-zag chains propagating along

the b axis (Fig. 2). In both types of zinc complexes, the N₂O₂-

ligands occupy the equatorial plane. Complexes Zn[2a] and

Zn[3a] are isostructural displaying the same zig-zag chain pat-

terns; for the sake of brevity only the structure of Zn[2a] will be

discussed in detail. The zinc atoms are slightly distorted from

the ideal geometry with a maximal distortion from the mean

N₂O₂-plane of 0.019 Å (0.024 Å for complex Zn[3a]), with the

N₂O₂-ligand being almost planar as found in the related iron

and zinc–N₂O₂complexes.^6,9Crystal data and structure refine-

ment details can be found in Table 1 while selected bond

lengths and angles for complexes Zn[2a] and Zn[3a] are listed

in Table 2. The bond lengths found within the N₂O₂-coordina-

tion sphere of Zn[2a] display a perceptible asymmetry probably

due to the influence of the intramolecularly coordinated nitrile

Zn[2a]

Zn[3a]

Crystal data

{[Zn(2a)(DMSO)]}_∞

{[Zn(3a)(DMSO)]}_∞

Empirical formula C₂₀H₂₀Cl₂N₄O₅SZn

C₂₂H₂₆N₄O₅SZn

523.90

Molecular mass

Crystal color

564.73

Yellowish

0.144 × 0.092 × 0.064

Monoclinic

P2(1)/c (no. 14)

10.7526(5)

11.5952(5)

19.6353(9)

90

Crystal size (mm³) 0.122 × 0.052 × 0.029

Crystal system

Space group

a (Å)

b (Å)

c (Å)

Monoclinic

P2(1)/c

1092.76(6)

1174.95(6)

1815.19(10)

90

α (°)

β (°)

97.7840(10)

90

2309.1(2)

4

100.7200(10)

90

2405.38(19)

4

γ (°)

V (Å³)

Z

D_calc.(g cm⁻³

)

1.624

1.447

group. Hence, the Zn–O and Zn–N bonds are a tad longer on

the side bearing the coordinating nitrile: Zn(1)–N(3) with

2.0600(10) Å and Zn(1)–O(3) with 2.1127(9) Å, whereas the

other side shows 2.0579(9) Å and 2.0692(10) Å for Zn(1)–N(1)

and Zn(1)–O(1), respectively. The Zn–O_DMSObond is, with

Zn(1)–O(5) of 2.1709(9) Å, significantly longer than that found

in the related DMSO-tetragonal pyramidal zinc-“salen” com-

plexes and a tad shorter than that found in the relatively scarce

hexacoordinated zinc salen DMSO educts like the salphen com-

plex reported by A.W. Kleij and co-workers which displays Zn–

O

_DMSOdistances ranging from 2.217 to 2.263 Å.¹⁵The intramo-

lecular Zn(1)–N(4) bond length is 2.1990(9) Å, being notably

longer than other intermolecular Zn–nitrile bonds as e.g.

reported by Kröger et al. (Zn–O: 2.040(9) Å).¹⁴Interestingly, the

bonding of the nitrilo groups to the zinc center has no influ-

ence on the length of the C–N triple bond. The four (N,O)–Zn

angles measured within the plane showed “well balanced” fea-

tures, with angle O(1)–Zn–O(3) being the widest with 98.66(3)°

while angle N(1)–Zn–N(3) is the smallest with 80.93(4)°. The

Table 2 Selected bond lengths (Å) and angles (°) of complexes Zn[2a]

and Zn[3a]

Complex Zn[2a]/bonds–angles

Complex Zn[3a]/bonds–angles

Zn(1)–N(1)

Zn(1)–N(3)

Zn(1)–O(1)

Zn(1)–O(3)

Zn(1)–O(5)

Zn(1)–N(4)

C(12)–N(2)

C(18)–N(4)

N(1)–Zn(1)–N(3)

N(3)–Zn(1)–O(3)

N(1)–Zn(1)–O(1)

N(4)–Zn(1)–O(5)

O(1)–Zn(1)–O(3)

N(1)–Zn(1)–N(4)

N(1)–Zn(1)–O(5)

O(3)–Zn(1)–O(5)

2.0600(10)

2.0692(10)

2.0579(9)

2.1127(9)

2.1709(9)

2.1990(9)

1.151(9)

80.93(4)

89.34(4)

91.07(4)

174.49(4)

98.66(3)

92.52(4)

89.95(4)

88.53(4)

Zn(1)–N(1)

Zn(1)–N(2)

Zn(1)–O(1)

Zn(1)–O(3)

Zn(1)–O(5)

Zn(1)–N(3)

C(10)–N(3)

C(16)–N(4)

N(1)–Zn(1)–N(2)

N(2)–Zn(1)–O(3)

N(1)–Zn(1)–O(1)

N(3)–Zn(1)–O(5)

O(1)–Zn(1)–O(3)

N(1)–Zn(1)–N(3)

N(1)–Zn(1)–O(5)

O(3)–Zn(1)–O(5)

2.0944(18)

2.0519(17)

2.0764(15)

2.0880(15)

2.1658(15)

2.2133(18)

1.149(9)

1.154(9)

80.42(7)

90.10(6)

88.96(6)

169.96(7)

100.56(6)

97.88(7)

91.55(6)

85.37(6)

Fig.

2 Displacement ellipsoid plot of Zn[3a] {[Zn(3a)(DMSO)]}_∞

showing the polymeric structure.

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angle involving zinc, DMSO and coordinated nitrile is

174.49(4)°.

commonly found alternating “tête-bêche” arrangement of the

complex in the crystal.¹⁷

In contrast, the presence in the malonate-based ligands

1b, 2b and 3b of an ester group hinders the formation of

polymeric structures in the complexes and leads to typical

monomeric structures for the zinc compounds Zn[1b], Zn[2b]

and Zn[3b], with DMSO or water occupying the remaining

coordination site(s). The coordination geometry is either

pentacoordinated (tetragonal pyramidal with H₂O or DMSO

as the apical neutral ligand) as found in related zinc salen

complexes¹⁶or, more uncommon, hexacoordinated, with a

distorted octahedral geometry and two axial DMSO.¹⁵Consid-

ering the tetragonal pyramidal aqua complex Zn[1b] (Fig. 3),

the bond lengths found within the N₂O₂-coordination sphere

are within a small range for both independent molecules.

Crystal data and structure refinement details can be found in

Table 5 while selected bond lengths and angles of complex

Zn[1b] can be found in Table 3. The shorter Zn–O bond is

Zn(2)–O(16) with 1.998(19) Å involving a coordinated water

molecule and is one of the shortest measured in related zinc-

“salen/salphen” aqua complexes. This can be tentatively

explained by the presence of an extended hydrogen bond net-

work. This network involves the coordinated water molecule

of one complex and the non-coordinated ester groups of two

neighbouring complexes as indicated by the distances O(14)–

O(9): 2.658 Å, O(9)–O(10): 2.676 Å and O(1)–O(18):2.642 Å and

O(18)–O(5): 2.654 Å. This contributes to some extent to the

In the related tetragonal pyramidal DMSO complex Zn[2b]

(Fig. 4), the bond lengths found within the N₂O₂-coordination

sphere are within a small range displaying a well balanced

structure as reported in many cases with discrete N₂O₂–metal

complexes. The shorter bond is Zn(1)–O(9) with 2.0082(11) Å

involving a strongly coordinated DMSO molecule.

In the case of the octahedrally coordinated complex

Zn[3b] (Fig. 5), the structure is slightly distorted from an

ideal octahedron, with a maximal distortion from the mean

N₂O₂-plane of 0.109 Å (plane N1, O5, N2, O1), with the N₂O₂-

ligand being almost planar and occupying the equatorial

positions as expected. The ligand is, in that particular case,

more bent than in the tetragonal pyramidal complexes. One

of the two apical DMSO molecules is disordered and displays

a longer Zn–O bond with 2.247(3) Å whereas the opposite

bond length is 2.121(3) Å. These distances are typical for

hexacoordinated N₂O₂–zinc complexes with DMSO in apical

positions.¹⁵The O(9)–Zn(1)–O(10) angle demonstrates, with

161.19°, higher distortion of the octahedral coordination

compared to the coordination geometries found in the

Fig. 4 Displacement ellipsoid plot of Zn[2b] [Zn(2b)(DMSO)].

Fig. 3 Displacement ellipsoid plot of Zn[1b] [Zn(1b)(H₂O)]₂showing

the two independent molecules.

Table 3 Selected bond lengths (Å) and angles (°) of complex Zn[1b]

Bond lengths

Angles

Zn(1)–N(1)

Zn(2)–N(3)

Zn(1)–N(2)

Zn(2)–N(4)

Zn(1)–O(3)

Zn(2)–O(12)

Zn(1)–O(7)

Zn(2)–O(16)

Zn(1)–O(9)

Zn(2)–O(18)

2.022(2)

2.024(2)

2.029(2)

2.031(2)

2.020(2)

2.023(2)

2.017(2)

1.998(19)

2.026(2)

2.020(2)

N(1)–Zn(1)–N(2)

N(3)–Zn(2)–N(4)

N(1)–Zn(1)–O(3)

N(3)–Zn(2)–O(12)

N(2)–Zn(1)–O(7)

N(4)–Zn(2)–O(16)

O(3)–Zn(1)–O(7)

O(12)–Zn(2)–O(16)

N(2)–Zn(1)–O(9)

N(1)–Zn(1)–O(9)

O(7)–Zn(1)–O(9)

O(3)–Zn(1)–O(9)

81.38(9)

81.49(9)

88.28(9)

88.53(9)

87.60(8)

87.51(8)

90.95(8)

89.69(8)

99.54(9)

106.19(9)

101.49(9)

105.12(9)

Fig. 5 Displacement ellipsoid plot of Zn[3b] [Zn(3b)(DMSO)₂].

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coordination polymers Zn[2a] and Zn[3a] (O–Zn–N angles:

174.49(4) and 169.96(7)). Crystal data and structure refinement

details of complexes Zn[2b] and Zn[3b] can be found in Table 5

while selected bond lengths and angles of both complexes can

be found in Table 4. Interestingly, the comparison of the vari-

ous intramolecular bonds in complexes Zn[2a–3a], Zn[1b–3b]

and the related Zn–salphen–DMSO complexes reported by A.

W. Kleij et al.^15,16,18shows that our complexes are on the

whole comparable to salphens (general trend: shorter Zn–O

and a tad longer Zn–N distances for the Zn–salphens).

Some significant reactivity trends could be observed while

running these catalytic screening tests with the 19 zinc com-

plexes (Tables 6 & 7). The presence of a cocatalyst is neces-

sary as it is commonly the case for most of the related

catalytic systems.¹⁹The use of ionic tetrabutyl ammonium

salts, especially Bu₄NI, is very successful due to the high

nucleophilicity of the anion, whereas the use of DMAP und

1-methyl imidazole delivered the cyclic carbonate in very low

yields. Both catalyst types, with either nitriles or ester

groups, display high catalytic activity in the coupling reac-

tion of PO with CO₂, delivering selectively propylene carbon-

ate. Modifying the catalyst

& cocatalyst concentrations

Catalytic tests

confirmed that the catalysts are highly active: it is necessary

to drastically lower the catalyst-to-substrate ratio to differen-

tiate the catalysts and evaluate the influence of the diamino-

linker (e.g. role of the ancillary CN and COOEt groups) and

the effect of the substituents of the aromatic linkers on the

reactivity. At a catalyst-to-epoxide ratio as low as 1 to 10 000

(0.01 mol%), a cyclic carbonate yield of 77% could be still

reached with the malonato derivatives (entry 8 and 9, cat.

Zn[1b], Zn[1d]).

The catalysts having an aromatic diamine-ortho-phenylene

linker and ancillary ethyl ester groups present reactivity

slightly higher than the ones with nitriles (Table 6, entries 8,

9 & 14, 15, ligands 1b–3b & 1d–3d). Interestingly, the catalysts

with an aromatic, non-conjugated spacer (Table 7, ligand 8a),

in contrast to the basic ortho-phenylene diamino linkers, dis-

play generally lower catalytic activity. Within this class of com-

plexes, however, the nitrile-bearing ligands have a slightly

higher reactivity than the ester-bearing ones (Table 7, entries

5, 7, ligand 8a). This trend was also apparent upon changing

to pure aliphatic linkers: the catalytic activity of the related

zinc complexes was definitely lower, requiring the use of

higher pressure and temperature to be competitive (Table 7,

comparison: entries 3, 4 vs. 5, 6 & 7, 8). The carbonate yields

were a tad better with the nitrile-containing ligands (Table 7,

entries 3, 5, 7, ligands 4a–6a). This suggests that in our case

an efficient N₂O₂catalyst needs a conjugated aromatic linker

and, as a corollary, good co-planarity of the metal and the

In order to evaluate the performance of various zinc com-

plexes in carbon dioxide/epoxide coupling reactions, we

performed catalytic screening using propylene oxide as the

test substrate to obtain the related propylene carbonate, vary-

ing some reaction conditions like temperature (T), pressure

(p) and catalyst concentration (c(cat)). For the catalytic

screening, a test bench with eight 70 ml autoclaves (“IKFT-

made”, Stainless Steel 316Ti) equipped with magnetic stirrer,

external heater and p,T-acquisition via PCs was applied.

Table 4 Selected bond lengths (Å) and angles (°) of complexes Zn[2b]

and Zn[3b]

Zn[2b]

Zn[3b]

Zn(1)–N(1)

Zn(1)–N(2)

Zn(1)–O(1)

Zn(1)–O(5)

2.0386(12)

2.0389(12)

2.0419(11)

2.0279(11)

2.0082(11)

80.60(5)

87.50(5)

86.59(5)

92.44(4)

Zn(1)–N(1)

Zn(1)–N(2)

Zn(1)–O(1)

Zn(1)–O(5)

Zn(1)–O(9)

Zn(1)–O(10)

N(1)–Zn(1)–N(2)

O(9)–Zn(1)–O(10)

O(5)–Zn(1)–O(1)

N(1)–Zn(1)–O(5)

O(1)–Zn(1)–N(2)

O(9)–Zn(1)–O(5)

O(9)–Zn(1)–O(1)

2.057(4))

2.081(4)

2.064(3)

2.077(3)

2.121(3)

2.247(3)

79.89(14)

161.19(4)

106.69(13)

86.70(14)

86.09(13)

85.69(13)

84.71(13)

Zn(1)–O(9)

N(1)–Zn(1)–N(2)

N(2)–Zn(1)–O(5)

N(1)–Zn(1)–O(1)

O(1)–Zn(1)–O(5)

N(1)–Zn(1)–O(9)

N(2)–Zn(1)–O(9)

O(5)–Zn(1)–O(9)

O(1)–Zn(1)–O(9)

109.83(5)

100.54(5)

99.64(4)

105.16(4)

Table 5 Crystal data and structure refinement details of complexes Zn[1b], Zn[2b] and Zn[3b]

Crystal data

Zn[1b]:[Zn(1b)(H₂O)]₂

Zn[2b]:[Zn(2b)(DMSO)]

Zn[3b]:[Zn(3b)(DMSO)₂]

Empirical formula

Molecular mass

Crystal color

Crystal size (mm³)

Crystal system

Space group

a (Å)

b (Å)

c (Å)

α (°)

C₄₄H₅₆N₄O₁₈Zn₂

1059.66

Yellowish

0.075 × 0.057 × 0.028

Monoclinic

P2(1)/n

15.8662(12)

13.3414(11)

23.2173(18)

90

C₂₄H₃₀Cl₂N₂O₉SZn

658.83

Yellowish

0.297 × 0.247 × 0.207

Monoclinic

P2(1)/n

1333.44(8)

914.75(6)

2418.87(15)

90

C₂₈H₄₂N₂O₁₀S₂Zn

696.12

Yellowish

0.131 × 0.056 × 0.053

Monoclinic

P2(1)/c

7.8991(5)

26.6878(18)

15.6509(11)

90

β (°)

96.3740(10)

90

4884.2(7)

4

103.9830(10)

90

4884.2(7)

4

97.0720(10)

90

3274.3(4)

4

γ (°)

V (Å³)

Z

D_calc.(g cm⁻³

)

1.441

1.528

1.412

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Table 6 Catalytic screening using PO and zinc complexes with aromatic diamine

p

T

c(cat)

R₁/

R₂/

Entry

(bar)

(°C)

(mol%)

ligand

Cat.

Yield (%)

TON

Cat.

Yield (%)

98

TON

Cat.

Yield (%)

95

TON

1

2

3

4

5

6

7

8

50

2

80

40

0.20

0.10

0.01

0.10

0.20

CN

COOEt

CN

COOEt

CN

COOEt

CN

COOEt

CN

Zn[1a]

Zn[1b]

Zn[1d]

Zn[1a]

Zn[1b]

Zn[1d]

Zn[1a]

Zn[1b]

Zn[1d]

Zn[1a]

Zn[1b]

Zn[1d]

Zn[1a]

Zn[1b]

Zn[1d]

99

97

>99

99

64

77

79

69

79

88

93

90

495

970

990

6400

7700

790

690

790

440

465

450

Zn[2a]

Zn[2b]

Zn[2d]

Zn[2a]

Zn[2b]

Zn[2d]

Zn[2a]

Zn[2b]

Zn[2d]

Zn[2a]

Zn[2b]

Zn[2d]

Zn[2a]

Zn[2b]

Zn[2d]

490

Zn[3a]

Zn[3b]

Zn[3d]

Zn[3a]

Zn[3b]

Zn[3d]

Zn[3a]

Zn[3b]

Zn[3d]

Zn[3a]

Zn[3b]

Zn[3d]

Zn[3a]

Zn[3b]

Zn[3d]

475

495

COOEt

CN

COOEt

CN

COOEt

CN

COOEt

CN

98

99

a

100

63

75

46

1000

6300

7500

4600

480

87

95

98

64

73

51

64

81

870

950

980

6400

7300

5100

640

810

780

9

10

11

12

13

14

15

48

71

710

510

51

78

a

CN

COOEt

CN

COOEt

97

68

485

340

92

91

460

455

a

Reaction conditions: cocatalyst Bu₄NI, c(cat) = c(cocat.), t = 20 h, the epoxide is the solvent. Not tested because the conversion under more

“friendly” reaction conditions was too low.

ligand. Considering the results of crystal structure determina-

tion of Zn[2a–3a] and Zn[1b–3b] (see above) and representing

both mesomeric forms of one typical complex, it is easy to

draw a parallel to the zinc salphen structure reported in the

literature (Scheme 4).^15,16,18The important role of planar,

delocalized ligand architectures has been well documented in

this kind of chemistry in the case of e.g. metalloporphyrins,²⁰

aluminum phthalocyanines²¹and, more directly, with related

aluminum²²and nickel²³“salophens” (other name for

salphens).

Logically, a nitrile group in such complexes should, via an

electron withdrawing effect, enhance even more the catalytic

activity of the zinc complexes. On the other hand, the forma-

tion of coordination polymers and the competition of nitrile/

epoxide at the coordination center of the zinc complexes

seem to go against this trend. Supporting this, in the case of

ligands exhibiting a nonconjugated linker, the nitrile groups

have again a positive influence on the reactivity of the zinc

complexes, with the nitrile playing its role as a withdrawing

group, enhancing thus the Lewis acidity of the metal center

Table 7 Catalytic screening using PO and Zn complexes with nonconjugated and aliphatic diamine linkers

Entry T (°C) c(cat) (mol%)

R

Cat.

Yield (%) Cat.

99 Zn[7a]

Yield (%) Cat.

Yield (%)

a

1

2

3

4

5

6

7

8

80

40

0.20

0.10

0.01

0.10

CN

Zn[8a]

Zn[4a] 97 Zn[5a] 99

Zn[6a] 98

a

COOEt Zn[8b] 99

CN Zn[8a] 90

COOEt Zn[8b] 98

CN Zn[8a] 45

COOEt Zn[8b] 19

Zn[7b]

Zn[4b] 92

Zn[4a] 96

Zn[4b] 77

Zn[4a] 13

Zn[5b] 99

Zn[5a] 96

Zn[5b] 48

Zn[5a] 25

Zn[6b] 80

Zn[6a] 61

Zn[6b] 37

Zn[7a] 95

Zn[7b] 97

Zn[7a] 11

a

Zn[6a]

Zn[6b]

a

Zn[7b]

Zn[7a]

Zn[7b] 19

4

9

Zn[4b]

Zn[4a] 37

Zn[4b] 17

7

Zn[5b]

a

CN

Zn[8a]

79

6

Zn[5a] 25

Zn[5b]

Zn[6a]

Zn[6b]

a

COOEt Zn[8b]

a

Reaction conditions: cocatalyst Bu₄NI, c(cat) = c(cocat.), t = 20 h, the epoxide is the solvent. Not tested because the conversion under more

“friendly” reaction conditions was too low.

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(Table 7, entries 3, 4 with ligands 4–6a & 4b–6b or entries 5,

6 with ligands 8a–7a & 8b–7b). The formation of coordination

polymers, albeit not as stable as in the case of compounds

with aromatic linkers, cannot be completely ruled out. The IR

spectra of Zn[5a] and Zn[7a] for instance display a weak split-

ting of the vCN band whereas the IR spectra of Zn[4a], Zn[6a]

and Zn[8a] exhibit no splitting of the vCN band at all.

The influence of the aromatic substituents, methyl or chlo-

ride, on the catalytic activity of most of the complexes is

minor in the case of the symmetrically substituted nitrilo and

ester ligands (e.g. Table 6, entries 7 and 8) and rather counter-

productive in the case of the asymmetrically substituted as

exemplified by entry 9 (Table 6) where the unsubstituted

ligand still delivers the best results with 77% yield (entry 9:

77% for Zn[1d]; 46% for Zn[2d] and 51% for Zn[3d]). The

same trend is found at a lower temperature, around 40 °C,

and upon adjusting the amount of the catalyst (0.1 mol%)

(entry 12: 79% for Zn[1d]; 51% for Zn[2d] and 78% for

Zn[3d]). Correlating the different reactions summarized in

Table 6, ligands displaying an ortho-phenylenediamine linker

give a small advantage to the symmetrically substituted ligand

with an ancillary ester function and dimethyl substitution at

the aromatic, with a rough reactivity trend being accordingly:

–Me ≳ –H > –Cl. Taking into account the diverse mechanisms

Scheme 5 Mechanism proposed for the zinc–N₂O₂/NBu₄I catalytic

system.

with the ammonium cation playing most probably a prepon-

derant role in the cyclization of the carbonato species. More

studies are in progress to understand the kinetics of the

reaction and get more insight into the mechanism at work

in this reaction.

Conclusions

We have synthesized

a range of new zinc complexes

1,19

found in the literature for the coupling of epoxide and CO₂

displaying chelating N₂O₂ligands with ancillary nitrilo and/

or ester groups. These complexes were revealed to be highly

effective in the production of PC, propylene carbonate, from

propylene oxide and carbon dioxide. The coupling can be

performed under mild reaction conditions and low catalyst

loadings, with the utilization of tetrabutyl iodide as the co-

catalyst being, however, obligatory for the success of the reac-

tion. Some of the new complexes, based on symmetric

ligands, two nitrilo-containing Zn[2a] and Zn[3a] and three

malonato ligands Zn[1b], Zn[2b] and Zn[3b], could be for the

first time structurally characterized via X-ray diffraction. In

comparison to the results obtained with the “parent com-

pound” Zn[1a], screening showed that the zinc complexes

with ortho-phenylenediamino linkers actually work more effi-

ciently than those with aliphatic or non-conjugated aromatic

linkers. In addition, the presence of ester groups at the back-

bone of the ligand instead of nitrile groups leads to higher

yield of PC. Within the range of the complexes displaying an

ortho-phenylenediamino linker, the influence of aromatic

substituents remains negligible.

and DFT studies involving in particular zinc salphen,²⁴a gen-

eral mechanism can be proposed for the Zn–N₂O₂/(n-Bu)₄NI

catalytic system (Scheme 5). Considering that the reports on

ionic zinc salens of the type [N₂O₂Zn-I][NR₄] have been scarce,

it seems reasonable to consider in our case a neutral Zn–N₂O₂

species as the starting point in the catalytic cycle. The first

step to the formation of the cyclic carbonate involves basically

the activation of the epoxide via coordination and ring open-

ing to form a reactive metal-alkoxide, the actual active species

in the catalytic cycle. Equivalent Zn salphen–epoxide educts

have been structurally characterized by Kleij and coworkers.²⁵

The ammonium halide co-catalyst comes into play in the

nucleophilic attack on the epoxide, hence supporting the for-

mation of the reactive zinc alkoxide. The second step of the

reaction would be the formation of a carbonate linkage via

CO₂insertion into the metal–alkoxide bond. This intermedi-

ate can either form a cyclic monomer via intramolecular

rearrangement or a polycarbonate through further alternating

insertions of epoxide and carbon dioxide molecules. In our

case, the system tends to form exclusively cyclic carbonates,⁹

Experimental

General

¹H- and ¹³C-NMR spectra were recorded operating at 399.91

and 100.56 MHz, respectively, by means of a Varian Inova

Unity 400 spectrometer (software VNMRJ 3.2) equipped with

an Oxford Magnet (9.4 T). IR spectra were obtained using a

Varian 660-IR FT-IR spectrometer. Mass spectra were mea-

sured using a Bruker ApexQe hybrid 9.4 T FT-ICR. Gel perme-

ation chromatography (GPC) was performed using a PSS SDV

5μ 1000 Å and a PSS SDV 5μ 100 Å column of the company

Scheme 4 Mesomeric forms of the Zn–N₂O₂structure and analogy

with zinc salphens.

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Polymer Standard Service (PSS). The molecules were detected

using a RI-Detector L-7490 (Merck). Tetrahydrofuran was

used as an eluent and toluene as an internal standard. Data

processing was done using the software PSS WINGPC 6 of the

company PSS. For the determination of the glass transition

temperature of the polycarbonates, differential scanning calo-

rimetry was applied using a Mettler Toledo DSC822e. For

inductively coupled plasma atomic emission spectroscopy

(ICP-AES) a 720/725-ES emission spectrometer with a CCD

detector from Agilent Technologies was used. The plasma was

generated with a 40 MHz quartz-controlled generator where

argon is the carrier gas. Elementary analysis was performed

using a CHNS-Analyser from the company Elementar. UV-Vis

spectra were measured using an MCS 501 UV-NIR (Zeiss). X-ray

analyses were performed using a Bruker Apex II Quazar diffrac-

tometer. 2124 frames were collected with an irradiation time of

1 s per frame. Integration of the data proceeded with SAINT,

the data were corrected for Lorentz and polarisation effects,

and experimental absorption corrections with SADABS were

performed.²⁶For searches relating to single-crystal X-ray dif-

fraction data, the Cambridge Structural Database was used.²⁷

Crystallographic data were deposited at the Cambridge Crystal-

lographic Database Centre (CCDC), supplementary publications

no. CCDC complex Zn[2a]: 97320, Zn[3a]: 97319, Zn[1b]: 97318,

Zn[2b]: 97321 and Zn[3b]: 97322. Figures were prepared using

the appropriate Mercury software of the CCDC.²⁸

reaction mixture. When the two starting materials were com-

bined, the mixture was refluxed for 4 h. The desired product

was precipitated at −20 °C in the freezer. After collecting by fil-

tration, it was washed with methanol and dried in vacuum.

Syntheses of the asymmetric ligands

Procedure L-e. One equivalent of ethyl 2-cyano-3-ethoxyacrylate

or diethyl (ethoxymethylene)malonate was dissolved in hot

methanol. Afterwards the N₂O-compound also dissolved in

methanol was added. The reaction mixture was refluxed for 4 h

and then cooled down to −20 °C. The solid precipitate was

collected by filtration, washed with methanol and dried.

Procedure L-f. The procedure was applied similar to L-e,

except the amount of ethyl 2-cyano-3-ethoxyacrylate or diethyl

(ethoxymethylene)malonate was raised to excess and the reac-

tion time was lengthened to refluxing overnight.

Procedure L-g. Instead of refluxing the reaction mixture

for 4 h, the reaction time was extended to overnight.

Everything else was done similar to procedure L-e.

Syntheses of the zinc complexes

Procedure Zn-a. Under an argon atmosphere the ligand

was suspended or dissolved in THF. Then diethyl zinc

solution (1 M in hexane) was added under stirring. The

reaction mixture was stirred overnight and then the solvent

was removed under reduced pressure leaving the zinc

complex, which was further dried at 75 °C in vacuum.

Procedure Zn-b. The same procedure as for Zn-a was done,

but after stirring the reaction mixture overnight a solid pre-

cipitate was formed. It was filtered under an argon atmo-

sphere and dried at 75 °C under vacuum.

The starting materials (ortho-phenylenediamine, ethyl

(ethoxymethylene)cyanoacetate, methanol, dry tetrahydrofuran,

epoxides, diethyl zinc solution (1 M in hexane) and the cocata-

lysts) were purchased from Sigma Aldrich. Except for the pro-

pylene oxide all of them were used without further purification.

The epoxide was distilled from CaH₂and stored under an

argon atmosphere before using them in the catalytic tests.

1a. 2-Propenoic acid, 3,3′-(1,2-phenylenediimino)bis[2-cyano-,

diethyl ester] [CAS 59747-06-7] (diethyl 1,2-phenylenediimino-2-

cyanoacrylate): procedure L-a with ethyl 2-cyano-3-ethoxyacrylate

(21.99 g, 130 mmol) and ortho-phenylenediamine (7.03 g,

65 mmol). Yield: white solid (22.95 g, 0.065 mmol, 92%).

Mp = 193 °C. T_e= 201.7 °C. ¹H-NMR (400 MHz, CDCl₃): δ = 1.36

(t, ³J_HH= 7.1 Hz, 6H, CH₃), 4.31 (q, ³J_HH= 7.1 Hz, 4H, CH₂), 7.22

Syntheses of the symmetric ligands

Procedure L-a. Two equivalents of ethyl 2-cyano-3-ethoxyacrylate

or diethyl (ethoxymethylene)malonate were dissolved in hot

methanol. Afterwards a solution of the diamine (also in metha-

nol) was added and the reaction mixture was refluxed for 4 h.

After cooling to −20 °C overnight a white solid precipitate was

formed, which was collected by filtration, and washed with

methanol and dried.

Procedure L-b. Same procedure as for L-a, but the reaction

mixture was refluxed overnight before cooling down.

Procedure L-c. Same procedure as for L-a. The collected

precipitate from the reaction mixture contained the products

as well as the diamine. The latter was, in contrast to the

product, not soluble in chloroform, so it can easily be

separated by filtration.

3

4

3

(dd, J_HH= 3.6 Hz, J_HH= 5.7 Hz, 2H, CH_aromat), 7.32 (dd, J_HH

=

4

3

3.5 Hz, J_HH= 5.8 Hz, 2H, CH_aromat), 7.75 (d, J_HH= 12.8 Hz,

2H, CH), 10.82 (d, J_HH= 12.6 Hz, 2H, NH). ¹³C{¹H}-NMR

3

(100 MHz, CDCl₃): δ = 14.3 (CH₃), 61.8 (CH₂), 78.3 (C_q),

117.2(CN), 120.1 (CH_aromat), 127.6 (CH_aromat), 130.9 (C_q,aromat),

153.6 (C–H), 167.4 (CO). MS (ESI+) m/z (%): 355 (15)

[M + H]⁺, 372 (100) [M + NH₄]⁺, 377 (16) [M + Na]⁺. IR

(KBr): ν = 3166 (m, ν_N–H), 2214 (s, ν_CN), 1696, 1674, 1639,

1618, 1597 (s, ν_CO

;

ν_CN

)

cm⁻¹. Anal. calcd. for

C₁₈H₁₈N₄O₄: C, 61.01; H, 3.86; N, 15.81; found: C, 60.94; H,

5.21; N, 15.90. UV/Vis (CH₂Cl₂): λ_max(ε) = 292 (31 990), 332

(25 750) nm (mol⁻¹dm³cm⁻¹).

1b. Propanedioic acid, 2,2′-[1,2-phenylenebis(iminomethylidyne)]bis-,

1,1′,3,3′-tetraethyl ester [CAS 4921-71-5] (malonic acid,

Synthesis of the N₂O-ligands

Procedure L-d. One equivalent of the diamine was

dissolved in hot methanol. Then another equivalent of ethyl

2-cyano-3-ethoxyacrylate or diethyl (ethoxymethylene)malonate

(dissolved in methanol) was slowly added dropwise to the

[o-phenylenebis(iminomethylidyne)]di-,

tetraethyl

ester):

procedure L-a with diethyl (ethoxymethylene)malonate

(43.25 g, 200 mmol) and ortho-phenylenediamine (10.81 g,

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3

100 mmol). Yield: yellow solid (30.34 g, 67.65 mmol, 68%).

7.32 (s, 2H, CH_aromat), 7.68 (d, J_HH= 12.5 Hz, 2H, CH), 10.83

Mp = 94.4 °C. T_e= 78.2 °C. ¹H-NMR (400 MHz, CDCl₃): δ =

(d, J_HH= 12.4 Hz, 2H, NH). ¹³C{¹H}-NMR (100 MHz, CDCl₃):

3

1.29 (m, 12H, CH₃), 4.20 (q, J_HH= 7.1 Hz, 4H, CH₂), 4.26

δ = 14.1 (CH₃), 62.0 (CH₂), 79.7 (C_q), 116.4 (CN), 121.2

(CH_aromat), 129.9 (C_q,aromat), 131.0 (C_q,aromat–Cl), 152.6 (CH),

167.0 (CO). MS (ESI+) m/z (%): 440 (100) [M + NH₄]⁺, 869

(11) [2M + Na]⁺. IR (KBr): ν = 3178 (m, ν_N–H), 2216, 2231 (s,

ν_CN), 1595, 1618, 1645 (s, ν_CO; ν_CN) cm⁻¹. Anal. calcd. for

C₁₈H₁₆Cl₂N₄O₄: C, 51.08; H, 3.81; N, 13.24; found: C, 50.99; H,

3.82; N, 13.38. UV/Vis (CH₂Cl₂): λ_max(ε) = 293 (34710), 335 (27

660) nm (mol⁻¹dm³cm⁻¹). UV/Vis (MeCN): λ_max(ε) = 291

(39 910), 325 (30 160) nm (mol⁻¹dm³cm⁻¹).

2b. Procedure L-b with diethyl (ethoxymethylene)malonate

(2.3 ml, 11.30 mmol) and 4,5-dichloro-1,2-phenylenediamine

(500 mg, 2.82 mmol). Yield: grey needles (1.15 g, 2.22 mmol,

78%). T_e= 137.0 °C. ¹H-NMR (400 MHz, CDCl₃): δ = 1.34

3

(q, J_HH= 7.1 Hz, 4H, CH₂), 7.21 (s, 4H, CH_aromat), 8.32 (d,

3

³J_HH= 13 Hz, 2H, CH), 10.94 (d, J_HH= 13.0 Hz, 2H, NH).

¹³C{¹H}-NMR (100 MHz, CDCl₃): δ = 14.4, 14.6 (CH₃), 60.4,

60.8 (CH₂), 95.9 (C_q), 120.1 (CH_aromat), 126.7 (CH_aromat),

131.9 (C_q,aromat), 153.5 (CH), 165.6, 168.8 (CO). MS (ESI+)

m/z (%): 449 (100) [M + H]⁺, 471 (19) [M + Na]⁺. IR (KBr):

ν = 3137 (m, ν_N–H), 1720, 1696, 1658, 1618, 1582 (m, ν_CO

;

ν_CN) cm⁻¹. Anal. calcd. for C₂₂H₂₈N₂O₈: C, 58.92; H, 6.29;

N, 6.25; found: C, 59.05; H, 6.533; N, 6.301. UV/Vis (CH₂Cl₂):

λ_max(ε) = 289 (30 500), 331 (26 000) nm (mol⁻¹dm³cm⁻¹).

1c. Procedure L-d with diethyl (ethoxymethylene)malonate

and (10.00 g, 50.0 mmol), ortho-phenylenediamine (5.40 g,

50.0 mmol). Yield: white solid (9.79 g, 35.1 mmol, 70%). T_e=

3

(m, 12H, CH₃), 4.26 (q, J_HH= 7.0 Hz, 4H, CH₂), 4.30

1

3

89.2 °C. H-NMR (400 MHz, CDCl₃): δ = 1.29 (t, J_HH= 7.1 Hz,

(q, J_HH= 7.0 Hz, 4H, CH₂), 7.33 (s, 2H, CH_aromat), 8.25

3

3H, CH₃), 1.35 (t, J_HH= 7.1 Hz, 3H, CH₃), 3.73 (s, 2H, NH₂),

(d, J_HH= 12.7 Hz, 2H, CH), 11.01 (d, ³J_HH= 12.6 Hz, 2H, NH).

3

4.20 (q, J_HH= 7.1 Hz, 2H, CH₂), 4.28 (t, J_HH= 7.1 Hz, 2H,

¹³C{¹H}-NMR (100 MHz, CDCl₃): δ = 14.17, 14.35 (CH₃), 60.45,

60.84 (CH₂), 97.18 (C_q), 120.93 (CH), 129.73 (C_q,aromat–Cl),

130.97 (C_q,aromat), 152.20 (CH), 165.04, 168.48 (CO). MS (ESI

+) m/z (%): 516 (100) [M + H]⁺, 539 (53) [M + Na]⁺, 1054 (71)

[2M + Na]⁺. HR-MS (ESI+) m/z: anal. calcd. for C₂₂H₂₇Cl₂N₂O₈:

517.11390; found: 517.11761. IR (KBr): ν = 3169 (m, ν_N–H),

1583, 1630, 1648, 1688, 1703 (s, ν_CO; ν_CN) cm⁻¹. Anal. calcd.

for C₂₂H₂₆Cl₂N₂O₈: C, 51.07; H, 5.07; N, 5.41; found: C, 50.87;

H, 5.02; N, 5.31. UV/Vis (CH₂Cl₂): λ_max(ε) = 291 (40 330), 335

(32 400) nm (mol⁻¹dm³cm⁻¹). UV/Vis (THF): λ_max(ε) = 245

(6661), 292 (40780), 335 (32360) nm (mol⁻¹dm³cm⁻¹).

3

CH₂), 6.81 (m, 4H, CH_aromat), 7.01 (t, J_HH= 7.6 Hz, 1H,

CH_aromat), 7.08 (t, J_HH= 7.8 Hz, 1H, CH_aromat), 8.39 (d, J_HH

3

=

13.6 Hz, 1H, CH), 10.81 (d, J_HH= 13.5 Hz, 1H, NH). ¹³C{¹H}-

NMR (100 MHz, CDCl₃): δ = 14.21, 14.30 (CH₃), 59.83, 60.21

(CH₂), 93.15 (C_q), 117.46 (CH_aromat), 118.99 (CH_aromat),

119.93 (CH_aromat), 126.32 (CH_aromat), 127.63 (CH_q,aromat),

137.85 (CH_q,aromat), 154.03 (CH), 165.55, 169.08 (CO). MS:

(ESI+) m/z (%): 279 (100) [M + H]⁺, 579 (56) [2M + Na]⁺. IR

(KBr): ν = 3399, 3342 (m, ν_N–H2), 3259 (m, ν_N–H), 2214 (s,

3

ν_CN), 1593 (s), 1609 (m), 1658 (s), 1697, 1597 (s, ν_CO; ν_CN

)

cm⁻¹. Anal. calcd. for C₁₄H₁₈N₂O₄: C, 60.42; H, 6.52; N, 10.07;

found: C, 60.16; H, 6.61; N, 10.12. UV/Vis (CH₂Cl₂): λ_max(ε) =

293 (9873), 332 (15 510) nm (mol⁻¹dm³cm⁻¹).

2c. Procedure L-d with diethyl (ethoxymethylene)malonate

(3.11 g, 14.4 mmol) and 4,5-dichloro-1,2-phenylenediamine

(97%) (2.63 g, 14.4 mmol). Yield: reddish black crystals (3.52

g, 10.14 mmol, 70%), T_e= 163.1 °C. ¹H-NMR (400 MHz,

CDCl₃): δ = 1.32 (t, J_HH= 7.1 Hz, 3H, CH₃), 1.37 (t, J_HH= 7.1

Hz, 3H, CH₃), 3.74 (s, 2H, NH₂), 4.24 (q, J_HH= 7.2 Hz, 2H,

1d. Procedure L-e with ethyl 2-cyano-3-ethoxyacrylate

(12.41 g, 71.9 mmol) and ligand 1c (20.00 g, 71.9 mmol).

Yield: white solid (27.97 g, 69.7 mmol, 97%). T_e= 138.7 °C.

¹H-NMR (400 MHz, CDCl₃): δ = 1.29 (m, 9H, CH₃), 4.23 (m,

3

CH₂), 4.30 (q, J_HH= 7.2 Hz, 2H, CH₂), 6.89 (s, 1H, CH_aromat),

3

6H, CH₂), 7.20 (m, 4H, CH_aromat), 7.73 (d, J_HH= 12.9 Hz, 4H,

7.16 (s, 1H, CH_aromat), 8.28 (d, J_HH= 13.2 Hz, 1H, CH), 10.74

3

CH), 8.30 (d, J_HH= 12.9 Hz, 4H, CH), 10.77 (d, J_HH= 12.8

(d, J_HH= 13.0 Hz, 1H, NH). ¹³C{¹H}-NMR (100 MHz, CDCl₃):

Hz, 4H, NH), 10.98 (d, J_HH= 12.9 Hz, 4H, NH). ¹³C{¹H}-NMR

δ = 14.25, 14.39 (CH₃), 60.23, 60.59 (CH₂), 94.93 (C_q),

118.30 (CH_aromat), 120.39 (CH_aromat), 122.63, 127.25, 129.31,

137.40 (C_q,aromat), 153.26 (CH), 165.28 (CO), 169.09 (CO).

MS (ESI+) m/z (%): 347 (100) [M + H]⁺, 717 (52), [2M + Na]⁺.

IR (KBr): ν = 3344, 3396 (m, ν_N–H2), 3247 (w, ν_N–H), 1589,

1609, 1666, 1700 (s, ν_CO; ν_CN) cm⁻¹. Anal. calcd. for

C₁₄H₁₆Cl₂N₂O₄: C, 48.43; H, 4.64; N, 8.07; found: C, 48.49; H,

4.77; N, 8.13. UV/Vis (CH₂Cl₂): λ_max(ε) = 250 (12 040), 299

(11 500), 341 (14 370) nm (mol⁻¹dm³cm⁻¹).

2d. Procedure L-f with ethyl 2-cyano-3-ethoxyacrylate (2, 92 g,

17, 28 mmol) and ligand 2c (2.00 g, 5.76 mmol). Yield: grey

needles (2.54 g, 5.39 mmol, 94%). T_e= 146.0 °C. ¹H-NMR

(400 MHz, CDCl₃): δ = 1.34 (m, 9H, CH₃), 4.28 (m, 6H, CH₂),

7.29 (s, 1H, CH_aromat), 7.36 (s, 1H, CH_aromat), 7.68 (d, J_HH

3

(100 MHz, CDCl₃): δ = 14.13, 14.30 (CH₃), 60.19, 60.62, 61.39

(CH₂), 77.51 (C_q), 95.96 (C_q), 117.27 (CN), 119.56,

120.09 (CH_aromat), 126.55, 127.21 (CH_aromat), 130.56 (C_qaromat),

131.63 (C_q,aromat), 153.28 (CH), 153.45 (CH), 165.19, 168.64

(CO), 167.09 (CO). MS (ESI+) m/z (%): 402 (100) [M + H]⁺,

424 (18) [M + Na]⁺, 825 (31) [2M + Na]⁺. IR (KBr): ν = 3200 (m,

ν_N–H), 2217 (s, ν_CN), 1589, 1630, 1649, 1684, 1716 (s, ν_CO

;

ν_CN) cm⁻¹. Anal. calcd. for C₂₀H₂₃N₃O₆: C, 59.84; H, 5.78; N,

10.47; found: C, 59.87; H, 5.92; N, 10.68. UV/Vis (CH₂Cl₂):

λ_max(ε) = 291 (30 470), 332 (25 410) nm (mol⁻¹dm³cm⁻¹).

UV/Vis (THF) λ_max(ε) = 291 (31 930), 328 (26 340) nm (mol⁻¹

dm³cm⁻¹).

3

2a. Procedure L-c with ethyl 2-cyano-3-ethoxyacrylate

(3.00 g, 16.9 mmol) and 4,5-dichloro-1,2-phenylenediamine

(5.73 g, 33.9 mmol). Yield: grey-brown solid (2.19 g, 5.18 mmol,

31%). T_e= 204.7 °C. ¹H-NMR (400 MHz, CDCl₃): δ = 1.37

=

3

12.6 Hz, 1H, CH), 8.24 (d, J_HH= 12.6 Hz, 1H, CH), 10.80 (d,

³J_HH= 12.5 Hz, 1H, NH), 11.04 (d, J_HH= 12.3 Hz, 1H, NH).

3

¹³C{¹H}-NMR (100 MHz, CDCl₃): δ = 14.08, 14.27 (CH₃), 60.50,

60.92, 61.74 (CH₂), 79.20 (C_q), 97.60 (C_q), 116.53 (CN),

3

(t, J_HH= 7.1Hz, 6H, CH₃), 4.32 (q, J_HH= 7.1Hz, 4H, CH₂),

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121.00, 121.12 (CH_aromat), 129.73 (C_q,aromat), 129.84, 130.80

(C_q,aromat–Cl), 131.09 (C_q,aromat), 152.02 (CH), 152.65 (CH),

164.89, 168.56 (CO), 166.92 (CO). MS (ESI+) m/z (%): 470

(100) [M + H]⁺, 492 (23) [M + Na]⁺, 963 (20) [2M + Na]⁺. IR

(KBr): ν = 3173 (m, ν_N–H), 2219 (m, ν_CN), 1586, 1611, 1636,

1691 (s, ν_CO; ν_CN) cm⁻¹. Anal. calcd. for C₂₀H₂₁Cl₂N₃O₆: C,

51.08; H, 4.50; N, 8.93; found: C, 50.97; H, 4.55; N, 8.89. UV/

Vis (CH₂Cl₂): λ_max(ε) = 292 (37 530), 336 (30 080) nm (mol⁻¹

dm³cm⁻¹). UV/Vis (MeCN): λ_max(ε) = 204 (26 180), 290 (40

360), 331 (30 280) nm (mol⁻¹dm³cm⁻¹).

120.08 (CH_aromat), 124.88 (C_q,aromat), 128.84 (C_q,aromat–CH₃),

135.13 (_Cq,aromat), 135.70 (C_q,aromat–CH₃), 153.92 (CH), 167.83

(CO). MS (ESI+) m/z (%): 260 (43) [M + H]⁺, 277 (100) [M +

NH₄]⁺, 282 (6) [M + Na]⁺, 519 (42) [2M + H]⁺, 541 (19) [2M +

Na]⁺. IR (KBr): ν = 3293, 3353 (m, ν_N–H2), 3139 (m, ν_N–H), 2211

(s, ν_CN), 1514, 1624, 1673 (s, ν_CO; ν_CN) cm⁻¹. Anal. calcd.

for C₁₄H₁₇N₃O₂: C, 64.85; H, 6.61; N, 16.20; found: C, 64.61;

H, 6.59; N, 16.44. UV/Vis (CH₂Cl₂): λ_max(ε) = 264 (6402), 300

(8999), 345 (14 240) nm (mol⁻¹dm³cm⁻¹).

3d. Procedure L-g with diethyl (ethoxymethylene)malonate

(0.24 g, 1.20 mmol) and ligand 3c (310 mg, 1.20 mmol). Yield:

3a. Procedure L-a with ethyl 2-cyano-3-ethoxyacrylate

(7.08 g, 42 mmol), 4,5-dimethyl-1,2-phenylenediamine (3.00 g,

21 mmol). Yield: white solid (6.78 g, 17.73 mmol, 84%). T_e=

190.0 °C. ¹H-NMR (400 MHz, CDCl₃): δ = 1.35 (t, ³J_HH= 7.1 Hz,

6H, CH₃), 2.28 (s, 6H, C_aromat–CH₃), 4.29 (q, ³J_HH= 4 Hz, 7.1H,

1

white solid (0.36 g, 0.84 mmol, 70%). T_e= 114.5 °C. H-NMR

(400 MHz, CDCl₃): δ = 1.32 (m, 9H, CH₃), 2.27 (s, 3H, C_aromat

–

CH₃), 2.29 (s, 3H, C_aromat–CH₃), 4.26 (m, 5H, CH₂), 6.97 (s,

3

1H, CH_aromat), 7.03 (s, 1H, CH_aromat), 7.77 (d, J_HH= 14.3 Hz,

3

CH₂), 6.97 (s, 2H, CH_aromat), 7.70 (d, J_HH= 2 Hz, 12.9H, CH),

1H, NH), 8.17 (d, J_HH= 14.2 Hz, 1H, CH), 8.32 (d, J_HH= 13.1

3

10.70 (d, J_HH= 12.9 Hz, 2H, NH). ¹³C{¹H]-NMR (100 MHz,

Hz, 1H, CH), 10.94 (d, J_HH= 12.7 Hz, 1H, NH). ¹³C{¹H}-NMR

CDCl₃): δ = 14.2 (CH₃), 19.5 (C_aromat–CH₃), 61.5 (CH₂), 77.3

(C_q), 117.4 (CN), 121.1 (CH_aromat), 128.2 (C_q,aromat), 136.6

(C_q,aromat–CH₃), 153.7 (CH), 167.4 (CO). MS (ESI+) m/z (%):

400 (100) [M + NH₄]⁺, 787 (29) [2M + Na]⁺. IR (KBr): ν = 3200 (m,

ν_N–H), 2215 (s, ν_CN), 1604, 1635, 1671 (s, ν_CO; ν_CN) cm⁻¹.

Anal. calcd. for C₂₂H₂₂N₄O₄: C, 62.82; H, 5.80; N, 14.65; found:

C, 62.90; H, 6.052; N, 14.90. UV/Vis (CH₂Cl₂): λ_max(ε) = 294 (31

820), 335 (25 880) nm (mol⁻¹dm³cm⁻¹).

(100 MHz, CDCl₃): δ = 14.13, 14.28 (CH₃), 19.25, 19.45

(C_aromat–CH₃), 60.19, 60.63, 61.17 (CH₂), 78.85 (C_q), 95.36

(C_q), 115.09 (CN), 120.72 (CH_aromat), 122.90 (CH_aromat),

127.86 (C_q,aromat), 129.87 (C_q,aromat), 135.36, 136.80 (C_q,aromat

–

CH₃), 153.26 (CH), 154.23 (CH), 164.18, 165.53, 168.82

(CO). MS (ESI+) m/z (%): 430 (100) [M + H]⁺, 859 (32) [2M +

H]⁺. HR-MS (ESI+) m/z: anal. calcd. for C₂₂H₂₈N₃O₆:

430.19726; found: 430.19781; anal. calcd. for C₄₄H₅₅N₆O₁₂

:

3b.

Propanedioic

acid,

2,2′-[(4,5-dimethyl-1,2-

859.38725; found: 859.39065. IR (KBr): ν = 3198 (w, ν_N–H),

2212 (s, ν_CN), 1595, 1631, 1698 (s, ν_CO; ν_CN) cm⁻¹. Anal.

calcd. for C₂₂H₂₇N₃O₆: C, 61.53; H, 6.34; N, 9.78; found: C,

61.31; H, 6.48; N, 9.76. UV/Vis (CH₂Cl₂): λ_max(ε) = 294

(30 040), 335 (23 730) nm (mol⁻¹dm³cm⁻¹). UV/Vis (MeCN):

λ_max(ε) = 291 (27 210), 330 (22 090) nm (mol⁻¹dm³cm⁻¹).

4a. Procedure L-a with ethyl 2-cyano-3-ethoxyacrylate (14.00 g,

82.8 mmol) and 1,2-ethylenediamine (2.8 ml, 41.4 mmol). Yield:

white solid (10 g, 32.7 mmol, 79%). T_e= 147.7 °C. ¹H-NMR (400

phenylene)bis(iminomethylidyne)]bis-, tetraethyl ester [CAS

79852-83-8]: procedure L-b with diethyl (ethoxymethyl-

ene)malonate (15.04 g, 14.06 ml, 69.6 mmol) and 4,5-

dimethyl-1,2-phenylenediamine (4.74 g, 34.8 mmol). Yield:

white solid (10.47 g, 22.0 mmol, 63%). T_e= 107.5 °C. ¹H-

NMR (400 MHz, CDCl₃): δ = 1.31 (t, J_HH= 7.2 Hz, 6H, CH₃),

1.35 (t, J_HH= 7.1 Hz, 6H, CH₃), 2.27 (s, 6H, C_aromat–CH₃),

4.27 (m, 8H, CH₂), 7.01 (s, 2H, CH_aromat), 8.33 (d, J_HH

13.2 Hz, 2H, CH), 10.88 (d, J_HH= 13.2 Hz, 2H, NH).

¹³C{¹H}-NMR (100 MHz, CDCl₃): δ = 14.23, 14.36 (CH₃), 19.8

(C_q,aromat–CH3), 60.08, 60.41 (CH₂), 94.94 (C_q), 121.03

(CH_aromat), 129.21 (C_q,aromat), 135.34 (C_q,aromat–CH₃), 153.68

(CH), 165.65, 168.57 (CO). MS (ESI+) m/z (%): 477 (100)

[M + H]⁺, 499 (9) [M + Na]⁺, 515 (3) [M + K]⁺, 975 (14) [2M +

Na]⁺. IR (KBr): ν = 3179 (m, ν_N–H), 1585, 1625, 1646, 1671,

3

=

3

MHz, CDCl₃): δ = 1.36 (t, J_HH= 7.1 Hz, 6H, CH₃), 3.53 (m, 4H,

3

CH₂–CH₂), 4.27 (q, J_HH= 7.1 Hz, 4H, CH₂), 7.29 (s, 2H, CH),

3

9.00 (d, J_HH= 11.6 Hz, 2H, NH). ¹³C{¹H}-NMR (100 MHz,

CDCl₃): δ = 14.25 (CH₃), 49.82 (CH₂–CH₂), 61.12 (CH₂), 73.78

(C_q), 117.74 (CN), 159.16 (CH), 167.75 (CO). MS (ESI+)

m/z (%): 307 (31) [M + H]⁺, 329 (100) [M + Na]⁺. IR (KBr): ν = 3288

(m, ν_N–H), 2204 (s, ν_CN), 1681, 1612 (s, ν_CO; ν_CN) cm⁻¹. Anal.

calcd. for C₁₄H₁₈N₄O₄: C, 54.89; H, 5.92; N, 18.29; found: C, 54.85;

H, 6.00; N, 18.56. UV/Vis (CH₂Cl₂): λ_max(ε) = 277 (26 730), 294 (26

890) nm (mol⁻¹dm³cm⁻¹). UV/Vis (MeCN): λ_max(ε) = 201 (21 320),

275 (29 570), 292 (28 690) nm (mol⁻¹dm³cm⁻¹).

1681, 1711 (s, ν_CO

;

ν_CN

)

cm⁻¹

.

Anal. calcd. for

C₂₄H₃₂N₂O₈: C, 60.49; H, 6.77; N, 5.88; found: C, 60.70; H,

6.99; N, 5.913. UV/Vis (CH₂Cl₂): λ_max(ε) = 293 (31 290), 335

(25 770) nm (mol⁻¹dm³cm⁻¹). UV/Vis (THF): λ_max(ε) = 292

(32 350), 332 (26 680) nm (mol⁻¹dm³cm⁻¹).

4b. Procedure L-a with diethyl (ethoxymethylene)malonate

(12.45 g, 57.6 mmol) and 1,2-ethylenediamine (1.72 g,

28.8 mmol). Yield: white solid (10.09 g, 28.8 mmol, 99%).

3c. Procedure L-d with ethyl 2-cyano-3-ethoxyacrylate

(3.33 g, 19.3 mmol) and 4,5-dimethyl-1,2-phenylenediamine

(2.76 g, 9.3 mmol). Yield: white solid (3.56 g, 13.7 mmol,

71%). T_e= 154.4 °C. ¹H-NMR (400 MHz, CDCl₃): δ = 1.35

1

3

T_e= 122.5 °C. H-NMR (400 MHz, CD₂Cl₂): δ = 1.20 (t, J_HH

=

7.1 Hz, 6H, CH₃), 1.25 (t, ³J_HH= 7.1 Hz, 6H, CH₃), 3.48 (m, 4H,

N–CH₂), 4.07 (q, ³J_HH= 7.1 Hz, 4H, CH₂), 4.15 (q, ³J_HH= 7.1 Hz,

4H, CH₂), 7.89 (d, ³J_HH= 13.9 Hz, 2H, CH), 9.14 (d, ³J_HH= 13.3

Hz, 2H, NH). ¹³C{¹H}-NMR (100 MHz, CD₂Cl₂): δ = 14.43, 14.48

(CH₃), 50.06 (CH₂–CH₂), 59.83, 60.11 (CH₂), 91.29 (C_q),

160.07 (CH), 165.72, 169.20 (CO). MS (ESI+) m/z (%): 401

(100) [M + H]⁺, 423 (11) [M + Na]⁺, 824 (13) [2M + Na]⁺. IR (KBr):

3

(t, J_HH= 7.1 Hz, 3H, CH₃), 2.18 (s, 6H, C_aromat–CH₃), 3.44

3

(s, 2H, NH₂), 4.28 (q, J_HH= 7.1 Hz, 2H, CH₂), 6.62 (s, 1H,

3

CH_aromat), 6.79 (s, 1H, CH_aromat), 7.71 (d, J_HH= 13.5 Hz,

1H, CH), 10.54 (d, J_HH= 13.0 Hz, 1H, NH). ¹³C{¹H}-NMR

3

(100 MHz, CDCl₃): δ = 14.30 (CH₃), 18.93, 19.31 (C_aromat–CH₃),

61.00 (CH₂), 74.45 (C_q), 118.19 (CN), 119.68 (CH_aromat),

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ν = 3266 (m, ν_N–H), 1698, 1659, 1602 (s, ν_CO; ν_CN) cm⁻¹. Anal.

calcd. for C₁₄H₂₆N₂O₈: C, 53.99; H, 7.05; N, 7.00; found: C,

53.82; H, 7.27; N, 6.98. UV/Vis (CH₂Cl₂): λ_max(ε) = 274 (25 040),

293 (27 220) nm (mol⁻¹dm³cm⁻¹).

6b. Propanedioic acid, 2,2′-[1,3-propanediylbis(imino

methylidyne)]bis-, 1,1′,3,3′-tetraethyl ester [CAS 1415327-35-3]:

procedure L-a with diethyl (ethoxymethylene)malonate

(22.37 g, 20.9 ml, 103.5 mmol) and 1,4-diaminobutane (4.56

g, 51.7 mmol). Yield: white solid (18.89 g, 44.09 mmol, 85%).

5a. 2-Propenoic acid, 3,3′-(1,2-ethanediyldiimino)bis[2-

cyano-, 1,1′-diethyl ester] [CAS 92325-24-1]: procedure L-a with

ethyl 2-cyano-3-ethoxyacrylate (21.14 g, 125 mmol) and 1,3-

diaminopropane (5.2 ml, 62 mmol). Yield: white solid (15.58 g,

1

3

T_e= 136.3 °C. H-NMR (400 MHz, CDCl₃): δ = 1.23 (t, J_HH

=

3

7.1 Hz, 6H, CH₃), 1.28 (t, J_HH= 7.1 Hz, 6H, CH₃), 1.62 (s, 4H,

3

CH₂–CH₂–CH₂), 3.32 (d, J_HH= 5.4 Hz, 4H, N–CH₂), 4.12 (dd,

1

4

3

48.62 mmol, 74%). Mp = 108.5 °C. T_e= 110.9 °C. H-NMR (400

³J_HH= 7.2 Hz, J_HH= 14.3 Hz, 4H, CH₂), 4.18 (dd, J_HH

=

MHz, CDCl₃): δ = 1.30 (m, 6H, CH₃), 1.94 (p, ³J_HH= 6.6 Hz, 2H,

CH₂–CH₂–CH₂), 3.43 (m, 4H, N–CH₂), 4.20 (m, 2H, CH₂), 7.07

(m, 1H, NH), 7.37 (m, 1H, CH), 7.84 (m, 1H, CH), 8.93 (m, 1H,

NH). ¹³C{¹H}-NMR (100 MHz, CDCl₃): δ = 14.29, 14.40 (CH₃),

31.25 (–CH₂–CH₂–CH₂), 46.25, 46.47 (–N–CH₂), 60.71, 60.80

(CH₂), 71.92, 72.25, 72.66, 72.72 (C_q), 116.72, 116.76, 118.38,

118.54 (CN), 159.15, 159.31 (CH), 165.02 (CO), 167.90

(CO). MS (ESI+) m/z (%): 321 (36) [M + H]⁺, 343 (100) [M +

Na]⁺. IR (KBr): ν = 3280 (m, ν_N–H), 2208 (s, ν_CN), 1689, 1635 (s,

ν_CO; ν_CN) cm⁻¹. Anal. calcd. for C₁₅H₂₀N₄O₄: C, 55.92; H,

6.38; N, 17.64; found: C, 56.24; H, 6.29; N, 17.49. UV/Vis

(CH₂Cl₂): λ_max(ε) = 288 (30 760) nm (mol⁻¹dm³cm⁻¹).

7.2 Hz, J_HH= 14.3 Hz, 4H, CH₂), 7.92 (d, J_HH= 14.0 Hz, 2H,

CH), 9.18 (m, 2H, NH). ¹³C{¹H}-NMR (100 MHz, CDCl₃): δ =

14.19, 14.29 (CH₃), 27.69 (CH₂–CH₂–CH₂), 49.10 (N–CH),

59.49, 59.73 (CH₂), 89.67 (C_q), 159.74 (CH), 165.81, 169.28

(CO). MS (ESI+) m/z (%): 429 (100) [M + H]⁺, 451 (42) [M +

4

3

Na]⁺. IR (KBr): ν = 3303 (m, ν_N–H), 1597, 1629, 1678 (s, ν_CO

;

ν_CN) cm⁻¹. Anal. calcd. for C₂₀H₃₂N₂O₈: C, 56.06; H, 7.53; N,

6.54; found: C, 55.99; H, 7.50; N, 6.60. UV/Vis (CH₂Cl₂): λ_max

(ε) = 284 (35 560) nm (mol⁻¹dm³cm⁻¹).

7a. 2-Propenoic acid, 3,3′-(1,2-cyclohexanediyldiimino)bis[2-

cyano-, diethyl ester, trans-] [CAS 156996-20-2]: procedure L-a

with ethyl 2-cyano-3-ethoxyacrylate (4.06 g, 24 mmol) and 1,2-

diaminocyclohexane (1.4 ml, 12 mmol). Yield: white solid (3.37

g, 9.35 mmol, 78%). Mp = 167.8 °C. T_e= 171.9 °C. ¹H-NMR (400

MHz, CDCl₃): δ = 1.27 (t, ³J_HH= 7.1 Hz, 6H, CH₃), 1.37 (m, 4H,

5b. Propanedioic acid, 2,2′-[(1,2-ethanediyl)bis(iminomethylidyne)]bis-,

1,1′,3,3′-tetraethyl ester [CAS 14452-46-1] (malonic acid,

[ethylenebis(iminomethylidyne)]di-,tetraethyl ester): procedure L-a

with diethyl (ethoxymethylene)malonate (10.43 g, 48.2 mmol)

and 1,3-diaminopropane (1.79 g, 24.1 mmol). Yield: white solid

(6.38 g, 15.4 mmol, 64%). T_e= 97.0 °C. ¹H-NMR (400 MHz,

3

CH_cyclo, CH_2,cyclo), 1.81 (d, J_HH= 7.92 Hz, 2H, CH_2,cyclo), 2.06

3

(d, J_HH= 12.6 Hz, 2H, CH_2,cyclo), 3.00 (m, 2H, CH_cyclo), 4.17 (q,

3

³J_HH= 7.0 Hz, 4H, CH₂), 7.20 (d, J_HH= 13.6 Hz, 2H, CH), 8.81

3

4

CDCl₃): δ = 1.24 (t, J_HH= 7.1 Hz, 6H, CH₃), 1.30 (t, J_HH= 7.1

(dd, ³J_HH= 6.5 Hz, J_HH= 11.8 Hz, 2H, NH). ¹³C{¹H}-NMR (100

3

Hz, 6H, CH₃), 1.90 (q, J_HH= 6.92 Hz, 2H, CH₂–CH₂–CH₂), 3.39

(q, J_HH= 6.7 Hz, 4H, N–CH₂), 4.14 (q, J_HH= 7.1 Hz, 4H, CH₂),

MHz, CDCl₃): δ = 14.5 (CH₃), 24.3 (CH_2,cyclo), 32.4 (CH_2,cyclo),

61.2 (CH₂), 64.0 (CH_cyclo), 72.9 (C_q), 118.3 (CN), 158.3 (CH),

168.1 (CO). MS (ESI+) m/z (%): 361 (100) [M + H]⁺, 383 (97)

[M + Na]⁺, 743 [2M + H]⁺. IR (KBr): ν = 3274 (m, ν_N–H), 2210 (s,

ν_CN), 1683, 1630 (s, ν_CO; ν_CN) cm⁻¹. Anal. calcd. for

C₁₈H₂₄N₄O₄: C, 59.99; H, 6.71; N, 15.55; found: C, 60.38; H,

6.583; N, 15.53. UV/Vis (CH₂Cl₂): λ_max(ε) = 277 (30750) nm

(mol⁻¹dm³cm⁻¹). UV/Vis (MeCN): λ_max(ε) = 203 (20740), 275

(38 180) nm (mol⁻¹dm³cm⁻¹).

7b. Procedure L-a with diethyl (ethoxymethylene)malonate

(9.56 g, 44.2 mmol) and 1,2-diaminocyclohexane (2.52 g,

2.1 mmol). Yield: orange-white solid (7.75 g, 17.13 mmol,

78%). T_e= 109.6 °C. ¹H-NMR (400 MHz, CDCl₃): δ = 1.17

3

4.19 (q, J_HH= 7.1 Hz, 4H, CH₂), 7.93 (d, J_HH= 13.9 Hz, 2H,

CH), 9.19 (m, 2H, NH). ¹³C{¹H}-NMR (100 MHz, CDCl₃): δ =

14.21, 14.30 (CH₃), 31.54 (N–CH₂), 46.34 (CH₂–CH₂–CH₂), 59.59,

59.86 (CH₂), 90.26 (C_q), 159.66 (CH), 165.63, 169.29 (CO).

MS (ESI+) m/z (%): 415 (100) [M + H]⁺, 437 (17) [M + Na]⁺, 851

(13) [2M + Na]⁺. IR (KBr): ν = 3266 (m, ν_N–H), 1697, 1663, 1605 (s,

ν_CO; ν_CN) cm⁻¹. Anal. calcd. for C₁₉H₃₀N₂O₈: C, 55.06; H, 7.30;

N, 6.76; found: C, 55.12; H, 7.42; N, 6.90. UV/Vis (CH₂Cl₂): λ_max

(ε) = 288 (31 510) nm (mol⁻¹dm³cm⁻¹).

6a. 2-Propenoic acid, 3,3′-(1,3-propanediyldiimino)bis[2-

cyano-, diethyl ester] [CAS 157737-86-5]: procedure L-a with

ethyl 2-cyano-3-ethoxyacrylate (8.12 g, 48 mmol) and 1,4-

diaminobutane (2.4 ml, 24 mmol). Yield: white solid (6.05 g,

18.09 mmol, 75%). T_e= 166.7 °C. ¹H-NMR (400 MHz,

SO(CH₃)₂): δ = 1.15 (m, 6H, CH₃), 1.43 (m, 4H, CH₂–CH₂–CH₂),

3

(t, J_HH= 7.1 Hz, 6H, CH₃), 1.25 (t, J_HH= 7.1 Hz, 6H, CH₃),

3

1.29 (d, J_HH= 10.6 Hz, 2H, CH_2,cyclo), 1.38 (m, 2H, CH_2,cyclo),

1.78 (d, J_HH= 8.3 Hz, 2H, CH_2,cyclo), 2.06 (d, J_HH= 13.1 Hz,

2H, CH_2,cyclo), 2.97 (m, 2H, CH_cyclo), 4.05 (q, J_HH= 7.1 Hz, 4H,

3

3.26 (m, 4H, N–CH₂), 4.06 (m, 4H, CH₂), 7.73 (d, J_HH= 14.5

CH₂), 4.14 (q, J_HH= 7.1 Hz, 4H, CH₂), 7.82 (t, J_HH= 13.8 Hz,

2H, CH), 9.14 (m, 2H, NH). ¹³C{¹H}-NMR (100 MHz, CDCl₃): δ

= 14.18, 14.21 (CH₃), 24.12 (CH_2,cyclo), 32.19 (CH_2,cyclo), 59.43,

59.78 (CH₂), 63.51 (CH_cyclo), 90.36 (C_q), 158.70 (CH), 165.31,

169.31 (CO). MS (ESI+) m/z (%): 455 (100) [M + H]⁺, 932 (15)

[2M + H]⁺. IR (KBr): ν = 3258 (m, ν_N–H), 1717, 1681, 1640, 1613

(s, ν_CO; ν_CN) cm⁻¹. Anal. calcd. for C₂₂H₃₄N₂O₈: C, 58.14; H,

7.54; N, 6.16; found: C, 58.12; H, 7.55; N, 6.15. UV/Vis (CH₂Cl₂):

λ_max(ε) = 274 (31120), 290 (19760) nm (mol⁻¹dm³cm⁻¹).

8a. Procedure L-b with ethyl 2-cyano-3-ethoxyacrylate

(27.70 g, 163.7 mmol) and 2-aminobenzylamine (10.00 g,

3

Hz, 6H, CH), 7.91 (d, J_HH= 15.0 Hz, 6H, CH), 8.63 (d, J_HH

=

14.7 Hz, 6H, NH), 9.07 (d, J_HH= 14.3 Hz, 6H, NH). ¹³C{¹H}-

NMR (100 MHz, SO(CH₃)₂): δ = 14.24, 14.34 (CH₃), 26.85 (CH₂–

CH₂–CH₂), 48.35 (N–CH₂), 59.46 (CH₂), 68.13, 68.86 (C_q),

116.82, 119.15 (CN), 159.50, 159.96 (CH), 165.09, 166.60

(CO). MS (ESI+) m/z (%): 335 (38) [M + H]⁺, 357 (100) [M +

Na]⁺. IR (KBr): ν = 3273, 3227 (s, ν_N–H), 2205 (s, ν_CN), 1690,

1623, 1540 (s, ν_CO; ν_CN) cm⁻¹. Anal. calcd. for C₁₆H₂₂N₄O₄:

C, 57.47; H, 6.63; N, 16.76; found: C, 57.32; H, 6.83; N, 16.94.

UV/Vis (CH₂Cl₂): λ_max(ε) = 284 (32 900) nm (mol⁻¹dm³cm⁻¹).

3

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81.9 mmol). Yield: white solid (20.6 g, 56.0 mmol, 68%). T_e=

179.70 °C. H-NMR (400 MHz, CDCl₃): δ = 1.25 (t, J_HH= 7.1

calcd. for C₁₈H₁₆N₄O₄Zn: C, 51.75; H, 3.86; N, 13.41; found: C,

51.60; H, 4.05; N, 13.47. Anal. calcd. for C₁₈H₁₆N₄O₄Zn: Zn,

15.65; found: Zn, 15.62. UV/Vis (CH₂Cl₂): λ_max(ε) = 241 (16

522), 307 (27550), 360 (23931) nm (mol⁻¹dm³cm⁻¹).

1

3

Hz, 3H, CH₃), 1.32 (t, J_HH= 7.1 Hz, 3H, CH₃), 4.17 (q, J_HH

=

3

7.1 Hz, 2H, CH₂), 4.28 (q, J_HH= 7.1 Hz, 2H, CH₂), 4.54 (d,

³J_HH= 5.3 Hz, 2H, N–CH₂), 6.29 (d, J_HH= 16.8 Hz, 1H, NH),

Zn[1b]. Procedure Zn-a with ligand 1b (2.00 g, 4.46 mmol),

THF (40 ml) and diethylzinc in hexane (1 M) (4.5 ml, 4.46

3

7.22 (m, 3H, CH_aromat), 7.29 (d, J_HH= 6.8 Hz, 1H, CH_aromat),

7.44 (t, J_HH= 7.7 Hz, 1H, CH_aromat), 7.85 (d, J_HH= 12.8 Hz,

1H, CH), 7.93 (d, J_HH= 14.9 Hz, 1H, CH), 11.12 (d, J_HH

3

1

mmol). Yield: dark green solid (2.28 g, 4.45 mmol, 99%). H-

3

=

NMR (400 MHz, SO(CD₃)₂): δ = 1.23 (t, J_HH= 7.1 Hz, 6H,

12.6 Hz, 1H, NH).¹³C{¹H}-NMR (100 MHz, CDCl₃): δ = 14.20,

14.23 (CH₃), 49.97 (N–CH₂), 61.83, 60.90 (CH₂), 77.14 (C_q),

73.24 (CN), 116.89 (CH_aromat), 117.99 (CN), 117.16 (C_q),

124.87 (C_q,aromat), 126.16 (CH_aromat), 130.71, 130.85 (CH_aromat),

137.09 (C_q,aromat), 152.28 (CH), 159.01 (CH), 167.73 (CO),

167.79 (CO). HR-MS (ESI+) m/z: anal. calcd. for C₁₉H₂₀N₄O₄:

368.1485; found: 368.1427. IR (KBr): ν = 3270 (m, ν_N–H), 2208

(s, ν_CN), 1696 (s), 1641 (s, ν_CO; ν_CN) cm⁻¹. Anal. calcd. for

C₁₉H₂₀N₄O₄: C, 61.95; H, 5.47; N, 15.21; found: C, 62.02; H,

5.56; N, 15.43. UV/Vis (CH₂Cl₂): λ_max(ε) = 285 (28440), 322 (21

070) nm (mol⁻¹dm³cm⁻¹). UV/Vis (MeCN): λ_max(ε) = 200 (28

530), 287 (32 640) nm (mol⁻¹dm³cm⁻¹).

CH₃), 1.29 (t, J_HH= 7.1 Hz, 6H, CH₃), 4.09 (q, J_HH= 7.1 Hz,

3

4H, CH₂), 4.25 (q, J_HH= 7.1 Hz, 4H, CH₂), 7.09 (dd, J_HH

=

4

3

3.4 Hz, J_HH= 6.0 Hz, 2H, CH_aromat), 7.36 (dd, J_HH= 3.4 Hz,

4J_HH= 6.0 Hz, 2H, CH_aromat), 8.91 (s, 2H, CH). ¹³C{¹H}NMR

(100 MHz, SO(CD₃)₂): δ = 14.27, 14.42 (CH₃), 58.58, 59.98

(CH₂), 87.79 (C_q), 114.39 (CH_aromat), 124.34 (CH_aromat),

139.42 (C_q,aromat), 158.46 (CH), 166.76, 171.33 (CO). MS

(ESI+) m/z (%): 449 (99) [Lig + H]⁺, 471 (100) [Lig + Na]⁺, 511

(10) [M + H]⁺. MS (ESI−) m/z (%): 447 (32) [Lig − H]⁻, 569

(100) [M + CH₃COO]⁻, 1079 (8) [2M + CH₃COO]⁻. HR-MS

(ESI+) m/z: anal. calcd. for C₂₂H₂₆N₂O₈Zn: 511.10534; found:

511.10607. IR (KBr): ν = 1525, 1584, 1606, 1673 (s, ν_CO

;

8b. Procedure L-a with diethyl (ethoxymethylene)malonate

(27.70 g, 16.5 ml, 81.85 mmol) and 2-aminobenzylamine (5.00

g, 40.93 mmol). Yield: yellowish solid (15.94 g, 34.46 mmol,

ν_CN) cm⁻¹. Anal. calcd. for C₂₂H₂₆N₂O₈ZnOH: C, 49.97; H,

5.15; N, 5.30; found: C, 50.27; H, 5.38; N, 5.40. ICP-AES: anal.

calcd. for C₂₂H₂₆N₂O₈Zn: Zn, 12.77; found: Zn, 13.04. REM-

EDX: anal. calcd. for C₂₂H₂₆N₂O₈Zn: Zn, 12.77; found: Zn,

12.21. UV/Vis (CH₂Cl₂): λ_max(ε) = 258 (12 210), 313 (24 720),

346 (20 620) nm (mol⁻¹dm³cm⁻¹).

1

84%). T_e= 113.0 °C. H-NMR (400 MHz, CDCl₃): δ = 1.30 (m,

3

12H, CH₃), 4.22 (m, 8H, CH₂), 4.57 (d, J_HH= 5.6 Hz, 2H, N–

3

CH₂), 7.18 (t, J_HH= 7.5 Hz, 1H, CH_aromat), 7.27 (d, J_HH= 7.3

Hz, 2H, CH_aromat), 7.39 (t, ³J_HH= 7.6 Hz, 1H, CH_aromat), 8.10 (d,

³J_HH= 13.9 Hz, 1H, CH), 8.47 (d, ³J_HH= 13.0 Hz, 1H, CH), 9.36

Zn[1d]. Procedure Zn-a with ligand 1d (750 mg, 1.87

mmol), THF (15 ml) and diethylzinc in hexane (1 M) (1.9 ml,

3

4

3

1

(dd, J_HH= 6.6 Hz, J_HH= 7.0 Hz, 1H, NH), 11.31 (d, J_HH

=

1.87 mmol). Yield: yellow solid (0.86 g, 1.84 mmol, 99%). H-

13.0 Hz, 1H, NH). ¹³C{¹H}-NMR (100 MHz, CDCl₃): δ = 14.19–

14.33 (CH₃), 49.32 (N–CH₂), 59.61–60.55 (CH₂), 91.12 (C_q),

94.65 (C_q), 116.97 (CH_aromat), 125.33 (CH_aromat), 126.12 (C_q,

_aromat), 129.26 (CH_aromat), 129.84 (CH_aromat), 137.52 (C_q,aromat),

152.50 (CH), 159.84 (CH), 165.30–169.24 (CO). MS (ESI+) m/z

(%): 463 (100) [M + H]⁺, 485 (29) [M + Na]⁺, 948 (17) [2M +

Na]⁺. IR (KBr): ν = 3281 (m, ν_N–H), 1589, 1615, 1641, 1665, 1693

(s, ν_CO; ν_CN) cm⁻¹. Anal. calcd. for C₂₃H₃₀N₂O₈: C, 59.73; H,

6.54; N, 6.06; found: C, 59.63; H, 6.75; N, 6.16. UV/Vis (CH₂Cl₂):

λ_max(ε) = 287 (24570), 320 (19420) nm (mol⁻¹dm³cm⁻¹).

Zn[1a]. Procedure Zn-a with ligand 1a (5.00 g, 14.11 mmol),

THF (75 ml) and diethylzinc in hexane (1 M) (14.1 ml, 14.11

NMR (400 MHz, SO(CD₃)₂): δ = 1.23 (t, J_HH= 7.1 Hz, 3H,

3

CH₃), 1.29 (t, J_HH= 7.1 Hz, 3H, CH₃), 1.30 (t, J_HH= 7.1 Hz,

3

3H, CH₃), 4.09 (q, J_HH= 7.1 Hz, 2H, CH₂), 4.25 (m, 4H, CH₂),

3

4

7.04 (dt, J_HH= 0.9 Hz, J_HH= 7.7 Hz, 1H, CH_aromat), 7.10 (dt,

4

3

³J_HH= 1.2 Hz, J_HH= 6.9 Hz, 2H, CH_aromat), 7.34 (d, J_HH= 7.3

3

Hz, 1H, CH_aromat), 7.58 (d, J_HH= 6.9 Hz, 1H, CH_aromat), 8.39

(s, 1H, CH), 8.89 (s, 1H, CH). ¹³C{¹H}-NMR (100 MHz,

SO(CD₃)₂): δ = 14.27, 14.35, 14.42 (CH₃), 58.58, 59.94, 60.57

(CH₂), 68.24 (C_q), 87.92 (C_q), 114.40 (CH_aromat), 115.16

(CH_aromat), 121.30 (CN), 124.06 (CH_aromat), 124.92

(CH_aromat), 138.27 (C_q,aromat), 139.45 (C_q,aromat), 156.74 (CH),

158.36 (CH), 166.85, 171.20, 171.25 (CO). MS (ESI+) m/z

(%): 402 (13) [Lig + H]⁺, 424 (100) [Lig + Na]⁺, 464 (10) [M +

H]⁺. MS (ESI−) m/z (%): 400 (41) [Lig − H]⁻, 522 (100) [M +

CH₃COO]⁻, 863 (6) [M + Lig − H]⁻, 985 (13) [2M + CH₃COO]⁻.

HR-MS (ESI+) m/z: anal. calcd. for C₂₀H₂₂N₃O₆Zn: 464.08056;

found: 464.08086; anal. calcd. for C₂₀H₂₁N₃NaO₆Zn:

486.06140; found: 486.06198; anal. calcd. for C₂₁H₂₄N₃O₇Zn:

494.09112; found: 494.09100. IR (KBr): ν = 1546, 1589, 1613,

1671 (s, ν_CO; ν_CN), 2205 (m, ν_CN) cm⁻¹. Anal. calcd. for

C₂₀H₂₁N₃O₆Zn: C, 51.68; H, 4.55; N, 9.04; found: C, 51.25; H,

4.74; N, 9.03. ICP-AES: anal. calcd. for C₂₀H₂₁N₃O₆Zn: Zn,

14.07; found: Zn, 14.23. UV/Vis (MeCN): λ_max(ε) = 251 (13

364), 311 (25 696), 359 (22 715) nm (mol⁻¹dm³cm⁻¹).

1

mmol). Yield: yellow solid (5.88 g, 14.08 mmol, 99%). H-NMR

3

(400 MHz, SO(CD₃)₂): δ = 1.29 (tr, J_HH= 7.1Hz, 6H, CH₃), 4.25

3

4

(q, J_HH= 7.0 Hz, 4H, CH₂), 7.05 (dd, J_HH= 3.4 Hz, J_HH= 6.1

3

4

Hz, 2H, CH_aromat), 7.56 (dd, J_HH= 3.5 Hz, J_HH= 6.1 Hz, 2H,

CH_aromat), 8.35 (s, 2H, CH). ¹³C{¹H}-NMR (100 MHz, SO(CD₃)₂):

δ = 14.1 (CH₃), 60.2 (CH₃), 68.1 (C_q), 114.9 (CH_aromat), 121.2

(CN), 124.4 (CH_aromat), 138.0 (C_q,aromat), 156.3 (CH), 170.8

(CO). MS (ESI+) m/z (%): 355 (17) [Lig + H]⁺, 377 (40) [Lig +

Na]⁺, 417 (100) [M + H]⁺, 833 (13) [2M + H]⁺. MS (ESI−) m/z

(%): 353 (13) [Lig − H]⁻, 475 (100) [M + CH₃COO]⁻, 893 (28)

[2M

+

CH₃COO]⁻. HR-MS (ESI+) m/z: anal. calcd. for

C₁₈H₁₆N₄O₄Zn: 416.04575; found: 416.04612; anal. calcd. for

C₁₈H₁₆N₄NaO₄Zn: 439.03552; found: 439.03590; anal. calcd.

for C₁₈H₁₆N₄O₄Zn: 417.05468; found: 417.05474. IR (KBr): ν =

1549, 1592, 1625 (s, ν_CO; ν_CN), 2203 (s, ν_CN) cm⁻¹. Anal.

Zn[2a]. Procedure Zn-b with ligand 2a (750 mg, 1.77

mmol), THF (15 ml) and diethylzinc in hexane (1 M) (1.8 ml,

1

1.80 mmol). Yield: beige solid (0.60 g, 1.23 mmol, 69%). H-

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3

NMR (400 MHz, SO(CD₃)₂): δ = 1.29 (t, J_HH= 7.1 Hz, 6H,

CH₃), 2.18 (s, 6H, C_aromat–CH₃), 4.23 (q, J_HH= 7.1 Hz, 4H,

3

CH₃), 4.25 (q, J_HH= 7.1 Hz, 6H, CH₃), 7.89 (s, 2H, CH_aromat),

CH₂), 7.39 (s, 2H, CH_aromat), 8.32 (s, 2H, CH). ¹³C{¹H}-NMR

(100 M Hz, SO(CD₃)₂): δ = 14.36 (CH₃), 19.09 (C_aromat–CH₃),

60.33 (CH₂), 67.67 (C_q), 115.84 (CH_aromat), 121.61 (CN),

132.82 (C_q,aromat–CH₃), 135.75 (C_q,aromat), 155.55 (CH), 170.96

(CO). MS (ESI+) m/z (%): 337 (89) [Lig − OEt]⁺, 383 (58)

[Lig + H]⁺, 400 (33) [Lig + NH₄]⁺, 405 (93) [Lig − H]⁺, 445 (100)

[M + H]⁺, 467 (5) [M + MeOH]⁺, 787 (42) [2Lig + Na]⁺, 889 (7)

[2M + H]⁺. MS (ESI−) m/z (%): 381 (14) [Lig − H]⁻, 503 (100)

[M + CH₃COO]⁻, 947 (29) [2M + CH₃COO]⁻. IR (KBr): ν = 1551,

1624 (s, ν_CO; ν_CN), 2202, 2220 (s, ν_CN) cm⁻¹. Anal. calcd.

for C₂₀H₂₀N₄O₄Zn: C, 53.89; H, 4.52; N, 12.57; found: C,

53.63; H, 4.70; N, 12.64. ICP-AES: anal. calcd. for

C₂₀H₂₀N₄O₄Zn: Zn, 14.67; found: Zn, 14.56. UV/Vis (CH₂Cl₂):

λ_max(ε) = 241 (15 820), 310 (25 630), 365 (21 270) nm (mol⁻¹

dm³cm⁻¹).

8.43 (s, 2H, CH). ¹³C{¹H}-NMR (100 MHz, SO(CD₃)₂): δ =

14.31 (CH₃), 60.61 (CH₃), 69.46 (C_q), 116.94 (CH_aromat),

121.03 (CN), 126.11 (C_q,aromat–Cl), 138.48 (C_q,aromat), 157.67

(CO), 170.70 (CO). MS (ESI−) m/z (%): 421 (12) [Lig − H]⁻,

523 (7) [M + Cl]⁻, 545 (100) [M + CH₃COO]⁻, 1029 (14) [2M +

CH₃COO]⁻. IR (KBr): ν = 1539, 1558, 1624 (s, ν_CO; ν_CN),

2208,

2223

(s,

ν_CN

)

cm⁻¹.

Anal.

calcd.

for

C₁₈H₁₄C_l2N₄O₄Zn·H₂O: C, 42.84; H, 3.20; N, 11.10; found: C,

43.04; H, 3.13; N, 11.14. ICP-AES: anal. calcd. for

C₁₈H₁₄Cl₂N₄O₄Zn: Zn, 13.44; found: Zn, 14.77. UV/Vis

(MeCN): λ_max(ε) = 219 (21 180), 234 (shoulder; ~16 080), 317

(44 040), 376 (35 990) nm (mol⁻¹dm³cm⁻¹).

Zn[2b]. Procedure Zn-a with ligand 2b (750 mg, 1.45

mmol), THF (15 ml) and diethylzinc in hexane (1 M) (1.5 ml,

1.50 mmol). Yield: dark green solid (0.81 g, 1.40 mmol, 96%).

Zn[3b]. Procedure Zn-a with ligand 3b (750 mg, 1.55

mmol), THF (15 ml) and diethylzinc in hexane (1 M) (1.6 ml,

¹H-NMR (400 MHz, SO(CD₃)₂): δ = 1.23 (t, J_HH= 7.1 Hz, 6H,

3

1

CH₃), 1.29 (t, J_HH= 7.1 Hz, 6H, CH₃), 4.10 (q, J_HH= 7.0 Hz,

4H, CH₂), 4.24 (q, J_HH= 7.0 Hz, 4H, CH₂), 7.54 (s, 2H,

1.60 mmol). Yield: brown solid (0.81 g, 1.49 mmol, 96%). H-

3

NMR (400 MHz, SO(CD₃)₂): δ = 1.23 (t, J_HH= 7.1 Hz, 6H,

CH_aromat), 8.80 (s, 2H, CH). ¹³C{¹H} NMR (100 MHz,

SO(CD₃)₂): δ = 14.21, 14.41 (CH₃), 58.79, 60.17 (CH₂), 89.23

(C_q), 115.95 (CH_aromat), 125.53 (C_q,aromat–Cl), 139.73 (C_q,

_aromat), 158.86 (CH), 166.77, 171.18 (CO). MS (ESI+) m/z

(%): 425 (52) [M − 2OEt]⁺, 471 (72) [Lig − OEt]⁺, 517 (29)

[Lig + H]⁺, 539 (99) [Lig + Na]⁺, 581 (100) [M + H]⁺, 1161 (22)

[2M + H]⁺. MS (ESI−) m/z (%): 515 (6) [Lig − H]⁻, 639 (100)

[M + CH₃COO]⁻, 1219 (21) [2M + CH₃COO]⁻. IR (KBr): ν =

1527, 1576, 1603, 1677 (s, ν_CO; ν_CN) cm⁻¹. Anal. calcd. for

C₂₂H₂₄Cl₂N₂O₈Zn: C, 45.50; H, 4.17; N, 4.82; found: C, 45.23;

H, 4.34; N, 4.71. ICP-AES: anal. calcd. for C₂₂H₂₄Cl₂N₂O₈Zn:

Zn, 11.26; found: Zn, 11.17. UV/Vis (CH₂Cl₂): λ_max(ε) = 253

(shoulder, ~13 390), 294 (21 190), 313 (25 490), 371 (22 930)

nm (mol⁻¹dm³cm⁻¹).

CH₃), 1.29 (t, J_HH= 7.1 Hz, 6H, CH₃), 2.22 (s, 4H, C_aromat

–

3

CH₃), 4.09 (q, J_HH= 7.1 Hz, 4H, CH₂), 4.23 (q, J_HH= 7.1 Hz,

4H, CH₂), 7.14 (s, 2H, CH_aromat), 8.88 (s, 2H, CH). ¹³C{¹H}-

NMR (100 MHz, SO(CD₃)₂): δ = 14.25, 14.41 (CH₃), 19.22

(C_aromat–CH₃), 58.51, 59.85 (CH₂), 87.32 (C_q), 115.25

(CH_aromat), 132.34 (C_q,aromat–CH₃), 136.96 (C_q,aromat), 157.79

(CH), 166.99, 171.27 (CO). MS (ESI+) m/z (%): 431 (100)

[Lig − OEt]⁺, 477 (35) [Lig + H]⁺, 499 (34) [Lig + Na]⁺, 539 (8)

[M + H]⁺, 975 (20) [2Lig + Na]⁺. MS (ESI−) m/z (%): 475 (38)

[Lig − H]⁻, 597 (100) [M + CH₃COO]⁻, 1139 (10) [2M +

CH₃COO]⁻. IR (KBr): ν = 1526, 1593, 1615, 1674 (s, ν_CO; ν_CN

)

cm⁻¹. Anal. calcd. for C₂₄H₃₀N₂O₈Zn: C, 53.39; H, 5.60; N, 5.19;

found: C, 53.27; H, 5.95; N, 5.12. ICP-AES: anal. calcd. for

C₂₄H₃₀N₂O₈Zn: Zn, 12.11; found: Zn, 11.35. UV/Vis (CH₂Cl₂):

λ_max(ε) = 292 (27320), 335 (22970) nm (mol⁻¹dm³cm⁻¹).

Zn[3d]. Procedure Zn-a with ligand 3d (0.54 g, 1.35 mmol),

THF (10 ml) and diethylzinc in hexane (1 M) (1.4 ml, 1.35

mmol). Yield: orange solid (0.63 g, 1.28 mmol, 95%). ¹H-NMR

(400 MHz, SO(CD₃)₂): δ = 1.23 (t, ³J_HH= 7.1 Hz, 3H, CH₃), 1.29

Zn[2d]. Procedure Zn-a with ligand 2d (500 mg, 1.06

mmol), THF (10 ml) and diethylzinc in hexane (1 M) (1.1 ml,

1

1.06 mmol). Yield: yellow solid (0.58 g, 0.88 mmol, 83%). H-

3

NMR (400 MHz, SO(CD₃)₂): δ = 1.23 (t, J_HH= 6.7 Hz, 3H,

3

CH₃), 1.28 (t, J_HH= 7.1 Hz, 6H, CH₃), 4.10 (q, J_HH= 6.0 Hz,

2H, CH₂), 4.24 (m, 4H, CH₂), 7.51 (s, 1H, CH_aromat), 7.90 (s,

1H, CH_aromat), 8.46 (s, 1H, CH), 8.77 (s, 1H, CH). ¹³C{¹H}-

NMR (100 MHz, SO(CD₃)₂): δ = 14.22, 14.30, 14.41 (CH₃),

58.79, 60.10, 60.70 (CH₂), 69.45 (C_q), 89.30 (C_q), 115.91

3

(t, J_HH= 6.3 Hz, 6H, CH₂), 2.19 (s, 3H, C_aromat–CH₃), 2.21 (s,

3H, C_aromat–CH₃), 4.09 (q, J_HH= 6.8 Hz, 2H, CH₂), 4.24 (m,

3

4H, CH₂), 7.12 (s, 1H, CH_aromat), 7.42 (s, 1H, CH_aromat), 8.36

(s, 1H, CH), 8.86 (s, 1H, CH). ¹³C{¹H}-NMR (100 MHz,

SO(CD₃)₂): δ = 14.27, 14.35, 14.45 (CH₃), 19.10 (C_aromat–CH₃),

19.27 (C_aromat–CH₃), 58.54, 59.84, 60.45 (CH₂), 67.68 (C_q),

87.40 (C_q), 115.13 (CH_aromat), 116.00 (CH_aromat), 121.41

(CN), 132.24 (C_q,aromat–CH₃), 132.96 (C_q,aromat–CH₃), 135.80

(C_q,aromat), 136.91 (C_q,aromat), 155.84 (CH), 157.71 (CH), 167.09

(CO), 171.19 (CO). MS (ESI+) m/z (%): 430 (100) [Lig + H]⁺,

452 (22) [Lig + Na]⁺, 492 (18) [M + H]⁺, 882 (13) [2Lig + Na]⁺.

MS (ESI−) m/z (%): 428 (21) [Lig − H]⁻, 550 (100) [M +

CH₃OO]⁻, 1041 (21) [2M + CH₃COO]⁻. IR (KBr): ν = 1547, 1600

(s, ν_CO; ν_CN), 2202 (s, ν_CN) cm⁻¹. Anal. calcd. for

C₂₂H₂₅N₃O₆Zn·2OH: C, 50.15; H, 5.17; N, 7.98; found: C,

50.40; H, 5.17; N, 8.11. UV/Vis (CH₂Cl₂): λ_max(ε) = 245 (9521),

310 (20 970), 367 (18 680) nm (mol⁻¹dm³cm⁻¹).

(CH_aromat), 117.00 (CH_aromat), 120.92 (CN), 125.46 (C_q,aromat

–

Cl), 126.12 (C_q,aromat–Cl), 138.51 (C_q,aromat), 139.79 (C_q,aromat),

157.90 (CH), 158.69 (CH), 166.89, 170.88, 171.00 (CO). MS

(ESI−) m/z (%): 592 (100) [M + CH₃COO]⁻, 1127 (32) [2M +

CH₃COO]⁻. IR (KBr): ν = 1558, 1602, 1635 (s, ν_CO; ν_CN),

2233 (s, ν_CN) cm⁻¹. Anal. calcd. for C₂₀H₁₉Cl₂N₃O₆Zn·3/

2H₂O: C, 42.84; H, 3.95; N, 7.49; found: C, 43.08; H, 3.94; N,

7.24. UV/Vis (CH₂Cl₂): λ_max(ε) = 315 (9645), 375 (8324) nm

(mol⁻¹dm³cm⁻¹).

Zn[3a]. Procedure Zn-b with ligand 3a (750 mg, 1.96

mmol), THF (15 ml) and diethylzinc in hexane (1 M) (1.9 ml,

1

1.90 mmol). Yield: yellow solid (0.61 g, 1.38 mmol, 70%). H-

3

NMR (400 MHz, SO(CD₃)₂): δ = 1.28 (t, J_HH= 7.1 Hz, 6H,

1670 | Catal. Sci. Technol., 2014, 4, 1658–1673

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Zn[4a]. Procedure Zn-b with ligand 4a (750 mg, 2.45

1603, 1659, 1696 (s, ν_CO; ν_CN) cm⁻¹. Anal. calcd. for

C₁₉H₂₈N₂O₈Zn·2H₂O: C, 44.41; H, 6.28; N, 5.45; found: C,

44.03; H, 6.37; N, 5.38. ICP-AES: anal. calcd. for

C₁₉H₂₈N₂O₈Zn: Zn, 13.68; found: Zn, 14.71.

mmol), THF (15 ml) and diethylzinc in hexane (1 M) (2.5 ml,

1

2.45 mmol). Yield: white solid (0.76 g, 2.04 mmol, 83%). H-

3

NMR (400 MHz, SO(CD₃)₂): δ = 1.23 (t, J_HH= 7.1Hz, 6H,

3

CH₃), 3.42 (s, 4H, CH₂–CH₂), 4.15 (q, J_HH= 7.1Hz, 4H, CH₃),

Zn[6a]. Procedure Zn-b with ligand 6a (750 mg, 2.24 mmol),

THF (15 ml) and diethylzinc in hexane (1 M) (2.2 ml, 2.20

mmol). Yield: white solid (0.56 g, 1.40 mmol, 62%). ¹H-NMR

7.82 (s, 2H, CH). ¹³C{¹H}-NMR (100 MHz, SO(CD₃)₂): δ =

14.40 (CH₃), 54.05 (CH₂), 59.58, 59.84 (CH₂–CH₂), 64.18

(C_q), 121.85 (CN), 162.66 (CH), 171.77 (CO). MS (ESI+)

m/z (%): 307 (64) [Lig + H]⁺, 324 (39) [Lig + H₂O]⁺, 329 (80)

[Lig + Na]⁺, 345 (36) [Lig + K]⁺, 369 (4) [M + H]⁺, 635 (100)

[2Lig + Na]⁺. MS (ESI−) m/z (%): 305 (100) [Lig − H]⁻, 368 (5)

[M − H]⁻, 673 (9) [M + Lig]⁻. HR-MS (ESI+) m/z: anal. calcd.

for C₁₄H₁₇N₄O₄Zn: 369.05358; found: 369.05401. IR (KBr): ν =

1528, 1562, 1649 (s, ν_CO; ν_CN), 2206 (s, ν_CN) cm⁻¹. Anal.

calcd. for C₁₄H₁₆N₄O₄Zn: C, 45.49; H, 4.36; N, 15.16; found:

C, 45.04; H, 4.57; N, 15.07. ICP-AES: anal. calcd. for

C₁₄H₁₆N₄O₄Zn: Zn, 17.69; found: Zn, 17.09.

3

(400 MHz, SO(CD₃)₂): δ = 1.22 (t, J_HH= 7.1 Hz, 6H, CH₃), 1.68

3

(s, 4H, CH₂–CH₂), 3.35 (m, 4H, CH₂–N), 4.14 (q, J_HH= 7.0 Hz,

4H, CH₂), 7.72 (s, 2H, CH). ¹³C{¹H}-NMR (100 MHz, SO(CD₃)₂):

δ = 14.856 (CH₃), 27.677 (CH₂–CH₂), 48.833 (CH₂–N), 59.97

(CH₃), 69.257 (C_q), 117.364 (CN), 165.068 (CH), 171.644

(CO). MS (ESI+) m/z (%): 243 (64) [Lig − 2OEt]⁺, 289 (100)

[Lig − OEt]⁺, 307 (70) [Lig − OEt + NH₄]⁺, 335 (44) [Lig + H]⁺, 357

(100) [Lig + Na]⁺, 397 (8) [M + H]⁺, 691 (15) [2Lig + Na]⁺. MS

(ESI−) m/z (%): 333 (100) [Lig − H]⁻, 351 (3) [M − OEt]⁻, 396 (6)

[M − H]⁻, 455 (4) [M + CH₃COO]⁻, 729 (4) [M + Lig − H]⁻. IR

(KBr): ν = 1463, 1623, 1678 (s, ν_CO; ν_CN), 2210 (s, ν_CN) cm⁻¹.

Anal. calcd. for C₁₆H₂₀N₄O₄Zn·2OH: C, 44.51; H, 5.14; N, 12.98;

found: C, 44.81; H, 5.50; N, 13.29. ICP-AES: anal. calcd. for

C₁₆H₂₀N₄O₄Zn: Zn, 16.44; found: Zn, 16.43.

Zn[4b]. Procedure Zn-a with ligand 4b (1.00 g, 2.50 mmol),

THF (20 ml) and diethylzinc in hexane (1 M) (2.5 ml, 2.50

mmol). Yield: white solid (0.8038 g, 1.73 mmol, 69%). ¹H-

3

NMR (400 MHz, SO(CD₃)₂): δ = 1.17 (t, J_HH= 7.1 Hz, 6H,

3

CH₃), 1.23 (t, J_HH= 7.1 Hz, 6H, CH₃), 3.45 (s, 4H, CH₂–CH₂),

Zn[6b]. Procedure Zn-a with ligand 6b (750 mg, 1.75

mmol), THF (15 ml) and diethylzinc in hexane (1 M) (1.8 ml,

3

3.99 (d, J_HH= 7.1 Hz, 4H, CH₂), 4.13 (d, J_HH= 7.1 Hz, 4H,

CH₂), 8.42 (s, 2H). ¹³C{¹H}-NMR (100 MHz, SO(CD₃)₂): δ =

14.70, 14.84 (CH₃), 55.53 (CH₂–CH₂), 58.35, 59.70 (CH₂),

84.50 (C_q), 165.60 (CH), 168.04, 173.93 (CO). MS (ESI−)

m/z (%): 399 (100) [Lig − H]⁻, 521 (16) [M + CH₃COO]⁻, 861

1

1.80 mmol). Yield: white solid (0.85 g, 1.64 mmol, 94%). H-

NMR (400 MHz, SO(CD₃)₂): δ = 1.19 (m, 12H, CH₃), 1.71 (s,

4H, CH₂–CH₂), 3.35 (s, 4H, CH₂–N), 4.05 (m, 8H, CH₂), 8.33

(s, 2H, CH). ¹³C{¹H}-NMR (100 MHz, SO(CD₃)₂): δ = 14.22,

14.28 (CH₃), 27.245 (CH₂–CH₂), 48.447 (CH₂–N), 58.63, 59.12

(CH₂), 87.854 (C_q), 159.381 (CH), 166.67, 167.70 (CO).

MS (ESI+) m/z (%): 337 (84) [Lig − 2OEt]⁺, 355 (5) [Lig −

2OEt + NH₄]⁺, 369 (16) [Lig − 2OEt + MeOH]⁺, 383 (100) [Lig −

OEt]⁺, 429 (5) [Lig + H]⁺, 451 (59) [Lig + Na]⁺, 491 (3)

[M + H]⁺. IR (KBr): ν = 1629, 1679 (s, ν_CO; ν_CN) cm⁻¹. Anal.

calcd. for C₂₀H₃₀N₂O₈Zn·H₂O: C, 47.02; H, 6.51; N, 5.48;

found: C, 47.07; H, 6.85; N, 5.47. ICP-AES: anal. calcd. for

C₂₀H₃₀N₂O₈Zn: Zn, 13.29; found: Zn, 14.25.

(4) [M + Lig − H]⁻. IR (KBr): ν = 1596, 1634, 1678 (s, ν_CO

;

ν_CN) cm⁻¹. Anal. calcd. for C₁₈H₂₆N₂O₈Zn·H₂O: C, 44.87; H,

5.86; N, 5.81; found: C, 44.65; H, 5.98; N, 5.83. ICP-AES: anal.

calcd. for C₁₈H₂₆N₂O₈Zn: Zn, 14.10, found: Zn, 14.58.

Zn[5a]. Procedure Zn-b with ligand 5a (750 mg, 2.34

mmol), THF (15 ml) and diethylzinc in hexane (1 M) (2.3 ml,

1

2.30 mmol). Yield: white solid (0.64 g, 1.66 mmol, 71%). H-

3

NMR (400 MHz, SO(CD₃)₂): δ = 1.23 (t, J_HH= 7.1 Hz, 6H,

CH₃), 1.70 (m, 2H, CH₂–CH₂), 3.53 (m, 4H, CH₂–N), 4.15 (t,

³J_HH= 7.1 Hz, 4H, CH₃), 7.63 (s, 2H, CH). ¹³C{¹H}-NMR (100

MHz, SO(CD₃)₂): δ = 14.53 (CH₃), 31.05 (CH₂–CH₂), 59.79

(CH₃), 60.60 (CH₂–N), 63.25 (C_q), 121.78 (CN), 163.96

(CH), 171.21 (CO). MS (ESI−) m/z (%): 319 (100) [Lig − H]⁻,

355 (2) [Lig + Cl]⁻, 382 (5) [M − H]⁻. IR (KBr): ν = 1562, 1637,

1683 (s, ν_CO; ν_CN), 2194, 2211 (s, ν_CN) cm⁻¹. Anal. calcd.

for C₁₅H₁₈N₄O₄Zn·H₂O: C, 44.85; H, 5.02; N, 13.95; found: C,

44.64; H, 5.02; N, 14.08. ICP-AES: anal. calcd. for

C₁₅H₁₈N₄O₄Zn: Zn, 17.04; found: Zn, 17.86.

Zn[7a]. Procedure Zn-b with ligand 7a (750 mg, 2.08 mmol),

THF (15 ml) and diethylzinc in hexane (1 M) (2.1 ml, 2.10

mmol). Yield: white solid (0.78 g, 1.85 mmol, 89%). ¹H-NMR

(400 MHz, SO(CD₃)₂): δ = 1.24 (m, 10H, CH₃, CH_2,cyclo), 1.80 (d,

3

³J_HH= 8.3 Hz, 2H, CH_2,cyclo), 2.25 (d, J_HH= 11.8 Hz, 2H, CH_2,

_cyclo), 2.83 (d, ³J_HH= 8.7 Hz, 2H, CH_cyclo), 4.16 (q, ³J_HH= 7.1 Hz,

4H, CH₂), 7.69 (s, 2H, CH). ¹³C{¹H}-NMR (100 MHz, SO(CD₃)₂):

δ = 14.395 (CH₃), 23.903 (CH_2,cyclo), 27.482 (CH_2,cyclo), 59.916

(CH₃), 64.123 (CH_cyclo), 121.996 (C_q), 158.983 (CH), 171.716

(CO). MS (ESI+) m/z (%): 269 (45) [Lig − 2OEt]⁺, 289 (40) [Lig

− 2OEt + NH₄]⁺, 315 (100) [Lig − OEt]⁺, 333 (45) [Lig − OEt +

NH₄]⁺, 361 (81) [Lig + H]⁺, 378 (52) [Lig + NH₄]⁺, 383 (44) [Lig +

Na]⁺, 423 (5) [M + H]⁺, 743 (20) [2 Lig + Na]⁺. IR (KBr): ν = 1563,

1639, 1680 (s, ν_CO; ν_CN), 2201, 2213 (s, ν_CN) cm⁻¹. Anal.

calcd. for C₁₈H₂₂N₄O₄Zn·1/2OH: C, 50.01; H, 5.25; N, 12.96;

found: C, 50.20; H, 5.40; N, 13.09. ICP-AES: anal. calcd. for

C₁₈H₂₂N₄O₄Zn: Zn, 15.43; found: Zn, 15.15.

Zn[5b]. Procedure Zn-a with ligand 5b (750 mg, 1.81

mmol), THF (15 ml) and diethylzinc in hexane (1 M) (1.8 ml,

1

1.80 mmol). Yield: white solid (0.80 g, 1.68 mmol, 93%). H-

3

NMR (400 MHz, SO(CD₃)₂): δ = 1.16 (t, J_HH= 7.1 Hz, 6H,

3

CH₃), 1.23 (t, J_HH= 7.1 Hz, 6H, CH₃), 1.74 (m, 2H, CH₂–

3

CH₂), 3.54 (m, 4H, CH₂–N), 3.99 (q, J_HH= 7.1 Hz, 6H, CH₂),

3

4.14 (q, J_HH= 7.1 Hz, 6H, CH₂), 8.25 (s, 2H, CH). ¹³C{¹H}-

NMR (100 MHz, SO(CD₃)₂): δ = 14.51 (CH₃), 31.74 (CH₂–CH₂),

57.90, 59.05 (CH₂), 61.35 (CH₂–N), 82.93 (C_q), 166.41 (CH),

166.57, 171.02 (CO). MS (ESI−) m/z (%): 367 (9) [Lig −

OEt]⁻, 413 (100) [Lig − H]⁻, 511 (4) [M + Cl]⁻. IR (KBr): ν =

Zn[7b]. Procedure Zn-a with ligand 7b (5.00 g, 1.10 mmol),

THF (10 ml) and diethylzinc in hexane (1 M) (1.1 ml, 1.10

mmol). Yield: yellowish solid (0.57 g, 1.11 mmol, >99%).

Catal. Sci. Technol., 2014, 4, 1658–1673 | 1671

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¹H-NMR (400 MHz, SO(CD₃)₂): δ = 1.20 (m, 14H, CH₃,

Procedure of the catalytic screening tests

3

CH_2,cyclo), 1.33 (m, 2H, CH_2,cyclo), 1.84 (d, J_HH= 5.7 Hz, 2H,

The efficiency of the zinc catalysts was tested in a “test

bench” consisting of eight 70 ml autoclaves (material 1.4571-

stainless austenitic steel-316Ti, 70 ml, P_max200 bar, T_max

250 °C) equipped with multimeters (Agilent 34970A Data

Acquisition/Data Logger Switch Unit + 34901A 20 Channel

Multiplexer) and PCs for p-,T-acquisition and aluminum

blocks for external heating. The selected catalyst and the

cocatalyst were loaded in an autoclave that was afterwards

heated under vacuum. After cooling, the autoclave was

purged with argon and the epoxide (10 ml, 0.143 mol) was

injected via a port of the autoclave. Afterwards, the autoclave

was loaded with a definite quantity of CO₂(weighted) and

the reaction started (heating). After a reaction time of 20 h

the autoclaves were cooled down to room temperature and

excess CO₂was removed by venting slowly the autoclaves

under a fume hood. The reaction mixtures/products were

collected from the autoclaves by dissolving them in

dichloromethane, which was afterwards removed from the

products in vacuum, like the traces of unreacted epoxide.

The experiments under a pressure of 2 bar were realized by

connecting the autoclave to a CO₂-cylinder during the whole

course of the reaction, the CO₂-line being equipped with a cali-

brated back pressure regulator. After adding the epoxide

(10 ml, 0.143 mol) into the autoclave, it was connected to the

CO₂-container and the autoclave was heated. After a short

period of time, the pressure in the autoclave evens out at 2 bar.

After drying the product mixture under vacuum, it was

analyzed by IR and NMR spectroscopy. IR spectroscopy was

used to check the presence of cyclic carbonate by its charac-

teristic CO-vibrations at 1800 cm⁻¹.

CH_2,cyclo), 2.17 (d, ³J_HH= 10.8 Hz, 2H, CH_2,cyclo), 2.85 (d, ³J_HH

=

6.5 Hz, 2H, CH_cyclo), 4.00 (q, ³J_HH= 7.1 Hz, 4H, CH₂), 4.14 (m,

4H, CH₂), 8.39 (s, 2H, CH). ¹³C{¹H}-NMR (100 MHz, SO(CD₃)₂):

δ = 14.16 (CH₃), 23.94 (CH_2,cyclo), 31.48 (CH_2,cyclo), 58.48, 58.65

(CH₂), 62.60 (CH_2,cyclo), 88.20 (C_q), 158.82 (CH), 164.83,

167.69 (CO). MS (ESI+) m/z (%): 455 (27) [Lig + H]⁺, 477 (88)

[Lig + Na]⁺, 517 (7) [M + H]⁺, 539 (17) [M + Na]⁺, 930 (100)

[2Lig + Na]⁺. IR (KBr): ν = 1592, 1654, 1676, 1713 (s, ν_CO

;

ν_CN) cm⁻¹. Anal. calcd. for C₂₂H₃₂N₂O₈Zn·H₂O·OH: C, 47.79;

H, 6.38; N, 5.07; found: C, 48.07; H, 6.56; N, 5.05. ICP-AES:

anal. calcd. for C₂₂H₃₂N₂O₈Zn: Zn, 12.62; found: Zn, 12.66.

Zn[8a]. Procedure Zn-a with ligand 8a (750 mg, 2.04

mmol), THF (15 ml) and diethylzinc in hexane (1 M) (2.0 ml,

2.00 mmol). Yield: white solid (0.26 g, 0.60 mmol, 29%).

3

¹H-NMR (400 MHz, SO(CD₃)₂): δ = 1.24 (t, J_HH= 7.1 Hz, 3H,

3

CH₃), 1.28 (t, J_HH= 7.1 Hz, 3H, CH₃), 4.16 (q, J_HH= 7.0 Hz,

3

2H, CH₂), 4.24 (q, J_HH= 7.1 Hz, 2H, CH₂), 4.46 (s, 2H, CH₂–

N), 7.11 (m, 2H, CH_aromat), 7.24 (dd, J_HH= 1.3 Hz, J_HH= 7.6

3

4

3

4

Hz, 1H, CH_aromat), 7.32 (dt, J_HH= 1.5 Hz, J_HH= 7.7 Hz, 1H,

CH_aromat), 7.87 (s, 1H, CH), 7.91 (s, 1H, CH). ¹³C{¹H}-NMR

(100 MHz, SO(CD₃)₂): δ = 14.35, 14.42 (CH₃), 59.97 (CH₂),

60.68 (CH₂), 61.47 (CH₂–N), 63.88 (C_q), 68.37 (C_q), 120.52

(CH_aromat), 120.97 (CN), 121.60 (CN), 124.61 (CH_aromat),

129.03, 129.13 (CH_aromat), 131.10 (C_q,aromat), 149.00 (C_q,aromat),

161.56 (CH), 164.04 (CH), 171.18 (CO), 171.72 (CO). MS

(ESI+) m/z (%): 369 (100) [Lig + H]⁺, 386 (62) [Lig + NH₄]⁺, 391

(98) [Lig + Na]⁺, 431 (10) [M + H]⁺, 453 (3) [M + Na]⁺. MS (ESI−)

m/z (%): 367 (100) [Lig − H]⁻, 489 (34) [M + CH₃COO]⁻, 797 (9)

[M

+

Lig

−

H]⁻. HR-MS (ESI+) m/z: anal. calcd. for

C₁₉H₁₉N₄O₄Zn: 431.06923; found: 431.06960. IR (KBr): ν =

1553, 1628 (s, ν_CO; ν_CN), 2202 (s, ν_CN) cm⁻¹. Anal. calcd.

for C₁₉H₁₈N₄O₄Zn: C, 52.86; H, 4.20; N, 12.98; found: C, 52.17;

H, 4.33; N, 12.83. ICP-AES: anal. calcd. for C₁₉H₁₈N₄O₄Zn: Zn,

15.14; found: Zn, 15.61. UV/Vis (MeCN): λ_max(ε) = 220 (30

290), 297 (35 960), 327 (21 240) nm (mol⁻¹dm³cm⁻¹).

After the NMR (in C₆D₆) revealed that the product con-

tains pure cyclic carbonate, its yield was determined by

weighing the dried product and subtracting the amount of

catalyst and cocatalyst from the result (this method delivers

more reliable results than the two-step method: distillation

and weighing of the cyclic carbonate).

Zn[8b]. Procedure Zn-a with ligand 8b (1.00 g, 2.16 mmol),

THF (15 ml) and diethylzinc in hexane (1 M) (2.2 ml, 2.20

Acknowledgements

1

mmol). Yield: beige solid (1.08 g, 2.05 mmol, 95%). H-NMR

3

(400 MHz, SO(CD₃)₂): δ = 1.19, 1.20, 1.24, 1.28 (t, J_HH= 7.1

We thank the Helmholtz Research School “Energy-Related

Catalysis” for financial support. We also thank Marion

Lenzner (DSC) and Hermann Köhler (ICP).

3

Hz, 12H, CH₃), 4.02, 4.06, 4.14, 4.22 (q, J_HH= 7.1 Hz, 8H,

3

CH₂), 4.47 (s, 2H, CH₂–N), 7.00 (d, J_HH= 7.7 Hz, 1H,

3

4

CH_aromat), 7.09 (dt, J_HH= 1.0 Hz, J_HH= 7.4 Hz, 1H,

CH_aromat), 7.33 (m, 2H, CH_aromat), 8.49 (s, 2H, CH). ¹³C{¹H}-

NMR (100 MHz, SO(CD₃)₂): δ = 14.34, 14.35, 14.41, 14.54

(CH₃), 58.05, 58.44, 59.31, 59.93 (CH₂), 62.70 (CH₂–N), 83.68,

87.54 (C_q), 120.15 (CH_aromat), 124.15 (CH_aromat), 129.09,

129.14 (CH_aromat), 131.63 (CH_q,aromat), 150.12 (CH_q,aromat),

163.59 (CH), 166.29 (CH), 166.53, 171.12 (CO). MS (ESI+)

m/z (%): 415 (7) [Lig − OEt − H]⁻, 461 (100) [Lig − H]⁻, 507 (5)

[Lig + HCOO]⁻, 583 (9) [M + CH₃COO]⁻. IR (KBr): ν = 1589,

1616, 1641, 1664, 1694, 1706 (s, ν_CO; ν_CN) cm⁻¹. Anal.

calcd. for C₂₃H₂₈N₂O₈Zn·H₂O: C, 50.79; H, 5.56; N, 5.15;

found: C, 50.99; H, 5.60; N, 5.23. ICP-AES: anal. calcd. for

C₂₃H₂₈N₂O₈Zn: Zn, 12.43; found: Zn, 12.31.

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New air-stable zinc complexes formed from cyanoacrylate- and methylenemalonate-based [N2O2]-ligands and their role as catalysts in epoxide-CO2 coupling

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