Tropilium fluoborate

Tropilium iodide Tropilium fluoborate Triphenylmethane Cycloheptatriene Triphenylmethyl fluoborate... 

In a 25-mL Erlenmeyer flask place 8.75 mL of acetic anhydride, cool the tube, and add 0.44 g of fluoboric acid. Add 1 g of triphenylmethanol with thorough stirring. Warm the mixture to give a homogeneous dark solution of the triphenylmethyl fluoborate, then add 0.4 g of cycloheptatriene. The color of the trityl cation should fade during this reaction and the tropilium fluoborate begin to precipitate. Add 10 mL of anhydrous ether to the reaction tube, stir the contents well while cooling on ice, and collect the product by filtration on the Hirsch funnel. Wash the product with 10 mL of dry ether and then dry the product between sheets of filter paper. 

To determine the nmr spectrum of the tropilium fluoborate collected on the Hirsch funnel, dissolve about 50 mg of the product in 0.3 mL of deuterated dimethyl sulfoxide that contains 1% tetramethylsilane as a... 

The tropilium fluoborate can be converted to tropilium iodide by dissolving the borate in the minimum amount of hot, but not boiling, water (a few drops) and adding to this solution 1.25 mL of a saturated solution of sodium iodide. Cool the mixture in ice, remove the solvent with a pipette, and wash the crystals with 2.5 mL of ice-cold methanol. Scrape most of the crystals onto a piece of filter paper and allow them to dry before determining the weight. To the crystalline residue in the test tube add a few drops of water warm the tube, if necessary, to dissolve the tropilium iodide and then add a drop of 2% aqueous silver nitrate solution and note the result. 

The fluoborate group can be displaced by the iodide ion to prepare tropilium iodide. You can see that the iodide ion is ionic by watching the reaction of the aqueous solution of this ion with silver ion. 

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