ELSEVI E R lnorganica Chimica Acta 258 (1997) 109-112

N o t e

Characterization and crystal structures of cadmium(II) halide complexes with amino acids and their derivatives

V 1. Crystal structure of dichloro(L-azetidine-2-carboxylic acid)- cadmium(II) monohydrate

T a k a s h i K o b a y a s h i , Y o s h i e I n o m a t a * , T o s h i o T a k e u c h i , F r a n k S. H o w e l l Department of Chemistry, Faculty of Science and Technology, Sophia University. 7-1 Kioicho. Chiyoda.lm. Tokyo 102, Japan

Received 2 July 1996

Abstract

The crystal structure of [CdCl2(Haze) ] (H20) was determined by the X-ray diffraction method; Haze denotes L-azetidine-2-carboxylic acid. The crystal is monoclinic, space group C2, a = 15.870(4), b =7.189(3), c= 8.906(3) .~, flffi 115.85(2) °, Vffi914.5(5) ~3 Zffi4 and R ffi 0.036. The structure consists of a one-dimensional polymer chain bridged by chlorine atoms and a carboxyl group. Four ~ atoms coordinate to a cadmium atom and form a square plane. The planes extend in the direction of the b-axis like an infinite folding screen.

Keywords: Crystal structures; Cadmium complexes; Amino acid complexes

1. Introduction

The molecular structures of cadmium(II) complexes with 4-hydroxy-L-proline (Hhpro) [ 1 ], L-proline (Hpro) [2], N-methylglycine (Hsar), N,N-dimethylglycine (Hdmgly) [3] and L-piperidine-3-carboxylic acid (nipecotic acid; Hnip) [4] have been extensively investigated in our laboratory.

From study of the structures of [CdCl2(Hhpro)[, [CdCl2(Hpro) ] (H20) and [CdCl2(Hnip) ], we concluded that the structure of [CdCI2(HL) ] (H20),, in which HL was an azacycloalkane carboxylic acid, consisted of a one-dimen- sional polymer chain bridged by chlorine atoms and carbox- ylato oxygen atoms of an azacycloalkane carboxylic acid which are coordinated in a fork-like manner to two cadmium atoms.

L-Azetidine-2-carboxylic acid (Haze) is a homologne of L-proline, from which it differs by the loss of one methylene group from the ring. White and Joesten have investigated the syntheses and properties of several transition metal com- plexes with Haze [5]. However there are few studies of crystal structures of metal complexes with Haze.

Conesponding author. For Parts I, II, Ill and IV see Refs. [ I ], [2], [3] and [4].

0020-1693197/$17.00 © 1997 Elsevier Science S.A. All rights rese~ed PIIS0020-1693(96)05527-2

Therefore in this work the structure of dichloro(L-azeti- dine-2-carboxylic acid)cadmium(H) nmnohydrate [CdCla- (Haze) ] (H20) was determined by X-ray diffraction in order to support our conclusion in the previous report [4].

2. Experimental

2.1. Preparationof[CdCl2(Haze)](H20)

An aqueous solution containing equimolar anmunts (0.01 mol) of L-azetidine-2-carboxylic acid and CAC12-2.SH20 was condensed in a wamr bath. Then this mixed solution w a s

kept in an acetone atmosphere for several days. Clear color- less crystals were obtained from this solution. Anad. Fonad: C, 15.90; H, 2.76~ N, 4.52. Calc. for CdC12C41-1~Oa: C, 15.89; H, 3.00; N, 4.63%.

2.2. Deuteration o f the compounds

L-Azetidine-2-carboxylic acid and its cadmium(H) plex were deutersted by dissolving these compounds in 99.75 at.% I)20 and drying them in a vacuum. The NH2 + moiety in this molecule was deuterated in this way.

110 T. Kobayashi et al. / Inorganica Chimica Acta 258 (1997) 109--112

2.3. lnfrared absorption spectra

The IR absorption spectra from 4000 to 400 cm-~ were measured using a JASCO spectrophotometer (Type IR-810). Samples were prepared as KBr disks.

Af ' and Af" were those of Creagh and McAuley [9]. The values for the mass attenuation coefficients are those of Creagh and Hubbell [ 10]. All calculations were performed using the teXsan [ 11 ] crystallographic software package of the Molecular Structure Corporation.

2.4. X-ray diffraction

A colorless needle crystal having approximate dimensions of 0.50×0.25 ×0.10 mm was mounted on a glass fiber. All measurements were made on a Rigaku AFC5 diffracto- meter with graphite monochromated Mo Kc~ radiation (A =0.71069/~). The lattice parameters of this crystal were obtained by using the 25 important reflections (25.84 < 2 0 < 29.91 ° ). The data were collected using the o>-2 0 scan technique to a maximum 20 value of 55.0 °. The crystal data are given in Table 1.

2.5. Structure determination

Of the 1181 reflections which were collected, 1140 were unique (Rin,=0.020). An empirical absorption correction based on azimuthal scans of several reflections was applied. This resulted in transmission factors ranging from 0.65 to 1.00. The data were corrected for Lorentz and polarization effects. The structure was solved by and expanded using Fourier techniques [6]. The non-hydrogen atoms were refined anisotropically. The final cycle of full-matrix least- squares refinement was based on 1085 observed reflections ( I> 3.00~r(1) ) and 106 variable parameters and converged with unweighted and weighted agreement factors of: R = El I F o l - IFcl I /~ lFol =0.036, R w = { ~ w ( I F o l - IFol)2/ Ewl Fol z} i/2 = 0.038. The weighting scheme was based on counting statistics and included a factor (p = 0.005) to down- weight the intense reflections. The maximum and minimum peaks on the final difference Fourier map corresponded to

3 0.94 and - 1.52 e / ~ - , respectively. Neutral atom scattering factors were taken from Cromer and Waber [7 ]. Anomalous dispersion effects were included in Fc~c [8]; the values for

Table 1 Crystal data of [CdCla(Haze) l (H20)

Formula CdCI2C4HgNO3 Formula weight 302.44 Crystal system monoclinic Space group C2 a (,~) 15.870(4) b (,~) 7.189(3) c ()~) 8.906(3) /3 (°) 115.85(2) V (~3) 914.5(5) Z 4 Dm (g cm -3) 2.156(1) Dx (gem -3) 2.196 /t(Mo Ka) (cm- ~) 29.35

3. Results and discuss ion

3.1. Infrared absorption spectra

3.1.1. L-Azetidine-2-carboxylic acid As the bands at 2974, 2914, 1637 and 1253 cm- t shift to

2224, 2078, 950 and 829 cm- t on deuteration, they are assigned to NH2 + antisymmetric stretching, symmetric stretching, scissors and wagging vibrations, respectively, by referring to N-methyiglycine [ 12]. The strong bands of 1597 and 1415 cm- t are tentatively assigned to C O 0 - antisym- metric and symmetric stretching vibrations, respectively. Thus L-azetidine-2-carboxylic acid has a zwitter ion structure in the solid state.

3.1.2. [CdCl2(Haze)I(H,O) The bands of 3154, 3060, 1585 m~d 1272 c m - i which shift

to 2362, 2338, 1140 and 995 cm - t on deuteration are assigned to NH2 + vibrations as in the case of Haze. The bands at 1600 and 1430 cm- t are assigned to C O 0 - antisymmetric and symmetric stretching vibrations, respectively. Therefore in this complex, L-azetidine-2-carboxylic acid has a zwitter ion structure. The C O 0 - symmetric stretching vibration shifts to a frequency region higher than that of the free ligand band.

The carboxylate ion may coordinate to a metal in one of the unidentate, chelating (bidentate) and bridging modes shown in Fig. 1. Unidentate complexes (structure I) exhibit the separation values (A) between the COO- antisymmetric and symmetric stretching vibrations which are much greater than those of the ionic complexes. Chelating (bidentate) complexes (structure II) exhibit A values which are signifi- cantly less than the ionic values. The values for bridging complexes (structure III) are greater than those of chelating (bidentate) complexes, and close to the ionic values [ 13]. In this complex A is 170 cm- l , which is roughly equal to that of L-azetidine-2-earboxylic acid ( 182 cm- ' ). Therefore, in [CdCle(Haze)] (H20) the carboxylate ion may coordi- nate to a cadmium atom in an oxygen bridging mode.

~-o\ / Q ' ~ ~--Q~--R C--R M "C~R

o// ' \o.-/ ~_.7 i ii llI

Fig. 1. Carboxylatc bonding.

T. Kobayashi et aL I lnorganica Chimica Acta 258 (1997) 109-112 I 11

3.2. C r y s t a l s t r u c t u r e

The final atomic parameters are listed in Table 2, the inter- atomic distances in Table 3 and the bond angles in Table 4. The deviations o f atoms from the least-squares planes are shown in Table 5. A perspective drawing of the complex and the numbering scheme of the atoms, except the hydrogen atoms, are shown in Fig. 2. The projection along the b-axis is given in Fig. 3.

This complex has a structure very similar to those of [CdCI2(HL)] (H20)n (Hhpro, Hpro and Hnip) and [CdCl2(Hbet)] (Hbet=N,N,N-trimethylglycine, betaine) [ 14]. It consists o f a one-dimensional polymer bridged by chlorine atoms which coordinate to a cadmium atom. Four chlorine atoms are almost on a plane (within 0.0014 ,~) as listed in Table 5. The planes extend in the direction o f the b-axis like an infinite folding screen. The dihedral angle between adjacent planes is 145 ° which is similar to that o f CdCl2(Hhpro) (142°). The closest Cd---Cd contact of 3.596( 1 ) .~ is much larger than that (2.980 ,~) in the metal. From the trough positions in the zigzag folding structure, the carboxyl oxygen atoms of Haze are coordinated in the syn- syn mode to two cadmium atoms. The bond lengths of C d - CI(1) , Cd-CI (2 ) , Cd-CI(1) t and Cd--CI(2) t are 2.637(5),

Table 2 Final positional parameters with e.s.d.s in parentheses and equivalent iso- tropic temperature factors ( Beq ( ~2 ) ) of [ CdCI2( Haze ) ] ( H20 )

Atom x y z Beq

Cd 0.2528(I) 0.0132(I) 0.O005(2) 2.36(I) Ci( I ) 0.2780( I ) 0.2675(I0) 0.2296(2) 2.99(4) Ci(2) 0.3002(2) 0 .2688(10) -0.1566(3) 3.40(5) O(11 0.4072(6) -0.065(2) 0.145(21 3.9(21 0(2) 0.4031(6) -0.381(21 0.122(2) 3.8(2) 0(3) 0.5063(7) 0.255(3) 0.326(2) 9.9(3) N(I) 0.5909(6) -0.419(I) 0.274(11 3.6(21 C(I) 0.4428(5) -0.225(3) 0.160(1) 2.5(2) C(2) 0.5493(5) -0.227(3) 0.239(!) 2.8(2) C(3) 0.6035(9) -0.175(2) 0.423(2) 5.2(4) C(4) 0.6522(9) -0.371(3) 0.451(2) 5.4(4)

Table 3 Selected bond lengths (./~) with e.s.d.s in parentheses for [CdCI2- (Haze)] (H20)

Cd-Cd" 3.596( 1 ) O( I )-C( I ) 1.26(2) Cd-Cl(l) 2.637(5) O(2)-C(I) 1.26(2) Cd-CI(2) 2.612(5) C(!)-C(21 !.52(I) Cd-CI(i) j 2.586(5) C(2)-C(3) 1.53(2) Cd-CI(2) ~ 2.597(5) C(3)-C(4) 1.57(2) Cd-O( 1 ) 2.286(9) C(2)-N 1.50(2) Cd-O(2) u 2.354(9) C(4)-N 1.49(I) CI(! 1""O(3) 3.34(!) CI(2)--N m 3.267(10) O(2)---N 2.70(i) O(3)...N w 2.83(2) O(I)--.O(3) 186(2) O(2)--.O(3) v 3.20(2) 0(3)...0(3) vl 3.20(3)

Key to symmetry operation: t 0.5 - x0 - 0.5 + y, - z; n 0.5 - x, 0.5 + y, - z; m 1.0-x, 1.0+y, - z ; I V x , i.0+y, z; vx, - 1.0+y, z; vt l . O - x , y , 1.0-z.

Table 4 Bond angles (°) with e.s.d.s in pmonlhnses for [CdCI~fHa2~)] (H20)

CI( I )-Cd-CI( I ) z 178.0(I) CI(I)--Cd-Cl(2) 86.8(2) CI( I)-Cd-CI(2)' 91.8(1) CI(I)--Cd-O(!) 88.4(3) CI( 1 )--Cd-O(2) u 84.7(3) CI( I )LCd-CI(2) 93.2(l) CI( ! )LCd-CI(2) z 88.2(2) CI(I)t-Cd-O(l) 93.6(3) CI( I )1-Cd-O(2) n 93.3( i ) CI(2)--Cd-CI(2) t 177.5(2) CI(2)-Cd-O(I) 89.2(3) C1(2)--Cd-O(2) u 90.8(3) Cl(2)t-Cd-O(I) 92.9(3) CI(2)LCd-O(2)" 87.0(3) O( I)--Cd-O(2)" 173.1(61 Cd-CI( 1 )-Cd ~ 87.03(6) Cd--CI(2)-CA( I )n 87.31 (6) Cd--O( I )-4=( 1 ) 127.3(8) Cd-O(2)-C( I ) 135.7(8) C(2)-N-C(4) 91.5(10) O( 1 )-C( I )-O( 21 129.4(7) O( ! )-C( 1 )-C(2) 114( 1 ) O(2)-C( ! )-C(2) ! 16( I ) N-C(2)-C( I ) 113(1) N-C(2)-C(3) 91.0(9) C(1)-C(2)-C(3) 119.0(9) C(2)-C(3)-C(4) 87(I) N(!)-C(4)-C(3) 89.6(9)

Key to symmetry operation: J 0.5 -- x, -- 0.5 + y. --z; u 0 .5--x , 0.5 + y, --Z.

Table 5 The deviations of atoms from the least-squares planes (~) of [CdClz- (Haze)] (H20)

Plane (I) [CI(1).CI(2),CI(1)I, CI(2)'I CI( I ), 0.0013; CI(2), -0.0014; Cl( I )t, 0.0013; CI(2) l, -0.0014

Plane (2) [Cd, O(I),O(2),C(i)] Cd, -0.001(i);O(!1, -0.05(1); O(2),0.01(1);C(1),0.044(8)

Plane (3) [O(1), O(2), C(I), C(2)] O( 1 ), 0.00( 1 ); O(2), 0.00( ! ); C(1), - 0.005(8); C(2), 0.001 (8)

Plane (4) [N,C(2), C(3), C(4)] N, - 0.018( 10); C(2), 0.02( I); C(3), -0.05(2); C(4), 0.04( I )

Key to symmetry operation: 10.5- x, - 0_5 +y, - z.

?

c1(x1( i

T o,,, % or,) ~

cdl c ( a ) N O

o131

Fig. 2. The perspective drawing of [ CdCI2(Hada) ] (H20) and the anmber- ing scheme of the non-hydrogen atoms.

2.612(5), 2.586(5) and 2.597(5) tL which are nearly equal to the values for [CdCl2(Hhpro) ] [1] , [CdC]2(HplD)]- (H20) [2] , [CdCl2(Hnip)] [4] and [CdCl2(Hbet)] [14] which have a zigzag double ribbon bridge. The bond angles of CI( 1 ) - C d - C I ( 2 ) , CI( 1 ) - C d - C I ( 2 ) s, CI( 1 )~--Cd--CI(2) and CI( I )S-Cd-CI(2) I are nearly equal to 90 °, as listed in Table 4. The bond lengths of C d - O ( 1 ) and C d - O ( 2 ) are

112 71". Kobayashi et al. / lnorganica Chimica Acta 258 (1997) 109-112

Fig. 3. The projection of [CdCl2(Hada) ] (H20) along the b-axis.

2.286(9) and 2.354(9) A, respectively, and the angle of O( 1 ) - C d - O ( 2 ) is 173.1 (6)o. Therefore the cadmium atom is in a distorted square bipyramidal geometry.

The bond length o f O ( 1 ) - C ( I ) (1.26(2) A) is exactly equal to that o f O ( 2 ) - C ( 1 ) ; this is longer than those of the free ligand (1.252(4) A for O( 1 ) - C ( 1 ) and 1.238(4) A for O ( 2 ) - C ( 1 ) ) [15]. The O ( 1 ) - C ( 1 ) - - O ( 2 ) angle is 129.4(7) ° which is larger than those o f CdCI2(Hhpro)] (126.3(3)°) , [CdCI2(Hpro) ] (H20) (127.2(6)°) , [CdCI2- (Hnip)] (122.9(3) °) and [CdCla(Hbet)] (126.9(3)°) . This phenomenon is due to the hydrogen bonds of O( 1 ) . . .O (3 ) (2.86(2) A) and O ( 2 ) . . . N (2.70( 1 ) A) . The C - O distances of 1.25 ,~ with the bond angles OCO approx- imately 125 ° are typical, but a dependence upon the acid strength has been reported [16,17]. It is likely due to the effect o f the positively-charged nitrogen atom that the O - C - O angle exceeds the average value of 125 ° in this complex.

4, Supp lementa ry mater ia l

Tables of the atomic coordinates and equivalent isotropic temperature factors for hydrogen atoms, the anisotropic tem- perature factors for non-hydrogen atoms, and observed and calculated structure factors for [CdCl2(Haze)] (H20) are available from the authors on request.

References

[ I ] Y. Yukawa, Y. Inomata, T. Takeuchi, M. Shimoi and A. Ouchi, Bull. Chem. Soc. Jpn., 55 (1982) 3135.

[2] Y. Yukawa, Y. Inomata and T. Takeuchi, Bull. Chem. Soc. Jpn., 56 (1983) 2125.

[3] J. Yamada, H. Hashimoto, Y. Inomata and T. Takeuchi, Bull. Chem. Soc. Jpn., 67 (1994) 3224.

[4] J. Yamada, Y. Inomata and T. Takeuchi, Inorg. Chim. Acta, 249 (1996) 121.

[5] C.R. White and M.D. Joesten, J. Coord. Chem.. 6 (1976) 53. [6] P.T. Bearskens, G. Admiraal, G. Beurskens, W.P. Bosman, S. Garcia-

Granda, R.O. Gould. J.M.M. Stairs and C. Smykalla, The DIRDIF program system, Tech. Rep., The Crystallography Laboratory. University of Nijmegen, Netherlands. 1992.

[7] D.T. Cromer and J.T. Waber, International Tables for X-ray Crystallography, VoL IV, Kynoch. Birmingham, UK, 1974, Table 2.2A.

[8] J.A. Ibers and W.C. Hamilton, Acta Crystallogr.. 17 (1964) 781. [9] D.C. Creagh and WJ. McAuley, in AJ.C. Wilson (ed.), International

Tables for Crystallography, Vol. C, Kluwer. Dordrecht. Netherlands, 1992, pp. 2 ! 9-222, Table 4.2.6.8.

110] D.C. Creagh and J.H. Hubbell, in AJ.C. Wilson (ed.), International Tables for Crystallography, VoL C, Kluwer, Dordrecht, Netherlands, 1992. pp. 200-206, Table 4.2.4.3.

[ I 1 ] teXsan: Crystal Structure Analysis Package. Molecular Structure Corporation, The Woodlands, TX, 1985 and 1992.

[ 12] Y. Inomata. A. Shibata, Y. Yukawa, T. Takeuchi and T. Morlwaki, Spectrochim. Acre, Part A, 44 (1988) 97.

[13] K. Nakamoto, lufrnred and Raman Spectra of Inorganic and Coordination Compounds. Wiley, New York, 4th edn.. 1986, p. 232.

[14] X-M. Chen and T.C.W. Mak, J. Crystallogr. Spectrosc. Res., 21 ( 1991 ) 27.

115] HM. Berman, E.L. McGandy, J.W. Burgner !I and R.L. VanEnen, J. Am. Chem. Soc., 91 (1969) 6177.

[ 16] Y.B. Koh and G.G. Christoph, lnorg. Chem.. 18 (1979) 1122. [ 17] I.D. Brown. J. Chem. Soc.. Dalton Trans., (1980) ! 118.