The i.r. spectra of several rare-earth formates

Spectroohimica

Ireland Press,1976. Printedin Northern Acta, Vol. 32A, pp. 1155to 1157. Persamon

The i.r. spectra of several rare-earth formates J. TH. M. DE HOSSON~, J. P. M. MAAS and M. P. GROENEWEGE Vakgroep Algemene Chemie, State University Utrecht, The Netherlrmds (Received 8 July 1976) Abstract-The i.r. spectr8 of some rem-earth formates 8re recorded in the mnge 400940 cm-‘. The following compounds were studied: CB(HCO~)~, Pr(HCO&, Nd(HCO,),, Sm(HCO,),, Eu(HCO,), and Gd(HCO,),. Some compounds were 81~0studied upon de&oration and at lowered temper&true. Nearly 811bands could be assigned asd the expected fctctor group splitting was observed. A shift to higher frequencies wes observed with increasing atomic number.

INTRODUCTION

RESULTS

FERRARO and BECKER [l] have studied La(HCO,),, Le(DCO,),

and Nd(HCO,),;

they

ment in terms of metaloxygen far

i.r. frequencies.

bands

according

We

to the factor

the c8se of gadolinium the

structure

formate,

has been

oerium-,

recorded clusion

formctte. spectra

are The

from

8nd indicates

that

all

an8lysis

in

by

18ttice

GY

and

with

gado-

resemblance

of all

supports

Mayers

con-

europium

formate

also

of gadolinium

belongs in this series.

has

spacegroup.

Table

of the factorgroup

1 contains

an8lysis.

Table

2

Ntot

Nac

N

tr

N

NpTm3te rot

activity

1nt

Table 2. W8venumbers and assignments for gadoliniumformate

EXPERIMENTAL All compounds were prepared by dissolving the oxydes (FLUKA, puriss.) in diluted nitric &cid, precipitating the carbonates by 8dding sodiumcarbonato (BDH, Analar). The precipitates were washed out with deionized water until 8 pH of ‘7-8 w&s obtained. These washed out precipitates were dissolved in formic 8cid (BDH, Analsr). When the precipitated carbonates were still wet, the formed formates st8yed dissolved and could be obtained by slow eveporation. Dried, the carbonates gave 8 solid state reaction without dissolution of the formate. Only gadolinium formate is soluble in water. We used both methods without distinction. Checking upon one compound revesled that there is no difference in the spectre, indicating, that the structure of the compounds, -made by the two methodsis identical. The spectra, were recorded 8s potassiumbromide discs and polyethylene discs on 8 Hitachi EPI G3 i.r. 8nd 8 Beckman-RIIC FS 720 Fourier f8r i.r. spectrophotometer. The low temperature spectra were recorded using &home-madeliquidnitrogen cryostat,which could attain st least -160’ C.

Description

”

C-8

Y

o-c-ii

2915

)

Gd(DC0 1: 2220

1583

c-o asp 6

cdiiico

0rvc-i) (

Ode-c-n

vC-O~w

7575

'15116

7413

1059

1368

( 1328

i 1360

%CO*) Or b(C0,)

13LO

917

6o-c-o 307 298 265 233 198 178 168

155

136

t present address: Laboratorium voor Fysische Metealkunde, Nijenborgh 18, Groningen, The Netherlands. 10

formate

It h8s 8 rhombohedml

Tctble 1. Fsotor group splitting for gadolinium formate with spacegroup Cgp

studies,

neodymium-

Css,(R3m)

the results

PAESST [Z].

his X-ray

isostnmtural striking

greatly

for some nearly

for which compound

praseodymium-,

semariumformate linium

group

revealed

MAYER [3] has concluded that

assign

structure

been studied by PAEST [2].

gave an assign-

stretching

could

The crystal

1156

Intensity

Overtone and combination

bands.

Ga(Hco2)3

2840

Gd(DC02)3

assignment

3545

2220 + 1328

2987

2220 + 780

2913

2 x 1583

2853

1546 + 1340

2633

2 x 1328

2375

1328 + 1059

2160 1328 + 780

2090 1426 (v)

1436 (str)

1358

Table 3. Wavenumbers for the rare-earth formates

rco 2

DCO2 3545 2987

'208'

*2856a

2918

2918

!915

2845

2845

!840

2220

v

2913 2840

2830 2750

2763

2675

2685

2853

2633 2375 2160 2090

*..1605~ * 1580"

158Sa 1550*,

1428' * 1405L

1056~

1600

1583

br ,str

1578

1575

1546

sh or shp

1432

1432

1436

1426

stlp.str

1408

1410

1410

1413

1059

silp,str

1382

1383

1380

1358

Y.Y.

1368

1340

shp,str sh or shp

1596

1586’

1595

1575

1544

1582

1577

1578

1425

1415

1429

1430

1404

1052

1409

1598

1594

1602

* 1358’

i334*

332

1362

I 365

1365

1366

*

1328

322

1357

1359

i357

1358

360

1328

915

?ngl

1100

1093

,090

917

T.V.

775

786

786

786

789

‘180

shp .m

778

780

778

780

283

286

292

282&

303

300

240~

265

* *

77ga

* *

307

shp

306

298

br,str

261

266

265

br ,str

306

*

280a

sh or shp

*

26aa

250

253

253

*

238

228

233

228

240

236

236

233

br,str

198

197

194

203

198

sh or shp

186

* 16ya

174

178

183=

185

178

180

178

br,str

150a

155

161

163~

169

166

168

155

m.shp

J(’ 1218

124

132

133a

139

t37-

141

136

m,shp

* *

a)

data from Ferraro

g

= fundamental

and Becker

[l]

1156

1167

The ix. spectra of several rare-earth formates Table 4. Calculations of the moments of inertia for the formatsgroup in Gd(HCO,), and Gd(DCO,),. Data for carbon and oxygen are taken from PABST [2]. The hydrogen atom is supposed to have a carbonhydrogen distance of 1.09 A and to make equal angles with the two carbon-oxygen bonds -

EC0

DCOp

L9.5cl4

8.281

0.95L

0.724

/

Rario

41.218

6.000

41.217

2

203fi9a

0.9753

100/17a

0.9888

2.3390

L1.820

1.ooo

0.0

7.8855

2.5307

0.0

6.0126

1.5063

0.0

5.9s

3.1357

0.0

6.387;

1 1

Nd

1

I 1 I

0.9645

the observed

ments

for

and the assign-

formate.

In

listed the data for all the studied indicating

the resemblance

as the shift

in frequency

Table

3 are

formates,

clearly

of the spectra

as well

with

increasing

atomic.

number.

The assignment formate hyde

[6],

assuming

numbers

formate

[l]

the E-mode

than the Al-mode;

“molecular”

argument,

that

The

higher

bands

on the vibra-

than the symmetfeature

in this region

Ferraro

and Becker

(I&,).

the shifted

in the 1400-

are assigned

as a splitting

Their

by

of the in plane

deuteration

study

showed

band to be single, thus the splitting

the rocking

being

showed

undetectable.

what

between

These

bands

the are

therefore

two

of the

very weak band some-

bands

from

temperature

that

of

Our deuteration

the same shift for the lower

two bands and a remaining

think

in wave-

region.

two

rocking

study

and formalde-

asymmetrical

There is a striking

1460 cm-l

wave-

for sodium

this is based

tions are higher in wavenumbers rical ones.

formate

on the assignment

[4], lanthanum

1

I

I

I I

I I

I

Gd(CHO,),.

independent;

this band

we

is a combination

I

I

I

I I

II I I I I

I I

I

I

I I

I

IA I

I

1550 1450

1400

In gadolinium

for the internal

is based

I I

I I

I

I?.

I’ I

I

1350

750

Fig. 1. Wavenumbers for the rare earth formates Ce, Pr, Nd, Sm, and Gd. The shift to higher wavenumbers and the increase of crystal field splitting in the series cerium to gadolinium. For comparison some of the wavenumbers of sodiumformate are given (Na: solid, Na* : aqueous solution).

DISCUSSION

numbers

I I

I600

frequencies

gadolinium

I

I I

I

I

Pr

100

I

I

Ce

Eu

iLlI

150

I

NO

Cd

0.9226

200

1

No*

Sml

16l3/155

contains

250

300

symmetry, metry

formate

the formate

species and can mix.

The assign

translational

modes

are more

diacult

to

; the spectra show 3 broad bands with in

some spectra

an additional

sharp band.

tion gives only a very small calculated cannot

be seen in the spectra,

accuracy

in the wave number

We think therefore the

ion has C,

thus R, and R, are in the same sym-

region

modes,

to distinguish additional

because

of the in-

of the broad

bands.

that the three broad bands in

200-300 cm-l

translational

Deutera-

shift, which

are

the

but we have

them between

sharp bands

T,,

three

species

no information T, and T,.

The

must then be assigned

to

the A, species. Assuming changes

an

identical

structure

in the cell dimensions

see the shift to higher frequencies the crystal

field

with increasing

splitting atomic

small to

and the increase of

of nearly

number,

with

it is remarkable

all vibrations

as shown in Fig. 1.

band, which owing to Fermi resonance has grown in intensity. Deuteration assignment

studies

are

very

of the librational

the results are listed of calculations of

inertia

formate.

for

Studies

site symmetry ‘Rw

’

formate.

the

‘RR.

formategroup

on sodium

for the formate

helpful

modes.

in

the

In Table

4

of the moments in

formate

gadolinium [6] with

ion indicate

C’s

QRz >

more clearly than in the case gadolinium

[l] [2] [3]

[4] [5]

[6]

J. R. FERRARO and M. BECKER: J. Iwor. Nucl. Chem., 24, 637 (1962). A. PABST: J. Chem. Phys., 11, 145 (1943). I. MAYER, M. STEINBERQ, F. FEIQENBLATT and A. GLASNER: J. Chem. Phya., 66, 1737 (1962). R. NEWMAN: J. C&m. Phys., 20, 1663 (1962). P. COSSEEand J. H. SCEACHTSCRNEIDER: J. Chem. Phys., 44, 97 (1966). to be published.