Preparation, characterization and crystal structure of [Ni(bpy)3][Fe(CN)5(NO)]3H2O and one-dimensional cyano-bridged [Ni(en)2Fe(CN)5(NO)]H2O

E L S E V I E R Inorganica Chimica Acta 258 (1997) 81-86

Preparation, characterization and crystal structure of

[ Ni (bpy) 3 ] [ Fe (CN) 5 (NO) ] 3H20 and one-dimensional

cyano-bridged [Ni(en) 2Fe(CN)5(NO) ]H20

* Department of Chemistry, Tomkang University. Tamsui. Toiwan b Department of Chemistry, National Taiwan University, Taipei, Taiwan Received 20 June 1996; revised 2 October 1996; accepted 23 October 1996

Abstract

Two new double complexes [Ni(bpy)s] [Fe(CN)s(NO) ] 3H20 (I) and [Ni(en)2Fe(CN)s(NO ) ] H20 (2) have been isolated from the reactions of the mixture of NiCI 2. 6H20 and Na2[Fe(CN)s(NO) ] in water, with bipyridine (bpy) and ethylenediammim: (en) in ethanol, respectively, and have been characterized by X-ray analysis, IR, EPR, MOssbauer spectroscopy and magnetic meam~meats. Crysml._logra#g¢ data for I and 2 are as follows: 1: triclinic, PI, a = 10.752(4), b = 13.321 (3), c = 13.791 (5) ,~, a = 79.834(25), ~ffi 81.39(3), 7ffi72.93(3)0, Z = 2; 2: triclinic, PI, a = 8.622(16), b = 8.832(3), c = 12.417(3) ]L a = 94.81 (3), t = 92.322(19), 7 = 112.820(23) °, Zffi2. The bond angles of Fe-N--O are nearly linear for 1 (178.3(4) °) and 2 (179.4(3)°). The structure of I consists of a double complex of a cation [Ni(bpy)3] 2+ and an anion [Fe(CN)s(NO)] 2-. The structure of 2 consists of a one-dimensional polymeric chain -Ni(en)2--NC- Fe ( CN ) 3 ( NO ) --CN-Ni ( en ) 2- in which the N i ( 11 ) and Fe ( II ) centers are linked by two CN groups. Cryomagnetic investigations (4-:i00 K) reveal a paramagnctic behavior for I and the presence of a one-dimensional Heisenberg weak antifermmagnctic chain with J = - 0.47 cm- t for 2. EPR spectra observed at ambient temperature for the Ni(ll) ions in both complexes are also reported.

Keywords: Crystal structures; Dinuclear complexes; Iron complexes; Nickel complexes; Cyano complexes; Magnetic

1. Introduction

The coordination chemistry of transition metal cyanides, especially of ferro- and ferricyanide complexes, has become of remarkable interest in recent years due to their unusual electronic state [ 1,2] and magnetic behaviors [ 3 - 7 ] . It has bcen shown that bexacyanometalate ions [M(CN)6] 3- (M = Mn, Fe, Cr, etc.) act as good building blocks to provide bimetallic assemblies exhibiting spontaneous magnetization [ 5 - 7 ] . Recently we have reported a series of ferromagnetic M3[Fe(CN)6]2 ( M = N i , Co, Cu) with Tc--10-25 K depending upon the combination of metal ( M ) ions [8].

Very recently, Okawa and co-workers [9-11] reported several complexes with ferromagnetism of [Ni(en)2]3- [ F e ( C N ) d 2 ) [ 10], [Ni(pn)2]2[Fe(CN)dCIO4 [ 11] and K[ {Mn(BS) }2{Fe(CN)6]2 [ 12] (BS =substituted Schiff- base salens} in which the cyano groups of Fe(CN)63- in

* Corresponding aulhor.

0020-1693197/$17.00 © 1997 Elsevier Science S.~. All rights reserved

PII S0020-1693 (96) 05542-9

the meridional mode coordinate to adjacent Ni ions o f [Ni(en)2] 2+, [Ni(pn)2] 2+ or [ M n ( B S ) ( H z O ) ] - to form a 2-D or multidimensional polymeric structure. Funlmnnom. Tang and co-workers [ 12] reported an a n f i f e n ~ 2- D cyano-bridged polymeric [ C u 2 ( o x p n ) F e ( C N ) s ( N O ) ] , complex, in which a nitrogen atom of a cyano group o f [Fe(CN)s(NO)] 2- coordinated to one o f the adjaceat Cu(n) ions of Cu2(oxpn) (oxlm=N,N'-bis(3-mmino - propyl)ozamide).

As the intention of these studies was to clarify more deeply the su'uctural correlation with magnetic property of double complexes with the [Fe(CN)s(NO) ]2- anion, w e have pared two new bimetallic complexes, fi~e discrete double complex [Ni(bpy) s] [Fe(CN)s(NO)]3H20 (I) (bpyffi bipyridine) and a one-dimensional polymeric complex [Ni(en)2Fe(CN)s(NO)]H20 (2) (en=ethykaedimnine) in which two cyano groups serve as a bridge to the N i ( l l ) atom through nitrogen. Here the results of crystal swacture, IR, EPR, M6ssbaucr, and cryomagnctic studies of these species are described.

82 H.L Shyu et al. / Inorganica Chimica Acre 258 (1997) 81--86

2. Experimental

2.1. Materials

Na2[Fe(CN)5(NO)]2H20, bipyridine (bpy), ethylene- diamine (en), and other materials were "~f analytical grade (Aldrich) and used as supplied. ~ --

Table I

Crystallographic data [Ni(bpy)3][Fe(CN)5(NO)]3H20 (1) and [Ni(en)2Fe(CN)s(NO) ]H20 (2)

1 2

Formula C35H3oNizO4FeNi CoHteNioOeFeNi

M 797.25 410.00

Crystal system triclinic lrielinic

Space group P- 1 P- 1

2.1.1. [Ni(bpy)~][Fe(CN)5(NO)]3HzO (1) and a (A) 10.752(4) 8.6221(16)

[Ni(en)~Fe(CN)5(NO)]H20 (2) b (A) 13.321(3) 8.832(3)

To a solution of NiCI26H20 ( 1 mmol in 20 ml water) and c (~) 13.791 (5) 12.417(3) 2,2'-bipyridine (2 mmol in 20 ml methanol) or ethylenedi- ~ (°) '79.834(25) 94.81(3)

(°) 81.39(3) 92.322(19)

amine (2 mmol in 20 cm 3 methanol) was slowly added a ~(o) 72.93(3) 112.820(23) solution of Na2[Fe(CN)5(NO)]2H20 (1 mmol) in 10cm 3 v(A 3) 1848.5(10) 865.7(4)

water. The solution turned violet to pink for 1 and violet to z 2 2

dark brown for 2. Upon standing for several days, the result- De (gcm - 3 ) 1.432 1.573 ing pink crystals of 1 (80% yield) and brown crystals of 2 F(000) _{/.L(Mo K¢~) (cm -~)} 814 _40.095 417 _82.123 (85% yield) were filtered off, air dried and recrystallized Crystalsize ( r a m ) 0.25×0.35×0.35 0.25×0.35×0A0 from methanol/water ( 1:1) to form single crystals, suitable No. of data used 7511 3422 for X-ray diffraction analysis. Anal. Found: C, 49.27; H, 3.81; Rf 0.051 0.056

N, 20.12. Calc. for C35H3oN2204FeNi (1): C, 49.33; H, 4.23; Rw 0.055 0.066

N, 19.74%. Found: C, 25.45; H, 4.09; N, 33.05. Calc. for CgI-ItsNtoO2FeNi (2): C, 25.23; H, 4.20; N, 32.70%.

2.2. Physical measurements

Table 2

Selected final atomic positional parameters and B~q values (A z) for !

Atom x y z Bcq *

IR spectra were recorded on a Bio-Rad FTS-40FTIR spec- Fe 0.37586(6) trophotometer as KBr pellets in the 4000-400 c m - t region. Ni 0.13996(6) X-band EPR spectra at 300 K for the complexes in powder N(6) 0.3182(4) were recorded on a Bruker ECS-106 spectrometer. Mtss- 0(I) 0.2779(5) bauer spectra at 80 K were recorded on a conventional Austin c(I) _c(2) 0.3844(5) _0.5565(4) S-600 Mtssbauer spectrometer. 57Co(Pd) was used as the c(3) 0.4427(4) source and all isomer shifts are represented with respect to c(4) 0.3808(4) a-iron foil. Temperature d~pendence of the magnetic suscep- c(5) 0.2042(4) tibilities of the polycrystalline samples was measured N(7) 0.0519(3) between 4 and 300 K at a field 1 T using a Quantum Design N(8) _{N ( 9 )} 0.1930(3) _0.3084(3) model MPMS computer-controlled SQUID magnetometer. N(10) 0.0948(3) Corrections for the diamagnetism of complexes I and 2 were N( I I ) - 0.0201 ( 3 )

estimated from Pascal's constants. N(12) 0.2174(3)

2.3. X-ray crystal structure analysis

Crystallographic data for complexes 1 and 2 were collected on an Enraf-Nonius CAD-4 diffractometer with graphite- monochromatized Me K a radiation at 25°C. The unit-cell parameters were determined from 25 reflections in the range 4 2 < 2 0 < 6 2 ° for 1 and 3 2 < 2 0 < 4 8 ° for 2. The details of data collection, crystallographic data, and reduction are sum- marized in Table 1.

The structures were solved by the standard heavy-atum method and refined by full-matrix least-squares. Reliability factors were defined as R f f f i E I I F o l - I F c l l l ~ l F o l and the function minimized was R w = [ ~ w ( I F o l - I F c l ) 2 / E IFol 2] t/2, where in the final least-squares calculation the unit weight was used. The hydrogen atoms were refined with isotropic thermal parameters. Final Fourier diff~'rence syn-

0.28791(5) 0.16886(5) 2.91(3) 0.79595(5) 0.28706(5) 2.73(3) 0.4181(3) 0.1475(3) 4.30(19) 0.5072(3) 0.1307(4) 8.61(3) 0.2750(4) 0.3107(4) 3.95(2) 0.2925(4) 0.1439(4) 3.89(22) J.1349(4) 0.1902(3) 3.23(19) 0.2672(4) 0.0327(3) 3.40(21) 0.2637(4) 0.2151(3) 3.89(22) 0.7399(3) 0.19093(24) 2.98(15) 0.8778(3) 0.15121(24) 2.97(15) 0.6681(3) 0.2872(3) 3.23(16) 0.6966(3) 0.41233(24) 3.04(16) 0.9275(3) 0.31249(24) 2.97(14) 0.8783(3) 0.36849(24) 2.89(14) * Boq is the mean of the principal axes of the thermal ellipsoid. theses were featureless. All refinement calculations were per- formed using the NRCVAX computer program [13]. Selected positional parameters of the non-hydrogen atoms of 1 and 2 are given in Tables 2 and 3, respectively.

3. Results and discussion

3.1. IR spectra

The most important aspects concerning the IR spectra of 1 and 2 deal with the vibrational stretching frequencies of NO and CN. Nitric oxide has an extra electron, occuping a ~rr* antibonding orbital, which is relatively easily lost. In the case

H.L Shyu et aL / lnorganica Chimica Acta 258 (1997) 81--86 83 Table 3

Selected final atomic positional parameters and Bcq values (~2) for 2

Atom x y z B~q" Fe 0 . 4 6 0 7 ( 1 0 ) 0.16630(10) 0.29693(6) 1.31(3) Ni( I ) i 0.5 0.5 1.35(5) Ni(2) 0 0 0 1.54(5) N(I) 0 . 7 5 4 4 ( 6 ) 0.3210(6) 0.4615(4) 2.03(19) N(2) 0.1~7S(6) -0.0300(6) 0.1259(4) 2.01(20) N(6) 0.4966(6) -0.0638(6) 0.3020(4) 1.89(19) N(7) 0 . 9 1 9 8 ( 6 ) 0.6695(6) 0.4324(4) 2.23(20) N(8) 1 . 0 5 5 5 ( 6 ) 0 . 4 5 5 1 ( 6 ) 0.3404(4) 1.94(20) r,'(9) 0 . 0 6 2 8 ( 6 ) 0.2433(6) 0.0685(4) 2.09(20) N(10) -0.2173(6) -0.1086(6) 0.0817(4) 2.29(22) C(I) 0 . 6 4 2 6 ( 6 ) 0.2404(6) 0.4030(4) 1.61(20) C(2) 0 . 2 7 0 2 ( 7 ) 0.0128(7) 0.1889(4) 1.71(21) C(3) 0 . 6 1 2 3 ( 7 ) 0.1888(7) 0.1841(5) 2.08(23) C(4) 0 . 4 1 7 9 ( 7 ) 0.3067(7) 0.2869(5) 2.13(24) C(5) 0 . 3 0 9 8 ( 7 ) 0.0650(7) 0.4112(4) 1.88(22) O(I) 0.5214(6) -0.1825(6) 0.3046(5) 4.4(3) "B~ is the mean of the principal axes of the thermal ellipsoid. of terminally bound NO, simple MO theory predicts that whilst M - N O ~ will be linear, M - N O - may be a bent bond. The potential thus exists to establish the formal oxidation state of the metal center in nitric oxide by examining the IR spectra [ 14]. The nitroprusside anion of Na2[Fe(CN)s- (NO) ] 2H20(SNP) has an F e - N - O angle of nearly 180 ° and IR active NO stretching frequency of 1940 c m - t indicating an NO + complex of iron(H) with extensive w-bonding. In general, IR absorption bands in the region 2200-1900 era- are due to the phonon involving C N - and NO + stretching vibrations [ 1,2,14,15 ]. In the present system, the IR spectrum of 1 shows a single absorption at 2143 c m - ~ which can be assigned to CN stretching, whereas two strong absorptions at 2141 and 2162 cm -m have been observed for complex 2, which probably arise from the bridging CN and terminal CN stretching vibrations, respectively. Strong single peaks at 1911 for I and 1933 c m - m for 2 are assigned toNO stretching, thus implying that the F e - N - O bonds are nearl3, linear.

C34

Table 4

Selected bond disUmces (~) and angles (') for I

Fe-N(6) 1.650(4) Fe-C( 1 ) 1.947(5) Fe--C(2) 1.937(5) Fe--C(3) !.937(5) Fe-C(4) 1.936(4) Fo-C(5) !.936(4) Ni-N(7) 2.086(3) Ni-N(8) 2.085(3) Ni-N(9) 2.090(3) Ni-N(10) 2.072(3) Ni-N(II) 2.103(3) Ni-N(12) 2.100(3) N(6)-O(I) 1.131(6) Fe-N(6)-.-O( I ) 1 7 8 . 3 ( 4 ) Fe-C(I)-N(I) 177.6(5) Fe-C(2)-N(2) 1 7 6 . 7 ( 4 ) Fe-C(3)-N(3) 179.0(4) Fe-C(4)-N(4) 1 7 8 . 0 ( 4 ) Fe-C(5)-N(5) 176.8(4) C(I)-Fe-C(4) 167.44(20) C(2)-Fe-C(5) 172.fi0(19) N(6)-Fe-C(3) 178.42(19) N(6)--Fe-C(2) 93.26(20) N(6)-Fe-C( I ) 97.26(20) N(6)-Fe-C(4) 94.83(20) N(7)-Ni-N(9) 94.35(13) N(?)-Wt--N(IO) 95.77(13) N(7)-Ni-N(12) 169.91(13) N(7)-Ni-N(I 1) 95.48(13) N(8)-Ni-N(10) 172.20(13) N(9)-I~t--N( ! | ) 169.30(I3)

3.2. Structure o f complex I

An ORTEP drawing of complex 1 with the atom number- ing scheme is shown in Fig. 1. Selected bond distances and angles are given in Table 4.

As depicted in Fig. I, complex I consists of a discrete [Ni(bpy)3] 2+ cation and [Fe(CN)s(NO)] 2- anion which form a double complex. The geometry of [Ni(bpy)3] 2+ has approximate point-group symmetry D 3. The average N i - N bond distance of 2.09 A is in agreement with the previous reported value of 2.09 ,~ for [Ni(bpy)3]Cl 2 [ 16].

The geometry of [Fe(CN)s(NO)] ±- is in good agree- ment with those of the previous studies [4,17,18]. The n c a n Fe-C, F e N , C=N and N - O bond distances in [Fe(CN)5- (NO)] 2- are 1.¢)39,1.650,1.390 and 1.131 ,~, respectively. These values ~ in accordance with the repotted values for other nitroprusside metal salts [2-4,17-19]. The bond angle of F e - N - O (178.3(4) °) is nearly linear. , ~ ~ C22 C19

c~2~

I c24(,-~ .~b~'c2o

84 H.L. Shyu et al. / lnorganica Chimica Acta 258 (1997) 81-86

C7

C8

N9 ~ N 1

C%

C8

C7

Fig. 2. ORTEP stereoview of [ Ni(en)2Fe(CN)5(CO)

] (without H20; 30% probability thermal e]lpsoids).

Fig. 3. View of the CN-btidged polymeric [Ni(en)2Fe(CN)s(NO) ] without H20. 3.3. Structure o f complex 2

An ORTEP drawing of complex 2 with the atom number- ing scheme is shown in Fig. 2. A view oftbe polymeric chain structure is given in Fig. 3. Relevant bond distances and angles are given in Table 5. The structure of 2 shows that the asymmetric unit consists of one trans-[Ni(en)2] 2+ cation and one [ F e ( C N ) s ( N O ) ] 2- anion. Two cyano nitrogens (N( 1 ) and N(2) ) in trans mode coordinate to the adjacent Ni ions, through N( 1 ) to H i ( I ) of trans- [Ni(en)2] 2 + and through N(2) to Ni(2) of another trans-[Ni(en)2] 2+, to form a quasi wave form of the alternate array of the linear Table 5

Selected bond diatances (A) and angles (°) for 2

Fe-N(6) 1.653(5) Fe--C(I) 1.930(5)

Fe-C(2) 1.940(5) Fe-C(3) i.945(6)

Fe-C(4) !.956(6) Fe--C(5) !.926(6) Ni(I)-N(I) 2.099(4) Ni(i)-N(7) 2.095(5) Ni(I)-N(8) 2.099(4) N(I)-C(I) 1.135(5) Ni(2)-N(9) 2.095(5) Ni(2)-N(10) 2.0f~3(5) N(6)-O(i) i.151(7) Fe-N(6)-O(I) 179.4(5) Fe--C(I)-N(1) 176.8(5) Fe-C(2)-N(2) 174.6(5) Ni(I)-N(I )-C(I) 153.5(5) C(I )-Fe--C(2) 168.26(23) N(I)-Ni(I)-N(10) 179.9(5) C(3)-Fe-C(5) 169.31(24) N(6)-Fe--C(1) 95.40(24) N(6)-Fe--C(2) -~6.33(23) N(6)-Fe--C(4) 178.55(23) N(6)-Fe--C(5) 95.68(24) N(6)-Fe--C(3) 94.81(24) N(I)-Ni(I)-N(7) 87.79(19) N(I)-Ni(I)-N(8) 88.84(18) N(7)-Ni(I)-N(8) 97.01(19) N(8)-Ni(I)-N(7) 82.99(19) N(9)-Ni(2)-N(10) 96.84(19) N(10)-Ni(2)-N(9) 96.84(19)

chain [Ni(en)2Fe(CN)s(NO)]n as shown in Fig. 3. As shown in Fig. 2 and Table 5, the average bond angle 176.8 ° of Fe--C ( 1 ) - N ( 1 ) and F e ( 2 ) - C ( 2 ) - N ( 2 ) is near linearity, hut the bond angle of Ni( 1 ) - N ( 1 ) - C ( 1 ) or N i ( 2 ) - N ( 2 ) - C (2) is non-linear with an angle of 153.5 (3) °. The geometry of the ligand field of the Hi ions is a six-coordination with tetragonal distorted-octahedral symmetry, the Ni-N bond lengths ranging from 2.093(5) to 2.099(4) A. The mean bond lengths of Fe-C, F e N , C - N and H--O in the [Fe(CN)s(NO) ]2- moiety are in accordance with the cor- responding observed values in complex 1. The bond angle of Fe--N-O (179.4(5) °) is also nearly linear.

3.4. EPR and Mi~ssbauer spectra

The X-band (9.81 GHz) EPR spectra of the polycrystalline powder recorded at 300 K for I and 2 show a typical transition of high-spin Ni(II) with the spin state of 5 = I. The observed absorptions with transitions arise from AMsffi + 1 and A M s = + 2 are located at 3406,1801 G for I and 3406,1860 G for 2, respectively. [Fe(CN)s(NO)] 2- is diamagnetic, thu~ no EPR signal can be observed. In general, it is observed that Ni(ll) often gives rise to quite broad EPR lines, even in presumably octahedral environments. Since Ni(ll) has an even number of electrons, Kramer's theorem does not apply [ 20]. Nevertheless, in some cases of Ni(II)-doped low sym- metry diamagnetic lattices, two resonances are observable at X-band [20-22]. One corresponds to the AMsffi 5:2 transi- tion, while the other results from either the Ms ffiO--* M s = + 1 o r M s = - 1 ~ 0 transition (depending on the sign

H.L Shyu et al. I lnorganica Chiraica Acta 258 (1997) 81--86 85

of the zero field splitting D). In the present work, the spin- Hamiltonian parameters of I and 2 were determined from the experimental data and fitted to the equation [21,22]

Zf = gtSHS + Ds 2 ( 1 )

with g--2.34, D = - 0 . 1 8 cm - l for 1 and g=2.11, D = - 0 . 3 1 cm - I for2.

MGsshauer spectra at 80 K for complexes I and 2 show a quadrupole doublet with the parameters of isomer shift (IS), - 0.39 for 1, - 0.18 mm s - ' for 2 and quadrupole splitting (QS), 1.87 for 1,1.80 mm s - i for 2, respectively. The neg- ative IS value at 80 K of I is higher than that of 2 indicating that total s-electron density at the iron nucleus in complex 2 is lower than that of 1. This can be interpreted by the addi- tional shielding effect of the 3d-electron at the iron atom of 2 by donating a 3d-electron from the nickel ion to the iron ion through the bridging CN ligand [23].

3.5. Magnetic susceptibility studies

The cryomagnetic behavior of the complexes [Ni- (bpy)3][Fe(CN)5(NO)]3H20 and [Ni(en)2Fe(CN)5- ( N O ) ] H 2 0 is shown in Figs. 4 and 5, respectively, in the forms of plots of XM versus T and xMT versus T. As shown

in Fig. 4, the plot ofXMTversus Tfor 1 appears to be invariant as a function of temperature indicative of a classical para- magnet following Curie-Weiss law behavior, fitted to

X M f C / T - - O , with Cffi0.98 cm 3 mol - I K and 0=0.0

suggesting no intermolecular magnetic exchange interaction in the present system.

In the plot XM T versus T shown in Fig. 5 for 2, the }(M y values keep invariant in the region 300 (xMT ffi 1.22 cm 3 m o l - ~ K,/L = 3.10/~a) to 20 K. As the temperature is lowered from 20 K, the x u T value gradually decreases to 1.04 cm 3

tool- I K (/~ = 2.85/ta) at 5 K, suggesting a very weak anti-

0.25

~

2

0.20

i o,,~

i

~

0

Fig. 4. Thermal variation of the molar magnetic susceI~ibifity for [Ni(bpy)3] [Fe(CN)s(NO) ]3HzO. _..

~ 0 . 1 0 0.05 0.00 5 0 100 150 2 0 0 2 5 0 3 0 0 T / K 1.5 .1.o - 0.5 o.o 350

Fig. 5. ~ vad~io~ of ~,e mo~ ~ s ~ c q ~ [Ni(en)zFe(CN)s(NO)IH20. The sofid lines ~ a fit based on Eq. (I).

ferromagnetic interaction. It is known that [Fe(CN)- (NO) ]2- is diamagnetic, therefore the exchange interaction between Ni(II)-Fe(II) through the cyanide ~ g ligand is negligible. However, the coupling between two Ni(H) ions could be through the [Fe(CN)s(NO) ]2- group. We have attempted to reproduce theorefica|ly the experimen- tal susceptibility in this one-dimensional regime by using the modified expression (2) calculated by Kaha [24,25] for a classical-spin Heisenberg chain, scaled to a real spin S - 1 which is valid for an antiferromageetic coupfing

}(M =Ng2[~21k( T - O) [A/B] -t- CI(T-- O) -I-N a (2)

A -- 2.0 + 0.0194x + 0.777x 2, B = 3.0 + 4.346x + 3.232x 2 + 5.834x 3

where x = J / k T . The symbols N,/3, g and k have their usual

meanings, C is the Curie constant for an imperity assumod in this model to be a simple S = 1 Curie paramagnet (non-cou- plod pmmnagnefic species), 0 is the Weiss constant of the impurity, and Na is the temperature-independent component of susceptibility. A very close agreement with experiment is obtained with J = - 0 . 4 7 cm - l , g ~ 2 . 1 0 , O ~- - 0 . 4 4 K, C=0.93 cm 3 mol - I K, N,,-- 100×10 -6 cm 3 moi - l and the disagreement factor R = [E(Xo~-X~)2/E~2obs] 1/2"~" 4 × 10-5. It is worthy of note that the fitted g value of 2.10 is in good agreement with 2.11 calculated from the result of the EPR measurement of 2.

One can notice that the magnitude of the exchange inter- action J of - 0 . 4 7 c m - i in [Ni(en)2Fe(CN)sNO)]H20 is much !ower than - 31.9 cm - i which was reported previously in the strong antiferromagnetic one-dimensional [Ni(en)2- (NO2)] + chain [24]. In the complex [Ni(en)2(NO2)] + ion, two Ni(II) ions are linked by an NO2 group along the chain with an intrachaln Ni-Ni distance of 5.15 ~ , whereas the nearest intrachain Ni-Ni distance in the [(Ni(en)2-

86 H.L. Shyu et al. / Inorganica Chimica Acta 258 (1997) 81--86 F e ( C N ) s ( N O ) ] chain is relatively large, namely 7.9143(23)

A, thus m a k i n g a very w e a k coupling.

A s a final c o m m e n t , we e m p h a s i z e that this study gives n e w evidence that the formation o f a discrete or cyano- bridged polymeric double c o m p l e x o f [ N i ( L ) , ] 2+ with [ F e ( C N ) 5 ( N O ) ] 2 - is dependent on the nature o f the iigands L o f the cation.

4. S u p p l e m e n t a r y m a t e r i a l

Tables containing a t o m positions, anisolropic displace- m e n t parameters, h y d r o g e n a t o m locations, and b o n d lengths and angles arc available from the authors on request.

A c k n o w l e d g e m e n t s

T h i s work was supported by a grant o f the National Science Council o f T a i w a n ( N S C 8 4 - 2 7 3 2 - M 0 3 2 - 0 0 1 ) .

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