Rhodium and iridium complexes of N-(2′-hydroxyphenyl)pyrrole-2-aldimine: Synthesis, structure, and spectral and electrochemical properties

Abstract

Reaction of N-(2′-hydroxyphenyl)pyrrole-2-aldimine (H 2 L) with [M(PPh 3 ) 3 Cl] (M = Rh, Ir) affords complexes of type [M(PPh 3 ) 2 (L)Cl]. Structures of both complexes have been determined by X-ray crystallography. In both complexes, the N-(2′-hydroxyphenyl)pyrrole-2-aldimine ligand is coordinated to the metal centre, via dissociation of the acidic protons, as a dianionic tridentate N,N,O-donor. The M(L)Cl fragment constitutes an equatorial plane with the metal at the centre and the two PPh 3 ligands occupying axial positions. The complexes are diamagnetic (low-spin d 6 , S = 0) and show intense MLCT transitions in the visible region. Cyclic voltammetry of the [M(PPh 3 ) 2 (L)Cl] complexes shows reversible M(III)-M(IV) oxidation near 0⋅5 V vs SCE and quasi-reversible ligand-centred oxidative response near 1⋅0 V vs SCE.

Synthesis characterization and hydroformylation activity of new mononuclear rhodium(I) compounds incorporated with polar-group functionalized phosphines

“…The bands in the visible region may be assigned to metal-ligand chargetransfer transaction [11], whereas the bands observed in the ultraviolet region are assigned to intra-ligand transitions. No d-d transitions were detected.…”

Synthesis, characterization and hydroformylation activity of 7‐azaindolate‐bridged dinuclear rhodium(I)phosphines with pendant polar‐groups

“…The bands in the visible region may be assigned to metal-ligand charge-transfer transaction, [9] whereas the bands observed in the ultraviolet region are assigned to intra-ligand transitions. No d-d transitions were detected.…”

Complexities of the interaction of Ni(II), Pd(II) and Pt(II) pyrrole-imine chelates with human serum albumin

“…[4][5][6] Such ligands are suitable for stabilizing metal ions in both typical and high oxidation states. 7 Examples include crystallographically characterized complexes of Co(II/III), [8][9][10][11] Rh(I/III), [12][13][14][15] Ir(III), 16,17 Ni(II), [18][19][20] Pd(II), [20][21][22] Pt(II), [23][24][25] Cu(II), [26][27][28][29] Ag(I), 30 and Au(III). 31 Pyrrole-based compounds are important building blocks for numerous organic pharmaceuticals, 32 as exemplified by the clinically-approved drugs Tolmetin (a non-steroidal antiinflammatory agent), 33 Sunitinib (multi-targeted receptor tyrosine kinase inhibitor for cancer chemotherapy), 34 and Glimepiride (used to manage type 2 diabetes mellitus by stimulating insulin release), 35 to name a few.…”