Tetranitratopalladate(II) Salts with Tetraalkylammonium Cations: Structural Aspects, Reactivity, and Applicability toward Palladium Deposition for Catalytic Applications

Deposition for Catalytic Applications

Article

Tetranitratopalladate(II) Salts with Tetraalkylammonium Cations:

Structural Aspects, Reactivity, and Applicability toward Palladium

Danila Vasilchenko,* Polina Topchiyan, Semen Berdyugin, Pavel Plyusnin, Vladimir Shayapov,

Iraida Baidina, Vladislav Komarov, Andrey Bukhtiyarov, and Evgeny Gerasimov

Cite This: Inorg. Chem. 2021, 60, 2983 −2995

Read Online

ACCESS

Metrics & More

Article Recommendations

sı Supporting Information

ABSTRACT: A series of salts (R N) [Pd(NO ) ] (R = CH , C H , n-

3 4

C H ; 1−3) were synthesized in high yield from a nitric acid solution of

palladium. The salts were characterized by a combination of

physicochemical methods, and their crystal structures were determined

2−

by X-ray diﬀraction. The conformation of the [Pd(NO ) ] anion was

studied in detail using crystal structure data and density functional theory

calculations. A combination of nonhygroscopicity and stability under

normal conditions, together with thermolability, high solubility in various

solvents, and the lability of nitrato ligands, makes salts 1−3 valuable

starting materials for the synthesis of Pd compounds and the preparation of Pd-containing catalysts. In this work, these applications

were illustrated by the synthesis of heteroleptic Pd(II) nitrato complexes with N-donor ligands and the preparation of Pd Ni /

.1 0.9

SiO catalysts, which worked well in H generation from hydrazine hydrate. Generally, it was shown that up to several weight percent

of Pd can be deposited on various oxide/hydroxide supports using a straightforward chemisorption procedure from acetone

solutions of 1−3.

. INTRODUCTION

after prolonged storage. The closely related thermolabile salts

NO) [Pd(NO ) ] and Pd(NO ) can be prepared by

(

3 2

Materials prepared by the deposition of palladium on diverse

supports are widely used in heterogeneous catalysis, account-

ing for about 90% of the annual demands of this metal. The

dissolution of Pd in liquid N O^o^r^f^u^mⁱⁿ^g^H^N^O3^;

18,19

unfortunately, they are extremely sensitive to moisture.

most resource-intensive application of such materials is in the

The series of salts M [Pd(NO ) ] (M = Na, K, Rb, Cs) were

2 3 4

20−22

automotive emission depollution system, but they are also

vital for important industrial processes, such as ethylene glycol

also synthesized

and characterized, but their lack of

solubility in organic solvents and the unavoidable residue of

synthesis (via dimethyl oxalate) and the production of

MNO salts make them less attractive as starting compounds

puriﬁed terephthalic acid. Along with other noble metals,

Pd-containing catalysts are of great interest to research

directed toward the development of hydrogen energy systems,

for catalyst preparation and synthesis.

Recently, we have reported on anionic platinum nitrato

complexes, which were isolated as the tetraalkylammonium

salts (R N) [Pt(NO ) ] and (R N) [Pt (OH) (NO ) ] (R =

8,9

including fuel cell fabrication, hydrogen storage,

hydrogen generation.

and

10,11

3 6

3,24

3 8

CH , ..., C H ).

These salts are stabile under normal

Among the palladium-containing compounds used for the

preparation of supported catalysts, the palladium nitrate trans-

conditions, possess a high solubility in various organic solvents,

and decompose at moderate temperatures. Moreover, the

chemisorption of platinum onto ceria and titania from acetone

solutions of the nitrato complexes was successfully utilized as a

method for the preparation of eﬃcient catalysts for CO

[

Pd(NO ) (H O) ] (CAS: 32916-07-7) is of great impor-

3 2 2 2

2−14

tance.

The thermolability of this reagent is a major

advantage (decomposition at about 100 °C), resulting in the

ready formation of metallic Pd nanoparticles or ionic Pd

species on the surface of the support under mild conditions.

Furthermore, the substitutional lability of the nitrato ligands in

Pd(NO ) (H O) ] provide a straightforward route to the

Received: October 14, 2020

Published: February 10, 2021

[

heteroleptic palladium(II) complexes by the sequential

reactions [Pd(NO ) (H O) ] → [Pd(NO ) L ] →

[

PdL L ].

2 2

Despite the noted beneﬁts, the hygroscopicity of this

palladium nitrate causes diﬃculties in handling, especially

2021 American Chemical Society

983

Inorg. Chem. 2021, 60, 2983−2995

Inorganic Chemistry

Article

3,25

oxidation

TiO₂).

(Pt/CeO ) and H₂photogeneration (Pt/

(pyHNO ) or 0.085 mmol of 1,10-phenanthroline-5,6-dione (phd),

correspondingly dissolved in 2 mL of acetone, was added to a freshly

prepared solution of the salt 2 (50 mg, 0.081 mmol) in 1 mL of

acetone. The mixture was stirred to obtain a clear solution and then

evaporated to about 1.5 mL in an air stream and placed in a

refrigerator (5 °C) for crystallization in a closed vial. After 40 min, the

ﬁne crystalline precipitates were ﬁltered oﬀ with a porous PTFE

membrane (0.22 μm), washed with acetone, and dried in an air

stream. The yields were 85% (4) and 80% (5). Single crystals for an

X-ray crystallographic study were picked directly from a mass of as-

prepared products.

In this work, we describe the method of preparation,

structure, and properties of the series of salts (R N) [Pd-

NO ) ] (R = CH , C H , n-C H , 1−3). Essentially, these

tetranitratopalladate anion containing salts are useful starting

compounds due to their stability under normal conditions and

nonhygroscopicity, combined with the general lability and

thermolability of nitrato complexes. The applicability of salts

(

−3 as suitable materials for the synthesis of palladium

complexes and the preparation of catalysts were demonstrated

by the synthesis of heteroleptic Pd(II) nitrato complexes with

N-donor ligands and the preparation of Pd Ni /SiO

2.2.2.1. [Pd(py) (NO ) ] (4). Anal. Calcd (found) for

3 2

Pd: C, 30.91 (30.9); H, 2.59 (2.6); N, 14.42 (14.1).

.2.2.2. (Et N)[Pd(phd)(NO ) ]NO ·C H O (5). Anal. Calcd (found)

3 2

3 6

0.9

for C H N O Pd: C, 39.98 (40.2); H, 4.67 (4.5); N, 12.16 (12.0).

catalysts, which are eﬀective in hydrazine hydrate decom-

23 32

.3. Apparatus. N NMR spectra were recorded at 50.7 MHz

position.

using an Avance III 500 Bruker spectrometer with a 5 mm broad-band

probe. A 90° excitation pulse of 14 μs was applied. The spectra were

. EXPERIMENTAL SECTION

recorded at −45 ± 0.2 °C. δ( N) values (ppm) are reported relative

2.1. Reagents. All reactants were purchased from commercial

to an external reference, a 1 M aqueous solution of Na NO . The

suppliers and used as received. Ultrapure nitric acid (70 wt %, 15.9

M), produced by EuroChem (Novomoskovskiy Azot), was used in all

cases. Pure palladium powder (99.99%) acid produced by “The

Gulidov Krasnoyarsk Non-Ferrous Metals Plant” Open Joint Stock

Company was used. The (R N)NO (R = Me, Et, n-Pr, n-Bu) nitrate

salts were prepared by the action of concentrated nitric acid on the

corresponding bromide salts ((R N)Br, Acros Organics, 98%),

spectral window was about 600 Hz (10−12 ppm), and the delay

between pulses was 100 s. N-enriched 10 M nitric acid (98 atom %

N) (Sigma-Aldrich, 609323) was used for the solution preparation.

An aliquot of the enriched nitric acid was mixed with a calculated

volume of the Pd solution in concentrated naturally abundant nitric

acid (15.9 M) to obtain 25 atom % N enrichment. To obtain

integral intensities for the signals and evaluate the Pd spices

recrystallized from H O/HNO solutions, and dried in a stream of

air. Acetone was dried prior to use by means of the NaI solvate.

distribution, the N NMR spectra were ﬁtted by the superposition

of Voight proﬁles as implemented in ACD/Laboratories NMR

processor software (version 12.01).

,10-Phenanthroline-5,6-dione was prepared according to the

reported method.

Elemental CHN analysis was carried out on a Vario MICRO cube

CHNS analyzer. The composition of Pd-Ni/SiO₂catalysts was

determined using micro beam X-ray ﬂuorescence analysis on a

M1MISTRAL Micro-XRF spectrometer (Bruker).

Cerium dioxide was prepared by the thermal decomposition of

Ce(NO )·6H O at 450 °C for 6 h in air. Ni(OH) was precipitated

from a solution of Ni(NO ) by the addition of NaOH and washed

thoroughly with water and then with acetone, and the product was

ﬁltered oﬀ and dried in an air stream and then under vacuum for 24 h.

SiO (Polisorb, 220 m /g), TiO (Hombiﬁne N, 320 m /g), and

Al O (Pural TM80, 180 m /g) were used as received.

Diﬀerential thermal analysis of the salts 1−3 was carried out with a

TG 209 F1 Iris instrument (NETZSCH) in a He (70 mL/min)

stream at a heating rate of 10 °C/min.

Infrared spectra for tablets of KBr were recorded in the range of

2.2. Complex Preparation. 2.2.1. Preparation of the Salts

−1

00−4000 cm on a Scimitar FTS 2000 apparatus. Electron

(

R N) [Pd(NO ) ] (R = Me (1), Et (2), n-Pr (3)). Compounds 1−3 were

3 4

absorbance spectra of the solutions were recorded with a PG

Instruments T60 UV−vis single-beam spectrophotometer; quartz cells

with a 1 cm optical path length were used. Diﬀuse reﬂectance spectra

were recorded in the 240−800 nm range with a Kolibri-2 compact

multichannel spectrometer (VMK-Optoelektronika) equipped with a

ﬁber optic cable (Ocean Optics, QR-400−7) and D/W lamp

synthesized using the procedure described below. Palladium powder

1 mmol) was dissolved in 3 mL of concentrated nitric acid with

(

constant stirring. The solution was heated at 60 °C until NO fumes

ceased, the resulting solution was cooled to room temperature, and 3

mmol of the corresponding salt (R N)NO (R = Me, Et, n-Pr) was

then added. After complete dissolution of the salt, the solution was

evaporated in an air stream to minimize the volume to about 0.75 mL.

The crystalline product was ﬁltered oﬀ and dried in an air stream

before being washed with 25 mL of diethyl ether and then dried in an

air stream. Due to the high solubility of the (R N)[Pd(NO ) ] salts,

the yield mainly depends on the degree of solution evaporation and

was about 80% in the described protocol. Single crystals of

compounds 1−3 were picked directly from the nitric acid solutions.

(

AvaLight-DHS). BaSO powder was used as a reference.

Raman spectra were collected using a LabRAM HR Evolution

(

Horiba) spectrometer with excitation by the 514 nm line of an Ar⁺

ion laser. The spectra at room temperature were obtained in the

backscattering geometry with a Raman microscope. The laser beam

was focused to a diameter of 2 μm using a LMPlan FL 50x/0.50

3 4

−

Olympus objective. The spectral resolution was 3 cm . The laser

power on the sample surface was about 0.2 mW.

.2.1.1. (Me N) [Pd(NO ) ] (1). Anal. Calcd (found) for

4 2 3 4

X-ray powder diﬀraction analysis of the polycrystalline samples was

carried out on a DRON-RM4 diﬀractometer (Cu Kα radiation,

graphite monochromator in the reﬂected beam, scintillation detector

with amplitude discrimination). The samples were prepared by

deposition of a suspension in hexane on the polished side of a cell

made of fused quartz. A sample of polycrystalline silicon (a = 5.4309

Å), prepared similarly, was used as an external standard.

The structure and microstructure of the samples were studied by

high-resolution transmission electron microscopy (TEM) using a

ThemisZ electron microscope (Thermo Fisher Scientiﬁc, USA) with

an accelerating voltage of 200 kV and a maximum lattice resolution of

0.06 nm. The device is equipped with a SuperX energy-dispersive X-

ray spectrometer (EDX) (Thermo Fisher Scientiﬁc, USA) with a

semiconductor Si detector with an energy resolution of 128 eV. For

electron microscopy studies, sample particles were deposited on

perforated carbon substrates attached to aluminum grids using the

C H N O Pd: C, 19.11 (18.8); H, 4.81 (4.8); N, 16.72 (16.6). IR

−

(

cm , KBr): 3046 (ν (CH )), 1495 (δ (CH )), 1412 (δ (CH )),

as 3 as 3 s 3

510, 1484 (ν (NO )), 1251 (ν (NO )), 967 (ν (NO )), 946

5 3 1 3 2 3

(

ν (C−N)), 797, 767 (ν (NO )).

.2.1.2. (Et N) [Pd(NO ) ] (2). Anal. Calcd (found) for

4 2 3 4

C H N O Pd: C, 31.25 (30.9); H, 6.56 (6.5); N, 13.67 (13.6).

−

IR (cm , KBr): 2989 (ν (CH )), 2954 (ν(C−H)), 1438

(

δ (CH )), 1389 (δ (CH )), 1504, 1480 (ν (NO )), 1250

as 3 s 3 5 3

ν (NO )), 975 (ν (NO )), 1002 (ν (C−N)), 789, 775 (ν (NO )).

.2.1.3. (Pr N) [Pd(NO ) ] (3). Anal. Calcd (found) for

4 2 3 4

C H N O Pd: C, 39.64 (39.2); H, 7.76 (7.4); N, 11.56 (11.5).

−

IR (cm , KBr): 2977 (ν (CH )), 2937 (ν (CH )), 2879 (ν (CH )),

470 (δ (CH )), 1387 (δ (CH )), 1480 (ν (NO )), 1252

as 3 s 3 5 3

(ν (NO )), 980 (ν (NO )), 968 (ν (C−N)), 799 (ν (NO )).

.2.2. Reactions of (Et N) [Pd(NO ) ] with N-Donor Ligands. To

4 2 3 4

prepare complexes 4 and 5, 0.17 mmol of pyridinium nitrate

984

Inorg. Chem. 2021, 60, 2983−2995

Inorganic Chemistry

Article

ultrasonic dispersant UZD-1UCH2. Images were recorded using a

Ceta 16 CCD sensor (Thermo Fisher Scientiﬁc, USA).

The XPS measurements of samples were performed on a SPECS

relativistic eﬀects were taken into account with a scalar zero-order

relativistic approximation (ZORA).

2.6. Pd Sorption on Supporting Materials. The general

(

Germany) photoelectron spectrometer equipped with a PHOIBOS-

50 hemispherical energy analyzer and Al Kα irradiation (hν = 1486.6

procedure described below was used to study the ability of Al

CeO , TiO , SiO , and Ni(OH) to chemisorb palladium species from

solutions of the complexes (R N) [Pd(NO ]. Oxides were calcined

prior to use at 150 °C under vacuum for 24 h; Ni(OH) was also

treated under vacuum at room temperature for 24 h. Then, 100 mg of

the appropriate solid material was added to a freshly prepared 10 mM

O ,

2 3

eV, 200 W). The binding energy (BE) scale was precalibrated using

the positions of the photoelectron of Au 4f₇_/₂(BE = 84.0 eV) and Cu

was better than 8 × 10 . The binding energy of peaks was calibrated

by the position of the C 1s peak (BE = 284.7 eV) corresponding to

the hydrocarbons present on the sample surface. Spectral analysis and

peak ﬁtting were performed with XPSPeak 4.1 software. Integral

intensities of the spectra were corrected by their respective atomic

)

3 4

p₃_/₂(BE = 932.67 eV) core level peaks. The residual gas pressure

−

solution of (R N) [Pd(NO ) ] in 1.5 mL of dry acetone in a 3 mL

3 4

vial, and the mixture was stirred vigorously. The resulting suspension

was centrifuged at 4000 rpm, and the color of the supernatant was

visually checked. Additionally, the completeness of the uptake was

conﬁrmed by UV−vis spectrophotometry at 380 nm. To evaluate the

maximum uptake for a given material, the protocol described above

was repeated with solutions of variable Pd concentrations.

sensitivity factors.

2.4. X-ray Crystallographic Data Collection and Reﬁnement.

Crystal data and experimental details for compounds 1−3 and 5 are

given in Table S1 in the Supporting Information. Experimental data

for the determination of the crystal structures of 1 and 4 were

collected on a Bruker D8 Venture diﬀractometer, while a Bruker

APEX-II CCD diﬀractometer at 150 K with graphite-monochromated

Mo Kα radiation (λ = 0.7107 Å) was used for the crystal structures of

.7. Preparation of the Pd-Ni/SiO Catalyst. Nickel nitrate was

dissolved in acetone, and 3 g of SiO was then added. The resulting

suspension was stirred for 15 min, and the solvent was then removed

in an air stream with constant stirring. The resulting solid product was

poured into 100 mL of a 0.2 M NaOH aqueous solution, and the

suspension was stirred for 30 min. The solid product was isolated by

centrifugation, washed with water up to the supernatant pH 7, and

then washed three times with acetone and dried under vacuum for 24

h. The Ni(OH) /SiO composite obtained was redispersed in

, 3, and 5. All calculations were carried out with the SHELX-97

crystallographic software package. The structures were solved by the

standard heavy-atom method and reﬁned by the anisotropic

approximation. The H atoms were reﬁned in their geometrically

calculated positions; a riding model was used for this purpose.

Absorption corrections were applied empirically using the SADABS

software. A Hirshfeld molecular surface analysis was performed

using the Crystal Explorer 3.1 program.

CCDC 2026407 (1), 2025660 (2), 2008746 (3), and 2026628 (5)

contain the supplementary crystallographic data for this paper. These

data can be obtained free of charge from the Cambridge Crystallo-

graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif .

acetone, and a solution of salt 2 (300 mg) in 5 mL of acetone was

added to the suspension, with constant stirring. After 10 min of

stirring, the solid material was isolated by ﬁltration on a PTFE

membrane (0.22 μm), washed with 50 mL of acetone, and dried in an

air stream. The resulting solid material was calcined at 200 °C in an

air atmosphere and then reduced at 400 °C in a stream of pure

hydrogen (30 min).

.8. Catalytic Hydrazine Decomposition over Pd-Ni/SiO

Catalyst. The release of a gaseous product during the catalytic

decomposition of hydrazine hydrate was carried out using an

installation that includes a closed 10 mL vial connected to a gas

buret. The temperature of the vial was maintained with a

thermostated water jacket. In a typical procedure, the as-prepared

catalyst (300 mg) was placed in the vial and dispersed in 1 mL of 1 M

NaOH. The vial was then closed and connected to a buret. The

reaction was initiated by injection of hydrazine hydrate (25 μL, 0.463

mmol of N H ; the exact concentration was determined by an acid−

2.5. Density Functional Theory (DFT) Calculations. Geometry

optimization was carried out using the Gaussian 09C software

package. Structures of [Pd(NO ) ] anions from X-ray crystallo-

graphic data were used as initial states. The calculations were

performed using the B3LYP

2−

34−37

38−42

method and the LANL2DZ

basis set for entire molecules placed in a cavity within the water

reaction ﬁeld (SCRF solvent method ). The calculations of IR

frequencies showed no imaginary vibrations, emphasizing that the

local minima were achieved in all cases. The rigid PES scans for

rotation of the nitrato group were performed by the following

procedure: the dihedral angle O−Pd−O−N was modiﬁed from 152

to −14° with a 2 or 4° step, and single-point calculations were

performed at each point.

base titration with methyl red indicator) to the suspension in the vial.

The volume of evolved gases (N + H ) was monitored using a water

replacement method. Water in the trap was acidiﬁed with H SO to

ensure complete NH₃capture. The selectivity (α) and turnover

frequency (TOF) values were calculated in accordance with the

formulas

The relaxed potential energy surface scans (PES scans) for

2−

transformations between two modiﬁcations of [Pd(NO ) ] (an

α = (3λ − 1)/8 where λ = n(N + H )/n(N H )

outer-sphere mechanism) and also for substitution of one nitrato

ligand with water or acetone were performed with the ADF-2016

software package using the TZP basis set for all atoms and the B3LYP

functional. Water, chosen as a solvent, was modeled with the

COSMO method. The relativistic eﬀects were taken into account with

a scalar zero-order relativistic approximation (ZORA). The scans

were performed by the following scheme: the substituent from the

TOF = n(H )/(n(Pd) × t)

3. RESULTS AND DISCUSSION

3.1. Synthesis and Properties of the Salts (R N) [Pd-

−

outer sphere of [Pd(NO ) ] (NO , H O, or acetone) was moved

(NO ) ]. Dissolution of metallic palladium in nitric acid results

3 4

to palladium atom by an oxygen atom; therefore, the Pd−O distance

decreased from 5.0 to 2.1 Å (the last distance is close to the

equilibrium Pd−O distance). The geometry was optimized at each

point of the scan. Also, the geometry of the ﬁnal state ([Pd-

in the formation of the palladium(II) aqua-nitratocomplex

46,47

series:

Pd + (4 + n)HNO + (4 − n)H O

n−

−

(

NO ) (L)] , L = NO , H O,r acetone, n = 1, 2) and NO was

3 3 3 2 3

−n

optimized in two independent calculations modeling the situation

when nitrate was moved far away from the obtained complex, and the

sum of the two energies (E([Pd(NO ) (L)] ) + E(NO )) was used

= [Pd(NO ) (H O)₄₋_n]

+ 2NO + 2NO

−

+ 2H2O + nH⁺

n−

−

for plotting.

As reported previously, in concentrated nitric acid solution

The calculations of the electron localization function (ELF) for all

−n

(

above 13 M), the anionic species [Pd(NO ) (H O)4−n^]

3 n 2

47,48

isomers were performed with the ADF-2016 software package, using

the TZP basis set for all atoms and the B3LYP

chosen as a solvent, was modeled with the COSMO method. The

34−37

functional. Water,

with n = 3, 4 dominate.

A fast ligand exchange around the

Pd centers was observed in such solutions, but direct

985

Inorg. Chem. 2021, 60, 2983−2995

Inorganic Chemistry

speciation studies using N NMR are possible at low

temperatures (below −40 °C). The typical N NMR spectrum

of the Pd nitric acid solution, which was used to prepare the

Article

data that conﬁrms their phase homogeneity (Figure S1). In the

infrared spectra of the prepared salts 1−3, the series of strong

bands observed at about 1500, 1250, 970, and 790 cm⁻

(Figure S2) correspond to the ν , ν , ν , and ν vibrations of

coordinated NO₃ions. The overall position of the signals is

consistent with the unidentate coordination mode of the

R N) [Pd(NO ) ] salts, is shown in Figure 1 . From a ﬁtting

4 2 3 4

−

nitrato ligand. The frequency of the ν band is considerably

lower than the position of the corresponding bands reported

−

2−

23,51

for [Au(NO ) ] and [Pt(NO ) ] anions,

which implies

3 6

−

a lower polarization degree of NO₃by Pd ions.

Interestingly, a close ν band frequency value was found for

a rhodium(III) complex salt containing a mixture of the trans-

−

3−

[

Rh(H O) (NO ) ] and [Rh(NO ) ] nitrato complexes.

2 2 3 4 3 6

Raman spectra of the salts 1−3 were also studied (Figure S3).

Aside from signals corresponding to the R N cations, which

were deduced by comparison with the spectra of the

corresponding chlorides (R NCl), strong bands at 320, 725,

−

80, and 995 cm can be found that are attributed to the

Figure 1. ¹⁵N NMR spectrum of a palladium nitric acid solution

C(Pd) = 0.33 M and C(HNO ) = 13.5 M) at −45 °C. The signals

stretching and bending vibrationa of Pd-ONO groups. The

(

positions of these signals are also in agreement with values

2−

are assigned according to previous data. Legend: 4, [Pd(NO ) ] ;

−

reported for salts containing the [Au(NO ) ] anion.

−

3 4

3₂

and 3 , [Pd(NO ) (H O)] ; 2t, trans-[Pd(NO ) (H O) ]; 2c−

3.2. Reactivity of the Salts. The salts 1−3 are not

cis-[Pd(NO ) (H O) ].

hygroscopic, and both the bulk crystals and powders can be

stored in open containers for prolonged periods (>1 year)

without notable moisture uptake. On the other hand, on

dissolution of the salts in water, hydrolysis proceeds almost

immediately. As evidenced from UV−vis spectra of the

of the spectrum with a superposition of Voigt proﬁles, the next

2−

fraction of the species can be calculated: 27% [Pd(NO ) ] ,

−

6% [Pd(NO ) (H O)] , 8% trans-[Pd(NO ) (H O) ], and

3 3 2 3 2 2 2

% cis-[Pd(NO ) (H O) ].

Evaporation of a nitric acid solution of palladium (13−16 M

2−

resulting yellow solutions (Figure 3A), [Pd(NO ) ] anions

3 4

are almost completely aquated, and the palladium(II) aqua ion

HNO , C(Pd) = 0.33 M) with an excess of the corresponding

53,54

(

380 nm, ε = 80)

dominates, accompanied by only traces

(

R N)NO (R = Me, Et, Pr) salt results in the formation of

4 3

of the aqua nitrato species. An additional weak band at 301 nm

salts (R N) [Pd(NO ) ] (1−3). Fast evaporation leads to the

3 4

corresponds to the absorption of the free nitrate ion.

precipitation of small, badly shaped crystals (Figure 2 a −c),

The salts can also be easily dissolved in acetone, THF, and

acetonitrile, but they are insoluble in toluene, hexane, dioxane,

ethyl acetate, and diethyl ether. On dissolution in organic

solvents, rapid solvolysis proceeds, accompanied by a color

change from brown to yellow and the corresponding changes

in the UV−vis spectra (Figure 3B). In addition to the long-

wave band at 450 nm, which is characteristic for d−d

46,53,54

transitions in nitrato complexes of Pd(II),

a strong

band arises at about 380 nm, corresponding to a ligand to

metal charge transfer. Such changes, by analogy with the

spectral changes observed during the aquation process, can be

attributed to the substitution of nitrato ligands by organic

solvent molecules S, leading to the formation of [Pd-

n−2

(

S) (NO )

]

species.

3 4−n

The prepared salts 1−3 possess suﬃcient thermal stability

and do not decompose up to 200 °C (Figure 4), which is in

Figure 2. Photographs depicting the typical morphologies of salts 1

a), 2 (b) and 3 (c), obtained by fast evaporation, and large crystals of

(d), grown by slow evaporation of the solution in a Petri dish. The

graduation for (a)−(c) is 1 mm; the linear size is given in centimeters

in (d).

contrast with palladium nitrate ([Pd(NO ) (H O) ]), which

(

starts to decompose below 100 °C. Above 200 °C, fast

decomposition of the salts occurs, with the formation of

metallic palladium and amorphous carbon. An interesting

peculiarity is the melting of salts 1−3 at about 190 °C, just

before decomposition begins. Melting is accompanied by a

notable endothermic eﬀect on the DTA curve (Figure S4 ),

while further decomposition to Pd metal is highly exothermic,

corresponding to the reaction between nitrato ligands and

organic cations. It should be noted that the decomposition of

the salts proceeds smoothly without any explosion or ignition,

which is in agreement with the general rule that strong

oxidizing properties are observed only for nitrato complexes

while slow evaporation of the solutions, especially in a thin

layer (Petri dish), allows large well-edged pinacoids (Figure

d) to grow. Attempts were also made to prepare a salt with a

tetrabutylammonium cation (Bu N ) in an analogous manner,

but these were without success: after evaporation, an oily mass

was formed that did not transform into a crystalline product,

even under freezing conditions.

X-ray powder diﬀraction analysis of the obtained solid

products 1−3 shows good agreement with the single-crystal

0,56

containing bidentate nitrato groups.

After complete

decomposition of the salts 1−3, a slow mass growth is

986

Inorg. Chem. 2021, 60, 2983−2995

Article

Figure 3. (A) UV−vis spectrum of salt 2 in 0.2 M HClO . (B) Evolution of the UV−vis spectrum of the salt 2 solution in acetone (C(Pd) = 5.2

mM). The diﬀuse reﬂectance spectrum of 2 is additionally presented (red line) for comparison.

observed above 350 °C, which corresponds to Pd oxidation

with the trace oxygen present in the helium stream. At

temperatures above 650 °C, the formed PdO becomes

unstable and decomposes back into metallic Pd and oxygen.

.3. Crystal Structures. The structures of salts 1−3 are

2−

built from [Pd(NO ) ] complex anions and R N cations,

packed without any solvent molecules into monoclinic unit

cells in the case of salts 1 and 3 (P2 /n and P2 /c space groups,

correspondingly) and a tetragonal (I4/mmm) cell in the case of

the tetraethylammonium salt 2. Increasing the organic cation

size leads to a decrease in the number of cations surrounding

the complex anions, from 12 in the case of salt 1 (Me N ) to 9

for salt 2 (Et N ) and 8 for salt 3 (Pr N ). As evidenced from

an analysis of Hirshﬁeld surfaces (Table 1) for anions and

cations in the structures of 1−3, elongation of the R alkyl chain

from CH to n-C H also results in an increase in the O···H

2−

contact fraction for [Pd(NO ) ] anions, from 86% to 93%.

Figure 4. TG curves depicting the thermal decomposition of salts 1−

in He. The dashed lines mark the calculated weight loss

corresponding to the complete decomposition of the salt to Pd metal.

In agreement with this, the fraction of O···O contacts on the

Hirshﬁeld surfaces of complex anions, corresponding to the

contacts between neighboring anions, falls from 5% for salt 1

to almost 0 in the case of salt 3. An analogous trend is also

Table 1. Hirschfeld Surface Analysis of Complex Salts 1−3

(

Me N) [Pd(NO ) ] (1)

(Et N) [Pd(NO ) ] (2)

anion (γ)

cation (1)

cation (2)

anion (α)

cation (1)

cation (2)

Pd−H

0.2

2.0

1.6

4.9

86.5

4.8

H−Pd

H−O

H−N

H−H

0.3

63.4

2.7

H−Pd

0.1

61.1

3.9

Pd−Pd

1.0

0.1

2.8

90.5

5.5

H−O

H−N

H−H

53.0

5.0

42.0

H−O

H−N

H−H

39.9

0.4

59.7

N−O

O−N

O−O

O−H

N−H

H−O

H−N

H−H

Pd−O

O−Pd

O−O

O−H

N−H

33.6

34.9

(

Pr N) [Pd(NO ) ] (3)

3 4

anion (β)

anion (γ)

cation (1)

cation (2)

Pd−H

O−H

N−H

1.2

92.7

6.0

Pd−H

O−H

N−H

0.2

93.2

6.6

H−Pd

H−O

H−N

H−H

0.2

33.6

3.5

H−Pd

33.8

3.5

H−O

H−N

H−H

62.7

987

Inorg. Chem. 2021, 60, 2983−2995

kJ/mol, respectively, while the highest energy value (4.98 kJ/

Article

−

Figure 5. Structure of α, β, and γ modiﬁcations of the complex anion [Pd(NO ) ] : the α form from the structure of 2, the β form from the

structure of 3, and the γ form from the structure of 1.

observed for N···O contacts. Such tendencies indicate that bulk

anions of the β and γ modiﬁcations. Complex anions of the β

modiﬁcation are located on the inversion centers, whereas the

remaining γ-[Pd(NO₃)₄] anions are arranged along the 2-

R N cations form voids around the complex anions

2−

[

Pd(NO ) ] and separate them from each other. A similar

isolation of complex anions was described for the platinum(IV)

fold helical axes. The organic cations are situated on glide

−

2−

nitrato complexes [Pt(NO ) ] and [Pt (μ-OH) (NO ) ]

3 8

planes. The structure of β-[Pd(NO ) ] is similar to that of

3 4

with R N cations, where R = n-Pr, n-Bu.

The palladium center of the [Pd(NO ) ] anions possesses

the previously described β-K [Pd(NO ) ] (Figure 5 and Table

3 4

2−

S4 ), and the structure of γ-[Pd(NO ) ] in complex salt 3 is

3 4

−

^a^dⁱ^s^t^o^r^t^e^d^-^s^q^u^a^r^e^-^p^l^aⁿ^a^r^g^e^o^m^e^t^r^y^wⁱ^t^h^f^o^u^r^N^O3 ligands

coordinated in a unidentate mode. In all cases, Pd−O bonds

are practically identical (2.00−2.01 Å), as are the the O−Pd−

O angles, which are close to 90°. A general peculiarity of the

almost the same as that in case 1 (Table S4 ).

It is interesting to note that one of the possible isomers of

2−

the [Pd(NO ) ] complex, featuring one nitrato ligand

rotated in the opposite direction with respect to the other

three ligands (designated further as the δ isomer), has not been

observed in the crystal structures to date. To investigate the

2−

[

Pd(NO ) ] structure is two possible arrangements of the

3 4

NO ligands with respect to the PdO plane, above and below

(

Figure 5); therefore, four diﬀerent isomers of this anion can

−

electronic structure of the [Pd(NO ) ] complexes, to

be assumed. Two isomers, designated as α and β modiﬁcations,

determine how the isomers are ranged by electronic energy,

and to ﬁgure out the possibility of their interconversion, we

proceeded further with DFT calculations.

were previously reported by Khranenko et al. in the structures

20−22,57

2−

of the salts with alkali-metal cations.

α-[Pd(NO ) ]

3 4

comprises four nitrato ligands situated on one side of the PdO

2−

3.4. DFT Calculations. The DFT-optimized structures of

plane; in the structure of β-[Pd(NO ) ] , two nitrato ligands

2−

each type of [Pd(NO ) ] complex (α, β, γ) are close to those

situated in positions cis to each other are located on one side of

found from crystallographic data, and no serious changes in

geometry were observed during the optimization. This

observation highlights that the electron energies of α, β, and

γ complexes observed in the crystal structure of salts 1−3

correspond to local minima on the potential energy surface.

the PdO plane and the other two ligands are on the opposite

side, forming a chairlike structure.

In the structure of salt 1, a previously unreported form of the

2−

[

Pd(NO ) ] anion was found, which we have designated the

3 4

2−

γ modiﬁcation. Two nitrato ligands of γ-[Pd(NO ) ] , located

2−

in positions trans to each other, are situated on one side of the

Additionally, the δ isomer of the [Pd(NO

)

]

complex was

PdO plane, while the other two are located on the opposite

considered, which has not been observed in the crystal

structures of the isolated compounds (Figure 6). Among all of

side (Figure 5 and Table S2 ). Interestingly, the N(1)O and

−

N(3)O ligands are located practically in one plane, whereas

the isomers, the α-[Pd(NO₃)₄] has the minimum electron

energy and was chosen as a reference (E = 0 kJ/mol) for

comparison. In this reference frame, the electron energies of β-

the ligands with N2 and N4 atoms are rotated with respect to

each other, at 22°. The system of weak hydrogen bonds (2.4−

2−

.5 Å) with the nearby tetramethylammonium cation is also

[Pd(NO ) ] and δ-[Pd(NO ) ] isomers are 1.24 and 1.71

3 4 3 4

observed in the structure (Figure S5 ).

2−

The basketlike structure of the α-[Pd(NO ) ] anion in the

crystal structure of salt 2 (Figure 5 and Table S3 ) is almost

identical with that described previously in KCs[Pd(NO ) ]·

1,22

.5H O and K [Pd(NO ) ] salts

and can also be

3 4

−

compared with the structure of the polar [Pd(IO ) ]

2−

complex. The nitrato ligands of the α-[Pd(NO ) ] anion

are turned in one direction, and in the structure of 2, pairs of

anions with diﬀerent directions of ligand rotation are arranged

side by side, with a Pd···Pd distance of about 3.2 Å (Figure

S6A ). The disorder of the positions of nitrato ligands and

tetraethylammonium cations is observed in the structure, and

all eight complex anions in the cell are located on a 4-fold axis

Figure S6B ).

2−

The structure of salt 3, with a tetrapropylammonium cation,

Figure 6. DFT optimized structures of [Pd(NO ) ] isomers and

3 4

their relative electronic energies.

2−

contains four crystallographically independent [Pd(NO ) ]

988

Inorg. Chem. 2021, 60, 2983−2995

5 kJ/mol for the switch from α -[Pd(NO ) ] to δ -[Pd-

Article

−

2−

(NO ) ] structures, with the transition state having the

3 4

rotated NO ligand aligned in the {PdO } plane.

In a nitric acid solution, on the other hand, due to the

substitutional lability of palladium(II) complexes,

outer-sphere mechanism should deﬁnitely operate as well,

including the formation of ﬁve-coordinated intermediates:

9,60

the

^α^‐^[^P^d⁽^N^O3⁾4^]+ NO ⁻→ {[Pd(NO ) ] }

−

3−

3 5

2−

₊_N_O−

→

^δ^‐^[^P^d⁽^N^O3⁾4^]

The relaxed PES scan was performed to model the given outer-

sphere mechanism of transformation. The maximum energy in

PES is related to the ﬁve-coordinated complex {[Pd-

−

(NO ) ] } with Pd−O distances of 2.2 Å, and an energy

barrier of 85 kJ/mol is observed. Despite the limitations of the

chosen calculation method, the energy of the transition state,

in this case, is lower than that calculated for the rotation of

−

NO , conﬁrming the hypothesis of the outer-shell trans-

formation mechanism.

where the nitrato ligand is rotated by 180°. The ELF around

the aforementioned atoms is also seen to repeat the shape of

the outer orbitals of oxygen (p orbitals) and palladium (d

orbitals), which means that the s orbitals of oxygen only take

part in σ bonds in nitrato ligands, and the π system of the

nitrato ligand does not take part in the formation of Pd−O

bonds. The localization of electrons over oxygen atoms is more

diﬀuse than for palladium, which is related to the large

diﬀerence in atomic charges of the atoms.

We also calculated relaxed PES scans for substitution of the

nitrato ligand by water or acetone to illustrate the lability of the

nitrato complex toward such reactions. The calculations were

performed in the same manner as for the NO₃⁻exchange

reaction. In both cases, the incoming ligand (acetone, water)

approaches the Pd atom by an O atom until the Pd−O

distance is decreased to about 2.1 Å (average Pd −O distance),

which refers to the maximum in PES (Figure S9 ). After this,

−

the ﬁve-coordinated complex decomposes, forming free NO

n−

The diﬀerences between electronic energy values for α-

ion and the [Pd(NO ) (L)] complex (L = H O, acetone).

2−

[

Pd(NO ) ] , β-[Pd(NO ) ] , and δ-[Pd(NO ) ] isomers

The energy barriers are 72 and 85 kJ/mol for acetone and₋

water, respectively, which is quite close to that found for NO₃

exchange. It should be noted that the models chosen are the

simplest ones; therefore, the energies obtained from the

relaxed PES scans may be overestimated, resulting in the sharp

shape of the plots.

3 4

are lower than that of RT under normal conditions; therefore,

the tetranitratopalladate anion can switch between these

structures under ambient conditions if the energy barriers for

these transformations are low enough. To analyze this

possibility, we performed the calculations for the interconver-

2−

sion of α-[Pd(NO ) ] to δ-[Pd(NO ) ] , conducting a rigid

3.5. Reaction with N-Donor Ligands. As evidenced from

3 4

2−

PES scan for one O−Pd−O−N dihedral angle, while the other

bonds and angles were kept constant. This situation imitates

the possible transformation of α-[Pd(NO ) ] to δ-[Pd-

the study of [Pd(NO

)

]

anion reactivity in water and

organic solvents, the nitrato ligands can be easily substituted by

various species. To illustrate this peculiarity, we studied the

interaction of salt 2 with two diﬀerent N-donor ligands,

pyridine (py) and 1,10-phenanthroline-5,6-dione (phd), in

acetone. Palladium complexes with such types of ligands are of

interest in antitumor therapy, as a building block for the

synthesis of heterometallic complexes, and as synthetic

2−

(

NO ) ] by the rotation of the nitrato ligand around the

3 4

Pd−O bond. The resulting energy proﬁle, described in Figure

, clearly shows that there is a relatively high barrier of about

17,61,62

metallopeptidases.

The addition of py or phd to a freshly prepared solution of 2

leads to an immediate color change from brown to yellow and

the gradual formation of a ﬁne crystalline precipitate. The

products, obtained in high yield, are the molecular complex

trans-[Pd(py) (NO ) ] (4) and the adduct (Et N)[Pd(phd)-

3 2

(

NO ) ](NO )·C H O (5), respectively. The formation of

3 2 3 3 6

Pd(py) (NO ) in the trans form can be attributed to the

3 2

much stronger trans inﬂuence of the py ligand in comparison

with the nitrato ligands, while the geometry is dictated by the

structure of the bidentate ligand in the case of cis-[Pd(phd)-

(

NO ) ].

3 2

The crystal structure data for complex 4 have already been

deposited in the structure database (CSD 1001419), but the

synthesis and description of the structure have not been

presented in the literature. Complex 4 crystallizes in the

triclinic space group P1 (Z = 2) without solvent molecules.

There are two crystallographically independent Pd centers in

the structure, both located on inversion centers and arranged

Figure 7. Rigid PES scan of the O−Pd−O−N dihedral angle during

2−

interconversion of α- to δ-[Pd(NO ) ] .

989

Inorg. Chem. 2021, 60, 2983−2995

Article

Figure 8. (A) Structure of trans -[Pd(py) (NO ) ] (4 ). (B) Structure of the [Pd(phd)(NO ) ] complex in the crystal structure of the adduct 5.

3 2

Figure 9. Solution of 2 in acetone (C(Pd) = 12 mM) before (A) and after the addition of CeO , Al O , TiO , SiO , and Ni(OH) solids (100 mg)

(

B). (C) Diﬀuse reﬂectance spectrum of the palladium species deposited on Al O (a) along with the UV−vis spectrum of the acetone solution of

salt 2 (b).

into chains that run along all axes (Figure S10). The palladium

whose molecules are strongly bound ligands (acetonitrile,

water, DMF), presumably accompanied by nitrato ligand

substitution that is evidenced from ESI-MS data (Figures S12

and S13 ). Such lability of the nitrato ligands in 4 and 5 or

analogous related compounds can be further exploited to

prepare heteroleptic palladium(II) complexes or polynuclear

frameworks.

atom in trans-[Pd(py) (NO ) ] coordinates in a square-planar

3 2

manner, without notable distortions (Figure 8 A), and Pd−O

and Pd−N bonds are close2.01−2.02 Å (Table S5). The

organic ligands are situated in positions trans to each other and

are practically coplanar, while the planes of the NO ligands are

parallel to each other.

3.6. Pd Deposition on Oxide or Hydroxide Supports.

The neutrally charged complex [Pd(phd)(NO ) ] with 1,10-

As mentioned in the Introduction, the supported palladium

catalysts are intensively used in various ﬁelds, and the

development of facile methods and precursors for the

preparation of such materials is an important task. Previously,

we have reported on a labile polynuclear platinum(IV) nitrato

complex that can be chemisorbed onto ceria or alumina

materials by means of nitrato ligand substitution and the

binding of platinum ions with −OH groups on the surface of

phenantrolinedione (phd) crystallizes in the triclinic space

group P1, along with the tetraethylammonium cation from the

parent salt 2 , the nitrate anion, and acetone, which was used as

a solvent (Figure S11 ). In the structure of 5, two molecules of

[

Pd(phd)(NO ) ] are arranged around the center inversion in

3 2

the middle part of the cell. The palladium atom has a distorted-

square-planar environment formed by two oxygen atoms from

the nitrato ligands and two nitrogen atoms from phd. The Pd−

O bond lengths are 2.01 −2.03 Å, and the Pd−N bond lengths

are about 2.00 Å (Table S6 ). Due to the tough geometry of

heteroaromatic rings, the N3−Pd−N4 angle diﬀers suﬃciently

from 90° (81.7°). Also, note that N3, N,4 and O1A atoms lie

practically in one plane, but the O2A atom is located out of

this plane; as a result, the O1A−Pd−N3 and O2A−Pd−N4

angles are noticeably diﬀerent.

the oxide. In this context, a combination of the stability of

−

salts 1−3 and lability of the [Pd(NO ) ] species toward

ligand substitution can be applied to the deposition of

palladium species onto various solid supports that have

reactive donor groups on the surface:

{

Pd‐NO } + M‐OH → Pd‐(OH)‐M_s_u_r_f+ NO ⁻

surf

Compounds 4 and 5 are both almost insoluble in acetone,

ethanol, and ether but can be readily dissolved in solvents

Indeed, the experiments with Al O and CeO have shown that

2 3 2

a fast uptake of palladium takes place from the solution upon

990

Inorg. Chem. 2021, 60, 2983−2995

Article

Figure 10. HAADF-STEM photographs of the Ni Pd /SiO catalyst combined with the elemental mappings showing the spatial distribution of

0.1

Ni, Pd, and Si.

addition of these oxides to acetone solutions of salts 1−3,

which is evident from the discoloring of the supernatant and

the color change of the solids (Figure 9A,B). Diﬀuse

reﬂectance spectra of the materials with sorbed Pd species

consist of a broad band at about 400 nm, which correlates with

the position of the bands observed in spectra of the salt 2

acetone solution (Figure 9C). Unlike the case of platinum

controlled (see the Experimental Section). Up to 3 mol % of

Pd can be deposited on Al O and TiO and 2 mol % can be

sorbed by CeO , while the uptake of Ni(OH) is up to 10 mol

−

% of Pd. The inability of SiO to interact with [Pd(NO ) ]

3 4

anions can be explained by the lack of negatively charged −OH

groups on the surface with which to attack the palladium

centers. On the other hand, this fact can be applied for the

selective deposition of palladium on oxide or hydroxide

2−

complexes, the sorption process for [Pd(NO ) ] anion salts

proceeds extremely quickly: generally, almost immediately after

the oxides are suspended. The sorption is irreversible, and

deposited palladium species cannot be washed out with excess

acetone. On the other side, palladium can be leached out from

the resulting materials by a treatment with aqueous solutions

of acids or strongly complexing agents. For example, under the

dispersion of the 2/Al O material in 2 M NaI (Figure S14)

materials dispersed over the SiO matrix.

3.7. Catalytic Hydrogen Generation from Hydrazine

Hydrate with Ni Pd /SiO . Previously, a synergetic eﬀect

0.9

0.1

was shown for Pd-Ni nanoparticles in the reaction of catalytic

decomposition of hydrazine hydrate with the formation of

65,67

H .

Hydrazine can decompose over metallic catalysts with

(1) hydrogen formation, N H → N + 2H , or (2) via a

almost complete transfer of the Pd(II) into the solution occurs

disproportionation reaction, 4N H → N + 3NH . Both

2 4 2 3

in the form of the [PdI₄]²complex. Analogously, complete

−

individual Ni and Pd nanoparticles show poor activity and

desorption of Pd can be achieved with 2 M HNO or 2 M HCl

selectivity, while the bimetallic nanoalloy Pd Ni shows 80%

40 60

(

but not with 2 M NaCl). These observations emphasize that

H selectivity (50 °C) with a relatively high rate of reaction.

−

Pd deposits from the solution of (R N) [Pd(NO ) ] salts as an

Therefore, we examined the [Pd(NO₃)₄] chemosorption

described above to prepare a Pd-Ni catalyst for the hydrazine

hydrate decomposition process.

3 4

ionic species and also support the proposed mechanism of Pd

binding by surface −OH groups. It is interesting to note in this

context that oxide-supported palladium species can be easily

reduced to metallic palladium by passing hydrogen through a

suspension of the material (Figure S15).

A silica-supported Pd-Ni catalyst was prepared by

2−

chemisorption of [Pd(NO ) ] species on SiO -supported

Ni(OH) particles from an acetone solution of 2. Treatment of

To extend the range of the supporting materials, TiO , SiO ,

the composite under a H atmosphere at 400 °C results in the

and Ni(OH) were also tested. Ni(OH) was introduced to

reduction of Pd and Ni to give the target Ni Pd /SiO

0.9

0.1

probe the transition-metal hydroxide as a target support due to

currently growing interest in bimetallic Pd-Ni materials for

hydrogen energy applications: for example, in the oxygen

material containing 10 wt % of Ni and 2 wt % of Pd (as

determined by X-ray ﬂuorescence analysis). The XRD pattern

of the as-prepared Ni Pd /SiO catalyst shows highly intense

0.1

reduction reaction a₅n₋d₆₇catalytic decomposition of hydrazine

and diﬀuse reﬂections of the SiO matrix (Figure S16) as well

hydrate (vide infra).

as wide reﬂections attributed to small- sized metallic Pd

particles. The positions of the reﬂections are slightly shifted in

comparison to that of a Pd etalon, which can be attributed to

In all cases, with the exception of silica, fast palladium uptake

was observed from an acetone solution of 2 (Figure 9A).

−

Overall, the quantities of [Pd(NO ) ]

that can be

the partial alloying with Ni. Additionally, a broad line is

chemisorbed by a given oxide or hydroxide depend on the

prehistory of this material (preparation method and con-

ditions). For the materials used in this work, these values were

estimated in experiments where the concentration of 2 was

gradually increased, while the color of the supernatant was

observed at 61° corresponding to the NiO oxide phase that is

well-known to cover highly dispersed Ni particles in an air

69,70

atmosphere.

The high-angle annular dark-ﬁeld scanning

TEM (HAADF-STEM) images and the corresponding

elemental mappings demonstrate that in the Ni Pd /SiO

0.1

991

Inorg. Chem. 2021, 60, 2983−2995

Inorganic Chemistry

It can be clearly seen from Figure 11 that the catalyst shows

Article

material Ni uniformly covers the surface of the SiO support,

while Pd particles, also being regularly distributed on the

the M/Si (M = Ni, Pd) ratios increase considerably (Figure

S18 and Table S7).

surface, are mainly concentrated in well-deﬁned domains

Among the catalysts tested so far for hydrazine decom-

position, the supported M-Ni materials with M = Pt, Ir, Rh

(Figure 10 ). These Pd-rich domains are observed in HR-TEM

images (Figure S17 ) as particles with a size of about 5−7 nm

have shown superior rates of H evolution (TOF values up to

−

with clearly deﬁned interplanar distances of 2.2 Å attributed to

400 h ) and almost 100% H selectivity, while the palladium

8,66

the (111) facets of the face-centered cubic Pd.

The survey X-ray photoelectron spectrum of Ni Pd /SiO

analogues demonstrated lower selectivity and TOF values.

An analogous tendency is observed for cobalt-containing

0.9

0.1

has shown that silicon, oxygen, carbon, palladium, and nickel

are situated on the surface. An analysis of the Pd 3d region

reveals the presence of a single palladium form with a binding

energy of 335.3 eV (Figure S18), which is typical for metallic

catalysts promoted with noble metals. At the same time, it

should be noted that the preparation method and precursors

highly inﬂuence the activity of the resulting catalysts; therefore,

new preparation techniques for such materials are crucial for

Pd. In the Ni 2p₃_/₂range the only nickel species is observed

with a binding energy of 856.5 eV, attributed to the surface

further development. The parameters achieved in this work

are close to the results reported earlier for Pd Ni and

NiO. The Ni Pd /SiO material was further tested in a

Pd Ni nanoparticles under the same conditions (n(N H )/

40 60 2 4

0.1

hydrazine hydrate decomposition reaction.

n(catalyst) = 10), which is quite an important achievement

with regard to the reduction of the percentage of noble metals

in catalysts.

At 50 °C, the Ni Pd /SiO catalyst shows up to 80% H

0.9

0.1

−

selectivity with a TOF value of about 13 h per Pd atom.

Experiments were also performed to test the stability of the

Ni Pd /SiO catalyst. After each step, when N H was

4. CONCLUSIONS

0.1

depleted, a new portion of hydrazine hydrate was introduced.

In summary, the series of quaternary ammonium tetrani-

tratopalladates (R N) [Pd(NO ) ] described here are non-

3 4

hydroscopic and demonstrate high stability under normal

conditions, in contrast to the commonly used palladium(II)

nitrate. On the other hand, the given salts are highly soluble in

various solvents, while the nitrato ligands can be readily

substituted by an appropriate donor fragment. These proper-

ties, in combination with a high-yielding synthesis and

thermolability (that is a general characteristic of transition-

metal nitrato complexes), ensure their applicability as

straightforward starting materials for the synthesis of palladium

compounds and the preparation of Pd-containing catalysts.

In the current work, the aforementioned aspects were

implemented by (a) the synthesis of compounds 4 and 5,

starting from salt 2, and (b) the Pd deposition on various

supports from solutions of (R N) [Pd(NO ) ] salts and the

3 4

preparation of a Ni Pd /SiO catalyst. To outline the other

0.1

perspectives, it should be noted that palladium nitrato

complexes can be utilized as homogeneous catalysts for alkene

nitration, as starting materials for the preparation of

Figure 11. Durability experiments for H generation from N H ·H O

heterometallic compounds, or in electrolytes for palladium

using a Ni Pd /SiO catalyst (300 mg) at 50 °C. C(NaOH) = 1 M,

electrodeposition. It is also worth noting that nitrato

complexes of palladium are components of spent nuclear fuel

and their separation is crucial for the stability of the vitreous

0.9

0.1

n(N H )/n(Pd) = 16.3.

solid used for prolonged storage of high-level waste.

stable hydrogen production over seven cycles, without notable

deactivation. Interestingly, during the ﬁrst step, the initial rate

of the reaction is almost twice as high as the average rate on all

of the next stages, while the selectivity grows slightly from cycle

to cycle. This fact can be attributed to the gradual reduction of

the oxide layer, covering the nickel surface (Figure S18 ), under

the reductive reaction conditions. An examination of the spent

Ni Pd /SiO catalyst (after durability tests) with XRD

Therefore, in view of the noted wide range of applications,

we believe that the tetranitratopalladates 1−3 will ﬁnd their

place in the arsenal of chemists.

ASSOCIATED CONTENT

sı Supporting Information

The Supporting Information is available free of charge at

https://pubs.acs.org/doi/10.1021/acs.inorgchem.0c03038.

■

0.1

Figure S16) and HAADF-STEM and HR-TEM (Figure S19)

Additional crystallographic data, XRD data, NMR, IR,

XPS, and MS spectra, additional micrographs, DFT-

computed IR spectra, ELF plots, and relaxed PES scan

data (PDF )

does not show notable changes in the morphology of the

catalyst in comparison to the as-prepared material. The

intensities of reﬂections corresponding to metallic phases in

the XRD pattern of the spent catalyst are slightly higher than in

the case of the as-prepared material, which can be due to

Accession Codes

partial dissolution of the SiO matrix in an alkaline media.

These ﬁndings also agree well with the XPS results, which

CCDC 2008746, 2025660 , 2026407 , and 2026628 contain the

supplementary crystallographic data for this paper. These data

can be obtained free of charge via www.ccdc.cam.ac.uk/

data_request/cif , or by emailing data_request@ccdc.cam.ac.

indicate that the nickel and palladium surface species remain

unchanged (NiO and Pd ) under the reaction condition but

992

Inorg. Chem. 2021, 60, 2983−2995

Inorganic Chemistry

V.; Boronin, A. I. Thermal Activation of Pd/CeO

Article

uk , or by contacting The Cambridge Crystallographic Data

Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44

-SnO

Catalysts for

Low-Temperature CO Oxidation. Appl. Catal., B 2020, 277 (March),

19275.

4) Wang, Z.-Q.; Sun, J.; Xu, Z.-N.; Guo, G.-C. CO Direct

Esterification to Dimethyl Oxalate and Dimethyl Carbonate: The Key

223 336033.

Functional Motifs for Catalytic Selectivity. Nanoscale 2020 , 12 , 20131.

AUTHOR INFORMATION

Corresponding Author

■

(5) Azarpour, A.; Zahedi, G. Performance Analysis of Crude

Danila Vasilchenko − Nikolaev Institute of Inorganic

Chemistry, Siberian Branch of the Russian Academy of

Science, 630090 Novosibirsk, Russian Federation;

orcid.org/0000-0002-4233-2105; Email: vasilchenko@

niic.nsc.ru

Terephthalic Acid Hydropurification in an Industrial Trickle-Bed

Reactor Experiencing Catalyst Deactivation. Chem. Eng. J. 2012, 209,

180−193.

(6) Tourani, S.; Khorasheh, F.; Rashidi, A. M.; Safekordi, A. A.

Hydro-Purification of Crude Terephthalic Acid Using Palladium

Catalyst Supported on Multi-Wall Carbon Nanotubes. J. Ind. Eng.

Chem. 2015, 28, 202−210.

Authors

Polina Topchiyan − Nikolaev Institute of Inorganic

Chemistry, Siberian Branch of the Russian Academy of

Science, 630090 Novosibirsk, Russian Federation;

orcid.org/0000-0002-0827-4917

Semen Berdyugin − Nikolaev Institute of Inorganic

Chemistry, Siberian Branch of the Russian Academy of

Science, 630090 Novosibirsk, Russian Federation;

orcid.org/0000-0003-3560-6873

(7) Banham, D.; Ye, S. Current Status and Future Development of

Catalyst Materials and Catalyst Layers for Proton Exchange

Membrane Fuel Cells: An Industrial Perspective. ACS Energy Lett.

8) Cheng, Y.; Wu, X.; Xu, H. Catalytic Decomposition of Hydrous

017, 2 (3), 629−638.

Hydrazine for Hydrogen Production. Sustain. Energy Fuels 2019, 3

2), 343−365.

9) Dong, Y.; Chen, Q.; Qiu, C.; Ma, X.; Wang, Y.; Sun, T.; Fan, G.

(

Synergistic Catalysis of Pd-Ni(OH) Hybrid Anchored on Porous

Pavel Plyusnin − Nikolaev Institute of Inorganic Chemistry,

Siberian Branch of the Russian Academy of Science, 630090

Novosibirsk, Russian Federation; orcid.org/0000-0002-

Carbon for Hydrogen Evolution from the Dehydrogenation of Formic

Acid. Int. J. Hydrogen Energy 2020, 45 (23), 12849−12858.

(10) Al-Azri, Z. H. N.; Chen, W.-T.; Chan, A.; Jovic, V.; Ina, T.;

494-6240

Idriss, H.; Waterhouse, G. I. N. The Roles of Metal Co-Catalysts and

Reaction Media in Photocatalytic Hydrogen Production: Performance

Vladimir Shayapov − Nikolaev Institute of Inorganic

Chemistry, Siberian Branch of the Russian Academy of

Science, 630090 Novosibirsk, Russian Federation

Iraida Baidina − Nikolaev Institute of Inorganic Chemistry,

Siberian Branch of the Russian Academy of Science, 630090

Novosibirsk, Russian Federation

Vladislav Komarov − Nikolaev Institute of Inorganic

Chemistry, Siberian Branch of the Russian Academy of

Science, 630090 Novosibirsk, Russian Federation

Andrey Bukhtiyarov − Boreskov Institute of Catalysis, 630090

Novosibirsk, Russia; orcid.org/0000-0002-0199-8111

Evgeny Gerasimov − Boreskov Institute of Catalysis, 630090

Novosibirsk, Russia

Evaluation of M/TiO Photocatalysts (M = Pd, Pt, Au) in Different

Alcohol-Water Mixtures. J. Catal. 2015 , 329 , 355 −367.

(11) Yang, Y.; Chang, C.; Idriss, H. Photo-Catalytic Production of

Hydrogen Form Ethanol over M/TiO Catalysts (M = Pd, Pt or Rh).

Appl. Catal., B 2006, 67 (3 −4), 217 −222.

(12) Wenzel, T. T. Palladium(II) Nitrate. In Encyclopedia of Reagents

for Organic Synthesis ; Wiley: Chichester, U.K., 2001; p 1.

DOI: 10.1002/047084289X.rp013 .

(13) Laligant, Y.; Ferey, G.; Le Bail, A. Crystal Structure of

Pd(NO ) (H O) . Mater. Res. Bull. 1991, 26 (4), 269−275.

(14) Khranenko, S. P.; Baidina, I. A.; Gromilov, S. A. Crystal

Structure Refinement for Trans-[Pd(NO ) (H O) ]. J. Struct. Chem.

2007, 48 (6), 1152−1155.

15) Venediktov, A. B.; Korenev, S. V.; Khranenko, S. P.; Tkachev, S.

(

Complete contact information is available at:

https://pubs.acs.org/10.1021/acs.inorgchem.0c03038

V.; Plyusnin, P. E.; Mamonov, S. N.; Ivanova, L. V.; Vostrikov, V. a.

Properties of Nitric Acid Palladium Solutions with a High Metal

Concentration. Russ. J. Appl. Chem. 2007, 80 (5), 695−704.

Notes

(16) Vasilchenko, D. B.; Gulyaev, R. V.; Slavinskaya, E. M.; Stonkus,

The authors declare no competing ﬁnancial interest.

O. A.; Shubin, Y. V.; Korenev, S. V.; Boronin, A. I. Effect of Pd

Deposition Procedure on Activity of Pd/Ce Sn O Catalysts for

.5 0.5

ACKNOWLEDGMENTS

■

Low-Temperature CO Oxidation. Catal. Commun. 2016, 73, 34 −38.

The authors deeply acknowledge S. V. Tkachev for the ¹⁵N

NMR data, Dr. A. P. Zubareva for assistance with the CHN

analysis, Dr. B. A. Kolesov for the Raman spectroscopy data,

and Dr. E. Yu. Filatov and Dr. Yu. V. Shubin for their

assistance with XRPD. The authors thank the XRD Facility of

NIIC SB RAS for the single-crystal data collection. The TEM

and XPS experiments were performed using facilities of the

shared research centre “National Center for the Investigation

of Catalysts” at the Boreskov Institute of Catalysis.

(17) Inci, D.; Aydin, R.; Vatan, O.; S ̧ahin, O.; C ̧inkilic ,̧ N. Water-

Soluble Binary and Ternary Palladium(Ii) Complexes Containing

Amino Acids and Intercalating Ligands: Synthesis, Characterization,

Biomolecular Interactions and Cytotoxicities. New J. Chem. 2019, 43

(

12), 4681−4697.

18) Wickleder, M. S.; Gerlach, F.; Gagelmann, S.; Bruns, J.; Fenske,

M.; Al-Shamery, K. Thermolabile Noble Metal Precursors: (NO)-

Au(NO ) ], (NO) [Pd(NO ) ], and (NO) [Pt(NO ) ]. Angew.

(

[

3 6

Chem., Int. Ed. 2012, 51 (9), 2199−2203.

19) Bruns, J.; Kluner, T.; Wickleder, M. S. Oxoanionic Noble Metal

Compounds from Fuming Nitric Acid: The Palladium Examples

REFERENCES

Pd(NO ) and Pd(CH SO ) . Chem. - Eur. J. 2015, 21 (3), 1294−

■

3 2

(

1) Cowley, A. PGM Market Report, February 2020 ; Johnson

Matthey PLC. Retrieved from http://www.platinum.matthey.com ,

1301.

(20) Khranenko, S. P.; Baidina, I. A.; Gromilov, S. A.; Belyaev, A. V.

Synthesis and X-Ray Investigation of Rb [Pd(NO ] and Cs [Pd-

(NO ]. J. Struct. Chem. 2005, 46 (6), 1060−1065.

(21) Khranenko, S. P.; Baidina, I. A.; Kuratieva, N. V.; Gromilov, S.

2) Shelef, M.; McCabe, R. Twenty-Five Years after Introduction of

019.

Automotive Catalysts: What Next? Catal. Today 2000, 62 (1), 35−50.

3) Slavinskaya, E. M.; Zadesenets, A. V.; Stonkus, O. A.;

Stadnichenko, A. I.; Shchukarev, A. V.; Shubin, Y. V.; Korenev, S.

)

3 4

(

A. X-Ray Structure of KCs[Pd(NO ) ]·0.5H O. J. Struct. Chem. 2009,

3 4 2

50 (1), 166−169.

993

Inorg. Chem. 2021, 60, 2983−2995

Inorganic Chemistry

Article

22) Khranenko, S. P.; Baidina, I. A.; Gromilov, S. A. Crystal

(38) Hehre, W. J.; Stewart, R. F.; Pople, J. A. Self-Consistent

Molecular-Orbital Methods. I. Use of Gaussian Expansions of Slater-

Type Atomic Orbitals. J. Chem. Phys. 1969 , 51 (6), 2657 −2664.

(39) Hay, P. J.; Wadt, W. R. Ab Initio Effective Core Potentials for

Molecular Calculations. Potentials for K to Au Including the

Outermost Core Orbitals. J. Chem. Phys. 1985, 82 (1), 299−310.

(40) Collins, J. B.; Schleyer, P. v. R.; Binkley, J. S.; Pople, J. A. Self-

consistent Molecular Orbital Methods. XVII. Geometries and Binding

Energies of Second-row Molecules. A Comparison of Three Basis

Sets. J. Chem. Phys. 1976, 64 (12), 5142 −5151.

Structure of a New Polymorphic Modification of β -K [Pd(NO ) ]. J.

3 4

Struct. Chem. 2009, 50 (2), 361−364.

23) Vasilchenko, D.; Topchiyan, P.; Berdyugin, S.; Filatov, E.;

(

Tkachev, S.; Baidina, I.; Komarov, V.; Slavinskaya, E.; Stadnichenko,

A.; Gerasimov, E. Tetraalkylammonium Salts of Platinum Nitrato

Complexes: Isolation, Structure, and Relevance to the Preparation of

PtO /CeO ₂ Catalysts for Low-Temperature CO Oxidation. Inorg.

Chem. 2019, 58 (9), 6075−6087.

(41) Wadt, W. R.; Hay, P. J. Ab Initio Effective Core Potentials for

24) Vasilchenko, D.; Tkachev, S.; Baidina, I.; Korenev, S. Speciation

of Platinum(IV) in Nitric Acid Solutions. Inorg. Chem. 2013, 52 (18),

0532−10541.

25) Vasilchenko, D.; Asanova, T.; Kolesov, B.; Tsygankova, A.;

Molecular Calculations. Potentials for Main Group Elements Na to Bi.

J. Chem. Phys. 1985, 82 (1), 284 −298.

(

Stadnichenko, A.; Slavinskaya, E.; Gerasimov, E.; Lomachenko, K.;

Boronin, A.; Korenev, S. Cerium(III) Nitrate Derived CeO Support

Stabilising PtO x Active Species for Room Temperature CO

Oxidation. ChemCatChem 2020, 12 (5), 1413−1428.

(

Kolesov, B.; Bukhtiyarov, A.; Kurenkova, A.; Kozlova, E. Photo-

induced Deposition of Platinum from (Bu N) [Pt(NO ) ] for a Low

Pt-Loading Pt/TiO Hydrogen Photogeneration Catalyst. ACS Appl.

(42) Hay, P. J.; Wadt, W. R. Ab Initio Effective Core Potentials for

Molecular Calculations. Potentials for the Transition Metal Atoms Sc

to Hg. J. Chem. Phys. 1985, 82 (1), 270−283.

(43) Tomasi, J.; Mennucci, B.; Cammi, R. Quantum Mechanical

Continuum Solvation Models. Chem. Rev. 2005, 105 (8), 2999−3094.

(44) Baerends, E. J.; Ziegler, T.; Atkins, A. J.; Autschbach, J.;

Bashford, D.; Baseggio, O.; Bérces, A.; Bickelhaupt, F. M.; Bo, C.;

Boerritger, P. M.; Cavallo, L.; Daul, C.; Chong, D. P.; Chulhai, D. V;

Deng, L.; Dickson, R. M.; Dieterich, J. M.; Ellis, D. E.; van Faassen,

M.; Ghysels, A.; Giammona, A.; van Gisbergen, S. J. A.; Goez, A.;

26) Vasilchenko, D.; Topchiyan, P.; Tsygankova, A.; Asanova, T.;

3 6

Mater. Interfaces 2020, 12 (43), 48631 −48641.

27) Shipsey, K.; Werner, E. A. CXXXII.The Purification of

Acetone by Means of Sodium Iodide. J. Chem. Soc., Trans. 1913, 103

c), 1255−1257.

28) Calderazzo, F.; Marchetti, F.; Pampaloni, G.; Passarelli, V. Co-

Jacob, C. R.; Jacobsen, H.; Jensen, L.; Joubert, L.; Kaminski, J. W.; van

Kessel, G.; Konig, C.; Kootstra, F.; Kovalenko, A.; Krykunov, M.; van

tz, A. W.; Gusarov, S.; Harris, F. E.; van den Hoek, P.; Hu, Z.;

(

Ordination Properties of 1,10-Phenanthroline-5,6-Dione towards

Group 4 and 5 Metals in Low and High Oxidation States †. J.

Chem. Soc., Dalton Trans. 1999 , No. 24, 4389 −4396.

Lenthe, E.; McCormack, D. A.; Michalak, A.; Mitoraj, M.; Morton, S.

M.; Neugebauer, J.; Nicu, V. P.; Noodleman, L.; Osinga, V. P.;

Patchkovskii, S.; Pavanello, M.; Peeples, C. A.; Philipsen, P. H. T.;

Post, D.; Pye, C. C.; Ramanantoanina, H.; Ramos, P.; Ravenek, W.;

(29) Scofield, J. H. Hartree-Slater Subshell Photoionization Cross-

Sections at 1254 and 1487 EV. J. Electron Spectrosc. Relat. Phenom.

976, 8 (2), 129−137.

30) Sheldrick, G. M. Crystal Structure Refinement with SHELXL.

Rodríguez, J. I.; Ros, P.; Ru

Schoot, H.; Schreckenbach, G.; Seldenthuis, J. S.; Seth, M.; Snijders, J.

G.; Sola, M.; M, S.; Swart, M.; Swerhone, D.; te Velde, G.; Tognetti,

V.; Vernooijs, P.; Versluis, L.; Visscher, L.; Visser, O.; Wang, F.;

Wesolowski, T. A.; van Wezenbeek, E. M.; Wiesenekker, G.; Wolﬀ, S.

K.; Woo, T. K.; Yakovlev, A. L. ADF2016; SCM, Theoretical

Chemistry, Vrije Universiteit: Amsterdam, The Netherlands, 2016;

Https://Www.Scm.Com .

ger, R.; Schipper, P. R. T.; Schluns, D.; van

̈ ̈

(

Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71 (1), 3−8.

(

31) SADABS; Bruker AXS Inc.: Madison, WI, USA, 2001.

32) Spackman, M. A.; Jayatilaka, D. Hirshfeld Surface Analysis.

CrystEngComm 2009, 11 (1), 19−32.

(33) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;

Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Petersson,

G. A.; Nakatsuji, H.; Li, X.; Caricato, M.; Marenich, A.; Bloino, J.;

Janesko, B. G.; Gomperts, R.; Mennucci, B.; Hratchian, H. P.; Ortiz, J.

V.; Izmaylov, A. F.; Sonnenberg, J. L.; Williams-Young, D.; Ding, F.;

Lipparini, F.; Egidi, F.; Goings, J.; Peng, B.; Petrone, A.; Henderson,

T.; Ranasinghe, D.; Zakrzewski, V. G.; Gao, J.; Rega, N.; Zheng, G.;

Liang, W.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;

Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.;

Throssell, K.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.;

Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V.

N.; Keith, T.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell,

A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Millam, J. M.;

Klene, M.; Adamo, C.; Cammi, R.; Ochterski, J. W.; Martin, R. L.;

Morokuma, K.; Farkas, O.; Foresman, J. B.; Fox, D. J. Gaussian 09,

Rev. C; Gaussian, Inc.: Wallingford, CT, 2009.

45) Klamt, A.; Schuurmann, G. COSMO: A New Approach to

̈ ̈

Dielectric Screening in Solvents with Explicit Expressions for the

Screening Energy and Its Gradient. J. Chem. Soc., Perkin Trans. 2

46) Frias, E. Palladium Complexes in Concentrated Nitrate and

993, No. 5, 799 −805.

Acid Solutions. Talanta 1995, 42 (11), 1675−1683.

(47) Vasilchenko, D. B.; Tkachev, S. V.; Tsipis, A. C. Aquanitrato

Complexes of Palladium, Rhodium, and Platinum: A Comparative 15

N NMR and DFT Study. Eur. J. Inorg. Chem. 2018, 2018 (5), 627−

639.

(48) Purans, J.; Fourest, B.; Cannes, C.; Sladkov, V.; David, F.;

Venault, L.; Lecomte, M. Structural Investigation of Pd(II) in

Concentrated Nitric and Perchloric Acid Solutions by XAFS. J. Phys.

Chem. B 2005, 109 (21), 11074−11082.

(49) Nakamoto, K. Infrared and Raman Spectra of Inorganic and

Coordination Compounds, Part B, 6th ed.; Wiley: 2009.

(50) Addison, C. C.; Sutton, D. Complexes Containing the Nitrate

Ion. In Progress in Inorgunic Chemistry 2007, 8, 195 −286.

(51) Addison, C. C.; Brownlee, G. S.; Logan, N. Tetranitratoaurates-

(III): Preparation, Spectra, and Properties. J. Chem. Soc., Dalton Trans.

1972, No. 14, 1440.

(34) Vosko, S. H.; Wilk, L.; Nusair, M. Accurate Spin-Dependent

Electron Liquid Correlation Energies for Local Spin Density

Calculations: A Critical Analysis. Can. J. Phys. 1980, 58 (8), 1200−

35) Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-

211.

Salvetti Correlation-Energy Formula into a Functional of the Electron

Density. Phys. Rev. B: Condens. Matter Mater. Phys. 1988, 37 (2),

(52) Vasilchenko, D.; Vorobieva, S.; Baidina, I.; Piryazev, D.; Tsipis,

A.; Korenev, S. Structure and Properties of a Rhodium(III)

Pentanitrato Complex Embracing Uni- and Bidentate Nitrato Ligands.

Polyhedron 2018, 147, 69−74.

(53) Fujii, T.; Egusa, S.; Uehara, A.; Kirishima, A.; Yamagishi, I.;

Morita, Y.; Yamana, H. Electronic Absorption Spectra of Palladium-

(II) in Concentrated Nitric Acid Solutions. J. Radioanal. Nucl. Chem.

2011, 290 (2), 475−478.

36) Becke, A. D. Density-functional Thermochemistry. III. The

85−789.

Role of Exact Exchange. J. Chem. Phys. 1993, 98 (7), 5648−5652.

37) Stephens, P. J.; Devlin, F. J.; Chabalowski, C. F.; Frisch, M. J.

Ab Initio Calculation of Vibrational Absorption and Circular

Dichroism Spectra Using Density Functional Force Fields. J. Phys.

Chem. 1994, 98 (45), 11623−11627.

994

Inorg. Chem. 2021, 60, 2983−2995

Inorganic Chemistry

Article

54) Jørgensen, C. K.; Parthasarathy, V.; Ahlgrén, M.; Rantala, M.

(74) Komarek, A. C.; Merz, P.; Guo, H.; Suard, E.; Chen, J.-M.;

Felser, C.; Jansen, M. Pb PdO (OH) and Pb PdO(OH) (H

The Influence of Nitrate and Other Anions on the Absorption Spectra

of Palladium(II). Acta Chem. Scand. 1978, 32a , 957 −962.

O): Synthesis and Crystal Growth at Ambient Conditions. Z. Anorg.

Allg. Chem. 2015, 641 (8−9), 1473−1479.

55) Bastian, R.; Weberling, R.; Palilla, F. Ultraviolet Spectrophoto-

metric Determination of Nitrate ···Application to Analysis of Alkaline

Carbonates. Anal. Chem. 1957, 29 (12), 1795−1797.

(75) Liu, S.; Liu, R.; Wu, Y.; Wei, Y.; Fang, B. Study on

Electrochemical Properties of Palladium in Nitric Acid Medium.

Energy Procedia 2013, 39, 387−395.

(56) Addison, C. C.; Logan, N.; Wallwork, S. C.; Garner, C. D.

(76) Kolarik, Z.; Renard, E. Recovery of Value Fission Platinoids

Structural Aspects of Co-Ordinated Nitrate Groups. Q. Rev., Chem.

Soc. 1971, 25 (2), 289.

from Spent Nuclear Fuel. Platin. Met. Rev. 2003, No. 2, 74−87.

58) Sun, C.-F.; Hu, C.-L.; Xu, X.; Mao, J.-G. Polar or Non-Polar?

57) Khranenko, S. P.; Baidina, I. A.; Gromilov, S. A.; Belyaev, A. V.

Synthesis and Crystal Structure of Na2[Pd(NO3)4]. J. Struct. Chem.

000, 41 (4), 709−712.

Syntheses, Crystal Structures, and Optical Properties of Three New

Palladium(II) Iodates. Inorg. Chem. 2010 , 49 (20), 9581 −9589.

(59) Rasmussen, L.; Jørgensen, C. K. Palladium(II) Complexes. I.

Spectra and Formation Constants of Ammonia and Ethylenediamine

Complexes. Acta Chem. Scand. 1968, 22 , 2313 −2323.

(60) Pilny, R.; Lubal, P.; Elding, L. I. Thermodynamics for Complex

Formation between Palladium(Ii) and Oxalate. Dalt. Trans. 2014, 43

32), 12243−12250.

61) Calderazzo, F.; Pampaloni, G.; Passarelli, V. 1,10-Phenanthro-

(

line-5,6-Dione as a Building Block for the Synthesis of Homo- and

Heterometallic Complexes. Inorg. Chim. Acta 2002, 330 (1), 136−

62) Parac, T. N.; Kostic, N. M. New Selectivity and Turnover in

42.

Peptide Hydrolysis by Metal Complexes. A Palladium(II) Aqua

Complex Catalyzes Cleavage of Peptides Next to the Histidine

Residue. J. Am. Chem. Soc. 1996, 118 (1), 51−58.

(63) Yamamoto, K.; Fujibayashi, T.; Motomizu, S. Liquid-Liquid

Distribution of Ion Associates of Tetrahalogenopalladate(II) with

Quaternary Ammonium Counter Ions. Solvent Extr. Ion Exch. 1992,

64) Feng, Y.; Shao, Q.; Ji, Y.; Cui, X.; Li, Y.; Zhu, X.; Huang, X.

0 (3), 459−476.

Surface-Modulated Palladium-Nickel Icosahedra as High-Performance

Non-Platinum Oxygen Reduction Electrocatalysts. Sci. Adv. 2018, 4

(

7), No. eaap8817.

(65) Singh, S. K.; Iizuka, Y.; Xu, Q. Nickel-Palladium Nanoparticle

Catalyzed Hydrogen Generation from Hydrous Hydrazine for

Chemical Hydrogen Storage. Int. J. Hydrogen Energy 2011, 36 (18),

66) Song, X.; Yang, P.; Wang, J.; Zhao, X.; Zhou, Y.; Li, Y.; Yang, L.

1794−11801.

NiFePd/UiO-66 Nanocomposites as Highly Efficient Catalysts to

Accelerate Hydrogen Evolution from Hydrous Hydrazine. Inorg.

Chem. Front. 2019, 6 (10), 2727−2735.

(67) Bhattacharjee, D.; Mandal, K.; Dasgupta, S. High Performance

Nickel e Palladium Nanocatalyst for Hydrogen Generation from

Alkaline Hydrous Hydrazine at Room Temperature. J. Power Sources

68) Singh, S. K.; Zhang, X.-B.; Xu, Q. Room-Temperature

015, 287, 96−99.

Hydrogen Generation from Hydrous Hydrazine for Chemical

Hydrogen Storage. J. Am. Chem. Soc. 2009, 131 (29), 9894−9895.

(69) Zhang, K.; Mukhriza, T.; Liu, X.; Greco, P. P.; Chiremba, E. A

Study on CO and CH Conversion to Synthesis Gas and Higher

Hydrocarbons by the Combination of Catalysts and Dielectric-Barrier

Discharges. Appl. Catal., A 2015, 502 (4), 138−149.

(70) Liu, Y.; Sheng, W.; Hou, Z.; Zhang, Y. Homogeneous and

Highly Dispersed Ni-Ru on a Silica Support as an Effective CO

Methanation Catalyst. RSC Adv. 2018, 8 (4), 2123−2131.

(71) Khudorozhkov, A. K.; Chetyrin, I. A.; Bukhtiyarov, A. V.;

Prosvirin, I. P.; Bukhtiyarov, V. I. Propane Oxidation Over Pd/Al2O3:

Kinetic and In Situ XPS Study. Top. Catal. 2017, 60 (1 −2), 190 −197.

(72) Firdous, N.; Janjua, N. K.; Wattoo, M. H. S. Promoting Effect

of Ruthenium, Platinum and Palladium on Alumina Supported Cobalt

Catalysts for Ultimate Generation of Hydrogen from Hydrazine. Int. J.

Hydrogen Energy 2020, 45 (41), 21573 −21587.

(73) Singh, S. K.; Xu, Q. Nanocatalysts for Hydrogen Generation

from Hydrazine. Catal. Sci. Technol. 2013, 3 (8), 1889.

995