Synthesis, characterisation and reactivity of the first heptamethylindenyl-molybdenum complexes: Crystal structures of [Mo(CO)(η²≡CMe) ₂(η⁵-C₉Me₇)]BF₄ and [Mo(CO) ₂(η³-C₃H₅)(η⁵-C₉Me₇)]

The synthesis and characterisation of the first (?⁵-heptamethylindenyl)molybdenum complexes are reported. Reaction of Li[C₉Me₇] with Mo(CO)₆ in refluxing THF readily forms Li[Mo(CO)₃(?⁵-C₉Me₇)], which is shown to be a useful precursor in the formation of (carbonyl)(?⁵-heptamethylindenyl)molybdenum complexes. The compounds [MoI(CO)₃(?⁵-C₉Me₇)] 3, [Mo(Me)(CO)₃(?⁵-C₉Me₇)] 4 and [Mo(CO)₂(?³-C₃H₅)(?⁵-C₉Me₇)] 5 have been prepared from this intermediate and characterised. Treatment of 3 with AgBF₄ and MeC=CMe affords [Mo(CO)(MeC=CMe)₂(?⁵-C₉Me₇)]BF₄ 6a; for this and the indenyl analogue, a new route to carbonyl-bis(alkyne)-molybdenum derivatives is demonstrated. Reaction of 3 with T1PF₆ in MeCN forms the complex [Mo(MeCN)₂(CO)₂(?⁵-C₉Me₇)]PF₆ 7. Protonation of 5 in the presence of MeC=CMe, or reaction of 7 with the same acetylene, also yields 6 with appropriate counter anions. Single crystal X-ray diffraction studies of compounds 5 and 6a are reported.