The below command searches my active directory for accounts that have been expired for more than 30 days and deletes them.  While running the below command, i get the below error.  The only thing that is different about these users is that they had iphones associated to their exchange account at some point.  How can i modify my command to remove the account.  If i try to delete the account in ADUC, i get the following error in the screen
If i click yes, the delete is successful.  How can i get the delete to work in powershell?

Search-ADAccount -AccountExpired -UsersOnly | Where { $_.AccountExpirationDate -lt (
Get-Date).AddDays(-30) } | Remove-ADUser


heres the error message i get
Remove-ADUser : The directory service can perform the requested operation only on a leaf object
At line:1 char:125
+ Search-ADAccount -AccountExpired -UsersOnly | Where { $_.AccountExpirationDate -lt (Get-Date).AddDays(-30) } | Remove
-ADUser <<<<
    + CategoryInfo          : NotSpecified: (CN=Doe\, John...DC=contoso,DC=org:ADUser) [Remove-ADUser], ADException
    + FullyQualifiedErrorId : The directory service can perform the requested operation only on a leaf object,Microsof
   t.ActiveDirectory.Management.Commands.RemoveADUser