REST API endpoint to update a user's ExtendedAttribute list

Hello,

I'm trying to update a user's ExtendedAttribute list via the REST API per the documentation here:
Update User REST Endpoint

However, it either appears as though the ExtendedAttribute list isn't supported via this request, or its request is formatted differently than the documentation.  Does anyone have documentation on how to update the user's ExtendedAttribute list via the REST API?

Here's what I've tried to far:

var userId = 2105;
var extendedAttributes = [{"Key":"Foo","Value":"Bar"}];

jQuery.telligent.evolution.put({
    url: jQuery.telligent.evolution.site.getBaseUrl() + 'api.ashx/v2/users/{id}.json',
    data: { 
        'id': userId,
        "ExtendedAttributes": extendedAttributes
    },
    success: function(response) {
        console.log("Saved user successfully" + JSON.stringify(response));
    }
});

Thank you,

Chris