-OtherAttributes <Hashtable> Specifies object attribute values for attributes that are not represented by cmdlet parameters. You can set one or more parameters at the same time with this parameter. If an attribute takes more than one value, you can assign multiple values. To identify an attribute, specify the LDAPDisplayName (ldapDisplayName) defined for it in the Active Directory schema.
Причем тут powershell? Тут незнание базовых вещей .Net.(Represents a collection of key/value pairs that are organized based on the hash code of the key.)