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The synthesis of the tetrahydroborate complex [(2-iPr2PC6H4-η7-C7H6)Mo(η2-BH4)(P–Mo)] 3 containing the linked cycloheptatrienyl-phosphane ligand [2-(diisopropylphosphanyl)phenyl]cycloheptatrienyl is described, which provides the possibility to generate the 14-electron complex [(2-iPr2PC6H4-η7-C7H6)Mo(P–Mo)]+ (4) on treatment with dimethylanilinium salts such as [HNMe2Ph][BPh4]. Generation of (4)BPh4 in the presence of 2,6-dimethylphenyl isocyanide, 2,5-norbornadiene or phenylacetylene affords the diisocyanide complex (5a)BPh4, the diolefin complex (5b)BPh4 and the alkyne complex (6)BPh4, respectively. The latter complex can be used for the catalytic oligomerization of phenylacetylene affording predominantly the cyclotrimers 1,3,5- and 1,2,4-triphenylbenzene. [Copyright &y& Elsevier]