Study of complexes of platinum group metals containing nitrogen bases derived from pyridine aldehydes: Interesting molecular structures with unpredicted bonding modes of the ligands

TLDR: A series of mono-cationic dinuclear half sandwich ruthenium, rhodium and iridium metal complexes have been synthesized using ((pyridin-2-yl)methylimino)nicotinamide (L1) and ((picolinamido)phenyl)picolinamide(L2) ligands as mentioned in this paper.

About: This article is published in Journal of Organometallic Chemistry.The article was published on 2011-05-15 and is currently open access. It has received 25 citations till now. The article focuses on the topics: Ruthenium & Hexafluorophosphate.

Figures

Fig. 1. Molecular structure of [(h6-C6H6)2Ru2(L2)(m-Cl)]þ (6) at 50% probability level. Hyd lengths (Å) and angles ( ): Ru(1)eRu(2) 4.0679(6), Ru(1)eCl(1) 2.4545(13), Ru(1)eN(1 2.4489(12); N(1)eRu(1)eN(2) 77.59(16), N(1)eRu(1)eCl(1) 83.14(11), N(2)eRu(1)eCl(1 83.17(11), Ru(1)eCl(1)eRu(2) 112.12(4).

Fig. 4. Hydrogen-bonded network observed in [4]PF6$H2O.

Fig. 5. Hydrogen-bonded network observed in [9]PF6$H2O.

Fig. 2. Molecular structure of [(h5-C5Me5)2Rh2(L1)Cl3]þ (4) at 50% probability level. Hydrogen atoms and hexafluorophosphate anions have been omitted for clarity. Selected bond lengths (Å) and angles ( ): Rh(1)eRh(2) 7.823(3), Rh(1)eCl(4) 2.389(2), Rh(1)eN(1) 2.089(6), Rh(1)eN(2) 2.139(6), Rh(2)eN(4) 2.152(6), Rh(2)eCl(1) 2.393(2), Rh(2)eCl(2) 2.428(2), N(2)eN(3) 1.406(8); N(1)eRh(1)eN(2) 75.8(2), N(1)eRh(1)eCl(4) 88.60(18), N(2)eRh(1)eCl(4) 88.57(16), N(4)eRh(2)eCl(1) 88.34(18), N(4)eRh(2)eCl(2) 85.88(17), Cl(1)eRh(2)eCl (2) 91.45(9).

Table 1 Crystallographic and structure refinement parameters for complexes [4](PF6)$H2O, [6](PF6) and [9](PF6)$H2O.

Frequently asked questions

Q1. What are the contributions in "Study of complexes of platinum group metals containing nitrogen bases derived from pyridine aldehydes: interesting molecular structures with unpredicted bonding modes of the ligands" ?

A series of mono-cationic dinuclear complexes using pyridi picolinamide ( L2 ) ligands have been synthesized using ( ( pyridi pyridyl-pyridazine ( L 2 ) ligands: [ ( h6-arene C5Me5 ) 2M2 ( m-L1 ) Cl3 ] þ ( M 1 Ω4 Rh, 4 p-PrC6H4Me, 7 ; C6Me6, 8 ), [ ( h-C5Me 6 ] isolated as their hexaflu 

Q2. What is the role of the wate molecule in the crystal packing?

It forms hydrogen bonds wit neighboring complexes, thus generating one-dimension hydrogen-bonded networks in the crystal, see Figs. 

Q3. What is the ligand peaks in the complexes 4 and 5?

In complexes 4 and 5, the ligand is coordinated in a bidentate fashion to the first metal atom while in a monodentate fashion to second metal atom with the nitrogen atoms of the ligand molecule. 

Q4. What is the role of the water molecule in the crystal packing?

the water molecule connects along the b axis dinuclear complexes, thus generating one-dimensional chains of 9 in the crystal. 

Q5. What is the molecular structure of PF6$H2O?

In the molecular structure of 4, interestingly, the first metal is bonded to two nitrogen atomswhereas the second metal center is coordinated to only one nitrogen atom with two terminal chloride ligands. 

Q6. What is the IR spectra of the free ligands?

The IR spectra of these complexes exhibit sharp bands due to chelated multidentate ligands between 1637 and 1437 cm 1 corresponding to the different stretching frequencies of C]O, C]C and C]N bondScheme 1. 

Q7. How many ligands are there in the complexes?

In addition to the ligand peaks, complexes 3 and 8 show a pair of singlets each between 2.18 and 2.02 ppm respectively corresponding to the eighteen protons of the hexamethlybenzene group of these complexes. 

Q8. What is the ligand peaks in the nPeF spectra?

The 1H NMR spectra of these complexes show ligand peaks a downfield shift in the position of signals associated with protons of ligands L1 and L2 compared to that of the uncoordinated ligands suggesting coordination of the nitrogen and oxygen atoms to the metal center in a monodentate and bidentate fashion. 

Q9. What are the common arene met complexes?

In recent years, the authors hav been carrying out reactions of arene ruthenium, rhodium and iridium dimers with a variety of nitrogen-based ligands [17e25] includin pyridyl-pyridazine and pyrazolyl-pyridazine ligands. 

Q10. What is the mode of coordination of the metals?

The decrease in the stretching frequencies and the presence of only one band shows that the metal has coordinated in only one fashion i.e., either NXN coordination or NXO coordination which has been finally confirmed by the single crystal X-ray structure analysis of 6 and found that the mode of coordination is through NXN and not NXO coordination. 

Q11. What is the role of arene met complexes in the oxidation of water?

Arene met complexes of these types of nitrogen-based ligands have the capacit to function as catalysts for the oxidation of water to dioxygen [26,27Herein, the authors describe the syntheses of interesting mono-cation dinuclear complexes of arenemetals havingN,O andN,N type dono ligands. 

Q12. Why do the ligands peaks in the complexes differ from the other two?

This mode of binding could be due to the bulky pentamethylcyclopentadienyl groups which do not allow the two metal centers to come closer to form chloride bridge as in the case of ruthenium dimers. 

Q13. What is the molecular structure of complex 6?

In the case of complexesomplexes 1(PF6)-3(PF6).n f le, - e l4, - ]. d , ].n s h ly tss e- - o e eScheme 2. Reaction scheme for the formation of complexes 6(PF6)-8(PF6).6, 7 and 8, the ligand L2 is coordinated to both the metals i a bidentate fashion through nitrogen atoms.