Expedient phosponium synthesis (for Wittig)

I have been making ethyltriphenylphosphonium bromide (somewhat of a time crunch, would have used iodoethane instead of bromoethane if we didn't have to wait for it). All the syntheses I see of Wittig salts are in aromatic solvents and they take large amounts of time for what I would have expected to be a fairly quick reaction, usually at least a day, if not several. I have come across the use of iodide salts as a catalyst, some of which I had already added because I figured it wouldn't hurt.


$$\ce{PPh3 + EtBr ->[\text{aromatic}][\text{solvent}] [EtPPh3]Br}$$


Why are these conditions standard/most effective? More specifically, **why is toluene (less often xylene, probably others but those are the two I've seen) used rather than some polar aprotic solvent?** Also, besides increased temperature and the use of iodide catalysts, **are there any common ways to decrease reaction time?**


* Is it simply that toluene boils at a relatively high temperature? Maybe the SN2 reaction is fairly easy once line up, but due to the large PPh3 being a bulky nucleophile, having the two reactive sites in close proximity is relatively rare, so increasing temperature is the most effect thing since random interaction is the driving force.
* I can't imagine a primary alkylbromide reacts through SN1 rather than SN2. I guess maybe the higher temperature could allow for an SN1 reaction, though? I kinda doubt it, though...
* I would think, even if the above was true, using THF and going through an SN2 mechanism at a lower temperature would be simpler than refluxing in toluene, and I still kind of doubt the SN1 on a primary bromide even at the elevated temperature.
* Another thought is that the phosphonium salt crashes out of toluene, and therefore this equilibrium serves as a driving force for the reaction. Technically, this doesn't speed up the reaction, but it does significantly hinder the reverse reaction, so it leads to a net decrease in reaction time (and increases yield, I guess, if the reverse reaction is significant). I wouldn't really think the halide anions would be strong enough nucleophiles to be able to kick off a phosphine, though.


$$\ce{RX + PPh3}\xrightarrow{\text{toluene}}\ce{\underset{\small{(\sim none\ in\ sol'n)}}{[RPPh3]X\_{$(s)$}} v}$$
$$\text{vs.}$$
$$\ce{RX + PPh3} \stackrel{\small{\text{THF}}}{\longrightleftharpoons} 
\ce{\underset{\small{(more\ than\ above)}}{[RPPh3]X\_{$(org)$}}}$$


I realize THF isn't all that polar, but relative to toluene or xylene, I would really expect it to facilitate this reaction better. 


  





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P.S. This question isn't really an attempt to get help with my current situation (especially since I just finished working up my last batch, anyway) as much as it is just trying to get general information about the reaction. 


I will mention for anyone who might be able to use it that I first tried to run mine in toluene at around 35 °C with catalytic KI (I've now seen LiI used instead of KI, not sure how much that matters). However, I was inspired by a literature report of a 7-day reaction at 30 °C (no iodide) to move the reaction in portions to pressure tubes and take it up to 130 °C. A paper reported 7 h (also no iodide) at this temp was effective, and I found that to be overkill. I didn't really see much difference between 2 h and 7 h (again, no iodide in their reaction, which may have caused the difference).


