Hexadentate chromium(III) complexes containing unsymmetrical edta-type ligands

www.elsevier.nl/locate/ica Inorganica Chimica Acta 292 (1999) 16 – 27

Hexadentate chromium(III) complexes containing unsymmetrical edta-type ligands Part IV. Crystal structures of (− )589-trans(O5)-Na[Cr(ed3ap)]·3H2O and Na[Cr(u-eddadp)]·3H2O and CD spectra correlation: structural parameters of [Cr(edta-type)] − complexes and their octahedral distortion in relation to the structure of the ligand Dusan J. Radanovic´ a, Narumi Sakagami b, Vitko M. Ristanovic´ a, Sumio Kaizaki c,* b

a Department of Chemistry, Faculty of Science, Uni6ersity of Kraguje6ac, YU-34000 Kraguje6ac, Yugosla6ia Department of Chemistry, Faculty of Science and Engineering, Ritsumeikan Uni6ersity, Kusatsu 525 -8577, Japan c Department of Chemistry, Graduate School of Science, Osaka Uni6ersity, Toyonaka, Osaka 560 -0043, Japan

Received 2 December 1998; accepted 19 March 1999

Abstract Structural data are given for two recently reported hexadentate chromium(III) complexes: trans(O5)-Na[Cr(ed3ap)]·3H2O (A) and Na[Cr(u-eddadp)]·3H2O (B) (ed3ap=ethylenediamine-N,N,N%-triacetate-N%-3-propionate ion; u-eddadp= ethylenediamineN-diacetate-N%-di-3-propionate ion). Only one, the favored (trans(O5)) isomer of the complex A was resolved. Also, the complex A was found to be spontaneously resolved. The absolute configuration around the chromium(III) ion in the crystal A has been determined to be L(LDL). The complexes crystallize in the space group P212121 (for A) and Pna21 (for B) of the orthorhombic crystal system. Final R values are 0.045 for A and 0.078 for B. The conformations of the chelate rings are found to be the envelope for the glycinate rings (R relatively flat and G with a significant deviation) and distorted skew-boat (half-chair) for the b-alaninate rings. Structural parameters and strain analysis data of complexes A and B and related [Cr(edta-type)] − chelates are compared and discussed in relation to the structure of the ligand and octahedral distortion of complexes. The CD spectra of the L-(− )589-trans(O5)-[Cr(ed3ap)] − (A) and the other edta-type Cr(III) complexes have been correlated and discussed. © 1999 Elsevier Science S.A. All rights reserved. Keywords: Chromium complexes; Edta-type complexes; Crystal structures

1. Introduction Factors determining the structural types of M(III)edta-type complexes include the d-electron configuration and the size of the central metal ion M. These influence differences in bond lengths (M – N and M–O), ring strain, and the ligand configuration [1 – 9]. In [Co(edta)] − [10] the ethylenediamine (E) ring and two * Corresponding author. Tel./fax: +81-6-6850 5408. E-mail address: [email protected] (S. Kaizaki)

glycinate (G) rings occupying an equatorial plane are more strained than the two glycinate rings coordinated axially (R rings). Similar results can be expected in the directly related [Co(S-pdta)] − and [Co(S,S-cydta)] − complexes [11,12] containing six-coordinate ligands forming only five-membered chelate rings (S-pdta= (S)-1,2-propanediaminetetraacetate ion; S,S-cydta= (1S,2S)-1,2-trans-cyclohexanediaminetetraacetate ion). With respect to the low-spin Co(III) ion with the ionic radius of 0.69 A, , the corresponding complexes of the larger Cr(III) ion (radius 0.76 A, ) are usually pentaden-

0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved. PII: S 0 0 2 0 - 1 6 9 3 ( 9 9 ) 0 0 1 6 4 - 4

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27

17

Fig. 1. (a) Two possible geometrical isomers of the [M(ed3ap)] − complex. (b) Structure of [M(u-eddadp)] − (L configuration). Fig. 2. Molecular structure (ORTEP) of the L-(−)589-trans(O5)[Cr(ed3ap)] − in L-( −)589-trans(O5)-Na[Cr(ed3ap)]·3H2O (A).

Table 1 Crystal data for L-(−)589-trans(O5)-Na[Cr(ed3ap)]·3H2O (A) and Na[Cr(u-eddadp)]·3H2O (B) Complex

A

B

Formula Formula weight Space group Crystal system Cell dimensions a (A, ) b (A, ) c (A, ) V (A, 3) Z Dcalc (g cm−3) Crystal size (mm) No. reflections for lattice parameters (2u range) (°) F(000) m (cm−1) Temperature (K) v-Scan speed (° min−1) v-Scan width (°) Absorption correction factors 2umax (°) Radiation l (Mo Ka) (A, ) Data collected Data used No. parameters varied Goodness-of-fit Ra Rw b Max., min. height in final DF map (e A, −3)

C11H20N2O11NaCr 431.27 P212121 orthorhombic

C12H22N2O11NaCr 445.30 Pna21 orthorhombic

11.220(6) 16.954(5) 8.767(5) 1667(1) 4 1.718 0.30×0.15×0.05 14 (11.8–26.0)

6.807(6) 20.168(4) 13.478(4) 1850(2) 4 1.598 0.25×0.05×0.05 13 (10.9–19.4)

892.0 7.75 296 16.0 1.31+0.30 tan u 0.8947–0.9976

924 7.01 296 16.0 1.21+0.30 tan u 0.9410–0.9944

55.0 0.7107 2231 2218 (Rint = 0.048) 236 0.90 0.045 0.062 0.34, −0.5

55.0 0.7107 2469 2468 (Rint =4.896) 271 1.16 0.078 0.105 0.53, −0.44

a b

R =S[ Fo − Fc ]/S Fo . Rw =[Sw( Fo − Fc )2/Sw Fo 2]1/2.

tates with one water molecule occupying the sixth coordination site [8,13–18]. However, the unstable Cr(III) hexadentates have been prepared in the solid state and the expected strain of chelate rings is apparent in the crystal structure of K[Cr(edta)]·2H2O [19] or Na[Cr(rac-cydta)]·4.5H2O [20]. For the preparation of stable hexadentate edta-type Cr(III) complexes it was reasonable to use the ligands structurally similar to edta but having longer diamine backbone or carboxylate chains. Studies of these complexes were directed to determine the influence of various structural changes of the ligand, relative effects of these structural changes and other factors on their chiroptical spectra [8,9].

Fig. 3. Molecular structure (ORTEP) of the [Cr(u-eddadp)] − in Na[Cr(u-eddadp)]·3H2O (B).

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27

18

The [Cr(1,3-pdta)] − [21] and the [Cr(tdta)] − [22] (1,3-pdta = 1,3-propanediaminetetraacetate ion; tdta= tetramethylenediaminetetraacetate ion) represent stable hexadentate edta analogues of Cr(III). All attempts at resolution of these complexes were fruitless, but a crystallographic study [23] indicates the spontaneous resolution of the [Cr(1,3-pdta)] − complex. The hexadentate [Cr(1,3-pddadp)] − complex (1,3-pddadp= 1,3-propanediamine-N,N%-diacetate-N,N%-di-3-propionate ion) was prepared and separated into the three geometrical isomers with respect to the N – O chelate ring size: trans(O5), trans(O5O6) and trans(O6). These isomers were characterized through the combined use of 2H NMR, magnetic circular dichroism (MCD) and singlecrystal X-ray diffraction analysis of one of the isomers [24]. The CD spectra in the spin-forbidden d – d transitions of trigonal and tetragonal Cr(III) complexes have been elucidated in comparison with those in the first spin-allowed d–d transitions by using the theoretical relations between the rotational strengths [25 – 27]. Optical isomers of the stable hexadentate of known L(LDL) configuration have been established for ( − )589trans(O5)-[Cr(eddadp)] − [28 – 30], (− )589-trans(O5O6)[Cr(eda3p)] − [31], ( +)589-trans(O5)-[Cr(S,S-edds)] − [28 – 30] (forming stereospecifically) and (+ )589[Cr(S,S-ptnta)] − [30] (forming stereospecifically) (eddadp=ethylenediamine-N,N%-diacetate-N,N%-di-3-propionate ion; eda3p=ethylenediamine-N-acetate-N,N%,N%tri-3-propionate ion; S,S-edds =(2S,2%S)-ethylene-

diamine-N,N%-disuccinate ion; S,S-ptnta= (2S,4S)-2,4pentanediaminetetraacetate ion). For all of these complexes, the lowest-frequency CD component in the first band region was assigned to the 4B(C2) state, for which CD signs are considered to be the same as those for the 4 B(C2) state with 4E(4T2g) trigonal parentage or with 4 E(4T2g) tetragonal parentage as in the case of 1A1g “ 1 T1g transitions for Co(III) complexes [8,9]. For [Cr(edtp)] − (edtp=ethylenediaminetetra-3-propionate ion) and structurally related, D-[Cr(S-pdtp)] − and L-[Cr(S,S-cydtp)] − complexes forming stereospecifically [32] (S-pdtp=(S)-1,2-propanediaminetetra-3propionate ion; S,S-cydtp= (1S,2S)-1,2-trans-cyclohexanediaminetetra-3-propionate ion), three conformational isomers (diastereoisomers), arising from a pairwise combination of two conformations at the propionate arms of the R rings have been separated and characterized: L[l(R)l(R), ob2], L[d(R)l(R), lelob] and L[d(R)d(R), lel2] (lel and ob denote the orientation of the 3-propionate ethylene C–C bonds with respect to the C2 axis of the complex). The ( + )589-[Cr(edtp)] − ion [33] with a positive major CD peak corresponding in energy to the absorption band of 4A2g “ 4T2g(Oh) parentage was assigned the D configuration, as was confirmed by the X-ray structure [7]. The CD spectra of the most stable lel2 isomers of the L-[Cr(S-pdtp)] − and L-[Cr(S,S-cydtp)] − complexes [32] are, as expected, nearly the mirror image of the CD spectrum of D[Cr(edtp)] − having the two ethylene gauche conformations in the R rings denoted as l [7].

Table 2 Selected bond distances (A, ) with e.s.d. values in parentheses for L-(−)589-trans(O5)-Na[Cr(ed3ap)]·3H2O (A) and Na[Cr(u-eddadp)]·3H2O (B) Complex A Cr–O(1) Cr–O(3) Cr–O(5) Cr–O(7) Cr–N(1) Cr–N(2) Na–O(2) Na–O(4) Na–O(6) Na–O(51) Na–O(52)

1.939(6) 1.974(5) 1.948(6) 1.945(6) 2.079(8) 2.055(6) 2.545(8) 2.518(7) 2.437(7) 2.440(7) 2.317(7)

Na–O(53) O(1)–C(4) O(2)–C(4) O(3)–C(6) O(4)–C(6) O(5)–C(8) O(6)–C(8) O(7)–C(11) O(8)–C(11) N(1)–C(1) N(1)–C(3)

2.455(7) 1.30(1) 1.24(1) 1.27(1) 1.22(1) 1.31(1) 1.24(1) 1.27(1) 1.26(1) 1.45(1) 1.49(1)

N(1)–C(5) N(2)–C(2) N(2)–C(7) N(2)–C(9) C(1)–C(2) C(3)–C(4) C(5)–C(6) C(7)–C(8) C(9)–C(10) C(10)–C(11)

1.50(1) 1.51(1) 1.48(1) 1.49(1) 1.51(1) 1.48(1) 1.55(1) 1.51(1) 1.50(1) 1.51(1)

Complex B Na(2)–Na(1) Na(2)–O(4) Cr–O(1) Cr–O(3) Cr–O(5) Cr–O(7) Cr–N(1) Cr–N(2) Na(1)–O(51) Na(1)–O(51) Na(1)–O(52) Na(1)–O(52)

3.29(4) 2.66(4) 1.95(2) 2.03(2) 1.95(2) 1.95(2) 2.03(2) 2.10(2) 2.27(3) 2.21(4) 2.59(3) 2.60(3)

Na(1)–O(53) O(1)–C(2) O(2)–C(2) O(3)–C(4) O(4)–C(4) O(5)–C(9) O(6)–C(9) O(7)–C(12) O(8)–C(12) N(1)–C(1) N(1)–C(3) N(1)–C(5)

2.39(3) 1.41(4) 1.21(4) 1.28(3) 1.33(3) 1.01(3) 1.25(3) 1.33(3) 1.23(3) 1.48(3) 1.43(4) 1.63(3)

N(2)–C(6) N(2)–C(7) N(2)–C(10) C(1)–C(2) C(3)–C(4) C(5)–C(6) C(7)–C(8) C(8)–C(9) C(10)–C(11) C(11)–C(12)

1.58(4) 1.43(4) 1.34(4) 1.50(4) 1.52(4) 1.55(5) 1.58(4) 1.63(4) 1.58(5) 1.46(4)

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27 Table 3 Selected bond angles (°) with e.s.d. values in parentheses for L(−)589-trans(O5)-Na[Cr(ed3ap)]·3H2O (A) and Na[Cr(u-eddadp)]· 3H2O (B) Complex A O(1)–Cr–O(3) O(1)–Cr–O(5) O(1)–Cr–O(7) O(1)–Cr–N(1) O(1)–Cr–N(2) O(3)–Cr–O(5) O(3)–Cr–O(7) O(3)–Cr–N(1) O(3)–Cr–N(2) O(5)–Cr–O(7) O(5)–Cr–N(1) O(5)–Cr–N(2) O(7)–Cr–N(1) O(7)–Cr–N(2) N(1)–Cr–N(2) O(2)–Na–O(4) O(2)–Na–O(6) O(2)–Na–O(51) O(2)–Na–O(52) O(2)–Na–O(53) O(4)–Na–O(6) O(4)–Na–O(51) O(4)–Na–O(52) O(4)–Na–O(53) O(6)–Na–O(53) O(51)–Na–O(52) O(51)–Na–O(53) O(52)–Na–O(53) Cr–O(1)–C(4) Na–O(2)–C(4) Cr–O(3)–C(6) Na–O(4)–C(6) Cr–O(5)–C(8) Na–O(6)–C(8)

92.6(2) 177.3(3) 88.9(3) 83.5(3) 95.1(3) 88.9(2) 101.6(2) 80.1(2) 163.2(3) 93.0(3) 94.7(3) 82.8(2) 172.2(3) 93.5(3) 85.9(3) 81.4(2) 168.8(3) 90.4(2) 93.8(2) 88.2(2) 106.2(3) 170.7(3) 82.7(2) 86.8(2) 84.1(2) 102.3(3) 88.7(2) 168.9(3) 116.7(6) 116.8(6) 116.9(5) 116.6(5) 117.7(5) 131.5(6)

Cr–O(7)–C(11) Cr–N(1)–C(1) Cr–N(1)–C(3) Cr–N(1)–C(5) C(1)–N(1)–C(3) C(1)–N(1)–C(5) C(3)–N(1)–C(5) Cr–N(2)–C(2) Cr–N(2)–C(7) Cr–N(2)–C(9) C(2)–N(2)–C(7) C(2)–N(2)–C(9) C(7)–N(2)–C(9) N(1)–C(1)–C(2) O(6)–Na–O(51) O(6)–Na–O(52) O(1)–C(4)–O(2) O(1)–C(4)–C(3) O(2)–C(4)–C(3) N(1)–C(5)–C(6) O(3)–C(6)–O(4) O(3)–C(6)–C(5) O(4)–C(6)–C(5) N(2)–C(7)–C(8) O(5)–C(8)–O(6) O(5)–C(8)–C(7) O(6)–C(8)–C(7) N(2)–C(9)–C(10) C(9)–C(10)–C(11) O(7)–C(11)–O(8) O(7)–C(11)–C(10) O(8)–C(11)–C(10) N(2)–C(2)–C(1) N(1)–C(3)–C(4)

129.3(6) 106.1(5) 107.3(6) 104.0(5) 112.9(6) 115.0(7) 110.7(7) 104.8(4) 109.9(5) 110.5(5) 111.4(6) 108.2(6) 111.8(6) 109.4(7) 81.4(3) 95.4(3) 122.6(9) 117.2(8) 120.2(9) 108.4(7) 125.2(8) 114.7(8) 120.1(8) 111.7(7) 122.9(8) 116.6(7) 120.4(8) 114.3(7) 119.7(7) 120.3(8) 123.6(8) 116.1(8) 109.2(6) 113.4(8)

Complex B Na(1)–Na(2)–O(4) O(1)–Cr–O(3) O(1)–Cr–O(5) O(1)–Cr–O(7) O(1)–Cr–N(1) O(1)–Cr–N(2) O(3)–Cr–O(5) O(3)–Cr–O(7) O(3)–Cr–N(1) O(3)–Cr–N(2) O(5)–Cr–O(7) O(5)–Cr–N(1) O(5)–Cr–N(2) O(7)–Cr–N(1) O(7)–Cr–N(2) N(1)–Cr–N(2) Na(2)–Na(1)–O(51) Na(2)–Na(1)–O(51) Na(2)–Na(1)–O(52) Na(2)–Na(1)–O(52) Na(2)–Na(1)–O(53) O(51)–Na(1)–O(51) O(51)–Na(1)–O(52) O(51)–Na(1)–O(52) O(51)–Na(1)–O(53)

100.5(5) 91.5(7) 176.9(8) 87.8(7) 83.4(8) 91.6(7) 85.8(7) 102.4(7) 78.0(7) 164.6(8) 94.1(7) 94.7(8) 90.7(6) 171.2(8) 92.8(7) 87.3(7) 101(1) 72(1) 81.3(7) 176.8(9) 68(1) 113(1) 162(1) 82(1) 83(1)

Cr–O(7)–C(12) Na(1)–O(51)–Na(1) Na(1)–O(52)–Na(1) Cr–N(1)–C(1) Cr–N(1)–C(3) Cr–N(1)–C(5) C(1)–N(1)–C(3) C(1)–N(1)–C(5) C(3)–N(1)–C(5) Cr–N(2)–C(6) Cr–N(2)–C(7) Cr–N(2)–C(10) C(6)–N(2)–C(7) C(6)–N(2)–C(10) C(7)–N(2)–C(10) N(1)–C(1)–C(2) O(1)–C(2)–O(2) O(1)–C(2)–C(1) O(2)–C(2)–C(1) N(1)–C(3)–C(4) O(3)–C(4)–O(4) O(3)–C(4)–C(3) O(4)–C(4)–C(3) N(1)–C(5)–C(6) N(2)–C(6)–C(5)

129(1) 106(1) 87(1) 111(1) 104(1) 109(1) 114(2) 110(1) 105(2) 106(1) 112(1) 114(1) 107(1) 112(2) 102(2) 112(2) 111(2) 113(2) 134(3) 109(2) 115(1) 113(2) 130(2) 103(2) 114(2)

19

Table 3 (continued) O(51)–Na(1)–O(52) O(51)–Na(1)–O(52) O(51)–Na(1)–O(53) O(52)–Na(1)–O(52) O(52)–Na(1)–O(53) O(52)–Na(1)–O(53) Cr–O(1)–C(2) Cr–O(3)–C(4) Na(2)–O(4)–C(4) Cr–O(5)–C(9)

83(1) 106(1) 139(1) 95(1) 80(1) 111(1) 116(1) 113(1) 135(1) 149(1)

N(2)–C(7)–C(8) C(7)–C(8)–C(9) O(5)–C(9)–O(6) O(5)–C(9)–C(8) O(6)–C(9)–C(8) N(2)–C(10)–C(11) C(10)–C(11)–C(12) O(7)–C(12)–O(8) O(7)–C(12)–C(11) O(8)–C(12)–C(11)

119(2) 116(1) 144(2) 111(2) 103(2) 115(2) 127(2) 115(2) 119(2) 124(2)

The unsymmetrical ed3ap ligand (ed3ap= ethylenediamine-N,N,N%-triacetate-N%-3-propionate ion) with hexadentate coordination can yield two geometrical isomers differing in the position of the six-membered ring: trans(O5) (I) and trans(O5O6) (II) (Fig. 1(a)). However, the unsymmetrical u-eddadp ligand, having N-geminal 3-alaninate and N-geminal acetate arms, can form one geometrical isomer only upon hexadentate coordination (Fig. 1(b)). The condensation mixture containing unsymmetrical ed3ap and u-eddadp ligands was used directly to prepare hexadentate complexes of Co(III) [34,35] and Cr(III) [36]. Two complexes, the favored less-strained trans(O5)-[M(ed3ap)] − (A) and [M(u-eddadp)] − (B) (M=Co(III) [34,35] or Cr(III) [36]) have been separated and characterized, but the resolution was only achieved for the corresponding Co(III) complexes. For complexes, (− )546-trans(O5)-[Co(ed3ap)] − (A) and ( + )546-[Cr(u-eddadp)] − (B) the same L(LDL) absolute configuration was proposed from the CD sign pattern. The geometry and absolute configuration (L) of the ( − )546-trans(O5)-[Co(ed3ap)] − (A) was recently verified by an X-ray crystallography [35]. In this paper the resolution was only achieved for the corresponding trans(O5)-[Cr(ed3ap)] − complex (A). Our attempts at resolution of the [Cr(u-eddadp)] − (B) were fruitless. X-ray data are reported for both Cr(III) complexes, trans(O5)-Na[Cr(ed3ap)]·3H2O (A) and Na[Cr(ueddadp)]·3H2O (B). The absolute configuration around the chromium atom was found to be L for (−)589trans(O5)-[Cr(ed3ap)] − (A). Structural parameters and strain analysis data of these and the other [Cr(edtatype)] − chelates are compared and discussed in relation to the structure of the ligand and octahedral distortion of complexes. The CD spectra of the L-( − )589-trans(O5)[Cr(ed3ap)] − (A) and the other edta-type Cr(III) complexes of known configurations have been correlated and discussed.

2. Experimental All commercially available reagent-grade chemicals were used without purification. The complexes,

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27

20

trans(O5)-Na[Cr(ed3ap)]·3H2O (A) and Na[Cr(u-eddadp)]·3H2O (B), were prepared by using a previously described procedure [36]. Optical isomers are identified by (+ ) or ( − ), corresponding to the sign of the lowest energy CD band, or by the sign of the optical rotation at a wavelength l[( +)l or (− )l]. The chirality is designated as D or L according to IUPAC rules [37].

2.1. Resolution of the trans(O5) geometrical isomer of sodium(ethylenediamine-N,N,N%-triacetato-N%-3 propionato)chromate(III) trihydrate, Na[Cr(ed3ap)] · 3H2O (A) Silver acetate (0.42 g, 0.0025 mol) and ( − )589-[Co(en)2(ox)]Br·H2O (0.91 g, 0.0025 mol) were stirred together at 60°C for 30 min in 15 ml of water. AgBr was removed by filtration and washed with 3 ml of water. The combined filtrate and washing were added to the solution obtained by dissolving 2.16 g (0.0050 mol) of trans(O5)-Na[Cr(ed3ap)]·3H2O in 10 ml of water. The resulting solution was stirred with heating (60°C) for 20 min and then allowed to stand at room temperature (r.t.) overnight. The precipitated less soluble diastereoisomer, ( − )589-[Co(en)2(ox)]-( +)546-[Cr(ed3ap)]·xH2O, was removed by filtration, washed with ethanol and then ether, and air-dried (1.3 g). This diastereoisomer was fractionally recrystallized from water to a constant value of optical rotation. Aqueous solution (0.05%) gave: [a]589 = − 540; [a]546 = − 196°. The corresponding enantiomer in the form of the sodium salt was obtained by dissolving the diastereoisomer in water and passing the solution through a cation-exchange column in the Na + form. The eluate was evaporated to a volume of 2 ml and then to dryness after standing in a desiccator over CaCl2. Red–violet crystals of (− )589-( + )546-trans(O5)Na[Cr(ed3ap)]·3-H2O were collected. Aqueous solution (0.05%) gave [a]589 = − 140; [a]546 = + 540°. Anal. Calc. for (−)589-(+ )546-trans(O5)-Na[Cr(ed3ap)]·3H2O = NaCrC11H20N2O11 (Mr =431.28): C, 30.63; H, 4.67;

N, 6.50. Found: C, 31.20; H, 4.54; N, 7.00%. The opposite enantiomer, (+ )589-(−)546-trans(O5)Na[Cr(ed3ap)]·3H2O was obtained by the same procedure using (+ )589-[Co(en)2(ox)]I as the resolving agent. [a]589 = + 142; [a]546 = − 542°.

2.2. Physical measurements 2.2.1. Complex A An X-ray analysis was performed on a red–violet crystal of trans(O5)-Na[Cr(ed3ap)]·3H2O (A) that was allowed to grow from an aqueous solution by adding a small amount of ethanol. The complex crystallizes in the space group P212121 of the orthorhombic crystal system, showing that it is resolved spontaneously. Intensity measurements were made for a crystal of approximate dimensions 0.30× 0.15× 0.05 mm on a Rigaku AFC7S diffractometer using graphite monochromated Mo Ka radiation. The unit-cell dimensions were obtained from the setting angles of 14 accurately measured reflections in the range 11.78B 2u B 25.96°. The intensity data were collected by the scan method to a maximum 2u value of 55.0°. The intensities of 2231 reflections were measured of which 2218 were unique. The intensities of three representative reflection were measured after every 150 reflections. The final cycle of full-matrix least-squares refinement was based on 1343 observed reflections [I\ 1.5s(I)] and 236 variable parameters. 2.2.2. Complex B A suitable crystal for X-ray analysis of Na[Cr(ueddadp)]·3H2O (B) was obtained by recrystallization from aqueous–ethanol solution. A red–violet crystal having approximate dimensions of 0.25×0.05×0.05 mm was mounted on the same diffractometer used for A, and examined by X-ray diffraction. The complex crystallizes in the space group Pna21 of the orthorhombic crystal system. The unit-cell dimensions were obtained from the setting angles of 13 accurately measured

Table 4 Comparison of bond distances (A, ) in hexadentate Cr(III)–edta-type complexes Complex

(1) (2) (3) (4) (5) (6)

[Cr(edta)]− [Cr(cydta)]− [Cr(ed3ap)]− a (A) [Cr(1,3-pdta)]− [Cr(u-eddadp)]− (B) [Cr(eddadp)]− a

(7) [Cr(1,3-pddadp)]− b (8) [Cr(edtp)]− a b

trans(O5) isomer. trans(O6) isomer

Cr–N

Mean

Cr–O(G)

Mean

Cr–O(R)

Mean

Cr–O (mean)

Ref.

2.044, 2.059 2.058(3), 2.060(3) 2.079(8), 2.055(6) 2.065(6), 2.065(5) 2.03(2), 2.10(2) 2.097(12), 2.072(12)

2.051 2.059 2.067 2.065 2.07 2.084

1.984 1.991 1.959 1.966 1.99 1.964

1.971 1.972 1.951 1.956 1.97 1.960

[5,19] [20] this work [7,23] this work [7,29]

2.085 2.087

1.952, 1.965 1.951(3), 1.954(3) 1.939(6), 1.948(6) 1.941(5), 1.949(5) 1.95(2), 1.95(2) 1.952(10), 1.962(10) 1.963(3), 1.958(3) 1.962(2), 1.961(2)

1.958 1.952 1.943 1.945 1.95 1.957

2.086(3), 2.084(3) 2.084(2), 2.091(2)

1.969, 1.999 1.985(3), 1.998(3) 1.974(5), 1.945(6) 1.960(5), 1.973(5) 2.03(2), 1.95(2) 1.957(10), 1.971(10) 1.970(3), 1.962(3) 1.967(3), 1.968(2)

1.960 1.961

1.963 1.964

[7,24] [7]

1.966 1.967

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27

reflections in the range 10.91B 2u B 19.39°. The intensity data were collected by the same scan method as given for A using the same radiation (2umax =55.0°). The intensities of 2469 reflections were measured of which 2468 were unique. The intensities of three representative reflection were measured after every 150 reflections. The final cycle of full-matrix least-squares refinement was based on 619 observed reflections [I\ 2s(I)] and 271 variable parameters. The intensity data of complexes A and B were corrected for Lorentz and polarization effects. The crystal data and experimental details for complexes examined are given in Table 1. The structures of complexes A and B were solved by direct methods [38], expanded using Fourier techniques [39] and refined by full-matrix least-squares techniques. The non-hydrogen atoms were refined anisotropically while hydrogen atoms, excluding those of water molecules, were included but not refined. Neutral atom scattering factors were taken from Cromer and Waber [40]. All calculations were obtained using the teXsan crystallographic software package [41]. The absolute configuration was identified based on the R values of enantiomers. The parameters for the L configuration of the complex (−)589-[Cr(ed3ap)] converted to R =0.045 and Rw= 0.062, whereas those for the enantiomer (D configuration) to R= 0.054 and Rw =0.074. This fact indicates that the ( − )589-[Cr(ed3ap)] takes a L configuration. The [a]l values were measured in a 1 dm tube at 20°C on a Perkin–Elmer SP polarimeter. CD spectra were recorded at r.t. on a JSCO Model J-720 spectropolarimeter.

21

Elemental microanalyses for carbon, hydrogen and nitrogen were carried out by the Microanalytical Laboratory, Faculty of Chemistry, University of Belgrade.

3. Results and discussion Two complexes, trans(O5)-[Cr(ed3ap)] − (A) (Fig. 1(a), isomer I) and [Cr(u-eddadp)] − (B) (Fig. 1(b)) have a rhombic field and C1 molecular symmetry. The resolution was achieved only for complex A. Our attempts at resolution of the [Cr(u-eddadp)] − (B) were fruitless. The crystallographic studies of these complexes indicate the spontaneous resolution of complex A. The crystal of A taken for X-ray work from the racemic mixture was found to have the same absolute configuration (L) as that obtained from the less-soluble diastereoisomer using (− )589-[Co(en)2(ox)] + as the resolving agent.

3.1. Description of the crystal structures of L-( − )589 -trans(O5) -Na[Cr(ed3ap)] ·3H2O (A) and Na[Cr(u-eddadp)] ·3H2O (B) The ORTEP diagrams of L-( − )589-trans(O5)[Cr(ed3ap)] − (A) and [Cr(u-eddadp)] − (B) are depicted in Figs. 2 and 3 where the numbering schemes adopted for the respective atoms are also given. The Cr(III) ion is encircled by all of the six ligand atoms (2N and 4O) of ed3ap (Fig. 2) or u-eddadp (Fig. 3) to form octahedral complexes.

Table 5 Strain analysis of hexadentate Cr(III)–edta-type complexes Complex

(1) (2) (3) (4) (5) (6) (7) (8)

[Cr(edta)]− e [Cr(cydta)]− trans(O5)-[Cr(ed3ap)]− (A)* [Cr(1,3-pdta)]− [Cr(u-eddadp)]− (B)* trans(O5)-[Cr(eddadp)]− trans(O6)-[Cr(1,3-pddadp)]− [Cr(edtp)]−

SD a

DS b

D{Cr–O–C} c

SD d

Oh

E(T)

R

G

R

G

N

74 60 56 56 37 42 17

−12 −17 −13 +35 −9 −15 +26 −16

−1 −2 0 +1 −3(+50) −1 +33 +39

−14 −15 −14(+43) −10 −22(+49) +37 −11 +39

+6 +8 +9 +7(+40) +8 +19 +23

+5 +7(+20) +7 +4(+20) +21 +5 +23

21 21(12) 14 17(23) 16 15 21

Ref.

[5,19] [20] this work [7,23] this work [7,29] [7,24] [7]

a SD(Oh) is the sum of the absolute values of the deviations from 90° of the L–Cr–L% bite angles. All values are rounded off to the nearest degree. b DS (ring) is the deviation from the ideal of the corresponding chelate rings% bond angle sum. A mean value for the two rings (R or G) is reported for listed complexes (except for 3 and 5), because the molecule is expected (in approximation) to have C2 symmetry. c D{Cr–O–C} (ring) is the mean value of the deviation of the corresponding rings% Cr–O–C bond angle from 109.5°. d SD(N) is the sum of the absolute values of the six bond angles made by the chelate nitrogen atoms. A mean value for the two nitrogens is reported. e Bond angle data are not available for this complex. * For complexes 3 and 5, having C1 molecular symmetry, the two values are reported. The values in parentheses are given for the b-alaninate rings and nitrogen atoms connecting 3-alaninate rings.

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27

22

3.1.1. Complex A The complex anion of A (Fig. 2) represents a trans(O5) isomer with the two glycinate (R) rings in the trans positions and the two (G) rings (one glycinate and one b-alaninate) coordinated in the equatorial plane. The absolute configuration of the complex anion is the L(LDL) according to IUPAC rules [37]. The asymmetric nitrogen donor (N(2) atom) of the L-[Cr(ed3ap)] − adopts the R absolute configuration [42]. The puckered diamine (E) ring, as expected, has a d-conformation. The two glycinate rings lying out of the G plane (R1 and R2) are relatively flat. The glycinate G1 ring (Fig. 2) shows a significant deviation from planarity with a l-conformation. The b-alaninate (G2) ring shows large deviation from an ideal twist-boat conformation. The conformation of this ring is close to half-chair (l). The two trans(O5) structures, the L-[Cr(ed3ap)] − (A) and recently reported L-[Co(ed3ap)] − [35] (assigned as A) are almost the same in conformations of their chelate rings. The distorted octahedron about the Na + ion is linked to three bridging carbonyl oxygen atoms of three neighboring complex units and three water oxygen atoms making six bonds (Na–O(2), 2.545(8); Na – O(4), 2.518(7); Na– O(6), 2.437(7); Na–O(51), 2.440(7); Na – O(52), 2.317(7); Na – O(53), 2.455(7) A, , Table 2). 3.1.2. Complex B Because of the structure of the u-eddadp ligand, the complex B (Fig. 3) has N-geminal acetate and N-geminal 3-alaninate rings. This structure possesses a five-membered diamine ring in a twist (l) configuration and the two five-membered glycinate rings (relatively flat R1 and G1 showing a significant deviation from planarity) both having the same (l)-conformation. The two six-membered (b-alaninate) rings (the G2 and R2) show a large deviation from an ideal twist-boat conformation (the G2 in a half-chair (d) and R2 in an envelope-like d-conformation). With respect to the pseudo C2 axis, the R2 ring seems to have ob form [32]. In the crystal structure, the distorted octahedron about the Na(1) + ion is linked to three water oxygen atoms, the Na(2) + ion belonging to neighboring complex unit and the bridging water oxygen atoms connecting two sodium ions (Na(2)–

Na(1), 3.29(4); Na(1)–O(51), 2.27(3); Na(1)–O(52), 2.59(3); Na(1)–O(53), 2.39(3); Na(1)–O(51), 2,21(4); Na(1)–O(52), 2.60(3) A, , Table 2). In general, the carbonyl oxygen atoms of the carboxylate rings of structures A and B are involved with either H-bonding to water molecules of crystallization or a sodium ion. What effects these interactions have on the conformations of the chelate rings is uncertain.

3.2. Structural parameters and strain analysis of [Cr(edtatype)] − complexes in relation to their octahedral distortion Our interest in [Cr(edta-type)] − complexes is related to the stereochemistry involved and to study the structural parameters and octahedral distortion of such complexes depending on the structure of edta-type ligand. Selected bond distances and angles for complexes A and B are listed in Tables 2 and 3. The Cr–L bond distances of complexes A and B and the other Cr(III)-edta-type complexes are given in Table 4 (complexes 1 to 8). For complexes 3 (A) and 5 (B) having C1 molecular symmetry, the Cr–N and Cr–O(G) bond distances are significantly different one from another (Cr–N(1), 2.079(8); Cr–N(2), 2.055(6); Cr–O(G1), 1.974(5); Cr–O(G2), 1.945(6) A, for 3 and Cr–N(1), 2.03(2); Cr–N(2), 2.10(2); Cr–O(G1), 2.03(2); Cr–O(G2), 1.95(2) A, for 5). These values are limited in a series of complexes in Table 4. However, the mean Cr–L bond distances (Cr–N, 2.067; Cr–O, 1.951 A, for 3 and Cr–N, 2.065; Cr–O, 1.97 A, for 5) are comparable with corresponding bond lengths in related Cr(III) complexes (mean Cr–N range 2.051– 2.087 A, , mean Cr–O range, 1.951–1.972 A, , Table 4) [5,7,19,20,23,24,29]. Mean Cr–N bond distances for the complexes listed are larger than mean Cr–O distances and these values slightly increase on going from 1 to 8 with increasing number of the six-membered rings (1,3-propanediamine or b-alaninate rings). This fit better for complexes 1, 2, 4 and 6 to 8 having (in approximation) C2 molecular symmetry. On the other hand, the axial Cr–O(R) bonds of these complexes are on average shorter (mean Cr–O(R) range 1.943–1.961 A, ) than the equatorial Cr–O(G) bonds

Table 6 Bond angles (°) of the b-alaninate (R and G) rings with their corresponding deviation given in parentheses for [Cr(edta-type)]− chelates a Ring

Cr–N–C

N–C–C

C–C–C

C–C–O

Cr–O–C

(3) G (5) R G (6) G (7) R (8) R G

110.5(+1) 112.0(+2.5) 114.0(+4.5) 111.2(+1.7) 115.6(+6.1) 117.6(+8.1) 108.7(−0.8)

114.3(+5) 119.0(+9.5) 115.0(+5.5) 113.0(+3.5) 114.3(+5) 117.0(+7.5) 114.0(+4.5)

119.7(+10) 116.0(+6.5) 127.0(+17.5) 118.2(+8.7) 113.8(+4.3) 113.2(+3.7) 120.5(+11)

123.6(+3.6) 111.0(−9) 119.0(−1) 121.4(+1.4) 118.0(−2) 117.3(−2.7) 121.5(+1.5)

129.3(+20) 149.0(+39.5) 129.0(+19.5) 130.8(+21.3) 128.8(+19.3) 132.0(+22.5) 132.0(+22.5)

a

For complexes 6, 7 and 8 the mean values are given for the two rings (R or G).

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27

(mean Cr–O(G) range, 1.959 – 1.991 A, ) as was the case for the corresponding Co(III) complexes [7,35]. Nearly the same mean Cr–O(R) and Cr – O(G) distances were found for complexes 6, 7 and 8 containing the 2-, 3- and 4-six-membered rings, respectively (complexes having trans(O5) (6) and trans(O6) (7, 8) coordination, Table 4). In general, the Cr– N bond distances are more sensitive to the structure of the ligand than are Cr – O bond distances as was the case for similar complexes of Co(III) [7,35]. Also, our results indicate that the mean Cr–O bond distances of Cr(III) – edta-type complexes are less sensitive to the structure of the ligand than was the case for the mean Co–O distances [7,35]. The main Cartesian axes (O(R1) – Cr – O(R2), O(G1)– Cr – N and O(G2)–Cr – N) for complexes listed (Table 4) are different lengths (the two in the G-plane being a few percent longer than the axis defined by the trans(O)-coordination). Of the three Cartesian axes mentioned, the O(R1)–Cr–O(R2) angles of complexes 3 (A) and 5 (B) deviate least from the ideal value of 180° (D = − 2.7° for 3 and D = − 3.1° for 5). This was also the case for the other complexes going from 2 to 5 (Table 4). The O(G1)–Cr–N and O(G2) – Cr – N angles of these complexes show relatively great deviations from the ideal bond angle of 180° which vary from −5.2 to −16.8°. The situation is different for the remaining complexes 6 [7,29], 7 [7,24] and 8 [7] containing 2-, 3- and 4-six-membered rings, respectively. For complexes 6 (trans(O5) coordination), 7 and 8 (having trans(O6) coordination) the main Cartesian axes deviate only minimally from the ideal bond angles of 180° (D varies from −2.8 to −7.2°). The results of a comparative study of the strain characteristics of related series of Cr(III)-edta-type chelates are given in Table 5. The strain characteristics data are reported for the complex 2 [20] and complexes 3 (A) and 5 (B) considered in this work. For comparison, data are given in Table 5 for complexes 4 [7,23], 6 [7,29], 7 [7,24] and 8 [7] of known strain characteristics [7]. The contributions to strain for these chelates were considered to be: (i) the octahedral angles around the Cr(III) ion, (ii) the ring angle sums of the various kinds of rings, (iii) the Cr– O –C bond angles and (iv) the bond angles that the chelating nitrogen atom makes with its connectors. The E rings and the G glycinate rings of these chelates are usually observed to be puckered, while the R glycinate rings are observed to be more planar than the G values and are referred to as having an envelope conformation. On the other hand, the six-membered rings (1,3-propanediamine (T rings) and b-alaninate rings (R and G)) are in distorted boat conformations. The equatorially coordinated b-alaninate (G) rings of these kind chelates deviate more than the axially coordinated (R) rings from an ideal twist-boat conformation. The octahedral bond angles in [Cr(edta-type)] − chelates vary from 80.9 to 112.9° for 2 [20], 80.1 to 101.6° for 3 (A) (Table 3), 81.7 to 99.7° for 4 [23], 78.0 to 102.4° for 5 (B) (Table 3), 81.6 to 93.0 for 6 [29], 82.1 to 99.1° for

23

7 [24], and 86.9 to 92.9° for the complex 8 [7]. In all of these Cr(III) chelates forming five- or six-membered diamine rings (Table 5) the O(G1)–Cr–O(G2) cis angles show greatest deviation. It should be pointed out that in corresponding Co(III) complexes forming six-membered diamine rings the greatest deviation was realized by the N(1)–Co–N(2) bond angles [7,35]. As was expected [7,35,43], the expanding of the E ring and/or the glycinate ring lowers the octahedral strain (Table 5). The total deviation of the octahedral angles sums 74° for the [Cr(cydta)] − (2) complex (the mean angular deviation is 6.16° angle − 1) indicating a greater octahedral distortion than among the other complexes listed. Following the Table 5, the complexes 3, 4 and 5 also show very large angular deviation which varies from 4.66° angle − 1 for complexes 4 and 5 to 5.0° angle − 1 for 3. The remaining complexes 6, 7 and 8 are relatively free of much octahedral angle strain (the mean angular deviation varies from 1.41° angle − 1 for 8 to ca. 3° angle − 1 for complexes 6 and 7). As was the case for the other transition M-edta-type complexes [43], the bond angle chelate-ring sums for the R glycinate rings are close to the ideal values (538.5°) (total deviations vary from − 3 to + 1°, Table 5). The bond angle chelate-ring sums for the G glycinate and E rings, as expected [7,35,43], are less (deviations are negative) than the corresponding ideal values (a negative total deviation varies from −11 to − 22° for the G rings and from − 9 to −17° for the E rings). The larger deviations are positive for all six-membered rings (T rings and b-alaninate rings) for listed complexes (Table 5) as was found for corresponding Co(III)-edta-type chelates [35]. The mean angular deviation in the T ring (complexes 4 and 7) is actually larger than was found for the E ring (4.3–5.8° angle − 1 versus 1.8–3.4° angle − 1). Positive total deviations of the b-alaninate (R and G) rings (mean values are taken for complexes 6, 7 and 8 having C2 molecular symmetry) are extremely large for complexes 3, 5 and 8 [of + 43° for the G ring for 3 (ca. 7.2° angle − 1); of + 50° for the R and G rings for 5 (8.3° angle − 1); and of + 39° for the R and G rings for 8 (6.5° angle − 1)]. This deviation is less for complexes 6 and 7 [of + 37° for the G rings for 6 (6.1° angle − 1); and of + 33° for the R rings for 7 (5.5° angle − 1)]. The extremely large mean angular deviation for the b-alaninate (R) rings of complexes 5 (8.3° angle − 1) and 8 (6.5° angle − 1) can be considered in fact that these kinds of rings (ob form) are expected to undergo thermal hydrolysis with C–N bond cleavage [32]. As was discussed for M-edta-type complexes [7,35,43], the main causes of strain in the b-alaninate rings are due to the M–O–C (except for Cu(II) [44]), C–C–C, N–C– C and M–N–C bond angles. These bond angles (except M–N–C) deviate more for the G b-alaninate rings (having distorted twist-boat conformation) than for the R b-alaninate rings which usually adopt nearly an ideal twist-boat conformation. This was also the case for

24

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27

Fig. 4. Absorption and CD spectra of hexadentate [Cr(edta-type)] − complexes: (thin unbroken line) D-(+ )589-[Cr(edtp)] − , (dotted line) L-(− )589-trans(O5O6)-[Cr(eda3p)] − , (thick unbroken line) L-(−)589trans(O5)-[Cr(ed3ap)] − (A), (dashed line) L-(− )589-trans(O5)[Cr(eddadp)] − , (dashed –dotted line) L-(+ )589-trans(O5)-[Cr(S,Sedds)] − .

complexes 6 to 8 of Cr(III) [7] (Table 5). For comparison, these bond angles of the b-alaninate rings of Cr(III)-edta-type chelates with their corresponding deviations given in parentheses are shown in Table 6. All complexes considered (Table 6) show a very large deviation of the Cr –O – C(R,G) bond angles of the b-alaninate rings. These bond angles are as high as approximately 130°, and the value is nearly of the same order of magnitude for both kinds of rings, R or G, for all complexes except of that for the R ring of the complex 5 for which an extremely large deviation was found (Cr –O – C(R) = 149.0 (+ 39.5°). It should be noted that the Cu – O – C(R) bond angles in the trans(O6)-[Cu(1,3-pddadp)]2 − complex [44] do not show any deviation from the ideal value (Cu–O– C(R) =109.0°) indicating that the deviation of these angles in this chelate system strongly depends on the length of the axial (Cu – O – C(R)) bond distances [44]. Also, data given in Table 6 show that the C–C– O(R,G) bond angles of these kinds of Cr(III) chelates deviate minimally (ca. − 2.7 – + 3.6°) except for that of the R ring of the complex 5 (C – C – O(R) = 111.0 ( − 9°)).

The bond angles of the G rings of complexes 3 and 5 show large deviation from an ideal twist-boat conformation (minimal deviation of the Cr–N– C(G) bond angles of +1 for 3 and of +4.5° for 5, following a larger deviation of the N–C–C(G) and C–C–C(G) bond angles, Table 6), as was the case for the corresponding rings of complexes 6 and 8 [7]. These G rings have all the participating atoms nearly coplanar except for the N atom and are in distorted twist-boat or nearly half-chair conformation. On the other hand, the Cr–N–C(R) bond angles of complexes 7 and 8 deviate more (ca. +6–8.1°) than the N–C–C(R) and C–C–C(R) bond angles, what was opposite for the G rings (Table 6). For the R rings of these complexes (except for 5) coplanarity is realized by all in the ring except the metal ion and the carbon atom opposed to it (as expected for twist-boat conformation). However, an unexpected large deviations were found for the corresponding bond angles of the R ring of the complex 5 (Cr–N–C(R), (+ 2.5°); N–C–C(R), +(9.5°); C–C–C(R), (+ 6.5°); C–C–O(R), (− 9°); and Cr–O– C(R), ( + 39.5°), Table 6) having an envelope-like dconformation. In general, the strain in the b-alaninate (R, and G) rings is greater than that for the corresponding glycinate rings in [Cr(edta-type)] − complexes (Table 5). An important source of strain in Cr(III)-edtatype chelates is the bonding geometry made by the chelating nitrogens [45]. This strain arises when the effect of chelation distorts the tetrahedral bonding geometry of the nitrogen atoms. When each of the deviations is summed for the six angles, the total deviations (absolute values) for each complex were obtained (Table 5). Total deviation about the chelating N atoms sums to roughly 21 (for 2), 21(12) (for 3), 17(23) (for 5), and 21° (for 8). These complexes having N atoms connecting two acetate or two 3-alaninate rings contain N atoms with the most highly strained bonds. Other listed complexes (Table 5) having N atoms connecting mixed (one acetate and one 3-alaninate) rings or two acetate rings and six-membered diamine ring show less total deviation about the N atoms. The total deviation about the N atoms of these complexes sums to roughly 12 (for 3), 14 (for 4), 16 (for 6), and 15° (for 7). These complexes contain the N atoms with relatively less-strained bonds. The greatest deviation about the N atoms in Cr(III)-edtatype chelates (Table 5) is not consistently and specifically due to any one of the six bond angles. In the complex 3 (N1 nitrogen) two bond angles, Cr–N1– C(G) and C(E)–N1–C(G) show very large deviations (104.0 (ca. −6°) and 115.0 (ca. + 6°), respectively). Also, in the complex 5 (N2 nitrogen) the two bond angles, Cr–N2–C(G) and C(R)–N2–C(G), show very large deviation [114.0 (ca. + 5°) and 102.0 (ca. −8°), respectively).

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27

3.3. Correlation of absolute configurations with CD spectra Electronic absorption and CD spectra for the L( − )589-trans(O5)-[Cr(ed3ap)] − complex (A) are shown in Fig. 4 in comparison to those of the L-( − )589trans(O5O6)-[Cr(eda3p)] − [31], L-( − )589-trans(O5)[Cr(eddadp)] − [28,30], L-( +)589-trans(O5)-[Cr(S,Sedds)] − [28,30], and D-( + )589-[Cr(edtp)] − [33]. Corresponding numerical data for these and related edtatype complexes are summarized in Table 7. Absorption spectra of these complexes (Fig. 4, Table 7) are very similar with two bands corresponding to transitions to the 4T2g and 4T1g(Oh) states. Bands I and II are symmetrical showing no obvious splitting. However, CD spectra of these complexes exhibit resolution of spectral components of these absorption bands. By comparison of positions of CD peaks within the envelope of the corresponding absorption band maxima, there are indications of three CD components under the first spin-allowed d – d absorption band for all of these complexes (Table 7). The complete removal of the degeneracy of the triplet state (Oh parentage) is expected for the actual symmetry of these complexes as was observed in some complexes of Cr(III) (S,Sedds and S,S-ptnta complexes, Table 7) and Co(III) [9] having C2 molecular symmetry. In the case of the S,S-ptnta and S,S-edds M(III) complexes, the absolute configuration L(LDL) based on the CD criteria is consistent with that determined from the stereospecific coordination of these hexadentate chiral ligands to M(III) (M= Co(III) [46,47] or Cr(III) [28,30]). The CD pattern in the lower energy spin-allowed absorption band for complexes listed (Table 7) show three prominent CD peaks (or two CD peaks with some indication of a shoulder at higher energy). However, the (−)589-trans(O5)-[Cr(ed3ap)] − (A) presented here, is the only complex of the ligands other than S,S-edds and S,S-ptnta that show three well defined CD peaks ( + − + ) in the first absorption band region (Fig. 4, Table 7). Three components are expected for the proper (or in approximation) C2 molecular symmetry and the lowest energy spin-allowed CD peak for these complexes (except for edtp, Table 7) was assigned 4B(C2) derived from 4Eg(4T2g) [9,30,31] as for the corresponding Co(III) complexes [8,9,34]. All complexes listed including the complex A (except for edtp, Table 7) with a L(LDL) configuration give a positive CD component at the lowest energy side of the first spin-allowed absorption band. The absolute configuration (L) of these complexes proposed from the CD sign pattern have been verified crystallographically for ( −)589-trans(O5)-[Cr(eddadp)] − [29], and ( − )589-trans(O5)-[Cr(ed3ap)] − (A) complex presented in this work (Fig. 2).

25

The CD spectrum of (+ )589-[Cr(edtp)] − (Fig. 4, Table 7) differs from the others in that it lacks a low energy peak near the extremity of the absorption maximum. This CD peak is assumed to be masked or canceled by the intense positive peak near the absorption maximum. The (+ )589-[Cr(edtp)] − ion was assigned the D configuration [33], because its dominant positive CD peak band of 4A2g “ 4T2g(Oh) parentage is opposite compared with the dominant bands of Land L-(lel2)-[Cr(S,S-cydtp)] − (lel2)-[Cr(S-pdtp)] − complexes [32]. This D absolute configuration for (+)589[Cr(edtp)] − was also confirmed by the X-ray structure [7]. The complexes (− )589-trans(O5O6)-[Cr(eda3p)] − [31] (− )589-trans(O5)-[Cr(eddadp)] − [28,30], and (+)589trans(O5)-[Cr(S,S-edds)] − [28,30] give similar CD spectra in the region of the lower energy absorption band (4T2g(Oh) parentage) which are much different from the others (Fig. 4, Table 7). Also, the CD spectra of the other Cr(III) complexes considered are much different from another. This was not the case for the corresponding Co(III) complexes having more similar CD spectra [9,34].

4. General conclusions It is tempting to conclude that unusually high strain is the result of chelation constrains, but the corresponding Cr(III)-edta-type complexes do not show anything quite like this. When 3-alaninate coordinates to Cr(III) ions, it forms chelate rings with distorted boat conformations having unusually high Cr–O–C bond angles. The presence of N-geminal mixed (one acetate and one 3-alaninate) rings or only one flexible diamine (T) ring serves to relieve some of the angular strain about the nitrogens, but cannot completely relieve the G ring distortion produced by the nitrogen rotation. The Cr(III) complexes with larger positive deviation of the T ring have less strained nitrogen tetrahedra (+ 35 (14°) for 4 and + 26 (15°) for 7, Table 5). Although the G rings of complexes 4 and 7 (with respect to complexes 1, 2, 3 and 5, Table 5) remained relatively strained, the presence of six-membered rings appears to compensate for the distortion induced in the Cr(III) coordination polyhedra. Variation in CD band positions and intensities of the Cr(III) complexes arise from changes in strain resulting from ring size and different configurational effects. In view of these facts, the contribution of the chelate rings to optical activity of these complexes, then, strongly depends on both their relative size and their disposition about an octahedron. We cannot yet say just how large the relative contributions are.

26

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27

Table 7 Absorption (AB) and circular dichroism (CD) data of [Cr(edta-type)]− complexes a Complex ion

L-(+)589-[Cr(edtp)]−

L-(−)589-[Cr(eda3p)]− b

L-(−)589-[Cr(ed3ap)]− c (A)

L-(−)589-[Cr(eddadp)]− c

L-(+)589-[Cr(S,S-edds)]− c

L-(+)589-[Cr(S,S-ptnta)]−

AB

CD

Ref.

n (×103 cm−1)

o

n (×103 cm−1)

Do

18.55

196.5

25.11

71.1

18.69

194.0

25.12

86.6

18.76

218.0 d

25.59

119.6

18.90

214.0

25.30

107.0

19.60

175.0

26.00

57.0

19.64

110.0

25.97

77.0

18.24 20.08 21.01 23.20 26.52 16.58 18.76 21.05sh 23.53 26.67 15.97 17.80 19.78 24.81 27.51 16.53 18.62 20.33sh 22.17sh 24.10 26.53 17.54 19.33 21.83 23.50sh 26.99 18.00sh 19.67 21.67 24.00 25.25sh 29.66

+0.37 −0.04 −0.02 −0.14 −0.18 +0.09 e −0.64 −0.14 +0.07 +0.23 +0.14 e −0.50 +0.72 −0.35 +0.05 +0.20 e −0.77 −0.20 −0.05 −0.08 +0.23 +0.41 e −0.39 +0.45 +0.34 +0.38 +0.20 e +0.44 −0.06 +0.44 +0.27 −0.02

[7,32,33]

[31]

this work

[28,30]

[28,30]

[30]

Values (o, Do) are given in units of mol−1 dm3 cm−1. trans(O5O6) isomer. c trans(O5) isomer. d Absorption data taken from Ref. [36]. e These peaks are presumed to be 4B(C2) components, indicative of the L configuration. a

b

More examples and more X-ray crystallographic data are needed for these studies. 5. Supplementary material The final atomic coordinates and anisotropic thermal parameters for non-hydrogen atoms, lists of structure factors and other relevant data of X-ray crystallographic structural studies of complexes A and B are available from the Cambridge Structural Database Centre. Acknowledgements The authors are grateful to the Serbian Ministry for Science and Technology for financial support.

References [1] T. Yamamoto, K. Mikata, K. Miyoshi, H. Yoneda, Inorg. Chim. Acta 150 (1988) 237. [2] R.H. Nuttall, D.M. Stalker, Talanta 24 (1977) 355. [3] J.J. Stezowski, R. Countryman, J.L. Hoard, Inorg. Chem. 12 (1973) 1749. [4] J.P. Fackler Jr., F.J. Kristine, A.M. Mazany, T.J. Moyer, R.E. Shepherd, Inorg. Chem. 24 (1985) 1857. [5] T. Mizuta, T. Yamamoto, N. Shibata, K. Miyoshi, Inorg. Chim. Acta 169 (1990) 257. [6] M. Parvez, C. Maricondi, D.J. Radanovic´, S.R. Trifunovic´, V.D. Miletic´, B.E. Douglas, Inorg. Chim. Acta 248 (1996) 89. [7] M. Parvez, C. Maricondi, D.J. Radanovic´, M.I. Djuran, B.E. Douglas, Inorg. Chim. Acta 182 (1991) 177. [8] D.J. Radanovic´, Coord. Chem. Rev. 54 (1984) 159. [9] B.E. Douglas, D.J. Radanovic´, Coord. Chem. Rev. 128 (1993) 139. [10] (a) H.A. Weakliem, J.L. Hoard, J. Am. Chem. Soc. 81 (1959) 549. (b) K. Okamoto, T. Tsukihara, J. Hidaka, Y. Shimura,

D.J. Radano6ic´ et al. / Inorganica Chimica Acta 292 (1999) 16–27

[11]

[12]

[13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32]

Bull. Chem. Soc. Jpn. 51 (1978) 3534. (c) K. Okamoto, T. Tsukihara, J. Hidaka, Y. Shimura, Chem. Lett. (1973) 145. (a) F.P. Dwyer, F.L. Garvan, J. Am. Chem. Soc. 81 (1959) 2955. (b) F.P. Dwyer, F.L. Garvan, J. Am. Chem. Soc. 83 (1961) 2610. (c) R.D. Gillard, G. Wilkinson, J. Chem. Soc. (1963) 4271. (a) B.J. Brennan, K. Igi, B.E. Douglas, J. Coord. Chem. 4 (1974) 19. (b) B.J. Brennan, Ph.D. Thesis, University of Pittsburgh, 1971. H. Ogino, T. Watanabe, N. Tanaka, Inorg. Chem. 14 (1975) 2093. W.D. Wheeler, S. Kaizaki, J.I. Legg, Inorg. Chem. 21 (1982) 3248. W.D. Wheeler, J.I. Legg, Inorg. Chem. 23 (1984) 3798. S. Kaizaki, H. Mizu-uchi, Inorg. Chem. 25 (1986) 2732. K. Kanamori, K. Kawai, Inorg. Chem. 25 (1986) 3711. H. Ogino, M. Shimura, Adv. Inorg. Bioinorg. Mech. 4 (1986) 107. Y. Kushi, K. Morimasa, H. Yoneda, 49th Annu. Meet. Chemical Soc. Jpn., Tokyo, April, 1984, Abstract 1N31. S. Kaizaki, M. Hayashi, K. Umakoshi, S. Ooi, Bull. Chem. Soc. Jpn. 61 (1988) 3519. J.A. Weyh, R.E. Hamm, Inorg. Chem. 7 (1968) 2431. H. Ogino, J.J. Chung, N. Tanaka, Inorg. Nucl. Chem. Lett. 7 (1971) 125. R. Herak, G. Srdanov, M.I. Djuran, D.J. Radanovic´, M. Bruvo, Inorg. Chim. Acta 83 (1984) 55. S. Kaizaki, M. Byakuno, M. Hayashi, J.I. Legg, K. Umakoshi, S. Ooi, Inorg. Chem. 26 (1987) 2395. S. Kaizaki, J. Hidaka, Y. Shimura, Inorg. Chem. 12 (1973) 142. S. Kaizaki, Y. Shimura, Bull. Chem. Soc. Jpn. 48 (1975) 3611. S. Kaizaki, M. Ito, Bull. Chem. Soc. Jpn. 54 (1981) 2499. D.J. Radanovic´, B.E. Douglas, J. Coord. Chem. 4 (1975) 191. F.T. Helm, W.H. Watson, D.J. Radanovic´, B.E. Douglas, Inorg. Chem. 16 (1977) 2351. S. Kaizaki, H. Mori, Bull. Chem. Soc. Jpn. 54 (1981) 3562. D.J. Radanovic´, M.I. Djuran, M.B. Dimitrijevic´, B.E. Douglas, Inorg. Chim. Acta 186 (1991) 13. (a) N. Sakagami, M. Hayashi, S. Kaizaki, J. Chem. Soc., Dalton

[33] [34] [35] [36]

[37] [38]

[39]

[40] [41] [42] [43] [44] [45] [46]

[47]

27

Trans. (1992) 285. (b) S. Kaizaki, M. Hayashi, J. Chem. Soc., Chem. Commun. (1988) 612. D.J. Radanovic´, M.I. Djuran, M.M. Djorovic´, B.E. Douglas, Inorg. Chim. Acta 146 (1988) 199. D.J. Radanovic´, M.I. Djuran, T.S. Kostic´, C. Maricondi, B.E. Douglas, Inorg. Chim. Acta 207 (1993) 111. D.J. Radanovic´, V.D. Miletic´, T. Ama, H. Kawaguchi, Bull. Chem. Soc. Jpn. 71 (1998) 1605. D.J. Radanovic´, V.M. Ristanovic´, B. Stojceva-Radovanovic´, A.D. Todorovska, N. Sakagami, A. Iino, S. Kaizaki, Transit. Met. Chem., in press. 1970 IUPAC Rules, Pure Appl. Chem. 28 (1971) 1; Inorg. Chem. 9 (1970) 1. A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M.C. Burla, G. Polidori, M. Camalli, SIR92, A program for automatic solution of crystal structures by direct methods, J. Appl. Crystallogr. 27 (1994) 435. DIRDIF-94: P.T. Beurskens, G. Admiraal, G. Beurskens, W.P. Bosman, R. de Gelder, R. Israel, J.M.M. Smits. The DIRDIF-94 program system, Technical Report of the Crystallography Laboratory, University of Nijmegen, The Netherlands, 1994. D.T. Cromer, J.T. Waber, International Tables for X-ray Crystallography, vol. IV, Kynoch Press, Birmingham, UK, 1974. teXsan: Crystal Structure Analysis Package, Molecular Structure Corporation, 1985 and 1992. R.S. Cahn, C.K. Ingold, V. Prelog, Angew. Chem., Int. Ed. Engl. 5 (1966) 385. D.J. Radanovic´, S. Ianelli, G. Pelosi, Z.D. Matovic´, S. Tasic´Stojanovic´, B.E. Douglas, Inorg. Chim. Acta 278 (1998) 66. D.J. Radanovic´, B.V. Prelesnik, D.D. Radanovic´, Z.D. Matovic´, B.E. Douglas, Inorg. Chim. Acta 262 (1997) 203. L.J. Halloran, R.E. Caputo, R.D. Willet, J.I. Legg, Inorg. Chem. 14 (1975) 1762. (a) J.A. Neal, N.J. Rose, Inorg. Chem. 7 (1968) 2405. (b) J.A. Neal, N.J. Rose, Inorg. Chem. 12 (1973) 1226. (c) W.T. Jordan, J.I. Legg, Inorg. Chem. 13 (1974) 2271. (a) F. Mizukami, H. Ito, J. Fujita, K. Saito, Bull. Chem. Soc. Jpn. 43 (1970) 3633. (b) F. Mizukami, H. Ito, J. Fujita, K. Saito, Bull. Chem. Soc. Jpn. 44 (1971) 3051.