Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S010827010001204X/bj1006sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S010827010001204X/bj1006Isup2.hkl |
CCDC reference: 156141
The complex was prepared by the addition of a Pr(NO3)3 hexahydrate (0.44 g, 1.0 mmol) solution in N,N-dimethylformamide (DMF) to an equivalent of anhydrous K3Cr(CN)6 (0.32 g, 1.0 mmol) dissolved in a minimal amount of distilled deionized water. The Pr3+/DMF solution was layered onto the separately prepared chromium(III) hexacyanide solution. Light-green crystals of (I) large enough for single-crystal X-ray analysis were obtained after 24 h. IR spectroscopy (KBr disc, Mattson-Cygnus 100 F T—IR spectrometer): ν(OH)/hydrogen bonding 3390(br), 3306(br), 3094(br); ν(CN) 2148, 2136; ν(CO) 1670, 1650; δ(HCO) 1381; δ(NCO) 671 cm-1.
Refinements were made by full-matrix least-squares on all F2 data with anisotropic displacement parameters for all non-hydrogen atoms. All hydrogen atoms, except those on the various water molecules were included in calculated positions and allowed to ride on their parent carbon or oxygen atoms with fixed isotropic displacement parameters (Uiso = 1.2Uiso of the parent atom except for Me protons where Uiso = 1.5Uiso). The water H atoms were located in Fourier syntheses. The positional parameters of these H atoms were allowed to refine with fixed isotropic displacement parameters [Uiso(H) = 1.2Uiso(O)].
Cyanometallate ions, [M(CN)x]n-, have been shown to act as buiding blocks for many cyanide-bridged rare-earth/transition metal bimetallic assemblies. These complexes have proven useful in homogenous and heterogeneous catalytic applications due to the electropositive nature, the retracted 4f orbitals, and the lability of ligands coordinated to the central lanthanide ion (Huskins et al., 1995). Recently, a dinuclear cyano-bridged complex based on hexacyanoferrate and samarium nitrate was crystallographically studied (Kou et al., 1998). The authors demonstrated that the compound, [(DMF)4(H2O)4SmFe(CN)6]·H2O, contained a nine-coordinate trivalent samarium ion in a distorted tricapped trigonal prism geometry. Attempts to reproduce these synthetic results with chromium(III) hexacyanide and praseodymium(III) nitrate yielded crystals with the stoichiometry [(DMF)4(H2O)3PrCr(CN)6]·H2O, (I). \sch
Figure 1 is a representation of the molecular structure of the title compound. The molecular units within the crystal lattice are separated by normal van der Waals contact distances. The PrIII ions exhibit a slightly distorted square-antiprism coordination geometry. The top face of the prism, comprised of atoms O71, O51, O21, and O(61), is essentially planar with a mean deviation of 0.074 Å while the bottom face, atoms N6, O31, O41, and O11, is slightly distorted from planarity by a mean deviation of 0.220 Å. The dihedral angle between the two faces is 3.2°.
Selected geometric parameters for (I) are presented in Table 1. The mean Pr—O (DMF) Pr—O (H2O) and Pr—N bond lengths are 2.436 (15) 2.469 (15) and 2.569 (3) Å, respectively. When considering the Pr—O bond distances of the coordinated DMF ligands, it is observed that the Pr—O11 and Pr—O31 lengths are somewhat shorter than the Pr—O21 and Pr—O41 lengths. Also, the corresponding C—O—Pr bond angles described by the same sets of oxygen atoms are significantly larger for the DMF ligands of O11 and O31 than those described by O21 and O41. This may be attributable to the fact that both DMF ligands corresponding to O11 and O31 are adjacent to the hexacyanochromate moiety, increasing the steric hindrance at those coordination sites. Other investigations on analogous compounds have shown similar results (Kou et al., 1998; Mullica et al., 2000).
The geometry about the central Cr3+ ion is approximately octahedral, with C—Cr—C bond angles in the range 88.07 (13) to 92.06 (13)°. The Cr—C bond lengths range from 2.062 (3) to 2.074 (4) Å [mean 2.068 (4) Å] and are normal when compared to the sum of the atomic radii for Cr and C. The overall mean C≡N bond length of 1.146 (2) Å is also in accord with the sum of the triple bond radii of C and N atoms (0.603 and 0.55 Å, respectively) found in the work of Pauling (1960). The Cr—C—N bond angles are almost linear and range from 176.7 (5) to 179.7 (4) ° for (I), indicative of strong directional bonding as the π orbitals of the cyano ligands interact with the d orbitals of the metal center. However, the isocyanide linkage to the central praseodymium(III) ion deviates significantly from linearity. The Pr—N—C bond angle for (I) is 164.1 (4)°. This phenomenon has been shown to occur in similar compounds containing Ln—NC—R linkages. Darensbourg (1985) has proposed that the angular position of the metal cation may facilitate interaction with the lone pairs or π orbitals of the ligand. However, it may simply be that the change in energy by bending the ligands is insignificant, thus allowing steric factors to promote the deviation from linearity in the Pr—NC—Cr linkages.
Hydrogen bonding is paramount in the intermolecular network in the crystal lattice of this complex. According to the work of Hamilton & Ibers (1968), hydrogen bonding of the O—H···N and O—H···O types may be present when O···N and O···O contact distances are within 3.2 Å. Such is the case in the crystal lattices of (I) where the free water of hydration, O91, along with the coordinated water molecules and the nitrogen ends of the cyano ligands are involved in a hydrogen-bonding network. Fig. 2 depicts the hydrogen-bonding network within the crystal lattice; specific intermolecular interactions are included in Table 2. An IR spectroscopic study of (I) supports the X-ray evidence of varying degrees of hydrogen bonding with broad peaks in the 3100 to 3500 cm-1 region.
Interest in lanthanide cyanide-bridged complexes will continue due to their possible ability to function as models for evaluating molecule-membrane interactions and molecular transport in permselective membranes. Both selectivity and permeation rates of the species of interest can be strongly influenced by the molecular structure of the exchange host. Furthermore, studies have shown that compounds containing both lanthanide and transition metals may serve as bimetallic catalysts or as precursors to bimetallic particles on oxide surfaces [White et al. (1994); Deng & Shore (1991)]. Of course, compounds containing direct lanthanide-transition metal bonds would be ideal for these purposes. Unfortunately, very few of these materials have been characterized as their synthesis has proven quite challenging. Nevertheless, the development of new materials with such possibilities is always of interest to this research laboratory.
Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: XCAD4 Software (Harms, 1993); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL/PC (Sheldrick, 1995); software used to prepare material for publication: SHELXL97.
[CrPr(CN)6(C3H7NO)4(H2O)3]·H2O | F(000) = 1444 |
Mr = 713.48 | Dx = 1.496 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 25 reflections |
a = 17.940 (3) Å | θ = 20–24° |
b = 8.9381 (8) Å | µ = 1.92 mm−1 |
c = 19.8691 (16) Å | T = 186 K |
β = 96.121 (10)° | Blocks, light-green |
V = 3167.9 (6) Å3 | 0.85 × 0.54 × 0.46 mm |
Z = 4 |
Enraf-Nonius CAD4 diffractometer | 5024 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.016 |
Graphite monochromator | θmax = 25.0°, θmin = 1.6° |
ω–5/3θ scans | h = 0→21 |
Absorption correction: numerical (SHELXTL/PC; Sheldrick, 1995) | k = 0→10 |
Tmin = 0.292, Tmax = 0.474 | l = −23→23 |
5760 measured reflections | 3 standard reflections every 120 min |
5538 independent reflections | intensity decay: 10.5% |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.027 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.071 | w = 1/[σ2(Fo2) + (0.0338P)2 + 6.8116P] where P = (Fo2 + 2Fc2)/3 |
S = 1.10 | (Δ/σ)max = 0.002 |
5538 reflections | Δρmax = 0.56 e Å−3 |
376 parameters | Δρmin = −0.90 e Å−3 |
8 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.00086 (12) |
[CrPr(CN)6(C3H7NO)4(H2O)3]·H2O | V = 3167.9 (6) Å3 |
Mr = 713.48 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 17.940 (3) Å | µ = 1.92 mm−1 |
b = 8.9381 (8) Å | T = 186 K |
c = 19.8691 (16) Å | 0.85 × 0.54 × 0.46 mm |
β = 96.121 (10)° |
Enraf-Nonius CAD4 diffractometer | 5024 reflections with I > 2σ(I) |
Absorption correction: numerical (SHELXTL/PC; Sheldrick, 1995) | Rint = 0.016 |
Tmin = 0.292, Tmax = 0.474 | 3 standard reflections every 120 min |
5760 measured reflections | intensity decay: 10.5% |
5538 independent reflections |
R[F2 > 2σ(F2)] = 0.027 | 8 restraints |
wR(F2) = 0.071 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | Δρmax = 0.56 e Å−3 |
5538 reflections | Δρmin = −0.90 e Å−3 |
376 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. Monochromated Mo Kα intensity data were collected on an Enraf–Nonius CAD4 diffractometer equipped with a 1.5 mm collimator. An ω-5/3θ scan mode was chosen after careful analyses of omega/theta intensity profile plots of the reference reflections as described in the Enraf–Nonius CAD4 User's Manual (1989). Data were processed using SHELXTL (Bruker, 1995). |
x | y | z | Uiso*/Ueq | ||
Pr | 0.477391 (9) | 0.085770 (19) | 0.230371 (8) | 0.01634 (8) | |
Cr | 0.28568 (3) | −0.24801 (5) | 0.03717 (2) | 0.01519 (12) | |
C1 | 0.19854 (19) | −0.2099 (4) | 0.09530 (16) | 0.0226 (7) | |
N1 | 0.14922 (18) | −0.1898 (4) | 0.12633 (16) | 0.0339 (7) | |
C2 | 0.37116 (19) | −0.2865 (4) | −0.02230 (17) | 0.0233 (7) | |
N2 | 0.41806 (19) | −0.3067 (4) | −0.05621 (17) | 0.0377 (8) | |
C3 | 0.24410 (19) | −0.0810 (4) | −0.02857 (17) | 0.0245 (7) | |
N3 | 0.2189 (2) | 0.0106 (4) | −0.06420 (18) | 0.0428 (9) | |
C4 | 0.2189 (2) | −0.4044 (4) | −0.01672 (18) | 0.0267 (8) | |
N4 | 0.1809 (2) | −0.4932 (4) | −0.04397 (19) | 0.0460 (9) | |
C5 | 0.32883 (19) | −0.4164 (4) | 0.10186 (17) | 0.0229 (7) | |
N5 | 0.35469 (18) | −0.5098 (4) | 0.13646 (16) | 0.0335 (7) | |
C6 | 0.35093 (18) | −0.0975 (4) | 0.09671 (17) | 0.0217 (7) | |
N6 | 0.38655 (16) | −0.0187 (3) | 0.13294 (15) | 0.0287 (7) | |
O11 | 0.55179 (14) | −0.0232 (3) | 0.14872 (14) | 0.0351 (6) | |
C11 | 0.5775 (2) | −0.0745 (4) | 0.09799 (19) | 0.0306 (8) | |
H11 | 0.5993 | −0.0073 | 0.0702 | 0.037* | |
N11 | 0.57641 (16) | −0.2151 (3) | 0.08057 (15) | 0.0277 (7) | |
C12 | 0.5402 (3) | −0.3259 (5) | 0.1199 (2) | 0.0456 (11) | |
H12A | 0.5447 | −0.4230 | 0.1000 | 0.068* | |
H12B | 0.4882 | −0.3011 | 0.1200 | 0.068* | |
H12C | 0.5640 | −0.3267 | 0.1655 | 0.068* | |
C13 | 0.6100 (3) | −0.2673 (5) | 0.0210 (2) | 0.0450 (10) | |
H13A | 0.6035 | −0.3736 | 0.0166 | 0.068* | |
H13B | 0.6625 | −0.2438 | 0.0259 | 0.068* | |
H13C | 0.5860 | −0.2188 | −0.0186 | 0.068* | |
O21 | 0.60530 (14) | 0.1801 (3) | 0.25858 (14) | 0.0391 (7) | |
C21 | 0.6561 (2) | 0.2132 (6) | 0.2239 (2) | 0.0460 (11) | |
H21 | 0.6435 | 0.2242 | 0.1776 | 0.055* | |
N21 | 0.72590 (17) | 0.2338 (5) | 0.24719 (17) | 0.0433 (9) | |
C22 | 0.7837 (3) | 0.2695 (9) | 0.2040 (3) | 0.086 (2) | |
H22A | 0.8310 | 0.2796 | 0.2312 | 0.129* | |
H22B | 0.7715 | 0.3618 | 0.1807 | 0.129* | |
H22C | 0.7869 | 0.1907 | 0.1716 | 0.129* | |
C23 | 0.7500 (3) | 0.2072 (11) | 0.3176 (3) | 0.106 (3) | |
H23A | 0.8026 | 0.2283 | 0.3264 | 0.159* | |
H23B | 0.7409 | 0.1045 | 0.3283 | 0.159* | |
H23C | 0.7225 | 0.2711 | 0.3449 | 0.159* | |
O31 | 0.37847 (14) | −0.0341 (3) | 0.28588 (13) | 0.0363 (6) | |
C31 | 0.34939 (19) | −0.0869 (4) | 0.33510 (18) | 0.0277 (8) | |
H31 | 0.3490 | −0.0277 | 0.3736 | 0.033* | |
N31 | 0.31953 (16) | −0.2196 (3) | 0.33602 (14) | 0.0251 (6) | |
C32 | 0.3163 (3) | −0.3173 (5) | 0.2778 (2) | 0.0469 (11) | |
H32A | 0.2919 | −0.4091 | 0.2877 | 0.070* | |
H32B | 0.3662 | −0.3384 | 0.2674 | 0.070* | |
H32C | 0.2886 | −0.2694 | 0.2398 | 0.070* | |
C33 | 0.2888 (2) | −0.2756 (5) | 0.3965 (2) | 0.0400 (10) | |
H33A | 0.2684 | −0.3738 | 0.3877 | 0.060* | |
H33B | 0.2499 | −0.2096 | 0.4081 | 0.060* | |
H33C | 0.3279 | −0.2801 | 0.4334 | 0.060* | |
O41 | 0.53320 (15) | −0.1322 (3) | 0.29067 (14) | 0.0337 (6) | |
C41 | 0.5361 (2) | −0.1624 (4) | 0.3522 (2) | 0.0346 (9) | |
H41 | 0.5416 | −0.0832 | 0.3826 | 0.041* | |
N41 | 0.53198 (19) | −0.2976 (4) | 0.37693 (19) | 0.0424 (9) | |
C42 | 0.5365 (3) | −0.3220 (7) | 0.4500 (3) | 0.0726 (18) | |
H42A | 0.5324 | −0.4271 | 0.4590 | 0.109* | |
H42B | 0.4963 | −0.2696 | 0.4680 | 0.109* | |
H42C | 0.5836 | −0.2855 | 0.4710 | 0.109* | |
C43 | 0.5228 (4) | −0.4263 (6) | 0.3337 (3) | 0.083 (2) | |
H43A | 0.5210 | −0.5148 | 0.3609 | 0.125* | |
H43B | 0.5643 | −0.4330 | 0.3071 | 0.125* | |
H43C | 0.4770 | −0.4173 | 0.3043 | 0.125* | |
O51 | 0.49086 (14) | 0.1869 (3) | 0.34625 (13) | 0.0302 (6) | |
O61 | 0.48596 (14) | 0.2975 (3) | 0.15271 (13) | 0.0302 (6) | |
O71 | 0.37463 (15) | 0.2710 (3) | 0.23634 (13) | 0.0346 (6) | |
O91 | 0.89607 (14) | 0.7655 (3) | 0.06465 (14) | 0.0326 (6) | |
H51A | 0.4532 (19) | 0.228 (5) | 0.359 (2) | 0.056 (15)* | |
H51B | 0.525 (2) | 0.217 (5) | 0.3748 (19) | 0.053 (14)* | |
H61A | 0.513 (2) | 0.304 (5) | 0.1209 (17) | 0.046 (13)* | |
H61B | 0.4533 (19) | 0.359 (4) | 0.139 (2) | 0.039 (12)* | |
H71A | 0.366 (2) | 0.339 (4) | 0.2076 (17) | 0.034 (11)* | |
H71B | 0.359 (3) | 0.294 (5) | 0.2726 (15) | 0.052 (14)* | |
H91A | 0.871 (2) | 0.688 (3) | 0.054 (2) | 0.044 (13)* | |
H91B | 0.8627 (18) | 0.830 (4) | 0.066 (2) | 0.036 (12)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Pr | 0.01563 (11) | 0.01580 (11) | 0.01755 (11) | −0.00035 (7) | 0.00159 (6) | 0.00095 (7) |
Cr | 0.0159 (2) | 0.0163 (2) | 0.0135 (2) | 0.0003 (2) | 0.00271 (19) | 0.00006 (19) |
C1 | 0.0237 (17) | 0.0232 (17) | 0.0206 (16) | −0.0033 (14) | 0.0011 (14) | 0.0012 (13) |
N1 | 0.0307 (17) | 0.0414 (19) | 0.0320 (17) | −0.0015 (14) | 0.0153 (14) | −0.0019 (14) |
C2 | 0.0282 (18) | 0.0211 (17) | 0.0214 (16) | 0.0033 (14) | 0.0064 (14) | 0.0042 (13) |
N2 | 0.0398 (19) | 0.0368 (18) | 0.0401 (19) | 0.0095 (15) | 0.0204 (16) | 0.0088 (15) |
C3 | 0.0237 (17) | 0.0265 (18) | 0.0237 (17) | 0.0005 (15) | 0.0043 (14) | −0.0011 (15) |
N3 | 0.047 (2) | 0.0346 (19) | 0.045 (2) | 0.0068 (16) | −0.0031 (17) | 0.0143 (17) |
C4 | 0.0314 (19) | 0.0247 (18) | 0.0237 (17) | 0.0007 (15) | 0.0008 (14) | 0.0021 (15) |
N4 | 0.053 (2) | 0.0323 (19) | 0.049 (2) | −0.0107 (17) | −0.0116 (18) | −0.0094 (17) |
C5 | 0.0242 (17) | 0.0239 (17) | 0.0211 (16) | −0.0016 (14) | 0.0058 (13) | −0.0028 (14) |
N5 | 0.0408 (18) | 0.0298 (17) | 0.0299 (17) | 0.0101 (15) | 0.0043 (14) | 0.0096 (14) |
C6 | 0.0206 (16) | 0.0229 (17) | 0.0219 (16) | 0.0017 (14) | 0.0030 (13) | 0.0023 (14) |
N6 | 0.0263 (15) | 0.0315 (16) | 0.0275 (16) | −0.0033 (13) | −0.0002 (13) | −0.0051 (14) |
O11 | 0.0336 (14) | 0.0345 (14) | 0.0392 (15) | 0.0032 (12) | 0.0127 (12) | −0.0086 (12) |
C11 | 0.0312 (19) | 0.0283 (19) | 0.034 (2) | 0.0022 (15) | 0.0110 (16) | 0.0011 (16) |
N11 | 0.0270 (15) | 0.0272 (16) | 0.0298 (16) | 0.0014 (12) | 0.0076 (13) | −0.0030 (13) |
C12 | 0.052 (3) | 0.030 (2) | 0.057 (3) | −0.0054 (19) | 0.018 (2) | 0.000 (2) |
C13 | 0.052 (3) | 0.047 (3) | 0.038 (2) | 0.007 (2) | 0.013 (2) | −0.010 (2) |
O21 | 0.0225 (13) | 0.0586 (19) | 0.0356 (15) | −0.0126 (13) | 0.0002 (11) | 0.0006 (13) |
C21 | 0.033 (2) | 0.070 (3) | 0.033 (2) | −0.019 (2) | −0.0030 (18) | 0.006 (2) |
N21 | 0.0236 (16) | 0.070 (3) | 0.0367 (18) | −0.0164 (17) | 0.0061 (14) | −0.0160 (18) |
C22 | 0.053 (3) | 0.139 (6) | 0.071 (4) | −0.048 (4) | 0.031 (3) | −0.024 (4) |
C23 | 0.043 (3) | 0.217 (10) | 0.057 (4) | −0.028 (4) | 0.002 (3) | −0.024 (5) |
O31 | 0.0316 (14) | 0.0422 (16) | 0.0363 (15) | −0.0132 (12) | 0.0093 (12) | 0.0093 (12) |
C31 | 0.0273 (18) | 0.0301 (19) | 0.0261 (18) | −0.0029 (15) | 0.0045 (14) | 0.0009 (15) |
N31 | 0.0288 (15) | 0.0225 (15) | 0.0246 (15) | −0.0030 (12) | 0.0058 (12) | 0.0008 (12) |
C32 | 0.061 (3) | 0.037 (2) | 0.045 (2) | −0.005 (2) | 0.012 (2) | −0.0102 (19) |
C33 | 0.046 (2) | 0.035 (2) | 0.040 (2) | −0.0080 (18) | 0.0119 (19) | 0.0098 (18) |
O41 | 0.0394 (15) | 0.0259 (13) | 0.0356 (15) | 0.0100 (11) | 0.0034 (12) | 0.0114 (11) |
C41 | 0.034 (2) | 0.031 (2) | 0.039 (2) | 0.0094 (17) | 0.0055 (17) | 0.0096 (17) |
N41 | 0.0323 (18) | 0.041 (2) | 0.054 (2) | 0.0044 (15) | 0.0038 (16) | 0.0259 (17) |
C42 | 0.060 (3) | 0.098 (4) | 0.064 (3) | 0.027 (3) | 0.026 (3) | 0.055 (3) |
C43 | 0.109 (5) | 0.035 (3) | 0.096 (5) | −0.013 (3) | −0.030 (4) | 0.022 (3) |
O51 | 0.0210 (13) | 0.0402 (15) | 0.0283 (14) | 0.0038 (12) | −0.0028 (11) | −0.0135 (12) |
O61 | 0.0312 (14) | 0.0305 (14) | 0.0320 (14) | 0.0100 (11) | 0.0175 (12) | 0.0144 (11) |
O71 | 0.0404 (15) | 0.0407 (16) | 0.0252 (14) | 0.0221 (13) | 0.0154 (12) | 0.0148 (12) |
O91 | 0.0268 (14) | 0.0306 (15) | 0.0382 (15) | −0.0013 (12) | −0.0064 (11) | 0.0013 (12) |
Pr—O11 | 2.413 (2) | N31—C32 | 1.445 (5) |
Pr—O31 | 2.435 (2) | N31—C33 | 1.463 (5) |
Pr—O41 | 2.445 (2) | O41—C41 | 1.247 (5) |
Pr—O21 | 2.453 (2) | C41—N41 | 1.310 (5) |
Pr—O61 | 2.457 (2) | N41—C43 | 1.434 (7) |
Pr—O51 | 2.461 (2) | N41—C42 | 1.462 (6) |
Pr—O71 | 2.490 (3) | O51—H51A | 0.835 (19) |
Pr—N6 | 2.569 (3) | O51—H51B | 0.839 (19) |
Cr—C2 | 2.062 (3) | O61—H61B | 0.831 (19) |
Cr—C4 | 2.065 (4) | O61—H61A | 0.842 (19) |
Cr—C1 | 2.069 (3) | O71—H71B | 0.824 (19) |
Cr—C3 | 2.069 (4) | O71—H71A | 0.838 (19) |
Cr—C6 | 2.070 (3) | O91—H91B | 0.834 (19) |
Cr—C5 | 2.074 (4) | O91—H91A | 0.841 (19) |
C1—N1 | 1.145 (4) | H51B—O91i | 1.805 (19) |
C2—N2 | 1.147 (4) | H61A—N2ii | 1.873 (19) |
C3—N3 | 1.144 (5) | H61B—N5iii | 2.117 (19) |
C4—N4 | 1.144 (5) | H71A—N5iii | 1.950 (19) |
C5—N5 | 1.148 (5) | H71B—N1iv | 2.035 (19) |
C6—N6 | 1.151 (4) | H91A—N4ii | 1.975 (19) |
O11—C11 | 1.240 (4) | H91B—N3v | 2.040 (19) |
C11—N11 | 1.303 (5) | H51A—N1iv | 2.026 (19) |
N11—C12 | 1.456 (5) | O51—N1iv | 2.849 (4) |
N11—C13 | 1.460 (5) | O61—N2ii | 2.711 (4) |
O21—C21 | 1.236 (5) | O61—N5iii | 2.908 (4) |
C21—N21 | 1.300 (5) | O71—N5iii | 2.785 (4) |
N21—C23 | 1.438 (7) | O71—N1iv | 2.828 (4) |
N21—C22 | 1.450 (6) | O91—N4ii | 2.807 (4) |
O31—C31 | 1.249 (4) | O91—N3v | 2.873 (4) |
C31—N31 | 1.302 (5) | ||
O11—Pr—O31 | 127.51 (10) | C11—N11—C13 | 121.9 (3) |
O11—Pr—O41 | 77.34 (9) | C12—N11—C13 | 117.6 (3) |
O31—Pr—O41 | 73.00 (9) | C21—O21—Pr | 133.1 (3) |
O11—Pr—O21 | 73.82 (9) | O21—C21—N21 | 125.2 (4) |
O31—Pr—O21 | 139.19 (9) | C21—N21—C23 | 120.0 (4) |
O41—Pr—O21 | 80.65 (10) | C21—N21—C22 | 122.9 (4) |
O11—Pr—O61 | 79.20 (9) | C23—N21—C22 | 116.9 (4) |
O31—Pr—O61 | 136.11 (9) | C31—O31—Pr | 155.0 (2) |
O41—Pr—O61 | 150.66 (9) | O31—C31—N31 | 124.2 (3) |
O21—Pr—O61 | 76.06 (9) | C31—N31—C32 | 121.4 (3) |
O11—Pr—O51 | 140.44 (9) | C31—N31—C33 | 121.0 (3) |
O31—Pr—O51 | 75.01 (9) | C32—N31—C33 | 117.6 (3) |
O41—Pr—O51 | 80.79 (9) | C41—O41—Pr | 128.7 (2) |
O21—Pr—O51 | 70.36 (9) | O41—C41—N41 | 124.7 (4) |
O61—Pr—O51 | 107.35 (9) | C41—N41—C43 | 121.5 (4) |
O11—Pr—O71 | 139.97 (9) | C41—N41—C42 | 120.8 (4) |
O31—Pr—O71 | 72.05 (9) | C43—N41—C42 | 117.7 (4) |
O41—Pr—O71 | 140.63 (8) | H51A—O51—H51B | 102 (5) |
O21—Pr—O71 | 116.11 (10) | H51A—O51—Pr | 117 (3) |
O61—Pr—O71 | 67.30 (8) | H51B—O51—Pr | 138 (3) |
O51—Pr—O71 | 73.18 (9) | H51A—O51—O91i | 105 (3) |
O11—Pr—N6 | 72.46 (9) | Pr—O51—O91i | 135.76 (12) |
O31—Pr—N6 | 75.36 (9) | H51B—O51—N1iv | 111 (3) |
O41—Pr—N6 | 105.87 (10) | Pr—O51—N1iv | 108.68 (11) |
O21—Pr—N6 | 143.11 (9) | O91i—O51—N1iv | 113.51 (13) |
O61—Pr—N6 | 83.32 (10) | H61B—O61—H61A | 99 (4) |
O51—Pr—N6 | 146.03 (9) | H61B—O61—Pr | 129 (3) |
O71—Pr—N6 | 82.19 (10) | H61A—O61—Pr | 127 (3) |
C2—Cr—C4 | 90.91 (14) | H61B—O61—N2ii | 103 (3) |
C2—Cr—C1 | 178.97 (14) | Pr—O61—N2ii | 123.67 (12) |
C4—Cr—C1 | 88.27 (14) | H61A—O61—N5iii | 114 (3) |
C2—Cr—C3 | 89.92 (13) | Pr—O61—N5iii | 114.95 (11) |
C4—Cr—C3 | 90.62 (13) | N2ii—O61—N5iii | 118.13 (13) |
C1—Cr—C3 | 89.46 (13) | H71B—O71—H71A | 111 (4) |
C2—Cr—C6 | 91.50 (13) | H71B—O71—Pr | 122 (3) |
C4—Cr—C6 | 176.41 (13) | H71A—O71—Pr | 123 (3) |
C1—Cr—C6 | 89.36 (13) | H71B—O71—N5iii | 115 (3) |
C3—Cr—C6 | 92.06 (13) | Pr—O71—N5iii | 118.26 (11) |
C2—Cr—C5 | 89.01 (13) | H71A—O71—N1iv | 122 (3) |
C4—Cr—C5 | 89.30 (14) | Pr—O71—N1iv | 108.49 (11) |
C1—Cr—C5 | 91.60 (13) | N5iii—O71—N1iv | 125.39 (14) |
C3—Cr—C5 | 178.93 (13) | H91B—O91—H91A | 102 (4) |
C6—Cr—C5 | 88.07 (13) | H91B—O91—N4ii | 105 (3) |
N1—C1—Cr | 178.5 (3) | H91A—O91—N3v | 101 (3) |
C1—N1—H51Aiv | 110.8 (3) | N4ii—O91—N3v | 105.17 (14) |
N2—C2—Cr | 178.9 (3) | O51—H51A—N1iv | 168.5 (15) |
N3—C3—Cr | 177.8 (3) | O51—H51B—O91i | 174.8 (15) |
N4—C4—Cr | 177.0 (3) | O61—H61A—N2ii | 173.5 (15) |
N5—C5—Cr | 177.8 (3) | O61—H61B—N5iii | 158.9 (15) |
N6—C6—Cr | 176.1 (3) | O71—H71A—N5iii | 173.5 (15) |
C6—N6—Pr | 163.5 (3) | O71—H71B—N1iv | 161.6 (15) |
C11—O11—Pr | 167.4 (3) | O91—H91A—N4ii | 169.9 (15) |
O11—C11—N11 | 125.2 (4) | O91—H91B—N3v | 177.5 (15) |
C11—N11—C12 | 120.6 (3) |
Symmetry codes: (i) −x+3/2, y−1/2, −z+1/2; (ii) −x+1, −y, −z; (iii) x, y+1, z; (iv) −x+1/2, y+1/2, −z+1/2; (v) −x+1, −y+1, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O51—H51A···N1iv | 0.83 (4) | 2.03 (3) | 2.849 (4) | 169 (4) |
O51—H51B···O91i | 0.83 (4) | 1.81 (3) | 2.641 (3) | 174 (4) |
O61—H61A···N2ii | 0.84 (3) | 1.88 (3) | 2.711 (4) | 173 (4) |
O61—H61B···N5iii | 0.83 (4) | 2.12 (3) | 2.908 (4) | 159 (4) |
O71—H71A···N5iii | 0.83 (3) | 1.95 (3) | 2.785 (4) | 174 (3) |
O71—H71B···N1iv | 0.83 (4) | 2.03 (3) | 2.828 (4) | 161 (5) |
O91—H91A···N4ii | 0.84 (3) | 1.97 (3) | 2.807 (4) | 170 (4) |
O91—H91B···N3v | 0.83 (3) | 2.04 (3) | 2.873 (4) | 177 (4) |
Symmetry codes: (i) −x+3/2, y−1/2, −z+1/2; (ii) −x+1, −y, −z; (iii) x, y+1, z; (iv) −x+1/2, y+1/2, −z+1/2; (v) −x+1, −y+1, −z. |
Experimental details
Crystal data | |
Chemical formula | [CrPr(CN)6(C3H7NO)4(H2O)3]·H2O |
Mr | 713.48 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 186 |
a, b, c (Å) | 17.940 (3), 8.9381 (8), 19.8691 (16) |
β (°) | 96.121 (10) |
V (Å3) | 3167.9 (6) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.92 |
Crystal size (mm) | 0.85 × 0.54 × 0.46 |
Data collection | |
Diffractometer | Enraf-Nonius CAD4 |
Absorption correction | Numerical (SHELXTL/PC; Sheldrick, 1995) |
Tmin, Tmax | 0.292, 0.474 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5760, 5538, 5024 |
Rint | 0.016 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.027, 0.071, 1.10 |
No. of reflections | 5538 |
No. of parameters | 376 |
No. of restraints | 8 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.56, −0.90 |
Computer programs: CAD-4 Software (Enraf-Nonius, 1989), CAD-4 Software, XCAD4 Software (Harms, 1993), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL/PC (Sheldrick, 1995), SHELXL97.
Pr—O11 | 2.413 (2) | Pr—N6 | 2.569 (3) |
Pr—O31 | 2.435 (2) | Cr—C2 | 2.062 (3) |
Pr—O41 | 2.445 (2) | Cr—C4 | 2.065 (4) |
Pr—O21 | 2.453 (2) | Cr—C1 | 2.069 (3) |
Pr—O61 | 2.457 (2) | Cr—C3 | 2.069 (4) |
Pr—O51 | 2.461 (2) | Cr—C6 | 2.070 (3) |
Pr—O71 | 2.490 (3) | Cr—C5 | 2.074 (4) |
O11—Pr—O31 | 127.51 (10) | O51—Pr—O71 | 73.18 (9) |
O11—Pr—O41 | 77.34 (9) | O11—Pr—N6 | 72.46 (9) |
O31—Pr—O41 | 73.00 (9) | O31—Pr—N6 | 75.36 (9) |
O11—Pr—O21 | 73.82 (9) | O41—Pr—N6 | 105.87 (10) |
O31—Pr—O21 | 139.19 (9) | O21—Pr—N6 | 143.11 (9) |
O41—Pr—O21 | 80.65 (10) | O61—Pr—N6 | 83.32 (10) |
O11—Pr—O61 | 79.20 (9) | O51—Pr—N6 | 146.03 (9) |
O31—Pr—O61 | 136.11 (9) | O71—Pr—N6 | 82.19 (10) |
O41—Pr—O61 | 150.66 (9) | N1—C1—Cr | 178.5 (3) |
O21—Pr—O61 | 76.06 (9) | N2—C2—Cr | 178.9 (3) |
O11—Pr—O51 | 140.44 (9) | N3—C3—Cr | 177.8 (3) |
O31—Pr—O51 | 75.01 (9) | N4—C4—Cr | 177.0 (3) |
O41—Pr—O51 | 80.79 (9) | N5—C5—Cr | 177.8 (3) |
O21—Pr—O51 | 70.36 (9) | N6—C6—Cr | 176.1 (3) |
O61—Pr—O51 | 107.35 (9) | C6—N6—Pr | 163.5 (3) |
O11—Pr—O71 | 139.97 (9) | C11—O11—Pr | 167.4 (3) |
O31—Pr—O71 | 72.05 (9) | C21—O21—Pr | 133.1 (3) |
O41—Pr—O71 | 140.63 (8) | C31—O31—Pr | 155.0 (2) |
O21—Pr—O71 | 116.11 (10) | C41—O41—Pr | 128.7 (2) |
O61—Pr—O71 | 67.30 (8) |
D—H···A | D—H | H···A | D···A | D—H···A |
O51—H51A···N1i | 0.83 (4) | 2.03 (3) | 2.849 (4) | 169 (4) |
O51—H51B···O91ii | 0.83 (4) | 1.81 (3) | 2.641 (3) | 174 (4) |
O61—H61A···N2iii | 0.84 (3) | 1.88 (3) | 2.711 (4) | 173 (4) |
O61—H61B···N5iv | 0.83 (4) | 2.12 (3) | 2.908 (4) | 159 (4) |
O71—H71A···N5iv | 0.83 (3) | 1.95 (3) | 2.785 (4) | 174 (3) |
O71—H71B···N1i | 0.83 (4) | 2.03 (3) | 2.828 (4) | 161 (5) |
O91—H91A···N4iii | 0.84 (3) | 1.97 (3) | 2.807 (4) | 170 (4) |
O91—H91B···N3v | 0.83 (3) | 2.04 (3) | 2.873 (4) | 177 (4) |
Symmetry codes: (i) −x+1/2, y+1/2, −z+1/2; (ii) −x+3/2, y−1/2, −z+1/2; (iii) −x+1, −y, −z; (iv) x, y+1, z; (v) −x+1, −y+1, −z. |
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Cyanometallate ions, [M(CN)x]n-, have been shown to act as buiding blocks for many cyanide-bridged rare-earth/transition metal bimetallic assemblies. These complexes have proven useful in homogenous and heterogeneous catalytic applications due to the electropositive nature, the retracted 4f orbitals, and the lability of ligands coordinated to the central lanthanide ion (Huskins et al., 1995). Recently, a dinuclear cyano-bridged complex based on hexacyanoferrate and samarium nitrate was crystallographically studied (Kou et al., 1998). The authors demonstrated that the compound, [(DMF)4(H2O)4SmFe(CN)6]·H2O, contained a nine-coordinate trivalent samarium ion in a distorted tricapped trigonal prism geometry. Attempts to reproduce these synthetic results with chromium(III) hexacyanide and praseodymium(III) nitrate yielded crystals with the stoichiometry [(DMF)4(H2O)3PrCr(CN)6]·H2O, (I). \sch
Figure 1 is a representation of the molecular structure of the title compound. The molecular units within the crystal lattice are separated by normal van der Waals contact distances. The PrIII ions exhibit a slightly distorted square-antiprism coordination geometry. The top face of the prism, comprised of atoms O71, O51, O21, and O(61), is essentially planar with a mean deviation of 0.074 Å while the bottom face, atoms N6, O31, O41, and O11, is slightly distorted from planarity by a mean deviation of 0.220 Å. The dihedral angle between the two faces is 3.2°.
Selected geometric parameters for (I) are presented in Table 1. The mean Pr—O (DMF) Pr—O (H2O) and Pr—N bond lengths are 2.436 (15) 2.469 (15) and 2.569 (3) Å, respectively. When considering the Pr—O bond distances of the coordinated DMF ligands, it is observed that the Pr—O11 and Pr—O31 lengths are somewhat shorter than the Pr—O21 and Pr—O41 lengths. Also, the corresponding C—O—Pr bond angles described by the same sets of oxygen atoms are significantly larger for the DMF ligands of O11 and O31 than those described by O21 and O41. This may be attributable to the fact that both DMF ligands corresponding to O11 and O31 are adjacent to the hexacyanochromate moiety, increasing the steric hindrance at those coordination sites. Other investigations on analogous compounds have shown similar results (Kou et al., 1998; Mullica et al., 2000).
The geometry about the central Cr3+ ion is approximately octahedral, with C—Cr—C bond angles in the range 88.07 (13) to 92.06 (13)°. The Cr—C bond lengths range from 2.062 (3) to 2.074 (4) Å [mean 2.068 (4) Å] and are normal when compared to the sum of the atomic radii for Cr and C. The overall mean C≡N bond length of 1.146 (2) Å is also in accord with the sum of the triple bond radii of C and N atoms (0.603 and 0.55 Å, respectively) found in the work of Pauling (1960). The Cr—C—N bond angles are almost linear and range from 176.7 (5) to 179.7 (4) ° for (I), indicative of strong directional bonding as the π orbitals of the cyano ligands interact with the d orbitals of the metal center. However, the isocyanide linkage to the central praseodymium(III) ion deviates significantly from linearity. The Pr—N—C bond angle for (I) is 164.1 (4)°. This phenomenon has been shown to occur in similar compounds containing Ln—NC—R linkages. Darensbourg (1985) has proposed that the angular position of the metal cation may facilitate interaction with the lone pairs or π orbitals of the ligand. However, it may simply be that the change in energy by bending the ligands is insignificant, thus allowing steric factors to promote the deviation from linearity in the Pr—NC—Cr linkages.
Hydrogen bonding is paramount in the intermolecular network in the crystal lattice of this complex. According to the work of Hamilton & Ibers (1968), hydrogen bonding of the O—H···N and O—H···O types may be present when O···N and O···O contact distances are within 3.2 Å. Such is the case in the crystal lattices of (I) where the free water of hydration, O91, along with the coordinated water molecules and the nitrogen ends of the cyano ligands are involved in a hydrogen-bonding network. Fig. 2 depicts the hydrogen-bonding network within the crystal lattice; specific intermolecular interactions are included in Table 2. An IR spectroscopic study of (I) supports the X-ray evidence of varying degrees of hydrogen bonding with broad peaks in the 3100 to 3500 cm-1 region.
Interest in lanthanide cyanide-bridged complexes will continue due to their possible ability to function as models for evaluating molecule-membrane interactions and molecular transport in permselective membranes. Both selectivity and permeation rates of the species of interest can be strongly influenced by the molecular structure of the exchange host. Furthermore, studies have shown that compounds containing both lanthanide and transition metals may serve as bimetallic catalysts or as precursors to bimetallic particles on oxide surfaces [White et al. (1994); Deng & Shore (1991)]. Of course, compounds containing direct lanthanide-transition metal bonds would be ideal for these purposes. Unfortunately, very few of these materials have been characterized as their synthesis has proven quite challenging. Nevertheless, the development of new materials with such possibilities is always of interest to this research laboratory.