REST API JSON VC:VmFolder

I am attempting to kick off a workflow via REST/JSON. The workflow takes two inputs:

     1. a string variable called vmName - self explanatory.

     2. a VC:VmFolder variable called FolderName - I have to get the VMs Folder in order to do some cloning. the issue is that I only have a folder name since that is the interface level my users are working at.

Once the Workflow has been called it kicks off a slew of cloning, snapshot, etc activity.

I pass in the following JSON and I get back an error message complaining about the request being "Syntactically Incorrect".

I know my issue is with the way the JSON is structured with regard to the VC:VmFolder as that is an object and not a basic type (string, number). How do I structure the call correctly and more importantly is there a good set of documentation or reference website that will guide me down the right path in the future when dealing with this or other complex data types / objects - I want to learn to fish?

Any help is greatly appreciated.

Thank you.