Synthesis, Structure, and Dynamic Behavior of (μ‐Aldimido)(μ‐η 1 : η 2 ‐alkyne)‐ biszirconocene Cation Complexes That Contain Planar‐Tetracoordinate Carbon

The benzonitrile hydrozirconation product Cp 2 ZrCl(NCHPh) 8 was treated with propynyl lithium to yield the (propynyl)(benzaldimido)ZrCp; complex 9 . Subsequent treatment with trityl tetraphenylborate generated [Cp 2 Zr(CCCH 3 ) − BPh − 4 ] that instantaneously added to 9 to eventually form the (μ‐aldimido)(μ‐η 1 :η 2 ‐hexadiyne)ZrCp 2 cation 11 . The X‐ray crystal structure analysis showed that 11 contains a planar‐tetracoordinate carbon atom that is stabilized by forming a three‐center‐two‐electron bond with the two adjacent metal atoms. Similarly, complex 9 reacted with [Cp 2 Zr(CH 3 ) + CH 3 B(C 6 F 5 ) 3 1 to yield the planar‐tetracoordinate carbon containing (μ‐aldimido)(μ‐η 1 :η 2 ‐2‐butyne) Cp; cation 12 . Both complexes 11 and 12 exhibit dynamic NMR spectra due to their rapid reorganization of the dimetallabicyclic frameworks (ΔG * = 10 kcal mol −1 ) in addition to an anchimerically assisted CN bond rotation (ΔG * =15 kcal mol −1 ).