If you are talking about folder in SCCM itself, there is another wmi class you need called SMS_ObjectContainerItem. It basically tells the driver which folder to go in.
I haven't actually scripted it in 2012, but in a script I wrote that creates advertisements, I had code that looked like this:
#This gets the folder from wmi. $advContName is the name of the folder I want the ADV to end up in
$advContainer = gwmi -name root\sms\site_ia1 -computer itsnt353 -query "Select * from SMS_ObjectContainerNode WHERE Name='$advContName' AND ObjectType='3'"
$moveADV = ([WMIClass]\\itsnt353\root\sms\site_ia1:SMS_ObjectContainerItem").CreateInstance()
$moveADV.InstanceKey = $advID
$moveADV.ObjectType = 2;
$moveADV.ContainerNodeID = $advContainer.ContainerNodeID
$moveADV.Put()
I hope this helps.