Error with REST/JSON while trying to unmanage node

I've been trying to work out a POSH script that can unmanage a node. I've successfully created one that can change a custom property here and i'm using that as my base.

I can unmanage the node via the Orion Web Console with the account that i'm using.

I have the Orion SDK 2.0.50 installed on my orion server. I'm really waning to get this working without having to install the SDK on my monitored nodes.

I get an error while trying to invoke the request within the SWQL. Here is a screenshot. Not sure where to go from here.

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I've tried to pull JSON examples from these articles but i'm still getting stumped.

Powershell scripts to automatically unmanage\remanage a node using the Orion SDK

REST API in PowerShell

REST · solarwinds/OrionSDK Wiki · GitHub