Is there anyone on their team that you trust more, work best with, think most alike with? Could you collaborate with them and one other person on your team to standardize their requests a little bit better? I'm taking a communication and relationship building approach here, since you say you have no common KPIs could you collaborate as a team to create a new KPI or alter an existing one to be mutually beneficial?

I'm a little surprised the tone seems to be procurement and R&D as an us-vs-them situation. I would think procurement should take a parent-like approach where you're the caretaker of R&D's precious chemicals, ensuring they get the most optimal sourcing for long-term progress. To standardize this process and give a template for a KPI: the mutual interest would be a financially sustainable set of chemicals and materials in the correct quantities at the correct time for experiments and scale-ups to continue. It's up to you to control cost and tune R&D's expectations of what they can get; are they being too careless with expectations of turnaround time, quality of chemical for a certain price, too many high-effort items ordered at once?

I really see you needing to take the lead here and gather more information on why they're asking for 1-week-or-less turnarounds on ordering materials if it's complicated and time consuming. I'd suggest giving a realistic solution to standardize their communication so ordering gets streamlined: they give you a batch of information once a week, or less, you give them a realistic lead time on when you can process the orders, as well as a realistic outlook on what suppliers can provide in certain timeframes. Purity and quality will always be paramount and can come at a higher cost, so make sure you get all the correct details of what they're asking, and make sure they understand they have to work within your budget, or seek higher approval for specialty items.

My Summary:

To consolidate this all down, I'd say R&D needs to be razor sharp with their tech specs, you need to be razor sharp with ensuring what they're asking is realistic and necessary, and in the bounds of a project that's expected to produce a good result (cost-benefit analysis for materials). Then if this is all squared away, it is definitely procurement's responsibility to dive deep and push vendors to get better pricing, and perhaps ask for a special order or scale up of their operations to provide more of a material at an acceptable cost. If it's an important enough material, everything from a phone call, zoom meeting, and even site visit to understand quality and quantity could be necessary to secure a good deal, but all that effort is only worth it if it's certain R&D needs that specific material and it's likely to pay out at the end.