Synthesis of Tris(2,2'-bipyridine)ruthenium(II) Tetrafluoroborate

The procedure was modified by Jonathan Breitzer and George Lisensky from John A. Broomhead and Charles G. Young, Inorg. Syn. 28, 338-340 (1990). The microwave procedure is from Chem. Letters (Japan) 23 (1994) 2443-2446 or J. Electroanal. Chem. 527 (2002) 33-40.

Clicking a thumbnail on this web page (http://chemistry.beloit.edu/edetc/nanolab/Rubipy/index.html) shows a movie of that step.

Procedure

Wear eye protection

Drying RuCl₃ (enough for 35 preparations)

Grind about 3 grams of commercial RuCl₃·3H₂O in a mortar and pestle and dry in a 100°C oven for a few hours. The color will change from dark black to a dark brown.

Preparation of the Ru(II) complex

Option I: Dissolve 0.083 g (0.40 mmol) RuCl₃·3H₂O in 8 mL of water in a 30-mL beaker equipped with a stirbar. Add 0.188 g (1.204 mmol) 2,2’-dipyridyl and 0.44 mL of 6M NaH₂PO₂. Cover the beaker with a watch glass and reflux for 30 minutes. Add water if necessary to maintain the volume.
Option II: Reflux a suspension of 0.083 g (0.40 mmol) RuCl₃·3H₂O, 0.188 g (1.204 mmol) 2,2’-dipyridyl and 10 mL 1,2-ethanediol (also known as ethylene glycol) for 3 hours on a hotplate or for 5-15 minutes in a microwave oven with condenser. The diol serves as the reducing agent. This method avoids the use of hypophosphorous acid which is a DEA List I restricted chemical.

Add 0.333 g of NaBF₄ dissolved in 1.5 mL of water. Let the solution cool to about room temperature and then cool in ice; crystals should form.

Collect the product by suction filtration and...

rinse with cold ethanol. Air dry.

The [Ru(bpy)₃](BF₄)₂ can be used to prepare an organic light emitting diode.

Materials

• Ruthenium(III) chloride trihydrate (Aldrich 20,622-9)
• 2,2’-Dipyridyl (Aldrich D21,630-5)
• Sodium tetrafluoroborate (Aldrich 20,221-5)
Option I:
• Hypophosphorous acid, 50 wt % in water (Aldrich 21,490-6)
• Sodium hydroxide
Option II:
• 1,2-ethanediol
• Ethanol
• Drying oven
• pH test paper
• Mortar and pestle, small beaker, watch glass, suction flask, Hirsh funnel

Preparation of NaH₂PO₂ from H₃PO₂ (enough for 35 preparations)

Hypophosphorous acid is monoprotic (two of the hydrogens are attached directly to phosphorus) with a pKa of 1.1. Use caution when handling. Add 10 mL of 50 % H₃PO₂ into a beaker containing 6 mL of water and a stirbar.

Slowly add pellets of NaOH until the pH is about 6-8. This will require about 3.9 g of NaOH. The final solution is about 6 M in NaH₂PO₂.

---