Addition of 2-adamantylMgBr in diethyl ether to Mo(NAr) 2 (Cl) 2 (DME) (Ar = 2,6-i-Pr 2 C 6 H 3 ) gave Mo(NAr) 2 (2-Ad) 2 (2-Ad = 2-adamantyl, DME = 1,2-dimethoxyethane), from which Mo(NAr)(Adene)(OTf) 2 (DME) (1, Adene = 2-adamantylidene) was prepared upon addition of triflic acid. Methods analogous to those that have been successful for synthesizing neopentylidene and neophylidene complexes were used to form Mo(NAr)-(Adene)(OMes) 2 (2; Mes = 2,4,6-trimethylphenyl), [Mo(NAr)(Adene)(OC 6 F 5 ) 2 ] 2 (3), Mo(NAr)(Adene)(OC 6 F 5 ) 2 (MeCN) (4), Mo(NAr)(Adene)(Cl) 2 (bipy) (5; bipy = 2,2′bipyridine), Mo(NAr)(Adene)(Cl)(OHMT) (6; OHMT = O-2,6-Mesityl 2 C 6 H 3 ), Mo(NAr)-(Adene)(Cl)(OHMT)(t-BuCN) (6(t-BuCN)), and Mo(NAr)(Adene)(OHMT)(Pyr) (7; Pyr = pyrrolide). Analogous methods beginning with Mo, and Mo(N-t-Bu)(Adene)(OHMT)(Pyr)(THF) (8d). X-ray structural studies of 1-5, 6(t-BuCN), 7, 8a, 8c, and 8d suggest that one of the Adene β protons is engaged in an agostic interaction with the metal when the electron count is less than 18. Preliminary olefin metathesis studies confirm that Adene complexes react with cyclooctene and 1-decene in the manner expected for high-oxidation-state Mo alkylidene complexes.