Molecular complexes of antimony trihalides with benzophenone, 4-Cl-, 4-Br- and 4-NH2-benzophenone.

Spectro&lmics Acts, vol. 32A, pp. 679 to 634. Pergamon Press,1978. Printedin Northern In&and

Molecular complexes of antimony trihalides with benzophenone, 4-C%, 4-Br- and 4-m-benzophenone. IDA M. VEZZOSI, GIORUIO

PEYRONEL

and ALINE ZANOLI

Istituto di Chimice Genera&ee Inorganica, University of Modena, 41100 Modena, Italy. (Recived 6 May 1976) &&a&-With benzophenone (Ph,CO) and its 4-Cl- and 4-Br-derivatives, antimony trichloride and tribromide form solid 1: 1 molecular complexes; their i.r. spectra show that the metal atom is not coordinated to the C=C group. 1: 1 complexes too 8re formed in dilute dichloromethane (DCM) solutions; their equilibrium constants, determined from their charge transfer bands by the Benesi-Hildebrand method, decrease in the order Ph,CO > 4-Br-Ph,CO > 4-Cl-Ph,CO and SbCl, > SbBr, in agreement with the decreasing dipole moments both of the donors and of the acceptors. The ligand 4-NH,-Ph,CO forms two solid, yellow and red, complexes with SbX,:ligand r8tios: 2: 1 and 1: 2 for SbCl,, 2: 3 ( : 6DCM) and 1: 1 for SbBr,, 2 : 1 and 1: 1 for SbI,, respectively. The yellow complex becomes spontaneously red in DCM solution and, for SbCl,, also in the solid state. The i.r. spectra show th8t 8160in these complexes the metal atom is not coordinated to the C=O group and in the red 1: 2 SbCl,- and in the yellow 2 : 1 SbI,-complex not even to the NH. eroun of the linand: in the other 4-NH,-Ph,CO-complexes the ligand seems to be N-bonded tothemetal. .

IBTRODUCTION Infrared

measurements

on the r(C0)

been used to investigate between

antimony

or benzophenone

the complex

trichloride

[l-5]

the Job’s continuous

band

have

formation

and acetophenone

in various solvents. variation method,

Using

the exist-

ence in solution

of two

complexes

with 1:

1 and 1: 2 stoichiometries [ 1, 61

has

recognized

been

measurements

and

SbCl, :donor from

the dissociation

i.r.

molecular absorbance

constants

of these

complexes have been calculated 12, 51. As neither solid complexes of benzophenone and its derivatives

with the VA

group trihalides

are known, nor their electronic spectra in solution have

been

vestigated

studied, by

we have

electronic

some molecular complexes

and

prepared i.r.

and

of benzophenone,

4-Br- and 4-NHs-benzophenone

in-

spectroscopy 4-Cl-,

with the antimony

trihalides. EXPERIBIEBTAL All reagents used were of the best chemical grade. Antimony trihalides (Hopkin and Williams) were dehydrated on phosphorus pentoxide, and for spectrophotometric measurements the trichloride 8nd tribromide were reorystallized from oyolohexane. Benzophenone and its derivatives (Fluka) were recrystallized from petroleum ether. All solvents were dehydr8ted and kept on metallic sodium wire. For spectrophotometric measurements 8 speotrograde dichloromethane (Merok) w8s used: it was dehydrated on calcium chloride and purified by fractional distillation, collecting the fraction boiling at 40°C. Because of the hygroscopicity of the anti-

mony t&elides and of their molecular oomplexes, all the manipulations were performed iu a dry-box. The y&low complexes SbX,*L (X = Cl, Br; L = Ph,CO, 4-Cl-Ph,CO, 4-Br-Ph,CO) were prepared from dichloromethane solutions of the reagents by adding petroleum ether or from cyolohexane solutions by very slow crystallization. All these complexes are decomposed by water. The red aomplex SbCl,.2(4-NH,-Ph,CO) ~8s obteined from 8 dichloromethane solution saturated with both components until it reached 8 deep red color. From the solution 8 red viscous mass slowly precipitates in one day and, after repeated washing with ligroin or petroleum ether, is transformed into a red powder. Sometime well shaped red crystals are formed on the walls of the vessel. The yellow complex 2SbC1,.(4-NH,-PhsCO) w8s obtained by adding petroleum ether to 8 freshly prepared dichloromothano solution of the components. From old prepared solutions of the same composition a mixture of the yellow 2 : 1 and of the red 1: 2 complex precipitates. From this mixture the yellow 2: 1 complex may be extracted with toluene, in which it is fairly soluble, and then precipitated with petroleum ether or by crystallization on cooling. The solid yellow 2 : 1 complex becomes red with time. The red complex SbBr,.(4-NHs-Ph,CO) was prep8red from 8 dichloromethane solution saturated with both components, by washing the red viscous mass, obtained from it, with ligroin or petroleum ether. The yellow complex 2SbBr,.(4-NH,-Ph,CO)* SDichloromethane was obtained by dissolving the solid SbBr, in 8 DCM solution of the ligand and rubbing the walls of the vessel with a glass rod. The yellow complex, if dry, is stable in air; in the mother solution it becomes red with time. The red complex SbI,*(4-NH,-Ph,CO) was obtained from an ethanol solution of the reagents containing

679

I. M. VE~~OSI, G. PEYRONEL and A. ZANOLI

680

an excess of the ligand. The complex is stable in air. The yellow complex 2SbI,*(4-NH,-Ph.&O) was obtained from an ethanol solution of the reagents containing an excess of the triiodide by adding petroleum ether. The yellow complex, if dry, is stable in air. The bulky precipitate in the mother solution becomes red with time. The antimony halide content was determined by dissolving the complexes in ethylbenzene, shaking the solution with an excess of an aqueous solution of silver nitrate and nitric acid and titrating the excess of silver nitrate by the Volhard method. In some cases the total halogen content was determined by the Volhard method after oxydation of the substance with sodium peroxide in a steel bomb. The ligand content was determined by carbon and hydrogen elemental analysis (Table 1). Electronic spectra were recorded with a double beam Beckman DK 1A speotrophotometer on diohloromethane solutions. Quantitative absorption measurements for the determination of the equilibrium oonstants by the Benesi-Hildebrand method were performed with a single beam Hilgher Uvispeok spectrophotometer with galvanometric reading giving a high precision in wave length and intensity reading. Diohloromethane was used as solvent because of its high transparency in the spectral region explored, its low donor properties toward antimony t&elides and the good solubility in it of the complexes investigated. Infrared spectra were recorded on the solid complexes in KBr disks (4000-260 cm-l) with a Perkin-Elmer 521 speotrophotometer and in nujol mulls on polythene (550-60 cm-l) with a Beckman IR 11 apeotrophotometer. RESULTS AND DISCUSSIOI Benzophenone give

with

and its 4-Cl- and I-&-derivatives

antimony

trichloride

Table 1. Analytical

and

solid

yellow

molecular

mony

trihalide

complexes

1: 1 complex,

forms with each anti-

(Cl, Br, I) two,

yellow

with different trihalide:

Complex yellow

S bC1, : L

red The yellow

SbBrs:L

2:l

2:3(:5DCM)

1:2

1:l

complex,

SbI,:L 2:l 1:l

containing

an excess of tri-

halide with respect to the composition complex,

COlOI-

of the red

is unstable and tends, even in the solid

state for SbCl,,

to change spontaneously

The (X

electronic

= Cl,

spectra

Br) + L(L

Br-Ph&O)

of

the

in dichloromethane

recorded in the region 310-390 antimony while

systems

trichloride

tribromide

solutions

nm.

a very

transparent

high

absorption

For each trihalide the spectra

of their solutions with the three ligands are very similar

(Fig.

the spectra

1).

The increase in absorbance

of the complexes

transfer band, even if not isolable in the case of the bromide. From the absorb&noes (A) measured at different wavelengths

on solutions with a constant. concen-

tration

of the ligand

of the

antimony

absorbanoes

and various

trihalide,

by

of the components

Benesi-Hildebrand

method

concentrations

substracting

the

and applying

the

calculation

[G],

of

C

H

SbX,

i

or

[x’

5C.)0(55.EC)

1:l

ye~low

33.98(35.:0)

2.14(2.04)

[31.8e(31.8$)7

4-kh2CO

I:1

yellow

32.07(31.91)

2.16(1.86)

4-NH*--Ph2CO

2:1

yellow

24.25(23.89),

l.gl(l.69)

70.07(6V.S2)

4-NH2-Ph2C0

1:2

red

4g.81(50.01)

3.89(3.%)

36.57(36.68)

I:1

yellow

28.26(28.71)

l.gd(1.85)

4-Cl-Ph2CO

1:l

yellow

26.98(27.00)

1 .79(1

4-Br-Ph2C0

I:1

yellow

24.62(25.07)

1.76(1.46)

yellow

30.46(30.35)

2.34(2.13)

:DCM

2:3:5

4-NH2-Ph2CO

I:1

red

4-NH2-Ph2CO

2:1

yellow

4-NH2-Ph2C0

Id *, = 2.42c2.67).

1 :I

red

in

is due to a charge

2.57(2.46)

4-NH2-Ph2CO

4were

In this region

is completely

gives

until about 360 nm.

SbX,

= Ph,C0,4-Cl-Ph,CO,

37.22(38.05)

SbBr3:Ph2CO

into the

red complex.

light :ifllOW

4-Cl-Ph2CO

and red,

ligand ratios:

1:1

SbC13Ph2CO

(a)

one

results, found y0 and (oalod. %) for the solid complexes of SbX, with benzophenone (Ph,CO) and its derivatives Ratm

Sb13:

tribromide

only

while 4-NHs-benzophenone

(27.98(27.94)

2.17(1

.57) C50.86(51.33)1

(a)

.V8)

13.35(12.98)

1.17(0.92)

22.54(22.29)

1.79(1.57)

-

681

Molecular complexes of antimony trihalides with benzophenone

Fig. 2. System SbCl, + Benzophenone in diohloromethane: (upper part) Benesi-Hildebrand plots at different wave-lengths; (lower part) stability constants at various wave-lengths. greater

than

agreement

those

with

of

halideinthevapourstate nm

constants

lc = [SbXs.

[SbXs][Ligand]

were determined

plots of [L] l/A

. 10Y3 versus l/[SbX,]

wavelengths SbCl,

and

of k versus

+ Benzophenone

positive

intercept

Ligand]/

(Table

2).

rZ for the

is given

in Fig.

system 2.

k values on a wide range of wavelengths in solution

The

for different

and the good constancy

[7] that the complex

(SbCl,

in

of the tri-

= 3.9 D; SbBra =

It may be of interest to note that the 1: 1 antimony

tribromide-pyrene

in dichloromethane constant

three

times

of the equilibrium trihalide

dipole

r-bonded

solution

analogous t&chloride

greater complex

constants

moments

to a possible participation the complexation.

equilibrium

SbBra-complexes moments

2.8 D) [8].

Fig. 1. Electronic speotra of the systems in dichloromethane : (left) SbCl, + Benzophenone with a constant oonoentration of the ligand (1.1 . lo-* M) (lower curve) and increasing concentrations (66-16.5 . IO-’ M) of SbCl, (a) reference: diohloromethane, (b) reference: an isotonio solution of benzophenone in dichloromethane; (right) SbBr, + Benzophenone: (a) ligand (1.2. IO-ZM), (b) SbBr, (13.0. 10-s M), (o) SbBr, + ligand with the same conoentrations. the

the

the dipole

complex

a B.H. than [9].

has

equilibrium that

of the

This inversion

with respect to the

[S] was attributed

[9]

of the bromine atom in

This conclusion

seems to be

confirmed by the crystal structure of the complex 2SbBra

* Pyrene [IO], and also by the B.H. equilib-

rium constants with

The

the

of the

[Ill.

several same

of the mercuric halide complexes aromatic

order

HgBrz

hydrocarbons, > HgCI,

was

for which observed

indicate

has a trihalide:

ligand ratio of 1: 1. The B.H. of

equilibrium

complexes

4-Br-PhaCO decrease

constants

decrease >4-Cl-

of the

2 and Fig.

stants

of

the

the

PhzCO

dipole

(Table

in

3).

of both series

order

linearly

moments

PhzCO with

of the

ligands

Also the equilibrium

SbC13-complexes

> the

con-

are significantly

k

Table 2. Equilibrium constants of the 1: 1 SbC1, and SbBr, complexes determined in DCM solution with the Benesi-Hildebrand method. Dipole moments (cc) of the ligands [ 171 SbC13

SbBr

3

u (TOC)

Benzophenone

1.70

1.55.

2.95

(200)

4-Cl-Benzophenone

1.23

1.19

2.73

(13O)

4-Br-Benzophenone

1.36

1.27

2.78

(200)

Fig. 3. Plot of B-H. equilibrium constants (k,) of the 1: 1 complexes of SbX, with Ph,CO, 4-Cl-Ph,CO, I-Br-Ph,CO in diohloromethane versus the dipole moment (/.J)of the ligands.

I. M. VE~~OSI, G. PICYBONELand A. Z~LNOLI

682

The values determined

of the B.H.

equilibrium

for 1: 1 complexes

constants

in dichloromethsne

solution:

- Pyrene HgX, - Arene SbX, * Ph,CO

Chloride

Bromide

o-22

0.65

SbXs

PI

0.20-0.43

0.30-0.54

[ 111

l-23-1-70

1.19-1.55

this work

dipole

bond

that,

1: 1 SbCI,

dipole-

the n-bond

in this

constant

+Benzophenone (k, = 2.71)

by B.H.

evaluated

complex

(5)

method

ancy ms,y depend

for

in

is greater

(k, = 1.70);

on the different

the

dichlorothan

measthat

this discrepmethods

used

The solid

1:

acetophenone

1 complexes cm-l)

of

the

infrared

of the ligand, indicating

atom is bonded the ligand

of benzophenone

and

with AlCI, and AlBrs show a strong

(120-145

frequency

of the v(C0)

to the carboxylic

[12, 131.

shift of the v(C0) plexes

with

(Table

3) was

oxygen

atom of

no significant

band in the solid 1: 1 SbXs com-

benzophenone

solid complexes

v(C0)

that the metal

The fact that

observed

a decrease

frequency

was observed

al bond through a donation of an electron loon pair the metal weaker

[2].

atom

to the 5d vacant

This

in solution

W-0 than

AlXs-complexes

appears

in the

bond,

solid

SbXs

solution

the molecules

bond

in the

completely

complexes

phenone and its derivatives.

of

much

the Al-O

[12, 131,

orbitals

already

dis-

of benzo-

It is possible that in

of the donor and acceptor

are more free to orient themselves

in the right

position to realize this type of “polar”

bond, while

in the solid state, for steric reasons, another type of bond like rr-interactions may occur.

for their determination.

decrease

cm-l

acetophenone

and interpreted [2, 51 as due to the dipole associd+ 6d+ dtion R, = C *. *(I-Sb (X,) leading to a coordination-

solid

solution from infrared absorbance

urements found

than

the

complexes.

equilibrium

methane

in solution,

is stronger

type of molecular The

of benzoof about

and

of the oxygen

to indicate

and carbon tetra-

phenone 24-26

Ref.

and d&v. seem

In both the dichloromethane

chloride solutions of the SbCl,-complexes

and

its

excludes

derivatives

that

such metal-oxygen

in these

coordination

The i.r. region their

spectra

4000-400 ligands,

benzophenone at 933(s) plane

of the solid complexes

cm-l except

for

the

bending,

attributable and

the

V(CO) 1650~s

SbCl3*Ph2CO

1655~

SbBr .Ph2CO 3

1651vs

4-Cl-Senzophenone

1650~s

SbC13*(4-Cl-Ph2CO)

1650~s

SbB+4-Cl-Ph2CO)

1650ms

4-Br-Benzophenone

1645~s

SbC13*(4-Br-Ph2CO)

1645s

SbBry(4-Br-Ph2CO)

1645s 1630~s

3423m,3343ms,3225m

ZSbC13.(4-NH2-Ph2CO)

(Y)

1648~s

3350-3550~

SbC13.2(4-NH2-Ph$O)

(R)

1627~~

3422m,3340ms,322bm

ZSbBr3*3(4-NH2-Ph2CO)-5DCM.(Y)

1645s

34301x1broad,3350m

SbB+4-NH2-Ph2CO)

(R)

163Ovs

3345~ broad

(Y)

1620s

34OOs,3317s,3205s

1615s

3300-345ow,

2Sb13*(4-NH2-Ph2CCJ) %I,-(4-NH,-Ph,CO)

(R)

69O(vvs),

are missing.

does not allow

the type of bond in the whole series

Table 3. v(C0) and v(NH) i.r. bands (cm-l) of the liganda and their complexes. Y = yellow, R = red

4-NH2-Benzophenone

at

in the i.r. spectra

concern only the strongest complex

Benzophenone

of

[Ia] to out-of-

given [ 141 as sensitive to substitutions,

to interpret

of

of the ligand

band

The fact that these variations

in the

those

SbCls-complex

of these complexes.

occurs.

to

for which the bands

and 863(w),

CH

are identical

very broad

broad

very broad

\ w

683

Molecular complexes of antimony trihalides with benzophenone

7

I

\ : \

.....*

..*__ / ...**” ‘..* \ q..:... ‘:,

::“”

1;

.A

‘, -*... \

I

\\_//

I 250

I 300

i

\

‘-..* \ --._i :

I 450

400

350

b

nm

Fig. 4. Electronic speotra in diohloromethane solution 4-NH,-Benzophenone; - - - - red complex of: SbCl&(4-NH,Ph,CO); . . . yellow complex ZSbC1,.(4-NH,-Ph,CO) changing into the red SbC1,.2(4-NH,Ph,CO) complex. The electronic spectrum of I-NHz-benzophenone in diohloromethane

solutions

maxima

at 238 and 314 nm;

2SbCls.

(4-NH,-PhzCO)

SbCl,

distinct yellow gives

and

- 2(4-NH,--PhzCO) transfer

pectively

(Fig.

into

bands 4).

the

red

the

red

complex

Fig. 6. Infrared z(NH) bands of (a) I-NH,-Ben(b) yellow complex 2SbCl,.(4-NH,zophenone; (0) red complex SbC1,*2(4-NH,Benzophenone); Benzophenone). in the spectra of the rod 1:2 the yellow 2: 1 SbIs-complex

at 366 and 422 nm,

res-

2:

the

only a weak and very broad maximum

transformation

complex

in DCM

isosbestic

two complex species in solution.

point

of

solution

at 366 nm

The red complex

shows a distinct SbBr, - (4-NH,-PhzCO) transfer band at 420 nm; no distinct band could be observed

The

i.r.

spectra

For

solid complexes of the v(C0)

weak and broad maxima

(Table 3).

tinct and intense v(NH)

too

are shown.

It is clear that in the first two complexes metal atom is not coordinated

The three very dis-

admitted;

it seems rather improbable

hycan

be responsible for the disappearance and sharp v(NH) bands. In the far i.r. spectra SbC1,*(4-Cl-Ph,CO)

SbC13.(4-CLPh2CO) 372s 329-32 3b 163ms 122w

of

the

the SbCl,

red

St+-2(4-NH2-Ph2CO) 376~ 31%302b laO-150b 126sh

complex complex

bands [Hi, IS]

(Table 4) seem to be almost unaltered

v, = 377*,360,355

165,164*,152

of so intense

of the yellow

and

SbCl,.2(4-NH,-PhzCO)

“3 = 356*,320,318 =

an

that

Table 4. Far i.r. bands of SbCl,

v4 = 134,128*,126

the

group

drogen bonds alone in these solid compounds

3 and Fig. 6) are shown, identical and undeformed,

v2

to the NH,

of the ligand to the metal can be

* benzophenone

*(15)

appears.

one or two

For the other four complexes

bands of the ligand (Table

SbC13 (14)

only

of the ligand.

do not show any significant shift

band

SbBrs-complexes

N-coordination

at lower wave-

4-NH,

the

and for the 1: 1 SbIs-complex

charge

of SbBrs under 360 nm.

of the

1 SbCls-complex

and

charge

lengths for the yellow tribromide complex because of the great absorbance

SbCls-complex

while for the yellow

and

(Fig. 5), which confirms the presence of only these

transfer

I 3500

I 3000

show very intense

,The

a well defined

shows two distinct the yellow complex

f

indicating

I. M. VEZZOSI, G. PEYRONEL and A. ZANOLI

684 that the SbCl, formed from

the

by

geometry the

is not substantially

complex&ion,

differences

of

ligand,

de-

independently trihalide:ligand

ratio and colour.

Acknowledgments-This work was supported by the Consiglio Nazionale delle Ricerche of Italy. REFERENCES [l] [2] [3] [4] [5] [6]

G. LECLBRE ZUR NEDDEN, Spectmchim. Acta, 24A, 473 (1968). G. LECLBRE ZUR NEDDEN and G. DUYCKAERTS, Bull. Sot. Chim. Belges, 79, 479 (1970). G. LECL~RE ZUR NEDDEN and G. DUYCKAERTS, Bull. Sot. Chim. Beiges, 79, 491 (1970). G. LECLBRE ZUR NEDDEN, Bull. Sot. Chim. Beiges, 81,497 (1972). G. LECL$RE ZUR NEDDEN, Bull. Sot. Chim. Beiges, 81, 505 (1972). H. A. BENESI and J. H. HILDEBRAND, J. Am. Chem. Sot., 71,2703 (1949).

[71 G. D. JOHNSON and R. E. BOWEN, J. Am. Chem. SOL, 87, 1655 (1965). p. 86 I81 J. W. SMITH, Electric Dipole Moments, Butterworths, London 1955. [91 G. PEYRONEL, I. M. VEZZOSI and S. BUFBAQNI, Irrorg. Chim. Acta, 4, 605 (1970). PO1 G. BOMBIERI, G. P~YRONEL and I. M. VEZZOSI, Inorg. Chim. Acta, 6. 349 (1972). [Ill I. M. VEZZOSI, G. PEYRO~EL and A, F. ZANOLI, Inorg. Chim. Acta, 8, 229 (1974). [121 B. P. Susz and I. COOKE, Helv, Chim. Acta, 37, 1273 (1954). [13] B. P. Susz and P. CHALANDON, Helv. Chim. _Jcta, 41,1332 (1958). [la] D. E. H. JONES and J. L. WOOD, J. Chem. Sot. (A), 1140 (1967). [15] T. R. MANLEY and D. A. WILLIAMS, Spectrochim. Acta, 21,1773 (1965). 1161 K. NAKAMOTO, Infrared Spectra of Inorganic a& Coordination Compounds, p. 86 Wiley, New York, 1963. DipoloCl71 A. L. MCELELLAN, Tables of Experimental Moments, p. 435, 439 Freeman San Francisco and London, 1963.