The sandwich complexes bis(η6-naphthalene)molybdenum(0) (1), bis(η6-1-methylnaphthalene)molybdenum(0) (2), and bis(η6-1,4-dimethylnaphthalene)molybdenum(0) (3) are synthesized by cocondensation of Mo-atoms with the naphthalene ligands. Complexes 1-3 are also obtained by reduction of MoCl5 or MoCl4. 2THF with highly activated Mg in the presence of the naphthalene ligands. Mg was activated by sublimation of the metal in a simple rotating solution reactor. Complex 2 exists as a mixture of regio- and stereoisomers. Three regioisomers, 3a-c, are formed in reactions of Mo-atoms with 1,4-dimethylnaphthalene, whereas 3a, the isomer with the Mo-atom coordinated to the unsubstituted rings, is formed selectively via the reductive method. The ligands in 1-3 are highly labile. CO displaces both naphthalene rings in 2 and 3 to give [Mo(CO)6], while PF3, P(OMe)3, and PMe3 displace only one coordinated naphthalene in 1 to yield the [Mo(η6-naphthalene)L3] complexes 4-6. In toluene, arene exchange is a competitive process in reactions of 1 with PF3. Complexes 5 (L = P(OMe)3) and 6 (L = PMe3) react with HBF4 to give the cationic metal hydride complexes 8 and 9. The X-ray crystal structures of [Mo(η6-naphthalene) {P(OMe)3}3] (5) and [Mo(H)(η6-naphthalene) {P(OMe)3}3][BF4] (8) are reported.