Synthesis, spectroscopic and structural elucidation of discrete, one dimensional and two dimensional coordination compounds of 1,3,5-triaza-7-phosphaadamantane, N-methyl-1,3,5-triaza-7-phosphaadamantane and silver(I).

The two binding modes of the trifluoroacetate groups also resulted in the formation of alternating segments exhibiting Ag…Ag interactions and non-Ag…Ag interactions along the helix-like polymer. All hydrogen atoms are omitted for clarity and ellipsoids are drawn at the 50% probability level. 59 Figure 28: Representation of the O-H…N intermolecular hydrogen bond (shown as dashed . green bonds) between the tri-coordinated silver-PTA complex and 4-nitrophenol molecules in DCC3.

60 Figure 29: Representation of the intermolecular O-H…O hydrogen bond (shown as dashed green bonds) between the 4-nitrophenol molecules in DCC3. The methylene hydrogens that do not exhibit intermolecular hydrogen bonding have been omitted for clarity. 79 Figure 52: Water molecules form rings via O-H…O hydrogen bonds (shown as dashed green bonds) in CN1.

Introduction
Aims of the project
Literature review

Factors that influence the topology of coordination compounds
Silver(I) coordination compounds containing 1,3,5-triaza-7-phosphaadamante
N-alkylated PTA compounds
Synthesis of coordination compounds
Characterization of silver(I)-PTA coordination compounds
Applications of PTA based silver(I) coordination compounds

References

To investigate the crystal structures of the silver(I)-based coordination compounds and investigate their thermal properties. The choice of the metal salt precursor used also affects the structure of coordination polymers. The reaction of the pseudopeptic ligand with manganese acetate and zinc acetate (as shown in Figure 2 as route (a) and (b) respectively) led to the formation of a manganese-based 3D coordination network and a zinc-based 1D coordination polymer.[35].

Some examples of the nitrogen-containing phosphine ligands are 3,6-bis(diphenylphosphino)Pyridazine (DPPPx), 2,6-bis(diphenylphosphino)pyridine (DPPPy), and 1,3,5-triaza-7-phosphadamantane (PTA). are shown in figure. Lis and colleagues reported this combination of P,N coordination of PTA with the bridging ability of the supporting terephthalate ligand to form 2D coordination networks (Figure 8a). Three-dimensional silver(I)-PTA coordination networks are constructed by combining the P-,N-,N' coordination mode of PTA (results in growth of a polymer in two dimensions) with the bridging ability of the auxiliary ligand.

One of the PTA derivatives we are interested in is N-methyl-1,3,5-triaza-7-phosphadamantane (PTAMe) as shown in Figure 10. Thus, one of the objectives of this work is to investigate the silver (I) compounds containing alkylated PTA derivatives.

Table 1: Possible coordination numbers and geometries of silver(I) coordinaiton compounds Coordination number Coordination geometry

Experimental

Materials and method
Experimental procedure

Synthesis of PTA
Synthesis of PTAMeI
Synthesis of [Ag(PTA) 3 (CN)]2H 2 O (DCC 1 )
Synthesis of [Ag(PTA) 2 (PTAH) 2 ](2CO 3 ) (DCC 2 )
Synthesis of [Ag(PTA) 3 ][4-NP] 10 (DCC 3 ) and [Ag 2 (PTA) 2 (μ 1 -
Synthesis of [Ag(PTA)(NO 3 )] n (CP 1 ) and [Ag(PTA)(H 2 O)] n (NO 3 ) n (CN 1 )
Synthesis of [Ag(PTA) 2 (µ-O 2 CCH 3 )] n 2H 2 O (CP 2 )
Synthesis of [Ag(PTA) 2 (µ-O 2 CCF 3 )] n (CP 3 )
Synthesis of [Ag(PTA)(O)] n (ClO 4 ) (CP 4 ) and [Ag(PTA) 2 (H 2 O)] n (ClO 4 ) (CP 5 ) 27
Synthesis of Ag(PTA)(O 3 SCH 3 ) (CN 3 )
Synthesis of Ag(PTA)(BF 4 ) (CN 4 )
Synthesis of [Ag(PTAMe)(CH 3 OH)(ClO 4 )] n ClO 4 (m-CP 1 )
Synthesis of Ag(PTAMe)(NO 3 ) (m-CP 2 )
Synthesis of Ag(PTAMe)(O 2 CCF 3 ) (m-CP 3 )
Synthesis of Ag(PTAMe)(O 3 SCF 3 ) (m-CP 4 )

X-ray crystal structure determinations
References

The black solid was filtered under gravity and the clear filtrate was kept in the dark for slow evaporation of the solvent. A fluffy white precipitate immediately formed and the contents of the flask were sonicated over a water bath for one hour at room temperature. The white precipitate was dissolved by the dropwise addition of 25% aqueous ammonia solution and the resulting mixture was filtered under gravity to give a clear filtrate, which was kept in the dark for its slow evaporation.

Further evaporation of the solvent led to the production of x-ray quality crystals of [Ag(PTA)2(H2O)]n(NO3)n (CN1) after an additional soak. The mixture was placed in an ultrasonic water bath for one hour and the white precipitate was dissolved by the dropwise addition of 25% ammonia solution. The solution was sonicated over a water bath for a further 30 min and then filtered under gravity to give a clear filtrate which was kept in the dark for slow evaporation of the solvent.

The solution was sonicated over a water bath for a further 30 minutes and then filtered under gravity to give a clear filtrate which was kept in the dark for slow evaporation of the solvent. Further evaporation of the solvent led to the production of colorless, block-like X-ray quality crystals of [Ag(μ-PTA)(PTA)(H2O)]n(ClO4) (CP5) after an additional week. A white fluffy precipitate formed immediately and the contents of the flask were placed in an ultrasonic water bath for one hour.

The white precipitate was dissolved by the dropwise addition of 25% aqueous ammonia solution and the resulting mixture was filtered under gravity to give a clear filtrate which was kept in a dark place under ambient conditions for slow evaporation of the solvent. In a clean 100 mL beaker, PTA (0.48 g; 3.0 mmol) was dissolved in 20 mL methanol and added to the conical flask containing the silver(I) solution. A white fluffy precipitate formed immediately and the contents of the flask were placed in an ultrasonic water bath for one hour.

The white precipitate was dissolved by the dropwise addition of 25% aqueous ammonia solution and the resulting mixture was filtered under gravity to give a clear filtrate which was kept in the dark for slow evaporation of the solvent. The mixture was vortexed and filtered under gravity to produce a clear colorless filtrate which was kept in the dark for slow evaporation of the solvent. Each of the three series of scans was collected at different starting angles and the APEX2 program series was used to index the reflections.[2] The data collection involves the use of omega scans of 0.5° width.

Table 2: Crystallographic data and structural refinement details for DCC 1-3 and CP 1

Results and discussion

Reactions of PTA with silver(I) salts

Spectroscopic studies of silver(I)-PTA coordination compounds
Solid state structural analysis of Ag-PTA coordination compounds

Reactions of PTAMeI with various silver(I) salts

Spectroscopic analysis of Ag-PTAMe coordination compounds
Crystal structure analysis of Ag-PTAMe coordination compounds

References

This suggests that the phosphorus atom in PTA is coordinated to Ag metal, as the 2JP-H value is comparable to the values published for Ag(I)-PTA compounds.[1] The N-CH2-N protons show spin type AB with JAB. The spectrum also shows one signal resonating at a much higher frequency of δ -77.9 ppm compared to that of free PTA and this is comparable to the signals of related silver(I)-PTA compounds in the literature.[1] The signal appears as a broad singlet with 107Ag-31P and 109Ag-31P spin-spin coupling, which is not observed in all cases due to the rapid ligand exchange phenomenon characteristic of silver monophosphine coordination compounds. [1a] Therefore, based on 31P NMR results, they confirmed the coordination of PTA through the phosphorus atom. In the temperature range from 213 to 272 °C, the decomposition of Ag-PTA complexes (associated with the loss of PTA) occurs as an exothermic event.

A discussion of the hydrogen bonding patterns observed in each of the structures is also included. The Ag-N bond distance histogram has a bimodal distribution as shown in Fig. 18(a) , with the shortest bond distance of 2.256 Å observed in the coordination compound shown in Fig. 19(a) . The histograms of Ag-P and Ag-O bond distances have a right-skewed distribution, as shown in Fig. 18(b) and (c).

Finally, a normal distribution with three extreme outliers is observed in the histogram of the Ag-O bond distances as depicted in Figure 20(c). The rest of the p-nitrophenol molecules with oxygen atoms O(21A), O(10), O(3) and O(30) exhibited O-H…O hydrogen bonds between the 4-nitrophenol molecules. Coordination to the Ag atom is via a P atom and a nitrogen atom of separate PTA molecules and two O atoms of the nitrate anion.

The Ag..Ag separation is 3.0810(2) Å and is shorter than the sum of the van der Waals radii for silver (3.44 Å).[7] The short Ag…Ag strain on the carboxylate anion leading to a slight tilt in the non-planar of the Ag-O-C-O-Ag units. Figure 38(a) and (b) show the asymmetric unit and the ORTEP diagram of the repeating unit of CP3 respectively while Table 20 lists important bond distances and angles. The coordination to the Ag atom is via a phosphorus atom and two nitrogen atoms from three separate PTA molecules, including an oxygen atom from the water group.

The second hydrogen atom of the water part is connected to the oxygen atom of the uncoordinated nitrate anion by hydrogen bonds O-H...O. This localizes the nitrate anions in the hexagonal cavities of the stacked 2D corrugated sheets, as shown in Fig. 53. The coordination to the Ag(1) atom occurs through the phosphorus atom and two nitrogen atoms of three separate parts of PTA, including the oxygen atom of the coordinated water part.

The asymmetric unit consists of the unit [Ag2(PTA)2(NO3)1.5(H2O)], an uncoordinated nitrate anion, a 4-nitrophenol molecule and a water molecule, making CN5 a salt complex as shown in Figure 57( a) shown. . This causes a decrease in the molecular symmetry of the PTA moiety compared to the parent compound. Figure 64(a) and (b) show the ORTEP diagram of the asymmetric unit and the repeating unit of m-CP1 while Table 33 lists important bond angles and distances.

The asymmetric unit consists of the unit [Ag(NO3)(CH3OH)(PTAMe)] and an uncoordinated nitrate anion, turning m-CP2 into a salt complex.

Figure 11: 1 H NMR spectrum of (a) free PTA in CDCl 3 , (b) free PTA in D 2 O and (c) CP 3 in D 2 O

Solution NMR studies of Ag-PTA and Ag-PTAMe coordination compounds
IR and ESI-MS studies of Ag-PTA and Ag-PTAMe coordination compounds
Thermal property studies of Ag-PTA and Ag-PTAMe coordination compounds
Solid state structural analysis of Ag-PTA and Ag-PTAMe coordination compounds
Recommendations and future work

This suggests that coordination via the nitrogen atom of PTAMe to the metallic silver(I) center is achieved in the silver-PTAMe coordination compounds. This suggests that the phosphorus atom of the PTAMe unit is coordinated to Ag metal as observed for Ag-PTA coordination compounds. Changing the anion appears to have no effect on the solution NMR results of the Ag-PTAme coordination compounds.

The IR spectra of all Ag-PTA and Ag-PTAMe coordination compounds exhibited related features with typical vibrations due to the anions and the main ligand; therefore, IR results provided evidence for the presence of the anion and the main ligand in the coordination compounds. ESI-MS results contained m/z peaks attributed to the product despite the fragmentation of the polymeric species and the formation of multiple charged ionic species with either solvent, sodium, or potassium adducts. Dihydrated coordination compounds (DCC1 and CP2) experience loss of water molecules at 78 °C and 70 °C, respectively.

Ag–PTA coordination compounds are thermally stable up to approximately 210 °C and beyond this threshold an exothermic event occurs that is attributed to the decomposition of the Ag–PTA complex and the loss of PTA. Similar TGA and DSC profiles were obtained for Ag-PTAMe coordination compounds although they decomposed in a lower temperature range (194–202 °C). Using SC-XRD helped investigate the influence of anions on the topology of molecular architectures with a detailed look at hydrogen bonding, weak intermolecular interactions and co-crystallization in silver(I)-PTA and silver(I)-PTAme complexes. .

The various general structures of Ag-PTA and Ag-PTAme are summarized in Table 39 from which general trends are observed. Ag-PTA and Ag-PTAme compounds containing carboxylate anions tended to result in polymeric structures with the carboxylate group having either μ1-O1 or μ2-O2 bonding modes, which resulted in the formation of ladder-like or helix-like 1D structures. The nitrate anion exhibited a wide variety of coordination modes leading to the formation of 1D linear coordination polymers and 2D sheet-like networks.

For Ag-PTA complexes, triflate and perchlorate anions showed very weak coordination abilities; therefore they are present in the outer coordination sphere.