Synthesis and Characterization of Novel Pyrazole‐Based Ligands of [η⁵‐Cyclopentadiene][η⁴‐Tetraphenylcyclobutadiene]Cobalt

Abstract

(η⁵‐N,N‐dimethylaminomethylcyclopentadienyl)(η⁴‐tetraphenylcyclobutadiene) cobalt was prepared by the Mannich reaction of the metallocene (η⁵‐Cp)Co(η⁴‐Ph₄C₄) with tetramethylmethylenediamine and phosphoric acid. The methyl iodide salt of this compound was reacted with 3,5‐dimethylpyrazole and 3‐methyl‐5‐trifluoromethylpyrazole to prepare the pyrazole derived metallocenes, [η⁵‐(C₅H₄CH₂)‐3,5‐(CH₃)₂(C₃HN₂)]Co[η⁴‐(Ph₄C₄)] (1) and [η⁵‐(C₅H₄CH₂)‐3‐CH₃‐5‐CF₃(C₄H₂N)]Co[η⁴‐(Ph₄C₄)] (2). Compounds 1 and 2 were structurally characterized.

Keywords:

• dimethylpyrazole
• methyltrifluoromethylpyrazole
• metallocene, cobalt
• dimethylaminomethylcyclopentadienyl
• tetraphenylcyclobutadiene

Acknowledgments

Dedicated to Prof. Dr. Herbert W. Roesky on the occasion of his 70^th birthday.

The authors wish to thank Council of Scientific and Industrial Research (CSIR) India and Department of Science and Technology, (DST) India for financial assistance in the form of research grants and IIT Delhi for an equipment grant. We acknowledge DST‐FIST and IITD for funding of the single crystal X‐ray diffraction facility at IIT Delhi. SAIF CDRI, Lucknow is acknowledged for mass spectral and analytical measurements.