Unwrapping on IE11 wroken?

I really need assistance on this.

Based on this documentation:

https://msdn.microsoft.com/en-us/library/dn302335(v=vs.85).aspx

On MS Edge following unwrapping code works:

window.crypto.subtle.unwrapKey("raw",
                                wrappedKey,
                                derivedKey,{"name":"AES-KW", iv: iv },{"name":"AES-CBC", iv: iv },false,["decrypt"])

Following does not throws an error but the resulting key is null:

var wrappedKey = base64DecodeToArray("FWPt4AZDKJaN1KssHCBo+ZFSX/rKvh3eLMpOfHILsVYbV7WWSwX8NQ==");

window.msCrypto.subtle.unwrapKey(
                                    wrappedKey,{"name":"AES-KW",
                                        iv: iv,
                                        hash:{ name:"SHA-256"}},
                                    e.target.result,false,["decrypt"])