Two mixed-ligand lanthanide–hydrazone complexes: [Pr(NCS)3(pbh)2]·H2O and [Nd(NCS)(NO3)(pbh)2(H2O)]NO3·2.33H2O [pbh is N′-(pyridin-2-ylmethylidene)benzohydrazide, C13H11N3O]

[Pr(C13H11N3O)2(NCS)3]·H2O contains an irregular PrN7O2 coordination polyhedron, whereas [Nd(C13H11N3O)2(NCS)(NO3)(H2O)](NO3)·2.33H2O contains a distorted NdN5O5 bicapped square antiprism.


Structural commentary
Compound (I) is a new neutral mixed-ligand complex of Pr 3+ : selected geometrical data are given in Table 1. The praseodymium ion is coordinated by two N,N,O-tridentate (via the pyridine nitrogen atom, the azomethine nitrogen atom and the carbonyl oxygen atom) pbh ligands and three N-bonded thiocyanate anions (Fig. 1), to yield a PrO 2 N 7 coordination polyhedron for the metal ion (Fig. 2). Its geometry is irregular, The molecular structure of (I) showing 50% displacement ellipsoids and atom labelling.

Figure 2
Detail of (I) showing the irregular PrO 2 N 7 coordination polyhedron (contacts between the pentagon and triangle of coordinated atoms shown as green lines). Displacement ellipsoids are shown at the 50% probability level. Table 1 Selected bond lengths (Å ) for (I). C25 torsion angle of À11.3 (5) . The dihedral angle between the near-planar parts of the pbh ligands (central chain plus pyridine ring) is 54.08 (6) . The three thiocyanate ligands show normal geometrical parameters (mean S C bond length = 1.641 Å , mean C N bond length = 1.169 Å , mean S C N bond angle = 179.0 ): their Pr-N bond lengths are all shorter than the pbh Pr-N distances, which can be justified electrostatically if it is not a steric effect. The three Pr-N C bond angles [159.0 (3), 150.7 (3) and 150.6 (3) ] are all substantially less than 180 . A single water molecule of crystallization completes the structure of (I). Compound (II) is a new mixed-ligand cationic complex of Nd 3+ : selected geometrical data are given in Table 2. The neodymium ion is coordinated by two N,N,O-tridentate pbh ligands, an N-bonded thiocyanate anion, a bidentate nitrate anion and a water molecule (Fig. 3), to yield a 10-coordinate NdN 5 O 5 coordination polyhedron. The coordination geometry about the Nd 3+ ion (Fig. 4) at least approximates to a bicapped square antiprism (Kepert, 1982) with the square faces defined by O1/O4/N1/O9 (r.m.s. deviation = 0.157 Å ) and O2/O3/N4/N7 (r.m.s. deviation = 0.105 Å ) and the capping atoms represented by N2 and N5 [N2-Nd1-N5 = 168.03 (6) ]. The dihedral angle between the nominal squares defined in the previous sentence is 8.11 (8) and Nd1 is displaced from the afore-stated mean planes by À1.1431 (9) and 1.1762 (9) Å , respectively.
The first pbh ligand (containing C1) in (II) bonds to the metal ion from its atoms N1, N2 and O1. The two fivemembered chelate rings that result are both close to planar (for N1/C5/C6/N2/Nd1, the r.m.s. deviation = 0.011 Å and for N2/N3/C7/O1/Nd1, the r.m.s. deviation = 0.019 Å ). The dihedral angle between the N1/C1-C5 and C8-C13 aromatic rings is 21.71 (8) and the metal ion is displaced from the pyridine ring by À0.204 (4) Å . For the second (C14) pbh ligand, atoms N4, N5 and O2 bond to the metal ion: one of the resulting chelate rings is close to planar (N4/C18/C19/N5/Nd1: r.m.s. deviation = 0.022 Å ). The second (N5/N6/C20/O2/Nd1) is probably better described as a shallow envelope, with O2 displaced from the other atoms by À0.131 (3) Å . The dihedral angle of 9.52 (10) between N4/C14-C18 and C21-C26 indicates that the second ligand is less twisted than the first. The metal ion is displaced by À0.045 (4) Å from the pyridine ring. The dihedral angle between the near-planar parts of the pbh ligands (central chain + pyridine ring) is 37.75 (3) . The Nd-N-C bond angle of 149.40 (19) is very similar to two of the corresponding angles in (I). The crystal structure of (II) is completed by a non-coordinating nitrate anion (also ensuring charge balance) and three water molecules, one of which (O12) is partially occupied [refined occupancy = 0.328 (7)], although there are no close contacts that enforce this crystallographically.

Supramolecular features
In the crystal of (I), the components are linked by N-HÁ Á ÁOw, N-HÁ Á ÁS and Ow-HÁ Á ÁS (w = water) hydrogen bonds ( Table 3). The N-HÁ Á ÁS bond generates [001] chains of complexes and the hydrogen bonds to and from the water molecules generate a three-dimensional network. Aromatic stacking between the N7-pyridine and C24-phenyl rings is suggested by the centroid-centroid separations of 3.524 (2) The molecular structure of (II) showing 50% displacement ellipsoids and atom labelling.

Figure 4
Detail of (II) showing the distorted bicapped square-antiprismatic NdO 5 N 5 coordination polyhedron (contacts between the atoms forming the square antiprism indicated with tan lines). Displacement ellipsoids are shown at the 50% probability level. and 3.628 (2) Å between rings in nearby molecules in the crystal and a short C-HÁ Á ÁO contact (Table 3) also occurs.
In the crystal of (II), numerous hydrogen bonds occur (Table 4), to link the components into a three-dimensional network. Any aromaticstacking must be very weak, as the minimum ring-centroid separation in the crystal is 3.9800 (13) Å . is also known (Richardson et al., 1999). Based on this search, compound (I) appears to be a new structure type, whereas compound (II) is isostructural with its cerium analogue (refcode FEBDOG; Paschalidis & Gdaniec, 2004). Interestingly, both (II) and FEBDOG have almost the same occupancy factor for the partially occupied water molecule.

κN)neodymium(III) nitrate 2.33-hydrate
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.64 e Å −3 Δρ min = −0.50 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.