Synthesis and structural characterization of iridium(I) complexes of 20-membered macrocyclic rings bearing chelating bis(N-heterocyclic carbene) ligands

by Thapa, Rajesh; Kilyanek, Stefan M.

The reactivities of two 20-membered macrocyclic ligands, each containing two N-heterocyclic carbene (NHC) and two amine groups, towards [IrCl(COD)](2) (COD is cycloocta-1,5-diene) were investigated. Macrocycles containing imidazolin-2-ylidene groups formed the monometallic complex [(1,2,5,6-eta)-cycloocta-1,5-diene](5,16-dibenzyl-1,5,9,12,16,20-hexaazatricyclo[,12]tetracosa- 10,21-dien-21,22-diylidene)iridium(I) bromide dichloromethane monosolvate, [Ir(C8H12)(C32H42N6)]Br eta CH2Cl2, 2a. The structure of iridium complex 2a at 100 K has triclinic P1 symmetry. The ligand in 2a coordinates to the Ir center through the NHC moieties in a cis fashion. Additionally, the ligand adopts an umbrella-like structure that appears to envelope the Ir center. The structure displays C-H center dot center dot center dot Br interactions. Macrocycles containing benzimidazolin-2ylidene groups formed the bimetallic complex [-5,20-dibenzyl-1,5,9,16,20,24hexaazapentacyclo[,30)]dotriaconta-10(15),11,13,25(30),26,28hexaene-31,32-diylidene]bis{bromido[(1,2,5,6-)-cycloocta-1,5-diene]iridium(I)}, [Ir2Br2(C8H12)(2)(C40H46N6)], 2b. The structure of complex 2b at 100 K has orthorhombic Pbca symmetry. Each NHC moiety in 2b coordinates in a monodentate fashion to an Ir(COD) fragment. The structure exhibits disorder of the main molecule. This disorder is found in the portion of the macrocycle containing an amine group. This structure also displays C-H center dot center dot center dot Br interactions. Finally, the structure of the hexafluorophosphate salt of the imidazolin-2ylidene-containing macrocycle, namely 5,16-dibenzyl-1 5,5,9,125,16,20-hexaazatricyclo[,12]tetracosa-1(23), 10,12(24), 21- tetraene-1,12-diium bis(hexafluorophosphate), C32H44N62+ center dot 2PF(6)(-), 1c, was determined. The structure of macrocycle 1c at 100 K has triclinic P1 symmetry and was found to contain CH center dot center dot center dot F interactions.

Acta Crystallographica Section C-Crystal Structure Communications
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