5508 THELOWERINGO F
THE
DROXIDES
TABLE I the solid state. The spectrum was interpreted as Cu++ bonds FREEZING FOIST O F SODIUM Hu- indicating essentially covalent N B Y \*ARIOUS SOLIJTES --f
Solute Na2C03
N AT, " C . i
0.00460 1.8 0.85
0.OO912 0.O136 0.0199 0.0261 4.6 7.1 10.0 12.8 1.13 1.09 1.07 1.10
Solute NaBr
N AT,
"c.
i
0.00765 0.0117 6.5 3.2 0,90 0.93
0.02320 O.OR7il 12.1 1i.i) 1.00 1 .OO
Solute K B r
N AT, " e .
i
0.00282 n . 0 0 n~. on021 ~ 0.om 0 ,oi7x 2.5 5.0 7.8 11.1 15.7 1.92 1.92 1.83 LS4 1.92
Solute KICOI
Av
[J,0051,5
AT, "C.
7.0 2.115
i
VOl. 77
hTOTES
0.0081X
11.9 3.17
0.iII IO
1-) . , I 3,!)7
iLl)l,'37 1%:)
and essentially ionic C < ---Cu++bonds in which -\O ' O r the carboxylate ion resonance is preserved.
Experimental Bis-(g1ycino)-zinc (11) monohydrate, Zn( NH2CH2COO)?, H20 was prepared according to the method of Dubsky and Rabas.6 The compound prepared in our laboratory was spectroscopically identical with :L samplc kindly supplied by Dr. Low. Spectra were obtained from samples prepared in accord: L I I C ~ with the KRr disk technique described previously.6 The zinc complex gave very well-defined spectra similar to those reported for the Cu(I1) and S i ( I 1 ) salts.4 The frequencies in cm.-' observed for bis-(g1pcino)-zinc( 11) monohydrate are as follows: 3450 ( m ) , 3270 ( m ) , 1603 (vs), 1447 (in),I419 ( i n ) , 1101 (in), 1350 (w),1314 (w),1100 (w), 114ii ( i n ) , 1100 ( m ) , lO(j0 (s), 951 (w),907 (w),719 (w). Ahbrrvi:ttiims: 111 = metliurn, s = stroiig, w = c \ . c : L ~ ,v = \-cry.
3.01)
Discussion It is to be noted that absorption bands are observed a t 3450 cm.-' (2.9 p ) , 3270 cm.-' (3.06 p ) do. and 1G03 cm.-' (6.24 p ) and no absorption band DEPARTMENT O F CHEMISTRY was observed in the region of 1720 cm.-l (,?.S p ) . THEPENNSYLVANIA STATEUNIVERSITE UNIVERSITY PARK,PESNSYLVANIA These regions are critical for the determination of the type of metal-ligand bonding present in amino acid-metal c o m p l e x e ~ . ~The appearance of the Infrared Absorption Spectra of Inorganic Co- N H stretching absorption maximurn a t Xi0 ordination Complexes. IV. The Infrared Spec- cm.-l, compared to the 3330 maximum in the spectrum of Bis-(g1ycino)-zinc(I1) Monohydrate'"," trum of sodium glycinate, indicates the presence of Zn++ coordination. The absence of an abBY DANIEL Jf. SWEENY,COLUMRA CURRASANI) J. V. N sorption band near 1720 c m - l (5.8 p ) and the presQUAGLIASO ence of a very strong band a t 1603 c m - ' (6.24 p ) RECEIVEDJUNE 10, 1955 indicate that the carboxyl to zinc bond has a high I n the course of the investigation of metal amino degree of ionic character. acid complexes in progress in this Laboratory, the These observations regarding the spectrum of infrared spectrum of solid bis-(g1ycino)-zinc(I1) his-(g1ycino)-zinc(I1) monohydrate are in accord monohydrate has been obtained. The spatial ar- with the evidence from X-ray diffraction of a square rangement of ligands about the zinc ion has usually planar configuration for the zinc(I1) complex. been considered to be tetrahedral2 corresponding They indicate that linear sp metal bond orbitals to sp3hybridization of the bond orbitals. However, are involved in the nitrogen-to-metal bonds in this the X-ray investigations of Low3 show conclusively complex as well as in the copper(I1) and nickel(I1) t h a t the glycine ligands are arranged in a planar complexes previously reported. It is to be expected that all complexes of the type ZriXz in fashion about the central zinc ion. I n a previous communication4 i t was postulated which X is a bidentate ligand having as one coiirdit h a t the trans planar configuration of bis- (g1ycino)- nating center a COO- group forming essentially copper(I1) monohydrate complex is the result of an electrostatic COO- -- - -. Zii++.bonds, should have a sp linear hybridization of copper bond orbitals. This trans square planar configuration if the other inetalexplanation was based upon the observed infrared to-ligand bonds are covalent. Further spectral absorption spectrum of the copper(I1) complex in studies on complexes of this type are brinq pursued in this Laboratory. (1) (a) Paper 111 in series, J. Cicm. Phyr., in press. (b) Supported
"2'factors come as close to wholr numbers
as
they
---f
in p a r t under A E C Contract A T ( l l - l ) - 3 8 , Radiatiou Project of t h e University of Notre Dame. 4 4 , 774 (1922); C . H. Mac( 2 ) R. G. Dickinson, THISJOURNAL, Gillavry and J. M. Bijvoet, Z. Kiisl., 9 4 , 249 (1936). (3) Private communication from Dr. Barbara Low, University Laboratory of Physical Chemistry Related t o Medicine and Piililic Health, Harvard University. (4) D . N. Sen, S . Mizushinia. C . Curran and 1. 1'. Oiiugliuno, 'THIS JOWRNAI., 77,21 1 ( 1 9 5 5 ) .
DEPARTMEST OF CHEMISTRY USIVERSITPOF NOTREDAME NOTREDAXE,INDIANA (3) J. V. Dubsky and A . R a b a s , Spisy vyd6vant privodovbdeckou Fakiiltou hIasarykovy Univ. No. 123, 3 (1930); C. A , , 26, 20.56 (ISXI). ( t i ) hT. 11,Stimson and & J. I. o'I)nnnell, 'THIS J O U R N A L , 74, 1805 (1952); 1. P. Faust unri I. \'. Qliaglianr), ihid, 76, 6340 f l 9 5 4 ) .
