Diversity in complexation of [Rh-I(cod)](+) and [Ir-I(cod)](+) by pyridine-amine-pyrrole ligands
de Bruin B, Kicken RJNAM, Suos NFA, Donners MPJ, den Reijer CJ, Sandee AJ, de Gelder R, Smits JMM, Gal AW, Spek AL
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY (9): 1581-1592 SEP 1999

Abstract:
Complexation of [Rh-I(cod)](+) and [Ir-I(cod)](+) by the new pyridine-amine-pyrrole ligands Py-CH2-N(R)-CH2-Pyr-H (HLR; R = H, Bzl, Bu) and the corresponding pyridine-amine-pyrrolate ligands [Py-CH2-N(R)-CH2-Pyr](-) (L-R(-); R = H, Bzl, Bu, CH2Py) has been investigated. The neutral ligands HLR (R = H, Bu, Bzl) give [(HLR)M-I(cod)](+) (M = Rh, Ir) in which HLR acts as a didentate ligand via the pyridine nitrogen (N-Py) and the amine nitrogen (N-amine(R)). The crystal structures of [(HLH)M-I(cod)]PF6 (M = Rh: [1]PF6 and M = Ir: [2]PF6) have been determined. Deprotonation of [(HLR)M-I(cod)](+) (M = Rh, Ir; R = H, Bzl, Bu) results in the neutral complexes [(L-R)M-I(cod)] (M = Rh, Ir) of the mono-anionic ligands L-R(-) (R = H, Bzl, Bu). In square-planar [(L-H)M-I(cod)] (M = Rh: 3, M = Ir: 4), L-H(-) is didentate via N-amine(H) and the pyrrolate nitrogen (N-Pyr). The X-ray structures of 3 and 4 reveal that in both cases the uncoordinated N-Py accepts a hydrogen bond from N-amine(H). The X-ray structures of [(L-Bzl)M-I(cod)] (M = Rh: 5, M = Ir: 6), show that L-Bzl(-) is didentate via N-amine and N-Pyr for M = Rh and tridentate for M = Ir. In solution L-Bzl(-) is tridentate for both M = Rh and M = Ir. The neutral complexes [{Py-CH2-N(R)-CH2-Pyr}M-I(cod)] (M = Rh, Ir) cannot be oxidised selectively with H2O2. This is in marked contrast to the previously observed selective oxidation of the corresponding cationic complexes [{Py-CH2-N(R)-CH2-Py}Rh-I(cod)](+). Rhodium complex 5 is an active catalyst for the stereoregular polymerisation of phenylacetylene, whereas iridium complex 6 is inactive.