Synthesis, crystal structure and Hirshfeld surface analysis of the tetrakis complex NaNdPyr4(i-PrOH)2·i-PrOH with a carbacylamidophosphate of the amide type

The crystal structure of neodymium tetrakis complex based on bis(N,N-tetramethylene)(trichloroacetyl)phosphoric acid triamide is reported and discussed.

The tetrakis complex of neodymium(III), tetrakis{�-N-[bis(pyrrolidin-1-yl)phosphoryl]acetamidato}bis(propan-2-ol)neodymiumsodium propan-2-ol monosolvate, [NaNd(C 10 H 16 Cl 3 N 3 O 2 ) 4 (C 3 H 8 O) 2 ]•C 3 H 8 O or NaNdPyr 4 (i-PrOH) 2 •i-PrOH, with the amide type CAPh ligand bis(N,N-tetramethylene)(trichloroacetyl)phosphoric acid triamide (HPyr), has been synthesized, crystallized and characterized by X-ray diffraction.The complex does not have the tetrakis-(CAPh)lanthanide anion, which is typical for ester-type CAPh-based coordination compounds.Instead, the NdO 8 polyhedron is formed by one oxygen atom of a 2-propanol molecule and seven oxygen atoms of CAPh ligands in the title compound.Three CAPh ligands are coordinated in a bidentate chelating manner to the Nd III ion and simultaneously binding the sodium cation by � 2 -bridging PO and CO groups while the fourth CAPh ligand is coordinated to the sodium cation in a bidentate chelating manner and, due to the � 2 -bridging function of the PO group, also binds the neodymium ion.
Among CAPh-based luminescent lanthanide compounds, tetrakis-complexes, (cation) [LnL 4 ], are of special interest because of the full saturation of the lanthanide coordination sphere with the formation of an LnO 8 polyhedron that shields the metal from the quenching effects of the solvent molecules.To date, CAPh-based lanthanide tetrakis-complexes are known only for the ester-type CAPhs (i.e.CAPhs with estertype substituents at the phosphorus atom) with no structures of tetrakis-complexes with amide-type CAPhs (i.e.CAPhs with amide-type substituents at the phosphorus atom) reported (Amirkhanov et al., 2014).Aiming to synthesize the tetrakis-complex with an amide-type CAPh [bis(N,N-tetramethylene)(trichloroacetyl)phosphoric acid triamide (HPyr)], the title compound of formula NaNdPyr 4 (i-PrOH) 2 •i-PrOH was obtained.Herein the synthesis and crystal structure, including characterization of the intermolecular contacts by Hirshfeld surface analysis, of NaNdPyr 4 (i-PrOH) 2 •i-PrOH are presented.

Structural commentary
The title compound crystallizes in the triclinic crystal system with two molecules in the unit cell.The molecular structure of the title compound is shown in Fig. 1.
The neodymium atom has coordination number eight; however, unlike typical CAPh-based tetrakis-complexes, the NdO 8 polyhedron is formed by seven oxygen atoms of CAPh ligands and one oxygen atom of a 2-propanol molecule.All of the four CAPh anions are involved in binding the neodymium ion, but each of them in a different mode.One of the CAPhs is coordinated to the neodymium cation in the typical bidentate chelating mode while two others are coordinated to the neodymium ion in the bidentate chelating mode and additionally, due to the � 2 -bridging function of the PO or CO group, are coordinated to the sodium cation as well.The fourth CAPh ligand is coordinated to the sodium cation in a bidentate chelating manner and, due to � 2 -bridging function of the PO group, is coordinated to the neodymium ion as well.
The coordination polyhedron of Nd III can be interpreted with the SHAPE2.1 program (Llunell et al., 2013) as a square antiprism (D 4d ) (Table 1).The sodium cation polyhedron, NaO 5 Cl, can be interpreted as a trigonal prism (D 3h ).The coordination environment of the sodium cation consists of five oxygen atoms and one chlorine atom.The two oxygen atoms are from CAPh ligands coordinated to sodium in a bidentate chelating mode, one more oxygen is from the � 2 -bridging PO group of the other CAPh, the chlorine atom and one more oxygen atom are from a bridging CAPh in which the CO group has the � 2-bridging function, and the fifth oxygen is from a 2-propanol molecule.
Selected bonds lengths for the title compound are given in Table 2.The Nd-O(P) bonds are shorter than the Nd-O(C) bonds.Among the Nd-O(P) bonds, the longest is that for the � 2 -bridging oxygen atom (Nd1-O3).Among the Nd-O(C) bonds, the longest is also that for the � 2 -bridging oxygen atom

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.All the hydrogen atoms and disordered chlorine atoms are omitted for clarity.

Table 1
Continuous shape measures values for Nd1 and Na1 in the title compound.
In the title compound, an intramolecular hydrogen bond is observed between the hydrogen atom H10 of the 2-propanol molecule coordinated to the sodium cation and the N6 nitrogen atom of the pyrrolidine substituent of the CAPh ligand (Table 3).The participation of the N6 atom as a proton acceptor in hydrogen bonding results in its pyramidalization (the sum of bond angles centered at the N6 atom is 340 � ).Another hydrogen bond exists between the hydrogen atom H11 of the solvate 2-propanol molecule and the N10 nitrogen atom of the chelating fragment of the CAPh ligand, coordinated to the sodium cation in the bidentate chelating mode (Table 3).Additionally to the hydrogen bonds, an intramolecular contact C49-H49A� � �Cl11 contact is observed (Table 3).

Supramolecular features
Numerous Cl� � �Cl, Cl� � �H and H� � �H intermolecular contacts are observed in the crystal of the title compound.The CCl 3 and pyrrolidine substituents of the CAPh ligand as well as the 2-propanol molecules participate in these contacts.The main Cl� � �Cl and Cl� � �H intermolecular interactions are given in Table 4.The Cl8� � �Cl6B interactions, at 3.04 A ˚, and Cl2� � �Cl6A interactions, at 3.42 A ˚, are less than the sum of the chlorine atoms van der Waals radii (3.5 A ˚) and are in the middle of the range (2.75-4.0A ˚) reported for Cl� � �Cl interactions (Capdevila-Cortada et al., 2016).The [� 1 -� 2 ] value equals 3.4 � and 39.3 � for the Cl8� � �Cl6B and Cl2� � �Cl6A interactions, respectively.Thus the first interaction can be assigned as Type I and the latter as Type II.Among the Cl� � �H contacts, the closest are Cl5B-H4A interactions (2.52 A ˚).

Hirshfeld surface analysis and fingerprint plots
The intermolecular interactions in the crystal structure of the title compound were visualized with a Hirshfeld surface analysis (Fig. 2) and the corresponding two-dimensional fingerprint plots (Spackman et al., 2009) using the Crystal-Explorer17 program (Turner et al., 2017).The strongest contacts, which are visualized on the Hirshfeld surface as darkred spots, correspond to the Cl� � �Cl interactions.The lighter red spots correspond to H� � �Cl/Cl� � �H and H� � �H contacts.The majority of the intermolecular interactions of the title compound are weak, which results in the blue colour of the Hirshfeld surface.According to the fingerprint plots, the H� � �H contacts make the largest contribution to the Hirshfeld surface (58.2%) with the shortest at d i + d e = 2.3 A ˚.The second largest contribution (37.4%) belongs to H� � �Cl/Cl� � �H contacts with the shortest at d i + d e = 2.5 A ˚.The Cl� � �Cl interactions are not numerous and contribute only 4.0% to the surface with the shortest at d i + d e = 3.0 A ˚.The H� � �O/O� � �H interactions make a 0.4% contribution to the Hirshfeld surface  x, y, z and represent hydrogen bonds to the carbonyl group oxygen atom O8 from the hydrogen atoms of the 2-propanol molecules.

Database survey
A search of the Cambridge Structural Database (CSD, Version 5.44, updated to June 2023; Groom et al., 2016) found 23 structures where a metal is coordinated by four CAPh ligands.The five tetrakis-complexes crystallize with two molecules in the unit cell.Three of the complexes are binuclear, containing bis-carbacylamidophosphate ligands.There are two complexes of La III , five of Nd III , one of Sm III , six of Eu III , three of Gd III , two of Tb III , one of Dy III one of Er III , and two of Yb III .Most often the coordination polyhedra of the central ions in the tetrakis-complexes are distorted square antiprisms (D 4d ).Six cases of triangular dodecahedral (D 2d ) Ln III ion coordination polyhedra have been reported for CAPh-based tetrakis-complexes.In the neodymium compounds, the central ions have coordination polyhedra in the form of distorted square antiprisms (D 4d ) and the Nd-O bonds lengths are in the range 2.303-2.516A ˚ (Kariaka et al., 2016(Kariaka et al., , 2022;;Pham et al., 2020b;Horniichuk et al., 2021).Eleven of the reported CAPh-based tetrakis-complexes of lanthanides contain a sodium cation as the counter-ion.All these sodium-containing complexes contain solvent molecules in their lattices, while the other twelve known tetrakis-complexes of lanthanides are solvent free.The sodium cations are six-or seven-coordinated in these complexes, being bonded to solvents, chelating core substituents of the CAPh ligands, and by bridging CO and PO groups of the chelating CAPh ligands.

Synthesis and crystallization
To obtain the complex NaNdPyr 4 (i-PrOH) 2 •i-PrOH, 0.1 mmol (0.03587 mg) of NdCl 3 •6H 2 O was dissolved in 2-propanol in the presence of the dehydrating agent HC(OC 2 H 5 ) 3 (0.6 mmol, 0.1 ml) by boiling this mixture for several minutes.This solution was added to a solution of NaPyr (0.4 mmol, 0.14826 g) in acetone.The resulting mixture was boiled for a minute then cooled to room temperature and left to stand tightly corked for a day for precipitation of NaCl.The clear solution was decanted and left to stand for slow evaporation of the solvent.In a few days, crystals of the target complex appeared.The crystals were filtered off, washed with cold isopropanol and dried in air.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 5.The C-bound H atoms were placed in calculated positions and refined using the riding model with xU eq (C, O), where x = 1.5 for hydroxyl groups and 1.2 for all other H atoms.
The structure exhibits disorder of the Cl atoms of one CCl 3 substituent.All Cl-C bond distances were restrained to be similar to each other (within a standard deviation of 0.002 A ˚) and with a target value of 1.76 A ˚.The U ij values of the disordered chlorine atoms were restrained to be similar to each other (within a standard deviation of 0.02 A ˚2).The disorder ratio was refined and is 0.757 (3):0.243(3).
One of the coordinated isopropyl groups is disordered over two positions.The C-O and C-C bond distances of the two components were restrained to be equal with an effective standard deviation 0.005 A ˚and the U ij values of the disordered C atoms were restrained to be similar to each other (within a standard deviation of 0.02 A ˚2).The disorder ratio was refined and is 0.529 (13):0.471(13).The Hirshfeld surface mapped over d norm and two-dimensional fingerprint plots for the H� � �H (58.2%),H� � �Cl/Cl� � �H (37.4%),Cl� � �Cl (4.0%) and H� � �O/O� � �H (0.4%) interactions of the title compound.

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.

Table 4
Intermolecular Cl� � �Cl and Cl� � �H interactions in the title compound (A ˚).

Table 5
Experimental details.