Best reagents state for air free chemistry. Choosing halide for grignard synthesis I am planning to synthesize a grignard and I have a choice between the iodo or chloro aryl halide. The iodo is a solid and the chloro is borderline. For my previous reaction I melted the chloro and then tranfered it using a flushed sringe. As an alternative I could just weigh out the iodo and then pull vacuum on it a few times before running my reaction. Is there a better option between the two or they are just the same?
The chloride can be a bit slow to react, particularly if the aryl halide is hindered. You might need a small amount of iodine to get the reaction started. (Maybe you ran into this already?)

Once you form the Grignard, they should be identical for most applications.

Personally, I would just go with iodide because the chloride is probably a bit less reactive, and frankly, weighing out substances that are almost solid is extremely annoying. Strongly prefer the actual solid.

The main reason I would elect the chloride over the iodide in this case is if the cost of the chloride were much lower, and even then only if the reactivity weren't seriously impeded by using the chloride.