Can you file a motion for contempt if the deceased's wife will not cooperate with the administrator of the estate regarding access to the assets?

Yes. Obtain yourself probate litigation counsel to bring this person to heel. You will have to support the motion with a very detailed declaration as to your efforts in trying to obtain the information and access you are seeking, and set the matter for hearing; if she fails to appear and proper notice of hearing is given as to time and place, then you can request an order to show cause as to why she should not be held in comtempt and request the court to have a court order to appear served on her by the sheriff; a failure to appear will cause the court to issue a bench warant for her arrest.