Strictly heterodinuclear compounds containing U4+ and Cu2+ or Ni2+ ions

Polyhedron 26 (2007) 645–652 www.elsevier.com/locate/poly

Strictly heterodinuclear compounds containing U4+ and Cu2+ or Ni2+ ions Lionel Salmon, Pierre Thue´ry, Michel Ephritikhine

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Service de Chimie Mole´culaire, DSM, DRECAM, CNRS URA 331, Laboratoire Claude Fre´jacques, CEA/Saclay, 91191 Gif-sur-Yvette, France Received 18 July 2006; accepted 25 August 2006 Available online 3 September 2006

Abstract Treatment of [M(H2Li)] with UCl4 in pyridine led to the formation of the dinuclear complexes [MLi(py)UCl2(py)2] and/or [Hpy][MLi(py)UCl3] [Li = N,N 0 -bis(3-hydroxysalicylidene)-R, R = 1,2-phenylenediamine (i = 1), R = trans-1,2-cyclohexanediamine (i = 2), R = 2-amino-benzylamine (i = 3), R = 1,3-propanediamine (i = 4), R = 2,2-dimethyl-1,3-propanediamine (i = 5); M = Cu or Ni]. The crystal structures show that the 3d and 5f ions occupy, respectively, the N2O2 and O4 cavities of the Schiff base ligand, the U4+ ion adopting a dodecahedral or pentagonal bipyramidal configuration in the neutral and anionic complexes, respectively.  2006 Elsevier Ltd. All rights reserved. Keywords: Uranium; Copper; Nickel; Schiff base; Dinuclear; X-ray crystal structure

1. Introduction Polynuclear complexes containing both d- and f-block transition metals attract much attention for their interesting magnetic behaviour [1] and their potential in the development of molecular-based materials with controlled properties [2,3]. Most studies were devoted to copper(II)– gadolinium(III) (3d–4f) complexes in which both ferro[4–8] and antiferromagnetic [9,10] interactions have been observed. When the lanthanide(III) ion, Ln3+, is different from gadolinium, the presence of a first-order orbital momentum complicates the analysis of the magnetic properties which are governed by both the thermal population of the Stark components of the 4f ion and the 3d–4f interaction. The nature of this interaction could be determined by subtracting the sole contribution of the lanthanide ion, which is reflected by the magnetic behaviour of isostructural derivatives in which the paramagnetic 3d ion, i.e. Cu2+, has been replaced by a diamagnetic ion, i.e. Zn2+

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Corresponding author. Fax: +33 1 69 08 66 40. E-mail addresses: [email protected], [email protected] (M. Ephritikhine). 0277-5387/$ - see front matter  2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2006.08.022

[11,12]. In the last past years, the first compounds containing both 3d and 5f ions have been isolated [13–18]. In addition to the challenge of their synthesis, such complexes are attractive for their magnetic properties which, by comparison with those of the 3d–4f derivatives, would reflect the greater spatial extension of the 5f orbitals. We have prepared a series of trinuclear compounds of general formula [{MLi(py)}2U] (M = Cu, Zn) which differ by the length of the diimino chain of the Schiff base ligand L and whose magnetic properties were found to be dependent on the Cu  U distance [15,16]. With L6 = N,N 0 -bis(3-hydroxysalicylidene)-2-methyl-1,2-propanediamine, we succeeded in isolating the first strictly dinuclear compound of paramagnetic 3d and 5f ions, [CuL6(py)U(acac)2], from an equimolar mixture of [Cu(H2L6)] and U(acac)4 [17]. This dinuclear compound was the sole to have been obtained pure since the use of the other Schiff base ligands led invariably to the straightforward formation of the Cu2U complexes. Here we present the crystal structure of new CuU and NiU compounds in this family which were synthesized by using UCl4 instead of U(acac)4 as the uranium precursor. Unfortunately, attempts to isolate and characterize the ZnU analogues were unsuccessful, precluding any magnetic studies.

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treatment of [Cu(H2L1)] with UCl4 in pyridine at 80 C, while similar reaction of [Cu(H2L2)] gave a mixture of green crystals of [CuL2(py)UCl2(py)2] (2) and orange crystals of [Hpy][CuL2(py)UCl3]. Under the same experimental conditions, the anionic compounds [Hpy][CuLi(py)UCl3] [i = 3 (3), 4 (4) and 5 (5)] were the sole products isolated from [Cu(H2Li)], as dark brown (i = 3), dark yellow (i = 4) and light green (i = 5) crystals. Similar reactions of [Ni(H2Li)] (i = 3, 5) and UCl4 led to the formation of the anionic complexes [Hpy]2[NiL3(py)2UCl3][NiL3(py)UCl3] (6) and [Hpy][NiL5(py)UCl3] (7). As mentioned in Section 1, the nature of the Cu–U or Ni–U interaction in these dinuclear compounds can be determined by comparison of their magnetic properties with those of the ZnU analogues. Unfortunately, reactions of [Zn(H2Li)] (i = 2–5) with UCl4 gave insoluble powders which could not be fully characterized. Only the products obtained from [Zn(H2L1)] were soluble in pyridine but, surprisingly, the 1H NMR spectra revealed the presence of two compounds with a dissymmetric structure, all the protons of the Schiff base ligands being magnetically unequivalent.

2. Results and discussion 2.1. Synthesis of the complexes The Schiff bases H4Li [Li = N,N 0 -bis(3-hydroxysalicylidene)-R, R = 1,2-phenylenediamine (i = 1), R = trans1,2-cyclohexanediamine (i = 2), R = 2-amino-benzylamine (i = 3), R = 1,3-propanediamine (i = 4), R = 2,2-dimethyl-1, 3-propanediamine (i = 5)] are represented in Scheme 1. Reactions of [M(H2Li)] (M = Cu, Ni or Zn) with one equivalent of U(acac)4 in refluxing pyridine afforded directly the trinuclear compounds [{MLi(py)}2U], without it being possible to isolate the [MLi(py)U(acac)2] intermediates [15,16]. Similar treatment of [M(H2Li)] (M = Cu, Ni) with UCl4 in place of U(acac)4 afforded the dinuclear compounds [MLi(py)UCl2(py)2] and/or [Hpy][MLi(py)UCl3] (Scheme 2). The synthesis of these complexes is likely favoured by the retention of the chloride ion on the metal centre while reactions with U(acac)4 lead to the irreversible elimination of acacH. The orange microcrystalline powder of [CuL1(py)UCl2(py)2] (1) was obtained in 97% yield by

N

OH N

OH

N

N

OH

N

N

N

N

N

=

N

N

N

N

N

OH

H4Li

Scheme 1. The H4Li Schiff bases.

OH N N

OH

OH

N

OH

OH

N

OH OH

N

M(acac)2

O

OH

M

THF, 20 °C

N

O

OH

OH [M(H2Li)]

H4Li

M = Cu, Ni

UCl4 py, 80 °C

N M N py

O Cl O py U O O Cl

O Cl O U Cl

N M

O

N py

py

[MLi(py)Cl2py2]

O

Cl

[MLi(py)UCl3]

Scheme 2. Synthesis of the complexes.

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L. Salmon et al. / Polyhedron 26 (2007) 645–652

Obviously, the ZnU analogue of 1 was not formed and, in the absence of crystallographic analysis, these complexes have not been identified. 2.2. Crystal structures of the complexes Crystals of 1Æ2py, 2Æ2py, 3Æ1.25py, 4, 5Æpy, 6Æ1.5py and 7Æpy suitable for X-ray diffraction analysis were obtained by crystallization from pyridine. Views of 1 and 4 are shown in Figs. 1 and 2, respectively, and selected bond lengths and angles are listed in Table 1. The asymmetric unit of 2Æ2py contains two independent enantiomer molecules, [Cu[(R,R)-L2](py)UCl2(py)2] and [Cu[(S,S)-L2](py)UCl2(py)2] (see Section 4.3), and the asymmetric unit of

Fig. 1. View of complex 1. The hydrogen atoms are omitted for clarity. Only the principal component of the disordered pyridine molecules is represented. Displacement ellipsoids are drawn at the 30% probability level.

Fig. 2. View of complex 4. The hydrogen atoms (except the pyridinium one) are omitted for clarity. The hydrogen bond is shown as a dashed line. Displacement ellipsoids are drawn at the 30% probability level.

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3Æ1.25py contains two identical independent molecules. In all the CuU complexes 1–5, the copper and uranium atoms occupy, respectively, the N2O2 and O4 cavities of the Schiff base ligand and are bridged by the two oxygen atoms O(2) and O(3) of the salicylidene fragments; the Cu2+ ions adopt a square pyramidal coordination mode, being displaced from the N2O2 base towards the pyridine ligand by 0.20– ˚ . In the neutral compounds 1 and 2, the U4+ ion is 0.27 A bound to two chloride ions and two nitrogen atoms of pyridine ligands and is found in a dodecahedral environment defined by the two trapezia O(1)–O(2)–O(3)–O(4) and Cl(1)–N(3)–Cl(2)–N(4) intersecting at an angle of 89.43(9) in 1 and 89.47(17) and 89.83(17) in 2. The anionic complexes 3, 4 and 5 differ by the displacement of the two pyridine ligands with a chloride ion, and the seven coordinate uranium atom is in a pentagonal bipyramidal configuration with Cl(1) and Cl(3) in apical positions. The charge is compensated with that of a pyridinium ion which is hydrogen bonded to a pyridine nitrogen atom in 3 (in which the pyridinium ions are disordered, Section 4.3) or to one phenoxide oxygen atom in 4 or 5 ˚ , N(4)–H  O(4) 166 in 4, [N(4)  O(4) 2.828(6) A ˚ (pyridinium proton not found) in N(4)  O(1) 2.667(9) A 5]. The length of the diimino chain of Li and the configuration of the U4+ ion in complexes 1–5 have no major influ˚ ence on the U–O distances, which average 2.44(3) A ˚ [terminal O(1) [bridging O(2) and O(3)] and 2.25(3) A and O(4)], and on the O(2)–U–O(3) and O(1)–U–O(4) angles which vary from 59.3(2) to 62.4(3) and from 164.0(3) to 167.7(2), respectively; these values are quite identical to those found in the series of [{CuLi(py)}2U] compounds. However, as also observed in the trinuclear complexes, the length of the diimino chain of Li has a marked effect on the coordination of the 3d metal, in particular the N(1)–Cu–N(2) and O(2)–Cu–O(3) angles which are, respectively, ca. 10 smaller and 6 larger in 1 and 2 than in 3, 4 and 5. In relation to these variations, the Cu..U distances increase by passing from L1 and L2 to L3, L4 and L5, with average values of 3.541(7) and ˚ . The mean values of the U–Cl bond lengths, 3.632(15) A ˚ in 1 and 2 and 2.68(2) A ˚ in 3, 4 and 5, are among 2.73(2) A the largest reported in the Cambridge Structural Database (CSD, Version 5.27) [19]. Crystals of 6Æ1.5py contain two different anionic complexes [NiL3(py)2UCl3] and [NiL3(py)UCl3], denoted A and B, respectively. The distinct configurations of the Ni atom, octahedral in A and square pyramidal in B, have no influence on the Ni–O(2,3) and Ni–N(1,2) distances. In fact, the 3d ion in complex A is in the mean plane of the N2O2 ˚ ] while it is out of this cavity [distance to the plane 0.026(3) A ˚ plane in complex B, by 0.364(3) A; however, the Ni–O and Ni–N distances are not shorter in A than in B because of the enlargement of the N2O2 cavity, in relation with the variation of the N–Ni–N and N–Ni–O angles which are larger in A than in B, by ca. 5 and 2, respectively. Comparison of the structures of 6 (complex B) and 3, and of 7 and 5, which are isomorphous, indicate that the

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L. Salmon et al. / Polyhedron 26 (2007) 645–652

Table 1 ˚ ) and angle () in the dinuclear complexes Selected bond lengths (A 1Æ2py U–O(1) U–O(2) U–O(3) U–O(4) U–Cl(1) U–Cl(2) U–Cl(3) U–N(3) U–N(4) ÆU–Oæ ÆU–Obæ ÆU–Otæ M–O(2) M–O(3) M–N(1) M–N(2) M–N(3) M–N(5) M  U O(1)–U–O(4) O(2)–U–O(3) Cl(1)–U–N(4) Cl(2)–U–N(3) Cl(1)–U–Cl(2) Cl(2)–U–Cl(3) N(1)–M–N(2) N(1)–M–O(2) N(2)–M–O(3) O(2)–M–O(3) M–O(2)–U M–O(3)–U ac a b c

2Æ2pya

2.227(4) 2.449(4) 2.491(4) 2.225(4) 2.7072(15) 2.7472(15)

2.247(8)/2.223(9) 2.422(9)/2.490(7) 2.483(8)/2.431(8) 2.219(9)/2.260(8) 2.721(3)/2.709(3) 2.751(3)/2.746(3)

2.595(5) 2.631(5) 2.35(12) 2.47(2) 2.226(1) 1.915(4) 1.925(4) 1.947(5) 1.948(5)

2.622(11)/2.582(12) 2.614(10)/2.604(10) 2.34(11)/2.35(11) 2.45(3)/2.46(3) 2.233(14)/2.24(2) 1.930(8)/1.913(8) 1.940(8)/1.933(8) 1.955(9)/1.949(10) 1.941(10)/1.937(10)

2.275(4) 3.5451(7) 164.08(15) 61.48(12) 142.97(12) 72.55(12)

2.287(10)/2.293(11) 3.5305(15)/3.5472(15) 164.0(3)/164.8(3) 62.4(3)/61.5(3) 141.8(2)/143.8(2) 73.5(2)/72.6(2)

84.6(2) 94.75(18) 95.17(19) 82.24(16) 108.04(17) 106.08(16) 13.5(3)

85.9(4)/86.0(4) 94.7(4)/94.4(4) 93.7(4)/94.6(4) 82.2(3)/81.7(3) 107.9(3)/106.6(3) 105.3(3)/108.2(4) 13.9(5)/12.9(5)

3Æ1.25pya

4

5Æpy

6Æ1.5pyb

7Æpy

2.248(6)/2.234(7) 2.405(7)/2.414(7) 2.423(6)/2.427(7) 2.273(7)/2.240(6) 2.655(3)/2.707(3) 2.683(3)/2.674(3) 2.706(3)/2.644(3)

2.232(4) 2.407(4) 2.420(4) 2.292(4) 2.6499(14) 2.6660(15) 2.6921(14)

2.305(5) 2.421(5) 2.412(5) 2.254(6) 2.659(3) 2.678(2) 2.687(2)

2.278(6)/2.247(6) 2.387(5)/2.398(5) 2.405(5)/2.427(5) 2.274(5)/2.242(6) 2.698(2)/2.650(2) 2.719(2)/2.706(2) 2.656(2)/2.714(2)

2.247(4) 2.410(4) 2.409(4) 2.284(4) 2.650(2) 2.687(2) 2.674(2)

2.34(8)/2.33(9) 2.414(9)/2.421(6) 2.261(12)/2.237(3) 1.928(6)/1.945(7) 1.940(7)/1.923(7) 1.967(9)/1.936(8) 1.972(8)/2.007(8) 2.270(8)/2.304(9)

2.34(8) 2.414(6) 2.26(3) 1.945(4) 1.964(4) 1.995(5) 1.996(5) 2.261(4)

2.35(7) 2.417(4) 2.28(3) 1.981(6) 1.957(6) 1.995(7) 1.983(7) 2.304(7)

2.34(6)/2.33(8) 2.396(9)/2.413(15) 2.276(2)/2.245(2) 1.988(5)/1.971(6) 1.983(5)/1.991(6) 1.985(7)/2.025(7) 2.022(6)/2.012(7) 2.197(7)/2.026(7)

2.34(7) 2.410(1) 2.27(2) 1.992(4) 1.994(5) 2.010(5) 2.034(6) 2.048(6)

3.6152(13)/3.6232(13) 167.7(2)/167.1(3) 59.3(2)/59.3(2)

3.6335(7) 166.77(14) 59.36(13)

3.6545(10) 167.34(19) 59.70(19)

3.6557(11)/3.6465(11) 168.97(19)/166.82(19) 60.09(18)/60.52(19)

3.6707(9) 166.87(16) 60.06(14)

88.83(10)/94.92(10) 89.62(9)/91.57(9) 95.5(4)/96.6(4) 91.8(3)/92.6(3) 92.8(3)/92.8(3) 76.3(3)/76.4(3) 112.7(3)/112.0(3) 111.4(3)/112.3(3) 4.6(5)/0.3(3)

88.44(5) 87.09(5) 99.7(2) 90.66(18) 91.83(18) 75.37(16) 112.76(17) 111.53(16) 8.7(2)

90.53(9) 88.98(8) 97.7(3) 91.4(3) 91.8(3) 75.3(2) 111.8(3) 113.1(3) 1.1(5)

86.91(7)/90.43(7) 91.85(7)/91.33(7) 100.4(3)/95.2(3) 92.1(2)/90.2(3) 93.2(2)/91.7(3) 74.3(2)/75.7(2) 113.1(2)/112.8(2) 112.5(2)/110.9(2) 0.9(1)/3.3(3)

91.40(10) 89.32(9) 97.4(2) 90.1(2) 91.1(2) 74.46(17) 112.68(18) 112.64(18) 3.6(4)

Values for the two independent molecules. ˚. Values for complexes A and B (see text); Ni–N(4) in complex A 2.236(7) A a is the dihedral angle between the two halves of the MO(2)O(3)U bridging core.

coordination geometry of the U4+ ion is quite identical in all the complexes. However, the Ni–O and Ni–N(1,2) distances are larger than the corresponding Cu–O and Cu– ˚ , whereas the radius of the N distances, by ca. 0.04 A ˚ smaller than that of Cu2+ [20]. The Ni2+ ion is 0.02 A Ni2+ ion is more displaced than Cu2+ from the N2O2 plane, ˚ , and the Ni–N(py) distances of by ca. 0.35 versus 0.25 A ˚ are much smaller than the average 2.026(7) and 2.048(6) A ˚ . The same variations in the Cu–N(py) distance of 2.29(2) A structural parameters of the square pyramidal Ni2+ and Cu2+ ions were observed in the trinuclear complexes [{NiL5(py)}2U] and [{CuL5(py)]U[CuL5}]. 3. Conclusion The difficulty in obtaining strictly dinuclear CuU and ZnU complexes from reactions of [M(H2Li)] (M = Cu, Ni or Zn) with U(acac)4 arises from the straightforward formation of the corresponding trinuclear compounds [{MLi(py)}2U]. Replacement of U(acac)4 with UCl4 permitted to prepare CuU and NiU complexes, either as neutral or anionic derivatives [MLi(py)UCl2(py)2] and

[Hpy][MLi(py)UCl3], but the unsuccessful isolation and characterization of the ZnU analogues precluded any studies of the Cu–U or Ni–U exchange interaction. 4. Experimental 4.1. General All reactions were carried out under argon (<5 ppm oxygen or water) using standard Schlenk-vessel and vacuumline techniques or in a glove box. Solvents were dried by standard methods and distilled immediately before use; deuterated pyridine (Eurisotop) was distilled over NaH ˚ molecular sieves. The 1H NMR spectra and stored over 3 A were recorded on a Bruker DPX 200 instrument and referenced internally using the residual protio solvent resonances relative to tetramethylsilane (d 0). Elemental analyses were performed by Analytische Laboratorien at Lindlar (Germany). The Schiff bases H4Li (i = 1–5) were synthesized by published methods [21]. The acac compounds M(acac)2 (Cu, Ni and Zn) (Aldrich) were used without purification; UCl4

L. Salmon et al. / Polyhedron 26 (2007) 645–652

was prepared as previously reported [22]. The complexes [M(H2Li)] were synthesized in THF by reaction of H4Li with 1 equiv. of M(acac)2. 4.2. Syntheses The complexes can be divided into two series of general formula [MLi(py)UCl2(py)2] and [Hpy][MLi(py)UCl3]. One example in each series, 1 and 4, has been characterized by its elemental analyses; all the complexes or their solvates were characterized by X-ray diffraction analysis. 4.2.1. [CuL1(py)UCl2(py)2] (1) A flask was charged with [Cu(H2L1)] (150 mg, 0.37 mmol) and UCl4 (139 mg, 0.37 mmol) in pyridine (25 mL). The reaction mixture was heated at 80 C for 12 h; the brown-orange powder of 1 was filtered off, washed with pyridine (20 ml) and dried under vacuum (340 mg, 97%). The complex could not be characterized by its 1H NMR spectrum because of its insolubility in organic solvents. Anal. Calc. for C35H27N5O4Cl2CuU: C, 44.05; H, 2.83; N, 7.34. Found: C, 43.89; H, 3.03; N, 7.49%. Crystals of 1Æ2py were obtained by heating a suspension of 1 in pyridine at 80 C. 4.2.2. [CuL2(py)UCl2(py)2] (2) and [Hpy][CuL2(py)UCl3] An NMR tube was charged with [Cu(H2L2)] (6.0 mg, 0.0144 mmol) and UCl4 (5.5 mg, 0.0144 mmol) in pyridine-d5 (0.4 mL). Immediately, at 20 C, a brown powder precipitated and the 1H NMR indicated the presence of two species A and B in the relative proportions of 2:1. The tube was heated at 80 C and the NMR spectrum showed the presence of both species in relative proportions 1:1. Prolonged heating at 80 C led to the crystallization of a mixture of light green platelets of [CuL2(py)UCl2(py)2] Æ 2py (2Æ2py) and orange platelets of [Hpy][CuL2(py)UCl3]. 1 H NMR of species A: 15.35, 18.29 and 41.61 (3 · 2 H, aromatic H). 1H NMR of species B: 16.57 and 42.79 (4 H + 2 H, aromatic H). Broad signals at 16.1, 12.8, 6.2 and 1.4 are attributed to the protons of the cyclohexyl rings of both compounds; a signal at d 21.2 can be attributed to the Hpy proton. 4.2.3. [Hpy][CuL3(py)UCl3] (3) An NMR tube was charged with [Cu(H2L3)] (5.0 mg, 0.0118 mmol) and UCl4 (4.5 mg, 0.0118 mmol) in pyridine-d5 (0.4 mL). The tube was heated at 80 C for 1 d and the spectrum indicated the presence of the sole complex 3. Prolonged heating at 80 C led to the crystallization of dark brown platelets of 3Æ1.25py. 1 H NMR (pyridine-d5, 23 C): 16.5, 6.84, 1.32 and 12.29 (4 · 1 H, Ph of the diimino chain), 17.52 and 18.15 (2 · 1 H, aromatic H), 23.12 (3 H, aromatic H and pyH), 40.23 (2 H, aromatic H), 106.2 and 107.8 (2 · 1 H, NCH2).

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4.2.4. [Hpy][CuL4(py)UCl3] (4) (a) An NMR tube was charged with [Cu(H2L4)] (5.0 mg, 0.0133 mmol) and UCl4 (5.1 mg, 0.0133 mmol) in pyridined5 (0.4 mL). After heating at 80 C for 5 d, the spectrum indicated the presence of the sole complex 4 which crystallized as dark yellow platelets. 1 H NMR (pyridine-d5, 23 C): 25.59 (2 H, CH2) 10.46, 19.69 and 44.10 (3 · 2 H, aromatic H), 93.42 and 116.90 (2 · 2 H, NCH2). (b) A flask was charged with [Cu(H2L4)] (50 mg, 0.13 mmol) and UCl4 (50 mg, 0.13 mmol) in pyridine (15 mL). The reaction mixture was heated for 6 h at 80 C; the brown powder of 4 was filtered off, washed with pyridine (10 mL) and dried under vacuum (55 mg, 47%). Anal. Calc. for C27H25N4O4Cl3CuU: C, 36.94; H, 2.85; N, 6.39. Found: C, 36.81; H, 3.05; N, 6.59%. 4.2.5. [Hpy][CuL5(py)UCl3] (5) An NMR tube was charged with [Cu(H2L5)] (5.0 mg, 0.0124 mmol) and UCl4 (4.7 mg, 0.0124 mmol) in pyridine-d5 (0.4 mL). The tube was heated at 80 C for 12 h and the NMR spectrum of the limpid dark brown solution indicated the presence of the sole complex 5. Prolonged heating at 80 C led to the crystallization of light green needles of 5Æpy. 1 H NMR (pyridine-d5, 23 C): 10.83 (6 H, Me) 10.34, 19.28 and 43.14 (3 · 2 H, aromatic H), 110.7 (4 H, NCH2); a signal at d 20.02 can be attributed to the Hpy proton. 4.2.6. [Hpy]2[NiL3(py)2UCl3][NiL3(py)UCl3] (6) An NMR tube was charged with [Ni(H2L3)] (5.0 mg, 0.0119 mmol) and UCl4 (4.5 mg, 0.0118 mmol) in pyridine-d5 (0.4 mL). After 30 min at 20 C, the spectrum of the red solution showed the formation of 6 as the sole product. Prolonged heating at 80 C led to the crystallization of orange platelets of 6Æ1.5py. 1 H NMR (pyridine-d5, 23 C): 13.37, 4.59, 0.52 and 13.72 (4 · 1 H, Ph of the diimino chain), 18.91 and 29.16 (2 · 2 H, aromatic H), 29.29 (1 H, Hpy), 35.60 and 35.92 (2 · 1 H, aromatic H), 94.9 (2 H, NCH2). 4.2.7. [Hpy][NiL5(py)UCl3] (7) An NMR tube was charged with [Ni(H2L5)] (5.0 mg, 0.0125 mmol) and UCl4 (4.8 mg, 0.0125 mmol) in pyridine-d5 (0.4 mL). After 30 min at 20 C, the spectrum of the dark green solution containing a small quantity of green powder showed the formation of 7 together with another unidentified compound. Light green crystals of 7Æpy were deposited after heating at 80 C for 2 d. 1 H NMR (pyridine-d5, 23 C): 7.14 (6 H, Me); 12.28, 22.25 and 38.55 (3 · 2 H, aromatic H), 99.6 (4 H, NCH2). 4.2.8. Reaction of [Zn(H2L1)] and UCl4 An NMR tube was charged with [Zn(H2L1)] (5.0 mg, 0.0122 mmol) and UCl4 (4.6 mg, 0.0122 mmol) in pyridine-d5 (0.4 mL). After 30 min at 20 C, the spectrum of the orange-red solution showed the signals of two

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complexes denoted A and B, in relative proportions of 50:50. Complex B was the sole complex in solution after 24 h at 80 C. 1 H NMR (complex A): 35.07, 16.25, 10.80, 7.42, 6.54 and 0.15 (6 · 1 H, Ph of the diimino chain and CH@N), 17.89, 18.76, 21.97, 34.08, 36.06 and 89.77 (6 · 1 H, aromatic H). 1 H NMR (complex B): 28.23, 23.50, 15.96 and 10.80 (4 ·1 H, Ph of the diimino chain), 8.78 and 6.23 (2 · 1 H, CH@N), 12.30, 20.81, 25.70, 29.50, 35.53 and 40.62 (6 · 1 H, aromatic H). 4.3. Crystallography The data were collected at 100(2) K on a Nonius KappaCCD area detector diffractometer [23] using graphite˚ ). The monochromated Mo Ka radiation (k 0.71073 A crystals were introduced in glass capillaries with a protecting ‘‘Paratone-N’’ oil (Hampton Research) coating. The unit cell parameters were determined from 10 frames, then refined on all data. A 180 u-range was scanned with 2 steps during data collection, with a crystal-to-detector distance fixed to 28 or 30 mm. The data were processed with HKL2000 and DELABS [24]. The structures were solved by direct methods with SHELXS-97 and subsequent Fourierdifference synthesis and refined by full-matrix least-squares on F2 with SHELXL-97 [25]. Absorption effects were corrected empirically with the program HKL2000 DELABS in PLATON [26]. All non-hydrogen atoms were refined with anisotropic displacement parameters, unless specified below. The carbon-bound hydrogen atoms were introduced at calculated positions in all compounds (except for some disordered parts). All hydrogen atoms were treated as riding atoms with an isotropic displacement parameter equal to 1.2 (NH, CH, CH2) or 1.5 (CH3) times that of the parent atom. Specific details are as follows: Compound 1Æ2py. Two of the metal-bound pyridine molecules are disordered over two sites, sharing only atom N(4) in the first molecule, and N(5) and the para carbon atom in the second. The disordered components were affected with occupancy factors constrained to sum to unity; these factors appeared to be identical (and were then constrained to be so) for the components of the two molecules which are nearly parallel to one another. The disordered carbon atoms were refined isotropically, with some restraints on bond lengths and displacement parameters. Compound 2Æ2py. The space group P21/c used for the seemingly isomorphous compound 1Æ2py would be correct for most of the structure, in particular for the metal atoms, but it does not permit a good refinement of some parts of the structure such as the pyridine molecules, even with the use of restraints. Moreover, it can be ruled out with reasonable confidence on the basis of systematic extinctions, in spite of the low crystal quality. The solution adopted corresponds to the chiral space group P21 with two independent molecules in the asymmetric unit, which constitute

an enantiomorph pair. The case of non-centrosymmetric racemates was investigated in detail, but that of the even more surprising racemates crystallizing in chiral space groups (i.e. containing only proper symmetry elements) seems to be illustrated by only 17 organic structures in the CSD [27]. In the present case, the presence of a pseudo-inversion centre is found with an 83% fit only by the program ADDSYM [26] and the passage from a centrosymmetric to a chiral space group could be due to the different positions of the coordinated pyridine molecules in the two complexes. Restraints on displacement parameters have been applied for some badly behaving atoms, particularly in the solvent molecules. Crystals of the compound [Hpy][CuL2(py)UCl3] were also obtained from the same preparation, but it was only possible to get a rough model of the structure due to the lack of crystals of sufficient quality. Compound 3Æ1.25py. Three pyridine molecules are disordered, one around a symmetry center and the others over two positions which have been refined with occupancy parameters constrained to sum to unity. Several locations for the pyridinium proton (which has not been found) are thus possible. Three pyridine molecules have been refined as idealized hexagons. The disordered carbon atoms have been refined isotropically and restraints have been applied for some badly behaving atoms in the pyridine molecules. Several short contacts indicate that some of the disordered pyridine positions cannot be occupied simultaneously with their equivalent through the symmetry centre. Compound 4. The pyridinium hydrogen atom has been found on a Fourier-difference map. Compounds 5Æpy and 7Æpy. The pyridinium hydrogen atom was not found in either of these two isomorphous compounds. Restraints on displacement parameters have been applied for five atoms of the pyridine molecules in 7. The absolute structure was determined, with Flack parameter values of 0.007(7) and 0.003(6) for 5 and 7, respectively, [28]. Compound 6Æ1.5py. Two pyridine molecules are disordered around a symmetry centre, one of them being further disordered over two positions which have been refined with occupancy parameters of 0.5. Several locations for the pyridinium proton (which has not been found) are thus possible, with two short N  N contacts indicating possible hydrogen bonds. Some restraints have been applied for some atoms in the more badly resolved pyridine molecules. Crystal data and structure refinement parameters are given in Table 2. The molecular plots were drawn with SHELXTL [29]. 5. Supplementary material CCDC No. 614903–614909 contains the supplementary crystallographic data for 1–7. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk, or from the Cambridge Crystallographic Data Centre, 12 Union

Table 2 Crystal data and structure refinement details 2Æ2py

3Æ1.25py

4

5Æpy

6Æ1.5py

7Æpy

C45H37Cl2N7O4CuU 1112.29 monoclinic P21/c 15.6919(7) 23.2164(11) 11.4594(3) 90 93.029(3) 90 4168.9(3) 4 1.772 4.571 2172 28 239 7418 5801

C45H43Cl2N7O4CuU 1118.33 monoclinic P21 11.4498(6) 23.8206(13) 15.7660(5) 90 92.372(3) 90 4296.4(4) 4 1.729 4.436 2196 28 427 14 815 12 293

C37.25H31.25Cl3N5.25O4CuU 1024.35 triclinic P 1 12.9433(5) 17.1945(13) 18.3548(12) 68.133(3) 74.384(4) 84.406(4) 3651.1(4) 4 1.864 5.280 1982 25 288 12 825 8478

C27H25Cl3N4O4CuU 877.43 orthorhombic Pbca 9.8277(4) 16.4947(4) 35.0982(15) 90 90 90 5689.6(4) 8 2.049 6.756 3352 33 332 5341 3911

C34H34Cl3N5O4CuU 984.58 orthorhombic Pna21 11.7091(4) 18.3821(9) 16.6790(8) 90 90 90 3590.0(3) 4 1.822 5.365 1908 23 890 6738 5118

C41H35Cl3N6O4NiU 1078.84 triclinic P 1 12.8890(10) 17.2459(16) 18.6269(15) 88.815(4) 73.460(5) 86.681(5) 3962.4(6) 4 1.808 4.810 2104 27 203 13 899 9853

C34H34Cl3N5O4NiU 979.75 orthorhombic Pna21 11.7070(5) 18.4073(8) 16.7945(8) 90 90 90 3619.1(3) 4 1.798 5.255 1904 23 608 6864 5909

0.083 531 0.039 0.086 1.005 1.10 0.94

0.073 1082 0.051 0.108 1.008 1.17 0.84

0.081 883 0.057 0.138 1.015 1.34 1.42

0.096 361 0.034 0.063 0.997 0.77 0.56

0.105 435 0.042 0.077 1.007 0.63 0.63

0.068 1027 0.051 0.112 1.011 1.25 1.50

0.071 435 0.034 0.070 1.044 0.92 0.75

L. Salmon et al. / Polyhedron 26 (2007) 645–652

Chemical formula M (g mol1) Crystal system Space group ˚) a (A ˚) b (A ˚) c (A a () b () c () ˚ 3) V (A Z Dcalc (g cm3) l (Mo Ka) (mm1) F (0 0 0) Total reflections Independent reflections Observed reflections [I > 2r(I)] Rint Parameters R1 (observed data) wR2 (all data) S ˚ 3) Dqmin (e A ˚ 3) Dqmax (e A

1Æ2py

651

652

L. Salmon et al. / Polyhedron 26 (2007) 645–652

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