Nitrosyl Complexes: Preparation of [NiBr(NO)(PPh3)2 ]

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Nitrosyl Complexes: Preparation of [NiBr(NO)(PPh3)2 ]                            

Monday  12th January 2009

Introduction and Aims

The aims of this experiment are as followed:

  1.  To distinguish between the linear and bent coordination and draw possible metal to NO coordination modes.
  2. To form the product [NiBr (NO) (PPh3)2]    and provide a balanced equation for the product.    
  3. To record the melting point, weight and infra-red spectrum of the product. Assign the band in the infra-red that is due to NO group. Calculate the percentage yield
  4. To assign the oxidation state  to the metal in the nitroxide complex [NiBr(NO)(PPh3)2]       
  5. To suggest a method for distinguish between possible square planar and tetrahedral coordination of [NiBr2(PPh3)2]                                                                

 This experiment provides a method for the generation of nitrosyl complexes without the use of free nitric oxide. The NO group in complexes can be classified in two groups. The NO can posses a linear coordination that can be considered as a 3 electron donor .With the nitrogen atom sp hybridized. The NO group can posses bent coordination and can be considered as a 1 electron donor. With the nitrogen atom sp 2 hybridized. The use of infra-red spectroscopy can clearly distinguish between the coordination’s.  

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Experimental details

Placed in a round bottom flask (100ml) powdered sodium nitrite (4g), [NiBr2(PPh3)2] (2.5g) ,triphenylphosphine(0.9g) and tetrahydrofuran (25cm3) .Mixture was refluxed for 35 minutes, then cooled and filtered. Volume was reduce to 12cm3 by use of rotary evaporation , petroleum sprit (60-80°C)(12cm3) slowly added to warm solution.  The formation of a purple solid was a result of the introduction of petroleum sprit. The purple product was filtered and dried .            

Discussion

The reaction condition required for the  experiment was reflex for 35mintues and use of solvents tetrahydrofuran and petroleum sprit.

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