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The Phenomenon of Conglomerate Crystallization. Part. 57. Control of the Crystallization Behavior by the Choice of the Counter Ion. Part 9. The Stereo...
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The Phenomenon of Conglomerate Crystallization. Part 57. Control of the Crystallization Behavior by the Choice of the Counter Ion. Part 9. The Stereochemistry and Crystallization Architecture of [(3,2,3-tet)Co(N3)2]X (X ) Cl(I), Br(II), I(III), NO3(IV), and PF6(V))

CRYSTAL GROWTH & DESIGN 2002 VOL. 2, NO. 3 205-212

Manas K. Saha,# Rathnakumar Ramanujam, and Ivan Bernal* Chemistry Department, University of Houston, Houston, Texas 77204-5641

Frank R. Fronczek Chemistry Department, Louisiana State University, Baton Rouge, Louisiana 70803-1804 Received January 22, 2002

ABSTRACT: Compounds of composition of [(3,2,3-tet)Co(N3)2]X (X ) Cl(I), Br(II), I(III), NO3(IV), and PF6(V)) were prepared, and their crystal structures were determined at 295 and 120 K. Unlike a previous study by this group, in which we reported [Saha, M. K.; Bernal, I. Inorg. Chem. Commun. 2002, accepted for publication] a change of space group (P21/n to P21) upon cooling a cis-bis-diazido compound of Co(III), all the compounds described here retain their space groups upon cooling from 295 to 120 K. There are measurable changes in cell constants but no larger than what one normally expects. Details of the syntheses and of the crystallographic determinations are given below. A full description of the changes in stereochemistry of the [(3,2,3-tet)Co(N3)2]+ cations, as a result of changes in the counteranions, are detailed quantitatively, and superposition diagrams of the cations have been included to illustrate the changes in bond angles and torsional angles concomitant with the changes in anions and thus producing channel frameworks of different architecture. As expected, variations in bond lengths are minute, if at all, statistically valid. Compounds (I)-(IV) are racemates at all temperatures, while (V) is a conglomerate (space group P61 at 295 and 120 K), neatly illustrating the counteranion dependence of the phenomenon of conglomerate crystallization. Water molecules occupy channels in the framework of compound (I), which can be dehydrated and rehydrated without destruction of the crystal lattice. Introduction Recently, we reported1 the syntheses and crystal structures of compounds of composition [(tren)Co(N3)2]X where X ) Br and I in which the bromide retains its space group (P212121) upon cooling from 295 to 120 K, while the iodide changes from P21/n to P21 when cooled over the same temperature range. Earlier, we2 reported the syntheses and the details of the crystallization behavior of a series of [triamineCo(III)tris-azido] complexes. In that report, we noted that four such complexes crystallized in centrosymmetric space groups, in accordance with the crystallization behavior of mer-3 and fac- isomers4 of [(dien)Co(N3)3] that crystallize as racemates. We are examining the crystallization behavior of several series of amine-Co-azido complexes to document their streochemical and crystallization behavior, and the dependence of this phenomenon on the nature of the counteranion and of the stereochemistry of the metal amine. This inquiry is dictated by the fact that the amount of information on the crystallization behavior of metal azides of the 3-d series is meager at best, and the variety of compositions of the few available is so large that one cannot derive useful information from the contents of the CCDC file.5 Thus, we decided to carry out a more organized study of these interesting compounds. Below we report the effect of the counteranion * Author for correspondence; e-mail: [email protected]. # Postdoctoral Fellow of the Robert A. Welch Foundation.

in determining the stereochmistry of the cations and the architecture of the pores in these materials. Experimental Section Syntheses. Warning: metal azido complexes are known to be explosive and, therefore, should be handled carefully and in small amounts. Heating and/or friction may cause them to explode violently. [trans-Co(3,2,3-tet)Cl2]Cl‚3/2H2O (3.3 g, 0.01 mol), prepared according to the literature method,6 was dissolved in water (40 mL), and an aqueous solution of NaN3 (1.3 g, 0.02 mol) was added to it. The solution was left to crystallize at room temperature. After one week, crystals of [trans-Co(3,2,3-tet)(N3)2]Cl‚2H2O were collected. The bromide, iodide, nitrate, and hexaflurophosphate analogue were prepared by mixing equivalent amounts of [trans-Co(3,2,3-tet)(N3)2]Cl‚2H2O and the corresponding ammonium salts (NH4Br, NH4I, NH4NO3, and NH4PF6) in the minimum amount of water. In all cases, single crystals suitable for crystallography were obtained through the slow evaporation of the solutions at room temperature. X-ray Diffraction Studies. Room temperature (295 K) data were obtained with a Nonius Diffractis 585 instrument using MoKR radiation, and absorption correction data were measured by the Psi-scan technique. A somewhat redundant data set was collected for each of the five substances. Details of data collection and processing of the 295 K data are not presented here; however, they are available in the CCDC compilations (for CIF data on these structures, see Supporting Information, below, for deposition numbers and other relevant information). Data collection at 120 K were carried out with a Nonius CCD instrument using MoKR radiation. Half a hemisphere of data were collected in each case. Data were corrected with SADABS.7 Details of data collection and processing are

10.1021/cg020003i CCC: $22.00 © 2002 American Chemical Society Published on Web 03/30/2002

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Table 1. Summary of Data Collection and Refinements for (I), (II), and (III) at 120 Ka data formula fw cryst size, mm cryst system space group a, Å b, Å c, Å β, deg V, Å3 Z Fcalc, g cm-3 µ, mm-1 F(000) θ range, deg index ranges (h, k, l) reflns collected independent reflns (Rint) reflns obsd [I > 2σ(I)] params refined GOF on F2 R (final)b [I > 2σ(I)] R (all data) largest diff. peak (hole, e Å-3)

(I) C8H26N10O2CoCl 388.7 0.27 0.23 0.20 orthorhombic Pbca 12.3720(2) 15.8687(3) 16.8796(3)

13 848

(II) C8H22N10CoBr 397.2 0.28 0.25 0.10 monoclinic P21/c 14.3546(5) 8.1446(2) 13.5195(4) 100.177(1) 1555.73 4 1.70 3.68 807.7 2 to 30 20,-10+11, -19 +18 7282

(III) C8H22N11CoI 444.2 0.15 0.15 0.12 monoclinic P21/n 10.0255(2) 10.3728(2) 15.0556(3) 92.695(1) 1563.94 4 1.89 3.08 879.7 2 to 40 18, -15 +18, (27 17 863

7268(0.033)

4454(0.032)

9768(0.047)

5189

3367

6407

287

269

269

1.033 R1 ) 0.042

1.029 R1 ) 0.044

1.014 R1 ) 0.041

wR2 ) 0.104 R1 ) 0.068 wR2 ) 0.116 0.650 (-0.870)

wR2 ) 0.101 R1 ) 0.068 wR2 ) 0.111 0.584 (-1.268)

wR2 ) 0.075 R1 ) 0.084 wR2 ) 0.087 0.979 (-1.553)

3313.93 8 1.56 1.22 1631.4 2 to 35 19, 25, (27

Common for all three structures: λ ) 0.71073 Å (Mo KR); refinements by full-matrix least-squares on F2. b R1 ) ∑||Fo| - |Fc||/ ∑|Fo|, wR2 ) [∑w(Fo2 - Fc2)2/∑w(Fo2)2]1/2. a

given in Tables 1 and 2. In all cases, the structures were solved, refined, and illustrated with the WinGx8 package of programs. Superposition diagrams comparing the stereochemistry of the cations present in (I)-(V) were generated with our program MATCHIT9 (see Figures 6-10). Selected bond lengths, angles, and torsional angles are listed in Table 3; there, we list only structural data obtained at 120 K.

Discussion Compounds (I)-(IV) crystallize from deionized water solutions of the racemate, at ca. 295 K in space groups Pbca, P21/c, P21/n, P21/n, respectively, which are uniquely determined by their systematic absences. (V) crystallizes as a conglomerate in space group P61, as suggested by the systematic absences. Upon cooling of the sample to 120 K, the space groups remain unchanged for all five compounds, and small changes in cell constants were recorded (compare results in the CIF files). A complete set of cell constants, space groups, and data processing parameters, for the 120 K data sets, are given in Tables 1 and 2. The room temperature and low-temperature structures were solved by the automatic Patterson, SHELXS, and Sir 92 routines,8 and only sensible results could be obtained for (V) by the above assignment of space group. Moreover, refining the low-temperature data of compound (V) resulted in a message indicating that the coordinates of the trial structure should be inverted. For details of the structures of the asymmetric units of compounds (I)-(V), see Figures 1 -5. Packing diagrams, generated with program DIAMOND,10 are

Saha et al. Table 2. Summary of Data Collection and Refinements at 120 K for (IV) and (V)a data

(IV)

formula fw crystal size, mm crystal system space group a, Å b, Å c, Å B, deg V, Å3 Z Fcalc, g cm-3 µ, mm-1 F(000) θ range, deg index ranges (h, k, l) reflns collected independent reflns (Rint) reflns obsd [I > 2σ(I)] params refined GOF on F2 R (final)b [I > 2σ(I)]

C8H22N11O3Co 379.3 0.28 0.25 0.10 monoclinic P21/n 9.9239(3) 10.0786(3) 15.1643(5) 92.782(1) 1514.93(1) 4 1.66 1.16 791.7 2 to 32 14, -11 +15, (22 9151 5189(0.034)

C8H22N10PCoF6 462.2 0.33 0.23 0.22 hexagonal P61 9.3817(2) 9.3817(2) 33.7473(4)

3763 269 1.046 R1 ) 0.037 wR2 ) 0.072 R1 ) 0.064 wR2 ) 0.080 0.569 (-0.692)

5752 236 1.034 R1 ) 0.067 wR2 ) 0.156 R1 ) 0.077 wR2 ) 0.165 2.958 (-0.756)

R (all data) largest diff. peak (hole, e Å-3)

(V)

2572.37(1) 6 1.79 1.173 1415.5 2 to 35 15, -12 0, -53+45 6484 6484(0.0000)

a Common for both structures: λ ) 0.71073 Å (Mo K ); refineR ments by full-matrix least-squares on F2 b R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2 ) [∑w(Fo2 - Fc2)2/∑w(Fo2)2]1/2.

Table 3. Stereochemical Parameters for Compounds (I)-(V) (I)

(II)

(III)

(IV)

(V)

1.996 1.987 1.979 1.983 1.975 1.944

Bond 1.995 1.979 1.975 1.982 1.959 1.964

1.985 1.987 1.991 1.975 1.946 1.980

1.983 1.981 1.988 1.977 1.934 1.988

1.986 1.972 2.005 1.994 1.975 1.949

Co-N1-C1 N1-C1-C2 C1-C2-C3 C3-N2-Co C3-N2-C4 N2-C4-C5 C4-C5-N3 C5-N3-Co N3-C6-C7 C5-N3-C6 C6-C7-C8 C7-C8-N4 C8-N4-Co Co-N5-N6 N5-N6-N7 Co-N8-N9 N8-N9-N10

119.99 110.75 112.51 119.95 109.61 106.86 107.83 109.15 112.26 110.23 113.47 111.44 119.59 117.80 178.21 121.05 176.36

Angle 119.93 111.49 113.77 120.14 110.43 106.75 107.17 107.85 113.11 109.77 113.68 111.32 119.93 120.50 177.49 120.67 176.73

120.69 111.59 113.39 119.47 110.20 107.44 107.02 108.43 112.00 110.81 112.69 111.75 119.53 125.13 174.96 128.02 174.71

120.77 111.95 113.25 119.12 110.76 107.15 107.75 107.66 112.60 111.03 113.39 111.63 119.90 125.69 175.04 125.55 175.13

121.38 113.11 113.79 120.85 109.75 106.09 107.29 109.67 111.00 110.35 114.50 111.29 118.65 127.99 175.38 131.47 176.24

N1C1C2C3 C1C2C3N2 N2C4C5N3 N3C6C7C8 C6C7C8N4 CoN5N6N7 CoN8N9N10

Torsion Angle 70.10 66.17 -66.33 -65.61 -65.88 -69.25 -65.35 67.98 68.30 67.48 52.06 54.73 -52.75 -53.30 -52.66 -64.16 -64.48 67.94 66.64 67.58 64.73 64.44 -69.13 -66.16 -71.70 177.14 -176.74 -162.33 -168.59 153.14 175.56 164.43 -167.60 -162.48 -178.16

Co-N1 Co-N2 Co-N3 Co-N4 Co-N5 Co-N6

given for (I), (II), (III), and (V) as Figures 11-14. The packing diagram of (IV) is unnecessary since it is identical with that of (III) with which it is isomorphous.

Phenomenon of Conglomerate Crystallization

Figure 1. The cation of [(3,2,3-tet)Co(N3)2]Cl‚2H2O (I) at 120 K. The cation is chiral because the Co(III) is an asymmetric center and the central five member ring is dissymmetric since it is nonplanar.

Crystal Growth & Design, Vol. 2, No. 3, 2002 207

Figure 4. The cation of [(3,2,3-tet)Co(N3)2]NO3 (IV) at 120 K.

Figure 5. The cation of [(3,2,3-tet)Co(N3)2]PF6 (V) at 120 K. Figure 2. The cation of [(3,2,3-tet)Co(N3)2]Br (II) at 120 K.

Figure 3. The cation of [(3,2,3-tet)Co(N3)2]I (III) at 120 K.

Stereochemistry of the Cations. It is obvious from Figures 6-10 that the stereochemistry of the [3,2,3tetCo] fragments are very similar, if not quite identical. A comparison of the bond lengths, angles, and torsional

angles of these fragments (see Table 3) clearly demonstrates such is the case. However, the torsional angles of the Co-diazido portion of the cations differ significantly. This fact is rather evident by comparison of the angles listed above for the Co-N5-N6-N7 and Co-N8-N9-N10 fragments. Graphically, the differences in stereochemistry of compounds (I)-(V) are depicted in Figures 6-9, in all of which the standard for matching was compound (V) whose absolute configuration must be preserved, as found in that crystal, since it crystallizes as a conglomerate. Compounds (I)-(IV) contain both enantiomers in their lattices since they are centrosymmetric. These superposition diagrams were generated with program MATCHIT.9 The observed differences in Co-azido torsional angles are, no doubt, the result of the differences in intercationic hydrogen bonds, which, in turn, are controlled by the choice of the anions (see Packing). The most significantly deviated atoms in the superimposition are N6, N7, and N10. The deviation of the corresponding atom pairs in the superposition were tabulated in Table 4. It is noteworthy that the match between compounds III and IV (which are isomorphous) shows the best fit (see Figure 10) with small deviations

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Figure 6. MATCHIT comparison of the conformation and configuration of the cation [(3,2,3-tet)Co(N3)2]Cl‚2H2O (I) (with dark blue bonds) and [(3,2,3-tet)Co(N3)2]PF6 (V) (with red bonds). Carbon atoms are colored in gray, nitrogen atoms are in blue, and cobalt atoms are in purple.

Saha et al.

Figure 8. MATCHIT comparison of the conformation and configuration of the cation [(3,2,3-tet)Co(N3)2]I (III) (with dark blue bonds) and [(3,2,3-tet)Co(N3)2]PF6 (V) (with red bonds). Carbon atoms are colored in gray, nitrogen atoms are in blue, and cobalt atoms are in purple.

Figure 7. MATCHIT comparison of the conformation and configuration of the cation [(3,2,3-tet)Co(N3)2]Br (II) (with dark blue bonds) and [(3,2,3-tet)Co(N3)2]PF6 (V) (with red bonds). Carbon atoms are colored in gray, nitrogen atoms are in blue, and cobalt atoms are in purple.

Figure 9. MATCHIT comparison of the conformation and configuration of the cation [(3,2,3-tet)Co(N3)2]NO3 (V) (with dark blue bonds) and [(3,2,3-tet)Co(N3)2]PF6 (V) (with red bonds). Carbon atoms are colored in gray, nitrogen atoms are in blue, and cobalt atoms are in purple.

between N6, N7, and N10 atom pairs which are otherwise highly deviated in the other cases. For the values of the strongest hydrogen bonds in these substances, see Table 5 that lists those shorter than 3.25 Å. The distances between chemically related atoms in the cations of compounds (I)-(V) are listed below. The Centrosymmetric Crystallization of (I)-(IV) and the Conglomerate Crystallization of (V). A search in the CSD compilation5 of mononuclear, coordination compounds whose counteranions are hexafluorophosphates, revealed only two examples once we removed those which contain pure, enantiomorphic, cations that were crystallized as a hexafluorophosphate salt for synthetic and/or crystallographic convenience:

they are [M(2,2′-bipyridine)3](PF6)3 [M ) Cr or Rh; space group ) R32; see FERYIK11]. The fact that [trans-3,2,3-tetCo(N3)2]PF6 (V) crystallizes as a conglomerate was a welcomed result since it is the first trans-diazido compound of the class [transN4-tetCo(N3)2]X (X ) any counteranion; N4 ) two diamines or a tetraamine) to thus crystallize. Inspection of the CCDC database5 for diazido complexes of the 3-d series that crystallize as conglomerates reveals that there are only two of them; namely, [trans-(1,4,8,11tetraaza-cyclotetradecane)Fe(N3)2]ClO4 (LAYXIS12; space group P212121) and [trans-bis(dimethylphosphinoethane)Fe(N3)2] (ZEBSAA13; space group P21). Thus, nothing resembling (V) has been reported in the literature, which is the first and only conglomerate of its class.

Phenomenon of Conglomerate Crystallization

Crystal Growth & Design, Vol. 2, No. 3, 2002 209 Table 5. Intermolecular Hydrogen Bonds (Å) and Angle (deg) for Compounds (I)-(V)a bond

Figure 10. MATCHIT comparison of the conformation and configuration of the cation [(3,2,3-tet)Co(N3)2]NO3 (IV) (with dark blue bonds) and [(3,2,3-tet)Co(N3)2]I (III) (with red bonds). Carbon atoms are colored in gray, nitrogen atoms are in blue, and cobalt are in in purple. Table 4. Distances between Corresponding Pair of Atom in Best Fit Position distances (Å) compound pairs atom pairs

(I) and (V)

(II) and (V)

(III) and (V)

(IV) and (V)

(III) and (IV)

C1-C1 C2-C2 C3-C3 C4-C4 C5-C5 C6-C6 C7-C7 C8-C8 N1-N1 N2-N2 N3-N3 N4-N4 N5-N5 N6-N6 N7-N7 N8-N8 N9-N9 N10-N10

0.028969 0.104972 0.097483 0.060488 0.064168 0.146961 0.141950 0.100116 0.054665 0.057096 0.065292 0.220589 0.217777 1.586741 3.334070 0.240217 1.124949 2.346673

0.044390 0.054700 0.056706 0.043529 0.044160 0.133777 0.109347 0.118179 0.120357 0.042420 0.044702 0.179972 0.380775 1.347652 3.040045 0.314193 1.100484 2.338832

0.033593 0.049109 0.034145 0.052522 0.041037 0.073278 0.055237 0.071860 0.089997 0.027493 0.026240 0.054452 0.304743 1.291471 2.742502 0.222282 0.841889 1.764574

0.081030 0.060701 0.049736 0.053549 0.050004 0.141614 0.099955 0.115187 0.117498 0.037111 0.030551 0.129067 0.328288 1.310604 2.807858 0.235052 0.832359 1.761633

0.057038 0.049858 0.037053 0.017357 0.019133 0.079294 0.072386 0.044217 0.027755 0.018773 0.025779 0.079863 0.035911 0.117716 0.263528 0.017932 0.071219 0.147123

By contrast (I), (II), (III), (IV) crystallize at 295 K as a racemates in space groups Pbca, P21/c, P21/n, and P21/ n, respectivelys space groups uniquely determined by their systematic absences. Such a counteranion control of the crystallization pathway has been noted by us many times. For relevant examples, including previous cases of changes of crystallization modes, among halide and other salts, see ref 14. Packing Considerations. Compound (I) crystallizes in an interesting pattern in which six cations form a hydrogen bonded cage; see Figure 11. This pattern is most easily observed in the central part of the figure. The red polyhedra are defined by the CoN6 fragments, while the other atoms of the cations are shown as individual atoms. This feature is common to all five packing diagrams. Inside the cavities are the chloride anions and the waters of crystallization. Pairs of cations are bonded to one another by three strong hydrogen bonds (see Table

D-H

H‚‚‚A

D‚‚‚A

D-H‚‚‚A

Compound (I) [(3,2,3-tet)Co(N3)2]Cl‚2H2O N1-H1‚‚‚N10 0.90 2.49 3.26 N1-H2‚‚‚Cl 0.88 2.58 3.38 N2-H9‚‚‚Cl 0.82 2.64 3.35 N3-H14‚‚‚Cl 0.87 2.42 3.25 N4-H21‚‚‚N9 0.86 2.59 3.00 N4-H21‚‚‚N7 0.86 2.35 3.16 N4 H22‚‚‚Cl 0.87 2.43 3.29

143 151 145 160 111 158 168

Compound (II) [(3,2,3-tet)Co(N3)2]Br N1 H1‚‚‚Br 0.87 2.64 3.39 N2 H9‚‚‚Br 0.74 2.75 3.41 N3 H14‚‚‚Br 0.83 2.68 3.40 N4 H21‚‚‚N9 0.82 2.58 2.98 N4 H21‚‚‚N7 0.82 2.31 3.09 N4 H22‚‚‚Br 0.83 2.55 3.39

144 151 146 111 161 177

Compound (III) [(3,2,3-tet)Co(N3)2]I N1 H1‚‚‚N7 0.91 2.21 3.09 N1 H2‚‚‚I 0.84 2.96 3.68 N2 H9‚‚‚I 0.85 3.02 3.71 N4 H21‚‚‚I 0.93 2.83 3.61 N4 H22‚‚‚N10 0.93 2.17 3.08

162 146 140 142 166

Compound (IV) [(3,2,3-tet)Co(N3)2]NO3 N1 H1‚‚‚N7 0.88 2.18 3.04 N1 H2‚‚‚O1 0.86 2.33 3.07 N2 H9‚‚‚O3 0.81 2.33 3.03 N4 H21‚‚‚N10 0.83 2.27 3.06 N4 H22‚‚‚O1 0.88 2.24 3.07

166 145 146 158 158

Compound (V) [(3,2,3-tet)Co(N3)2]PF6 N1 H1‚‚‚N10 0.92 2.25 3.10 N1 H2‚‚‚F4 0.92 2.53 3.35 N1 H2‚‚‚F6 0.92 2.55 3.42 N2 H9‚‚‚F3 0.93 2.39 3.26 N3 H14‚‚‚F2 0.93 2.17 3.04 N4 H21‚‚‚N7 0.92 2.22 3.01 N4 H22‚‚‚F5 0.92 2.47 3.18

154 148 159 157 157 143 134

a Estimated standard deviation on distances ) 0.02 Å; in angles ) 2 deg.

5) between an azide nitrogen of one and an amine hydrogen of another, and vice-versa, thus forming pseudohexagonal channels parallel to b-axis. The chloride anions are hydrogen bonded to the other amine hydrogens. The distance between two opposite methylene hydrogens directed into the channel and constructing the narrowest dimension is ∼8 Å. When compound (I) is heated at ∼140 °C for 24 h it shows a weight loss of 9%, which corresponds to the loss of the two water molecules. This dehydrated sample reabsorbs water at ambient temperature and pressure which is evident by the gain of weight of the sample by same percentage. Some single crystals were heated at 140 °C for 24 h and then allowed to stand at ambient atmosphere for 24 h. Surprisingly, the crystals are found to be stable and produce the same cell as that for original compound. Thus, it is concluded that the water molecules occupying the cavity can be removed and reabsorbed without destruction of the framework. The absence of strong hydrogen bonding interaction by the water molecules facilitate their removal and reabsorption process. Compound (II) also forms cavities that are shaped more like an elongated parallelogram, inside of whose cavities are the bromide anions; see Figure 12. This feature is most easily seen in the central region of the diagram. Incorporation of bromide ion instead of chlo-

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Figure 11. View along the b-axis showing the hexagonal cages for compound [(3,2,3-tet)Co(N3)2]Cl‚2H2O (I). The red octahedra are the CoN6 units.

Figure 12. A polyhedral representation of the structure of [(3,2,3-tet)Co(N3)2]Br (II).

ride affects the hydrogen bonding and resulted in a change in architecture of the framework. Unlike compound (I), there is no hydrogen bonding interaction between the hydogen atom of N1 with any of the azido nitrogens. Azido nitrogens N9 and N7, of a given cation, form only two hydrogen bonds with other amino (N4) hydrogen (H21) of the cation at its right, and a second one with another, above it. The hydrogen bonded pattern is quite different from that prevalent in compound (I). The bromide anion is hydrogen bonded to a

Saha et al.

Figure 13. A polyhedral representation of the structure of [(3,2,3-tet)Co(N3)2]I (III).

terminal -NH2 hydrogen, as shown in the leftmost molecule of the central row. For magnitudes of the hydrogen bonds present in (II), see Table 5. Compound (III) packs totally differently (see Figure 13) from that observed in (II) despite the fact that the space groups of (II) and (III) are interconvertible. Here, four cations are hydrogen bonded to one another by -N1‚‚‚H-N and -N4‚‚‚H-N bonds (see Table 5 for details), and the iodides are trapped within the cavities thus formed by the cations. Those cavities contain only four cations in contrast with those found in (I), (II), and (V), which are formed by the union of six. The packing and hydrogen bonding interaction are remarkably identical in compounds (IV) and (III), which are isomorphous; therefore, no further discussion and figures are necessary for (IV). The nitrate anions are trapped in the same cavities, and, in fact, the fractional coordinates of the nitrate nitrogen are essentially identical with those of the iodide present in (III). The unique (conglomerate) crystals of (V) produce a complex packing of cations wrapped around the 6-fold screw axis of its space group. Clusters of cations are packed in a spiral array generated by the 61 screw as regular, hexagonal, cavities parallel to the c-axis; see Figure 14. Adjacent helices are held together by the PF6- anions. Also note the hydrogen bonded strings along the b-axis, which are readily displayed at the lower part of the figure. For details see Table 5. The dimension of the channels are defined by the six hydrogen atoms (H6) that are shown in Figure 14. These hydrogen atoms are related by the 61 screw axis forming equilateral hexagons with a H-H distance of 5.685 Å at the side of the hexagon. The diagonal of the hexagon is 16.95 Å. Assuming 1 Å for the van der Waals radius of the hydrogen atoms, the effective hexagons that describes the channel dimension is ∼5 Å in length.

Phenomenon of Conglomerate Crystallization

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Figure 14. View of the cavities along c-axis for compound [(3,2,3-tet)Co(N3)2]PF6 (V). The hydrogen atom labeled by H6 define the narrowest point of the channels. For clarity, P-F bonds are marked with purple color and other bonds are labeled with black.

Conclusions We have synthesized a set of trans-diazido complex cations that exhibit a remarkable set of changes in the mode of crystallization they select. These changes in space group are a direct consequence of the changes in counteranions used in the syntheses. Also, while four of them crystallize as racemates, one crystallizes as a conglomeratesthe first of its kind thus far observed. Therefore, while it was not known that trans-diazido complexes of CoN4 moieties could crystallize as a conglomerate, our results document that this is certainly possible if the appropriate anion is used. Another unexpected result is the large changes in the Co-N-N-N torsional angles observed in this study. And, since the only change introduced in compounds (I)-(V) are the anions, one is forced to conclude that these variations are the result of the hydrogen bond patterns introduced by such a change. In turn, the hydrogen bonds that the cations make with one another (and the size and shape of the cages that result) are influenced by such torsional angle variations. The final, and possibly most important, conclusion to be derived from this study is the following: in solution, counteranions such as chloride, bromide, nitrate, hexafluorophosphate, etc. are considered to be innocent, spectator anions whose sole function is to provide charge compensation to a cation undergoing some chemical or stereochemical process in that solution. In the solid state, this is not the case as we have amply demonstrated above that the stereochemistry of the cations have undergone considerable modifications, which, in turn, affect the crystalline packing rather drastically in a way not clearly illustrated before. Therefore, it is hopeful that these observations may be useful in controlling chemical and stereochemical processes in the solid state. Acknowledgment. We thank the Robert A. Welch Foundation for support of these studies (Grant 592 to I.B.) and for postdoctoral support to Dr. Manas K. Saha. Support for Mr. Rathnakumar Ramanujam, who worked

with us on the program MATCHIT, was also provided by the Welch Foundation. Nomenclature 3,2,3-tet ) 1,5,8,12-tetraazadodecane, H2N-CH2-CH2CH2-NH-CH2-CH2NH-CH2-CH2CH2-NH2 tren ) tris(2-aminoethyl)amine or H2N-CH2-CH2)3N, dien ) (H2N-CH2-CH2)2NH. Mer isomers contain ligands occupying three meridonial positions of an octahedron; fac isomers have ligands occupying three positions defining a triangular face of the octahedron. Supporting Information Available: X-ray crystallographic data for compounds (I)-(V). This material is available free of charge via the Internet at http://pubs.acs.org. X-ray crystallographic files in CIF format also have been deposited with the Cambridge Structural Database as files CCDC 174110-174114, respectively, for crystals I, II, III, IV, and V for 120 K. However, room temperature data are also deposited with deposition no. as CCDC 174105-174109. The material can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223 336033 or e-mail: [email protected]).

References (1) Saha, M. K.; Bernal, I. Inorg. Chem. Commun. 2002, accepted for publication. (2) Chun, H.; Bernal, I. Acta Cryst. 2000, C56, 1326-1329. (3) Lukaszewski, D. M.; Sancilio, F. D.; Druding, L. F. Am. Crystallogr. Assoc. Abstract Papers (Winter) 1976, 12. (4) Druding, L. F.; Sancilio, F. D. Acta Cryst. 1974, B30, 23862389. (5) Cambridge Structural Database, Cambridge Crystallographic Data Centre, 12, Union Road. Cambridge. CB2 1EZ. UK. Telephone +44 1223 336408. Fax +44 1223 336033, WWW: http://www.ccdc.cam.ac.uk Released by Wavefunction, Inc., 18401 Von Karman Ave., Suite 370, Irvine, CA 92612, (949) 955-2120, (949) 955-2118 (fax), http:// www.wavefun.com. Release of April 2001. (6) Bernal, I.; Somoza, F.; Chen, Y.; Massoud, S. S. J. Coord. Chem. 1997, 41, 233-247. (7) Sheldrick, G. M.; SADABS: Program for Absorption Correction Using Area Detector Data, University of Go¨ttingen, Germany, 1996. (8) Solution, refinement, and graphics were carried out with the various routines available in Ferrugia’s L. University of Glasgow, package WinGX (see J. Applied Crystallogr. 1999, 32, 837. Structural Solution and Refining: (a) Sheld-

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rick, G. M. SHELXS-97: Program for the Solution of Crystals Structures and SHELXL-97: Program for the Refinement of Crystal Structures, University of Go¨ttingen, Germany, 1997. (b) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano G.; Giacovazzo C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. SIR92: A Program for Solving and Refining Crystals Structures. Graphics: (a) Burnett Michael N.; Johnson Carroll K. ORTEP-III Oak Ridge Thermal Ellipsoid Plot Program for Crystal Structure Illustrations. Oak Ridge National Laboratory Report ORNL - 6895, 1996. The main website is URL http:// www.ornl.gov/ortep/ortep.html. A printed reference manual is available. (b) Spek, A. L.; PLATON: Multipurpose Crystallographic Tool; Utrecht University: Utrecht, The Netherlands, 1999. (9) MATCHITsA Program for the Superposition of Related Molecular Fragments, written by Ramnujam Rathnakumar under the direction of Ivan Bernal, 2001. (10) Berndt, M.; Brandenburg, K.; and Putz, H. GbR, DIAMONDVisual Crystallographic Structural Information System. Version 2.1, Postfach 1251, D-3002 Bonn, Germany. (11) Hauser, A.; Robinson, W. T.; Murugesan R.; Ferguson, J. Inorg. Chem. 1987, 26, 1331-1338.

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