Stable crystalline annulated diaminocarbenes: Coordination with rhodium(i), iridium(i) and catalytic hydroformylation studies

Stable annulated diaminocarbene ligands 7,9-bis(2,4,6-trimethylphenyl)-6b, 9a-dihydroace naphtha[1,2-d]imidazolin-2-ylidene and 7,9-bis(2,6- diisopropylphenyl)-6b,9a-dihydroacenaphtho[1,2-d]imidazolin-2-ylidene; designated as (BIAN-SIMes, 5a,) and (BIAN-SIPr, 5b), respectively, have been prepared. The base dependent decomposition of imidazolinium salts via ring opening at the backbone was also observed. The corresponding rhodium(i) and iridum(i) complexes (η⁴-1,5-COD)M(BIAN-SIMes)Cl and (η⁴-1,5-COD)M(BIAN-SIPr)Cl; M= Rh (6a, 6b) and Ir (7a, 7b) have been synthesised by the reaction of free carbene with [M(η⁴-1,5- COD)(μ-Cl)]₂; where M= Rh, Ir. The cationic Ir(i) complexes [(η⁴-1,5-COD)Ir(BIAN-SIMes)Py]BF₄8a and [(η⁴-1,5-COD)Ir(BIAN -SIPr)Py]PF₆8b have also been synthesised. Compounds 4b, 5a, 6a, 6b, 7b and 8b have been structurally characterised. The catalytic activities for the rhodium(i) complexes 6a and 6b were evaluated for the hydroformylation of 1-octene.