Syntheses of Metal Carbonyls, XVI¹⁾. Metal‐Metal Multiple Bonds: Synthesis, Crystal and Molecular Structure of Tri‐μ‐carbonyl‐bis[(η⁵‐pentamethylcyclopentadienyl)manganese](<i>Mn ≡ Mn</i>) – The First Manganese‐Manganese Triple Bond

Abstract

Abstract Photolysis of the manganese half‐sandwich complex (η 5 ‐C 5 Me 5 )Mn(CO) 3 ( 1 ) in tetrahydrofuran (thf) cleanly yields the solvent complex (η 5 ‐C 5 Me 5 )Mn(CO) 2 (thf) ( 2 ). Compound 2 is stable as solid at temperatures well below 0°C but undergoes spontaneous elimination of carbon monoxide at ambient temperature with concomitant formation of the novel dinuclear complex (η 5 ‐C 5 Me 5 ) 2 ‐Mn 2 (μ‐CO) 3 ( 3 ). While elemental analysis, infrared and mass spectroscopy as well as the 1 H NMR and 13 C NMR spectra unequivocally demonstrate this compound to adopt a highly symmetrical triply carbonyl‐bridged structure, a single‐crystal X‐ray diffraction study supports the presence of the first triple bond between manganese atoms ( d Mn – Mn 217.0(1) pm). An improved synthesis of tricarbonyl(η 5 ‐pentamethylclopentadienyl)manganese ( 1 ) is also described.