Organometallic oxides: oxidation of [(.eta.-C5Me5)Mo(CO)2]2 with O2 to form syn-[(.eta.-C5Me5)MoCl]2(.mu.-Cl)2(.mu.-O), syn-[(.eta.-C5Me5)MoCl]2(.mu.-Cl)(.mu.-CO3H)(.mu.-O), and [C5Me5O][(.eta.-C5Me5)Mo6O18]