Rhodium and Iridium Amino, Amido, and Aminyl Radical Complexes

Autor: Nicola Donati, Sreekanth Anadaram, Hansjörg Grützmacher, Hartmut Schönberg, Torsten Büttner, Jeffrey Harmer, Daniel Stein
Jazyk: angličtina
Rok vydání: 2008
Předmět:
Zdroj: EUROPEAN JOURNAL OF INORGANIC CHEMISTRY. 2008(30)
ISSN: 1099-0682
1434-1948
Popis: The chlorido-bridged dimeric complex [Rh 2 (μ-Cl) 2 (trop 2 -NH) 2 ] [trop 2 NH =bis(benzo[a,d]cycloheptenyl)amine] or the acetonitrile complexes [Rh(trop 2 NH)(MeCN) 2 ] + (CF 3 SO 3 - ) and [IrCl(MeCN)(trop2NH)] are well-suited precursor complexes for phenanthroline-type complexes [M(trop2NH)(R,R-phen)] + A - (M = Rh, Ir; R = H, Me, Ph substituents in the 4,7-or 5,6-positions of the phen ligand, A - = CF 3 SΟ 3 - , PF 6 - ). These complexes contain 18-valence-electron configured metal centers in a trigonal-bipyramidal coordination sphere with the amino (NH) group in an axial position and each of the olefinic C=C trop units is in an equatorial position. The cationic amino complexes [M(trop 2 NH)(R,R-phen)] + are sufficiently acidic (pK a in dmso: 18.2-19.0) to be quantitatively deprotonated by one equivalent of KOtBu to give neutral amido complexes [M(trop2N)(R,R-phen)] (M = Rh, Ir). These can be easily oxidized to give aminyl radical complexes [M(trop 2 N - )(R,R-phen)] + A - , which for M = Rh can be isolated as green crystals. The iridium complex [Ir(trop 2 N . )(phen)] + is unstable. High-resolution pulse EPR spectroscopy was used to gain insight into the electronic structure of the aminyl radical complexes. Remarkably, the rhodium and iridium complexes have a very similar electronic structure, as revealed by their EPR parameters ([Rh(trop 2 N . ](phen)] + : g 1,2,3 = 2.084(2), 2.049(2), 2.027(2); lA iso l = 45.4 (N1), 10.4 (N 2 ), 3.1 (N3) 27.0 (Rh) MHz; [Ir(trop 2 N . )(phen)] + : g 1,2,3 = 2.140(2), 2.107(2), 2.015(2); lA iso l = 47 (N1), 7.9 (N2), 3.5 (N3), 26.8 (Ir) MHz} and these show that about 60 % of the spin population is localized on the nitrogen center (N1) of the trop 2 N ligand. In reactions with stannanes (R 3 SnH) and thiols (RSH), H-atom transfer to the trop 2 N nitrogen atom is observed, [M(trop 2 N . ](phen)] + + EH→ [M(trop 2 NH)(phen)] + + 1/2HE-EH.
Databáze: OpenAIRE
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