Serendipitous Self-Assembly of Cyclometalated Complexes through Hydrogen Bonds: Dimers or Chains within Compact or Porous Networks

X-ray
diffraction analysis of cyclometalated, chiral-at-metal rhodium
and iridium complexes with the general formula [Cp*MCl­{κ2(N,C)-(2-phenyl-2-imidazoline}]
reveals that they undergo noncovalent self-assembly through intermolecular
NH···Cl hydrogen bonding and, in some cases, CH/π
interactions. Compound (±)-6b coordinated with an
unsubstituted, achiral phenylimidazoline ligand forms dimers, whereas
(SM)-7a,b and (RM)-8a,b (a, M =
Ir; b, M = Rh) generated from chiral, (RC,RC)-phenylimidazoline ligands
crystallize as infinite 1D chains. The pitch of the chains is ca.
35–50% higher for 8a,b than for 7a,b. 8a,b display
a C2-helical motif. However, 8b differs from 8a by (1) the existence of intermolecular
CH/π interactions within the helix and (2) a head-to-head self-assembly
of the helices, yielding hydrophobic, worm-screw channels.