Sciencemadness Discussion Board

Issue forming Bis(triphenylphosphine)nickel chloride coordination complex

FireLion3 - 19-7-2014 at 19:59

This is the complex:
https://en.wikipedia.org/wiki/Bis%28triphenylphosphine%29nic...

I have both Triphenylphosphine (MP tested) and Nickel (II) Chloride (which is as green as green can be). Both Reagents are 99.95%+ purity

The dark blue complex should form by reacting these in an organic solvent. I used store bought 70% Isopropyl Alcohol as the solvent. Mixing the two reagents in the proper ratio, for 2+ hours, did not result in any significant color change in solution. The solution was still the same green color as it was prior to adding the triphenylphosphine. Afterwards I added a 2x excess of PPH3 to see if maybe too much Nickel Chloride were added, but stirring under these excess conditions did not result in any color change. The excess PPH3 was added to ensure there was no leftover Nickel II Chloride.

Is Isopropyl Alcohol not a suitable solvent for this? Alcohols are supposed to be just fine. I am going to try again after I pick up some acetone, but other than solvent, I don't know why this complex did not form readily.

I would have thought the water in the solution would be an issue, by keeping the NiCl2 in the aq. phase, and PPH3 in the organic phase, but the write-ups of this complex say that hydrated NiCl2 can be used - which contains water by default.

The other possibility is that the blue (or red) color doesn't show until the compound is crystalized? Or have I simply not given it enough time?

[Edited on 20-7-2014 by FireLion3]

Texium - 19-7-2014 at 20:05

Check and see if your local store sells 95% isopropanol. Mine sells both 70% and 95%. Maybe the more concentrated stuff would have a noticeable effect on the reaction.

FireLion3 - 19-7-2014 at 20:11

I didn't see that concentration there. I do know I can get some pretty high purity acetone at another store, which I might have better luck with.

I see here
http://www.ukessays.com/essays/chemistry/synthesis-of-nickel...

They used pure isopropanol and pure ethanol, though I am skeptical of their right up because it says they filtered the solid that precipitated. The NiCl2-PPH3 complex is soluble in organics so I am not sure how they got it to precipitate. I just read the Chloride complex is less soluble than the bromide complex... might have to look into getting some Nickel Bromide

[Edited on 20-7-2014 by FireLion3]

forgottenpassword - 20-7-2014 at 03:50

Same preparation given here: http://personal.strath.ac.uk/m.d.spicer/docs/Experiment3.doc

Dry your IPA with NaOH.

Perhaps nickel chloride doesn't dissolve in dry IPA. I'm not sure.

[Edited on 20-7-2014 by forgottenpassword]

blogfast25 - 20-7-2014 at 04:34

@FireLion3:

Try home distilled methylated spirits (the clear type), that should give you 95 % ethanol with some methanol substituting for ethanol (or distil gin a couple of times!)

Dissolve a molar ratio = 2 mix of NiCl<sub>2</sub> hydrate and P(Ph)<sub>3</sub> in that solvent and reflux for some time at BP.

If your product doesn't crystallise out on cooling, slowly evaporate the solvent and see what gives.

Just a thought.

DraconicAcid - 20-7-2014 at 09:02

Quote: Originally posted by FireLion3  
This is the complex:
https://en.wikipedia.org/wiki/Bis%28triphenylphosphine%29nic...

I have both Triphenylphosphine (MP tested) and Nickel (II) Chloride (which is as green as green can be). Both Reagents are 99.95%+ purity

The dark blue complex should form by reacting these in an organic solvent. I used store bought 70% Isopropyl Alcohol as the solvent. Mixing the two reagents in the proper ratio, for 2+ hours, did not result in any significant color change in solution. The solution was still the same green color as it was prior to adding the triphenylphosphine.


There's far too much water in 70% alcohol.

Brain&Force - 20-7-2014 at 10:24

91% IPA (isopropyl alcohol, not Indian Pale Ale) can be bought from certain stores (I think Target is one of them, but I'm not sure). Methanol works to dissolve nickel chloride, if you want to try that.

FireLion3 - 20-7-2014 at 11:12

If Nickel II Chloride is soluble in both alcohol and water, I didn't think excess water would be an issue. Since it is soluble in both, its equilibrium should exist in both, and even alternate between the miscible layers.

I probably wont be bothering with this complex until I get a different nickel salt, since the chloride-based complex seems to have low solubility. I need one that will be completely homogenous.

DraconicAcid - 20-7-2014 at 13:11

Quote: Originally posted by FireLion3  
If Nickel II Chloride is soluble in both alcohol and water, I didn't think excess water would be an issue.


Water can act as a ligand and compete with the phosphine.

kristofvagyok - 20-7-2014 at 14:09

I've done this reaction long ago in acetic acid.

Take 0,6g of Nickel(II)-chloride hexahydrate and add it to the mixture of 0,5 cm3 water and 12,5 cm3 glacial acetic acid. To this mixture (a pale green suspension) with stirring add 1,31g triphenylphosphine what is dissolved in 6 cm3 glacial acetic acid. During the addition a deep green crystalline mass forms, what turns black on standing.
After a half hour of crystallization filter the solution on a Büchner funnel, wash the crystals with a little glacial acetic acid and dry them in vacuum.

Deep green, near black crystals should be obtained in high yield.

AvBaeyer - 25-7-2014 at 18:34

The procedure that I have used successfully many times (many years ago during my thesis work) is given below. It is very important that the isopropanol and the ethanol be very dry to start with. Some water is added, of course, with the nickel chloride hexahydrate but this is not important if the solvents are anhydrous to begin with.

Preparation of Dichlorobis(triphenylphosphine)nickel(II)

- Dissolve nickel chloride hexahydrate (1.2 g) in dry ethanol (15 cm3) and warm gently.
- Place triphenylphosphine (2.8 g) and isopropanol (30 cm3) in a 100 cm3 round-bottomed flask, fit a reflux condenser and dissolve the phosphine by refluxing gently.
- When the phosphine has dissolved, remove from the heat and carefully add the warm nickel chloride solution.
- Reflux the mixture for a further 10 minutes and then cool to room temperature.
- Filter the product, wash with cold ethanol (15 cm3 ) followed by diethyl ether (15 cm3) and draw a stream of air through the product to dry.

This procedure gives a very crystalline product in nearly quantitative yield.

The cobalt complex can be made in a similar manner except that the cobalt chloride needs to be anhydrous (blue not pink) for the reaction to work well.

FireLion3 - 25-7-2014 at 19:13

Quote: Originally posted by AvBaeyer  
The procedure that I have used successfully many times (many years ago during my thesis work) is given below. It is very important that the isopropanol and the ethanol be very dry to start with. Some water is added, of course, with the nickel chloride hexahydrate but this is not important if the solvents are anhydrous to begin with.

Preparation of Dichlorobis(triphenylphosphine)nickel(II)

- Dissolve nickel chloride hexahydrate (1.2 g) in dry ethanol (15 cm3) and warm gently.
- Place triphenylphosphine (2.8 g) and isopropanol (30 cm3) in a 100 cm3 round-bottomed flask, fit a reflux condenser and dissolve the phosphine by refluxing gently.
- When the phosphine has dissolved, remove from the heat and carefully add the warm nickel chloride solution.
- Reflux the mixture for a further 10 minutes and then cool to room temperature.
- Filter the product, wash with cold ethanol (15 cm3 ) followed by diethyl ether (15 cm3) and draw a stream of air through the product to dry.

This procedure gives a very crystalline product in nearly quantitative yield.

The cobalt complex can be made in a similar manner except that the cobalt chloride needs to be anhydrous (blue not pink) for the reaction to work well.


I've definitely got some anhydrous cobalt laying around, though I'm not sure if it will suit my purposes. The main reason I wanted to make this complex was for having a homogenous catalyst for transfer hydrogenations, and to utilize it for halide oxidative addition reactions. Now I just face the problem of finding a complex that can do this and is adequately soluble in organics so I don't have to filter it off. I read the NiBr2 PPH3 complex is more soluble in organics than the chloride complex but I can't find much information on this.

Cobalt may work for the latter, but I'm not sure if cobalts radical properties will come into play with phosphines. I know its an issue with carbon-cobalt bonded complexes. https://en.wikipedia.org/wiki/Cobalt-mediated_radical_polyme...

forgottenpassword - 26-7-2014 at 00:15

The bromide is prepared identically to the chloride, as it says in the instructions I linked to above.

FireLion3 - 26-7-2014 at 11:46

Quote: Originally posted by forgottenpassword  
The bromide is prepared identically to the chloride, as it says in the instructions I linked to above.


I would imagine.... I just need to get some Nickel Bromide first.