Ifarch 5 - 1933
NORMAL VIBRATIONSOF TETR~WY.~NOPLATINATE(~~) ION
ing and finally disappears completely. The assignment of this band to one of the nitrito stretching frequencies seems reasonable. The band a t 1430 cm.-', however, grows in intensity on aging the sample. ,ki described above, this band is identified with the unsymmetrical stretching vibration of the nitro ligand. In the spectrum of [Co(hTH3)&TO2]Clz, the broad shouldered absorption band with a peak a t 1315 cm.-' results from an overlapping of the two peaks previously assigned to the symmetric nitro and the symmetric ammonia vibrations. X comparison of the spectrum of [Co(XH3)5r\;02]Clz with
[CGNTRIBUTIGN FROM TWE
889
the superposition of the spectra of Xa3[CO(NOz)~] and [Co(NH&]C& which show absorption bands a t 1338 and 1333 a n - ' , respectively, makes this evident. Only a single relatively sharp band, however, appears in this region for the freshly prepared nitrito complex. It has been shown that the nitrito isomer on standing several days a t room temperature gives rise to an absorption spectrum almost identical with the spectrum of the pure nitro compound. This experimental result can be explained as a change in the cohrdinating group from (Co-ONO) to (Co-hTO2). SOTRE DAME.INDIASA
DEPARTMENT OF CHEMISTRY,
U N I V E R S I T Y OB YOTRE D A M E ]
Infrared Absorption Spectra of Inorganic Coordination Complexes. VIII. Vibrations of Tetracyanoplatinate (11)Ion1 B Y D. 5 2 . S T V E E NICHIRO Y , ~ ~ NAXAGAWA, SAN-ICHIRO ~[IZUSHIMA'~
hND
Normal
J. \'. QUAGLIANO
RECEIVED APRIL 6, 1955 The infrared absorption spectra of potassium tetracyanoplatinate(I1) have been recorded over the range from 2 to 40 p . In addition to the characteristic peak observed a t about 2100 cm.-', there were observed several peaks in the low frequency region. The frequency values of these peaks, together with those of the known Raman lines in the same region, can be brought into good agreement with the values of the calculated normal frequencies of the complex cyanide ion. The calculation was made as a nine-body problem on the basis of the Urey-Bradley field.
Introduction
Experimental
An understanding of the nature of the metalligand bonds in complexes is of fundamental significance in the study of coordination compounds. Investigations of the infrared absorption of metal cyanide complexes offer an interesting problem in this field, since these compounds are expected to show relatively simple spectra. Specifically, cyanide frequencies are present a t about 2100 cm. -l, but no other fundamentals would be expected to appear until the KBr region, where the metal to ligand bond frequencies appear in the vibrational spectra. That such is actually the case may be expected from the Raman studies of Mathieu3 who calculated only the AI, vibration of the skeleton. Later, this calculation of skeletal motions was improved by Maccoll, using the modified valenceforce field but still regarding C=N as a dynamical unit. However, the nine-body calculation is not very difficult and, as has been shown in previous pap e r ~the , ~ Urey-Bradley field is much more suitable to explain the vibrational spectra of such a rnolecule. Therefore, the normal frequencies were calculated as a nine-body problem using this field, and the computed frequencies have been compared with those obtained in the present investigation, in the region from 5000 to 250 cm.-' (2 to 40 p ) .
Preparation of Compounds.-Potassium tetracyanoplatinate (11) trihydrate, K2Pt( CN)r,3HnO, was prepared ( a ) according to the method of h'Ieillet.6 The analysis was carried out on sample dried in at1 Abderhalden drier a t 110" for 3 days. Anal. Calcd. for KnPt( C N ) 4 . 3 / j H 2 0 : C, 12.51; S, 14.56. Found: C, 12.46; iY, 14.56. ( b ) The compound was also prepared according t o the method of Claus.? This preparation gave a product spectroscopically identical with that of the analyzed sample (a). In the region of the OH stretching frequency some slight differences exist which probably are attributable t o different degrees of hydration in the two samples investigated. Absorption Measurements.-Spectra were obtained by means of a Perkin-Elmer, model 21, infrared spectrophotometer, using CaFa, riaC1, KBr and CsBr prisms. Preparation of potassium bromide disks was carried out according to the direction of Stimson and O'Donnell.s The disks were used for observation in the region of 2 t o 24 p, and the resulting spectra were checked using Nujol mulls of these ZO compounds. I n the spectrum of K I P ? ( C N ) ~ . ~ Hobtained by the potassium bromide disk technique a few absorption peaks were observed in the region between 1500 and 600 cm.-' which should not appear according t o our calculations. The positions and intensities of these peaks depend upon the previous history of the sample. I t has been possible to demonstrate that these absorption peaks are due t o the water of crystallization and can be avoided by dehydrating the material a t 197" i n vacuo. Unusual optical behavior of hydrated planar Pt(CN)a= complex compounds has been r e p ~ r t e d . ~ ,Tetrahedral '~ metal cyanide complexes examined in this Laboratory do not show these additional absorption peaks. Beyond 24 fi the Nujol mull technique was employed; however, KBr disks can be used conveniently up to about 32 p .
(1) For paper VI1 in this series see THISJOURXAL, 78, 887 (1956) (2) (a) Presented in part before t h e 126th meeting of the American Chemical Society, September, 1954. Supported in part under A E C Contract AT(l1-1)-38, Radiation Project of t h e University of h'otre Dame. Abstracted in part from t h e P h . D . Thesis of D. M. Sweeny, Notre Dame, 1955. (b) Visiting Professor, from the Faculty of Science, University of Tokyo. (3) J . Mathieu, J. chim. $hys., 36, 308 (1939). (4) A. Maccoll, Proc. R o y . SOC.N.S.W., 77, 130 (1943). (5) T. Shimanouchi, J . Chem. Phys., 17, 245, 7 3 4 , 848 (1949); see also reference 12.
( 6 ) A. Meillet, J . Pharm. Chim., [31 3 , 444 (1843). (7) C. Claus, A n n . , 107, 132 (1855). (8) M. M. Stimson and M. J. O'Donnell, THISJ O U R N A L , 7 4 , 1805 (1952); see also J. P. Faust and J. V. Quagliano, i b i d . , 76, 5346 (1954). (9) L. A. Levy, J . Chem. SOC.,93, 1446 (1908). (IO) S. Yamada, Bzdl. Chem. SOL.Japan, 24, 125 (1951).
Results The spectrum of the Pt(CN)4=ion is showii in Fig. 1 and Table I shows the frequency values i n cm. recorded for potassium tetracyanoplatinate(I1) trihydrate together with those for potassium cyanide. This table represents a composite of
i
A. Fig. 1.-Infrared
B. absorption spectra of I;?Pt(CS),.II,O: A, in KBr disk; B, in nujol inull.
the spectra of each of these substances obtained with the four prisms employed. TABLE I
INFRARED ABSORPTION SPECTRAOF K*Pt(CK)r-RH2OT
KCS
&Pt( CS)4.SH*0“ KIP~(CT)~*RH~O~
..
3610 s
3600 s
..
3430 s 2150 vs
3400 s 2150 vs
..
2090 sh 2090 sh 1630 in 1630 m 1ri10 1v 1610 \v .. 505 s XI5 s .. 411 m 411 in .. 300 m 300 rn a Abbreviations: w = weak; rn = medium; s = strong; sh = shoulder; v = very. 2080 m 1630 w 1600 \T-
Calculation of Normal Vibrations.-The point group of the planar complex ion (M(CN)4)- is D4h. Therefore, the twenty-one normal vibrations are grouped into nine classes as shown in Table 11, in which the vibrational modes and activities are also shown. The normal modes of the eleven in-
N
C
47
-- -
‘a044’
TABLE 11 S O R M A L \’IRRATIO’L’S O F
Pt(CS)n= I O S BEI O X G I N G
TO E A C H
CLASSOF SYMMETRY NO.
Class
of
vibrations
Activity Infrared
Rarnan
V i b r a t i o n a l mode“
C-N) v(Pt-C) C?(Pt--C=.S) V(
61
62
CEX) Pt-C) u(C=N) v( Pt-C 1
V( V(
N
Fig. P.-Internal
r
3’’
coordinates of [Pt(CN),]- ion.
Using these symmetry coordinates, the secular equation is set up according to Wilson’s procedure.“ The G and F matrices of this equation are calculated as:
81
AP“
2
B2U
1 1
E,
1
B1“
-
-
+
f -
-
VI1
82
VIP
?i
VI3 V14
?i
VI6
%‘
V16
77
(degenerate) T h e symbols V , 8 and a See Fig. 3 and Tables V and V I . T are, respectively, stretching, in-plane deformation and nut-of-plane deformation vibrations.
i l l ) E. R . Wilson. J . Chern. P h y s . , 7 , 1017 (1939); 9 , 76 (1941)
-P
/J
FB,~ = (ki
I,l / 5
+
GE" =
2~0
p
-I*
Fq
-I* P+P'
24% (2PO 7
T
0 0
22/21*0 T 0
2POT 0
+
2(2M I*h2 d/2[2@oT2 p(Tz f
+
TT')]
try coordinate. Such calculations have been made for all the in-plane vibrations and the results are shown in Table V, where the figures in italics refer to the larger amplitudes (see also Fig. 3). In some of these vibrations the amplitude of a symmetry coordinate is nearly the same &[2poTz + U ( T z + T T ' ) ] as that for another and therefore, the assignment of the 2@OT2 /L'7'2 vibrational mode such as made + p ( T ~+ 2TTf + in Table I1 becomes ambiguous. I n order to make a more reasonable assignment in such a case, as well as to distinguish between stretching and deformation vibrations, we
)
+
T t ~ )
FEU =
kl
+ 9/10 Fq
(1
-9*/20
0
K2 rF, 0 0
-9.\/2/20 0
(HI
rFq
+ 11/20 F4)r? 0
")
0
H2rr'
Here r and Y' are the bond lengths of Pt-C and C=N, T and T' the reciprocals of r and Y', p, p' and po the reciprocals of the masses of C, N and Pt, K1 and Kz the Pt-C and C=N bond stretching force constants, HI and H Z the force constants for the deformation of the C-Pt-C and Pt-CkN bond angles, and F , the force constant for the nonbonded C , . . C distances. ( F ; is assumed to be equal to F,.5,12) The values of force constants are shown in Table 111. These values have
been selected to give the best fit with the observed Raman frequenciesSshown in Table IV. With these values of the force constants, the calculation has been made according to the usual procedure12and the results are shown in Table IV. TABLE IV CALCULATED AND OBSERVED FREQUEXCIES I O N IS CM.-' 2168 465 P3(A2g) 249 338 Y4(Blp) 91 vg(Big) vg(Bzg) 2166 ~ ( B z e ) 458 v s ( E u ) 2168 YQ(E") 519 299 vlo(E,) vII(Eu) 80 vi(A~g)
vz(A1g)
2168 465 Inactive 318 95 2149 455 Inactive Inactive Inactive Inactive
t
O F THE
Pt( CN)(-
Infrared
Inactive Inactive Inactive Inactive Inactive Inactive Inactive 2150 505 300 Outside the region of observation
I n order to determine the nature of the vibrations, we have calculated the relative amplitude for each of the internal symmetry coordinates in a given normal mode of vibration. The internal symmetry coordinates, S, are related linearly to the normal coordinates, Q, through the matrix expressionl* s = LQ If, therefore, we calculate the elements of the Lmatrix for a given normal vibration, we can at Once determine the relative amplitude for each symme(12) S. Mizushima, "The Structure of Molecules and Internal Rotation," Academic Press, Inc., New York, N . Y . , 1054.
+ + +-
+
~
a pv,
*
+
+
~~
f
9
+
**
++
4
-
+*;
.
+
a
0
+ V,
1
(
t t
4
1
*
+
+v3(A2gI
0
4 4
~~. *,
0
*
lB,gl
+ +
f
+ V6 ( b p )
fV7(b9)
4
b
. - .
0
.
+%(A~gI
0
i
c
s (A,gl
e
+ v.
FORCE CONSTANTS OF Pt( CN)4- IN lo6 DYNESICM. Ki = 3.425 Hi = 0.080 Fq = 0.050 Hz = 0.077 Kz = 16.823
Raman
b
t +--.
TABLE I11
Calcd.
t
f *
=
*
.
$
*
a
4
*
+
i
f
4 4
s
(",'E"'
+V,(E"I
Fig. 3.-In-Plane
* V,,IE")
.V,JE"l
normal vibrations of [ P ~ ( C ~ ) I ]ion. '
have calculated the distribution of energy in the internal symmetry coordinates for each normal vibration' TABLE V THE L-MATRICESOF IN-PLANE SORMAL VIBRATIONS OF P t ( cs)4= 10s"
(Au)
QI
S I
-0.222 ,393
SP (A2g)
0.191 Q4
Q6
0.289 .447
5-4
S6 (B21)
Q E
SS
-0.222 .393
s7
0.184 ,022
43
s 3
(Big)
Q2
Q8
-0.078 .119 Q7
0.184 ,021 QQ
Qlo
Q1i
Sa
-0.225 0.207 -0.004 -0.001 ss ,392 ,024 - .001 .000 'lo - ,002 ,038 ,206 - ,080 - ,001 ,033 .457 ,085 a Calculations have been made with bond lengths in A . , bond angles in radians and masses in atomic weight units. I t should be noted that the dimension of L for the stretching coordinates is different from that for the deformation COordinates. However, the deformation displacement of each atom can be obtained by multiplying by the equilibrium bond length in Bngstrijm units.
The kinetic energy ( T ) and potential energy (v)
R A S U D ~DAS R SARMA
8934"
Vol. 78
of the whole molecule for a given normal mode of vibration (QA), may be expressed as13
Assignment.-The absorption bands observed a t 3600-3400 ern.-' and a t 1630-1600 ern-' are assigned, respectively, to the stretching and deformation vibrations of the water molecules present in the crystal.'' There is no doubt as to the assign1 ment of the bands in the 2100 cm.-l region t o the V = 5 Q~ZF~IL~XLIX various C=N stretching vibrations. According to our calculation made for the planar where (G-')iiLix2 and FiiLiiz are the distribution of Pt(CN)4' ion, we should observe in the absorption energies in the coordinate, Si, in a normal mode of spectra no other in-plane fundamental vibration vibration (Qh). The results of the calculation of down to the region of 500 ctn.-' where the E, vithe potential energy distribution, FiiLii2, for each bration (one of the metal to ligand vibrations) is normal mode of vibration, are shown in Table VI, expected to appear a t 319 ern.-'. This is nicely where figures in italics refer to the largest terms. shown by our experiment, the difference between In this way we determined the nature of each vibra- the computed value, 519 cm.-', and the observed tion more reasonably. value, 505 cm.-', being only 37,. One of the inplane deformation vibrations is expected to appear TABLE VI at 299 cm. - l and this is in complete agreement with THE POTENTIAL ENERGY DISTRIBUTION FiiLi2 FOR EACII our observation of an absorption band a t 300 cm.-l. h-ORMAL h f O D E O F \IIBRATIONa The other in-plane deformation vibration with the (AIS) J'I Vd calculated frequency of 80 cm.-l lies outside the S I 0.174 0.119 observable region. Therefore, the absorption peak SZ 2.594 ,008 observed a t 411 ern.-' is not an in-plane deforma(-4d Y 3 tion vibration. but one of the out-of-dane vibras3 0.036 tions (VIZ, ~13). (BI~) ~'4 v5 The determination of the metal to ligand freS4 0.033 0.0024 quencies has been a subject in which inorganic SS ,034 ,0024 chemists as well as molecular spectroscopists have (B2g) J'6 v7 been interested. As our results described above s6 0.168 0.116 are based on the experimental data of infrared abS7 2.594 ,008 sorption and the Raman effect as well as the normal v9 VI0 VI1 (E") va vibration calculation with a suitable force field, we Sa 0.176 0.149 0,000 0.000 can consider that our assignment of the metal to ,010 ,000 ,000 s 9 2.592 ligand frequency is very reasonable. Furthermore, SI0 0.000 ,000 ,017 ,0025 from the value of the force constant ICl, we can con,000 ,035 ,0012 ,000 s1I clude that the metal to ligand bond should be fairly covalent in this cyanide complex. 0 The values of force constants are given in the unit of IO5 dynes/cm. (13) I. Nakagawa, J Chrm. SOL.J a p a n , 74, 243 (1953); Y . Morino and K. Kutchitsu, J . C l z e ) n P h y s . , 20, 1809 (1952).
[COXTRIRUTIOS
(14) T h e weak bands a t 1630 and 1600 cm.-l of K C N are also due t o t h e trace of water present in t h e crystal. ?;OTRE
D A M E , ISDI.4S.4
FROM THE S O Y E S C H E M I C A L 1,ABORATORY O F T H E U S I V E R S I T Y O F I T
The Structure of Copper Monoglutamate B Y BASUDEBDAS
SARhI.4
RECEIVED L~CGUST 4, 1
(1)
O=C-CHCH2--CH?--C=O
I
0
\
\
SHa
,,'
/
I
FI
/
0
cu.--------o.----..~~.. cu
b H/
\
I
O==d'--CH2-CH2--CH-C=0
LIetal complexes with ghltalTIiC acid have been
described by various workers. The compounds with Cu(I1) were studied by Cheronis,2 hbderhalden,3Pfeiffer,' H ~ r r i g a and n ~ ~Rebertus.6b ( 2 ) 1;.n. Cheronis, U. S Patent 1,985,977 (Jan. 1, 1934). ( 5 ) E. Abderhalden a n d K. Kautzsch, Z. fihysioi. C h c n . , 64, 447 (1910); 68, 487 (1910); 78, 333 (1912). (4) P. Pfeiffer a n d H. Werner, i b i d . , 246, 212 (1937). ( 6 ) (a) P A . Horrigan, Thesis, University of Illinois, 1953, (b) R. r,. Rtll,ertiis, Thesis, University of Illinois, 1954.
