Question

Synthesis of Bromonitrosylbis(triphenylphosphine)nickel(O), NiBr(NO)(PPh3)2

Put a wide-based pyrex dish on a stirrer-hotplate, and put a medium-large stirrer bar in the dish. (If appropriate pyrex dishes are not available, use a metal water bath.) Set up a 100 cm3 round-bottom flask with a reflux condenser in the dish, leaving enough room below the bottom of the flask for the stirrer bar in the dish. Fill the pyrex dish with water so that the water come about ½ way up the round-bottom flask. Dissolve finely powdered, dry sodium nitrite (5.3 g), dibromobis(triphenylphosphine)nickel(II) (3.3 g), and triphenylphosphine (1.2 g) in tetrahydrofuran (50 cm3) and put into the flask. Put a medium-sized magnetic stirrer bar into the flask., heat the flask with stirring and bring to reflux. The water in the water bath will need to be boiling. Stir the boiling mixture under gentle reflux for about 35 minutes. NB Don’t allow the water bath to boil dry – top up at intervals with small amounts of water.

After refluxing for 35 minutes, allow the solution to cool and filter into a 100 cm3 conical flask. Return the filtrate to the round-bottom flask. Reduce the volume to about 15 cm3 using a rotary evaporator. Warm the solution in its round-bottom flask over a warm water bath. Add petroleum ether (17 cm3, b.p. 40-60 C) slowly to the warm solution and allow it to cool slowly to room temperature. Collect the purple product in a Buchner funnel and suck it dry. Record your yield.

Question: What is the therical mass and the percentage yield if the actual mass is 2.3480 g ?

Answer 1

In the complex Ni(Br)(NO)(PPh₃)₂ formation reaction, the stoichiometric ratios are 1:1:

So, If we calculate the number of moles of each of the reagents, the smallest of them corresponds to the limiting reagent:

For Ni(Br)₂(PPh₃)₂ (MW=743.07g/mol)

For NaNO₂ (MW=69g/mol)

For PPh₃ (MW=262.69g/mol)

The reagent  Ni(Br)₂(PPh₃)₂ is the  limiting reagent, so the the theoretical grams of the complex Ni(Br)(NO)(PPh₃)₂ (MW=693.18g/mol) are:

Thus the percentage of yield is: