Organometallic clusters containing oxygen atoms, (CPV)(m)O-n (Cp = C5H5), are generated by photochemical reaction of CpV(CO)(4) in CH2Cl2 solution with control of oxygen concentration. Mass spectra of single batch reactions exhibit strong signals assigned to low mass oxide clusters: (CpV)(4)O-4, (CpV)(5)O-6 and (CPV)(6)O-n (n = 6-8). Successive addition of reactant solution into the photochemical reaction vessel shows the addition of (CpV)(m') to the low, mass oxide clusters, producing (CpV)(m)O-n (m much greater than n = 4-7). The magnetic susceptibility (chi(g)) of the mixture of the former low mass products shows antiferromagnetic behavior, while that of the latter high mass products is as high as 4.6 x 10(-4) cm(3) g(-1) at 10 K. The additional part due to high mass products behaves ferromagnetically at temperatures higher than 70 K.