Diversity in Complexation of [RhI(cod)]+ and [IrI(cod)]+ by Pyridine-Amine-Pyrrole Ligands

Abstract

Complexation of [RhI(cod)]+ and [IrI(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]− (LR−; R = H, Bzl, Bu, CH2Py) has been investigated. The neutral ligands HLR (R = H, Bu, Bzl) give [(HLR)MI(cod)]+ (M = Rh, Ir) in which HLR acts as a didentate ligand via the pyridine nitrogen (NPy) and the amine nitrogen (NRamine). The crystal structures of [(HLH)MI(cod)]PF6 (M = Rh: [1]PF6 and M = Ir: [2]PF6) have been determined. Deprotonation of [(HLR)MI(cod)]+ (M = Rh, Ir; R = H, Bzl, Bu) results in the neutral complexes [(LR)MI(cod)] (M = Rh, Ir) of the mono‐anionic ligands LR− (R = H, Bzl, Bu). In square‐planar [(LH)MI(cod)] (M = Rh: 3, M = Ir: 4), LH− is didentate via NHamine and the pyrrolate nitrogen (NPyr). The X‐ray structures of 3 and 4 reveal that in both cases the uncoordinated NPy accepts a hydrogen bond from NHamine. The X‐ray structures of [(LBzl)MI(cod)] (M = Rh: 5, M = Ir: 6), show that LBzl− is didentate via Namine and NPyr for M = Rh and tridentate for M = Ir. In solution LBzl− is tridentate for both M = Rh and M = Ir. The neutral complexes [{Py–CH2–N(R)–CH2–Pyr}MI(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}RhI(cod)]+. Rhodium complex 5 is an active catalyst for the stereoregular polymerisation of phenylacetylene, whereas iridium complex 6 is inactive.

Synthesis of Rh(I) diamine complexes and their exploitation for asymmetric hydrogen transfer processes

“…The bond lengths and angles are in agreement with similar complexes in the literature, [16][17][18][19][20] with the typical Rh-C distance of 2.14 Å and Rh-N of 2.14 Å. To the best of our knowledge this is the first example of a crystallographically characterised example of ligand 1, although there are reports in the literature of the preparation of the pure ligand [14].…”

Monomeric, dimeric and 1D chain polymeric copper(ii) complexes of a pyrrole-containing tridentate Schiff-base ligand and its 4-brominated analogue

“…4 In contrast, for the ligand L B , with the 6-methyl substituent at the ortho position of the 2-iminopyridine ring, only monomeric complexes, [Cu(L B )X 2 ] (X = Br -, NCS -, N 3 -) 1 and [Cu(L B )Cl(H 2 O)]PF 6 , 2 were isolated. These examples, together with those obtained with other closely related tridentate Schiff-base ligands, [6][7][8] indicate that the use of less flexible tridentate ligands tends to result in the formation of monomeric and dimeric complexes while the use of more flexible tridentate ligands tends to give rise to dimeric or polymeric complexes. These dimeric and polymeric complexes also exhibit interesting magnetic behaviour.…”

“…11 The rhodium(I) and iridium(I) complexes of the amine analogue of HL 2 have also been studied, by Gal and co-workers, in order to investigate their potential as catalysts for the polymerisation of phenylacetylene. 8 More recently, a copper(I) complex of (L 2 )has been reported and the X-ray crystal structure analysis carried out on the complex shows that it is an unusual asymmetric copper(I) dimer with two-coordinate and four-coordinate copper(I) sites. 10 No other transition metal complexes of (L 2 )have been reported in the literature to date.…”

Pyrrole-based metallo-macrocycles and cryptands

“…1H-pyrrol-2-ylmethylbenzylamine 1 (1 equivalent, prepared as previously reported) 42 was dissolved in THF and CS 2 (1.1 equivalents) added. KOH (1 equivalent) and the M() salt (1 equivalent, see below) were dissolved in water and added to the solution, the base was added before the M() salt.…”