Synthesis and Characterization of Pyridino ( 1 , 4-Η-cyclohexa-1 , 3-diene ) Derivatives of Iron Tricarbonyl Complexes

In this synthesis, we have been able to show that, the addition of xsubstituted pyridines, (X = H, 2Me, 3Me 4Me, 4-NH2 and 4-N(CH3)2 to the dienyl ring of the organometallic cation, [(Fe(CO)3 (1-5η-2-Me0C6H6)]BF4 and [(Fe(CO)3 (1-5η-C6H7)]BF4 gives ionic substituted diene products, (X C5H4-C6H6Y (Fe(CO)3] BF4,Y=H or 2-MeO. The reaction takes place at ordinary room temperature. The resulting products were isolated and characterized.

In this paper, we present the syntheses and characterizations of these novel pyridine-(1, 4η -cyclohexa-1, 3-diene) derivatives of iron tricarbonyl.The reactions between pyridine and selected pyridines with the organometallic complex of the type [Fe (CO) 3 (1-5η-C 6 H 6 Y]BF 4 (Y=H or 2-MeO), at room temperature is represented as shown in Scheme 1.

Experimental
The organometallic compound [(Fe(CO) 3 (1-5η -C 6 H 6 Y)]BF 4 was synthesized and purified by published procedure 1 and was crystallized from hot water.The pyridine/ pyridines derivatives were purchased (BDH or Aldrich) in the purest grade available.The liquid samples were freshly distilled before use.Acetonitrile (Solvent) was distilled in bulk and magnesium sulphate added to remove traces of water before use.0.15 mmol of the organometallic complex was dissolved in 5 cm 3 of acetonitrile, 1.5 mmol of the nucleophiles, each dissolved in 5 cm 3 of acetonitrile and all dissolutions were done at room temperature.The two solutions were mixed in 50 mL beaker while stirring continuously.The mixtures were allowed to stand at room temperature for 10 minutes.

Results and Discussion
The reaction of complex with pyridine/pyridine derivatives (X=H,2Me, 3-Me, 4-Me 4-NH 2 and 4-N(CH 3 ) 2 showed intense sharp ν(co) bands (in acetonitrile) at 2055 and 1980 cm -1 as well as a broad band (nujol mull) due to the tetrafluoroborate anion at ca 1060 cm -1 in their IR spectra.Product 1 was isolated as a pale yellow crystalline, air-stable solid, fully characterized by IR, 1 H NMR and microanalytical measurements.Its 1 H NMR spectrum is shown in Figure 2.This clearly demonstrates that, the products are tricarbonyl (1,4,-η-5 exo-N-pyridino 2-methoxycyclohexa-1,3-diene iron tetrafluoroborate.The features shown in this spectrum (Figures 1 and 2) together with νco, IR bands at 2055 and 1980 cm -1 in Figure 3 have been reported as characteristic features 23,24 .

Conclusion
We have succeeded in synthesizing twelve new organometallics resulting from the nucleophilic addition of pyridine/pyridine derivatives to the organometallic compound [(Fe(CO) 3 (1,5,η -2-MeoC 6 H 6 )]BF 4 and [(Fe(CO) 3 (1,5-η-C 6 H 7 )]BF 4 in acetonitrile.This work has clearly demonstrated the application of organometallic to the synthesis of novel coordinated organics and the ease with which these products could be prepared.
The synthetic utility of these complexes cannot be over-emphasized here, particularly when it is born in mind that careful treatment of the products with oxidizing agents such as Trimethylamine oxide in benzene leads to the cleavage of the Iron tricarbonyl, thus affording a novel 1,3-diene substituted organics.