Synthesis and structures of organometallic derivatives of 1,2,3,4,5,6,7,8-octamethyl-1,5-dihydro-s-indacene

Abstract

A new fused-ring compound 1,2,3,4,5,6,7,8-octamethyl-1,5-dihydro-s-indacene (H₂L¹) has been synthesized from p-xylene. Three transition-metal derivatives [Mn(η⁵-HL¹)(CO)₃], [Rh(η⁵-HL¹)(η-C₅Me₅)]⁺[SbF₆]⁻ and [Cr(η⁶-H₂L¹)(CO)₃] have been characterised: spectroscopic and crystallographic data for these compounds show the ligand system is strongly electron donating. Although H₂L¹ is readily deprotonated to the monoanion by potassium metal or potassium hydride, surprisingly we have been unable to form (L¹)². The crystal structure of [K]⁺[HL¹]⁻·18-crown-6 reveals the potassium ion to be sandwiched between the crown ether (1,4,7,10,13,16-hexaoxacyclooctadecane) and the (HL¹)⁻ anion.