Deprotonation of a heterodinuclear transition-metal hydride complex and reactions of the anion with electrophiles: X-ray crystal structures of [(η5-C5H5)(OC)2Mo{µ-Ag(PPh3)}(µ-PPh2)Mn(CO)4] and [(η-C5H5)(OC)2Mo(µ-I)(µ-PPh2)Mn(CO)4]