The binuclear molybdenum carbonyls Mo-2(CO)(n) (n = 11, 10, 9, 8) have been studied by density functional theory using the BP86 and MPW1PW91 functionals. The lowest energy Mo-2(CO)(11) structure is a singly bridged singlet structure with a Mo-Mo single bond. This structure is essentially thermoneutral toward dissociation into Mo(CO)(6) + Mo(CO)(5), suggesting limited viability similar to the analogous Cr-2(CO)(11). The lowest energy Mo-2(CO)(10) structure is a doubly semibridged singlet structure with a Mo=Mo double bond. This structure is essentially thermoneutral toward disproportionation into Mo-2(CO)(11) + Mo-2(CO)(9), suggesting limited viability. The lowest energy Mo-2(CO)(9) structure has three semibridging CO groups and a Mo-Mo triple bond analogous to the lowest energy Cr-2(CO)(9) structure. This structure appears to be viable toward CO dissociation, disproportionation into Mo-2(CO)(10) + Mo-2(CO)(8), and fragmentation into Mo(CO)(5) + Mo(CO)(4) and thus appears to be a possible synthetic objective. The lowest energy Mo-2(CO)(8) structure has one semibridging CO group and a Mo Mo triple bond similar to that in the lowest energy Mo-2(CO)(9) structure. This differs from the lowest energy Cr-2(CO)(8) structure, which is a triply bridged structure. A higher energy unbridged D-2d Mo-2(CO)(8) structure was found with a very short Mo-Mo distance of 2.6 angstrom. This interesting structure has two degenerate imaginary vibrational frequencies. Following the corresponding normal modes leads to a Mo-2(CO)(8) structure, lying similar to 5 kcal/mol above the global minimum, with two four-electron donor bridging CO groups and a Mo=Mo distance suggesting a formal double bond. All of the triplet Mo-2(CO)(n) (n = 10, 9, 8) structures were found to be relatively high energy structures, lying at least 22 kcal/mol above the corresponding global minimum. The singlet triplet splittings for the Mo-2(CO)(n) (n = 10, 9, 8) structures are significantly higher than those of the Cr-2(CO)(n) analogues. The Mo-Mo Wiberg bond indices confirm our assigned bond orders based on predicted bond distances.