Oxidative Addition Reactions of [RhI(Br)(Tpy)] (Tpy = 4‘-(4-tert-Butylphenyl)-2,2‘:6‘,2‘ ‘-terpyridine) with Alkyl Bromides

• Published in: Organometallics 2004-01, Vol.23 (2), p.269-279
• Main Authors: de Pater, Boke C, Zijp, Eric J, Frühauf, Hans-Werner, Ernsting, Jan M, Elsevier, Cornelis J, Vrieze, Kees, Budzelaar, Peter H. M, Gal, Anton W
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om0305418

Oxidative addition reactions with the highly nucleophilic complex [RhI(Cl)(4‘-(4-tert-butylphenyl)-2,2‘:6‘,2‘ ‘-terpyridine)] (1) and alkyl halides containing chlorine and bromine atoms gave mixtures of uncharacterized products. In contrast to this, oxidative addition reactions with the complex [RhI(Br)(4‘-(4-tert-butylphenyl)-2,2‘:6‘,2‘ ‘-terpyridine)] (2) and various alkyl bromides, containing (mainly terminal) carbon−bromine bonds, gave clean single products in almost quantitative yield. The corresponding air-stable yellow Rh(III)−terpyridine complexes are, in contrast to the parent Rh(I)−terpyridine complex, soluble in various organic solvents. Consequently, these products have been further characterized by means of 1H, 13C, 15N, 103Rh and 2D NMR techniques. NMR techniques were also used to determine the geometry of the studied Rh(III)−terpyridine complexes, which were found to be octahedral with the alkyl moiety axially positioned with respect to the Rh−terpyridine plane (except for complexes 3 and 4). The oxidative addition reaction of complex 2 with 1-bromodecane in ethanol was monitored by UV/vis spectrometry. The recorded electronic absorption spectrum of this reaction showed two distinct isosbestic points in the visible region. It is most likely that first the carbon−bromine bond of 1-bromodecane is activated by the Rh metal followed by the arrangement of the alkyl moiety in an axial position. Unfortunately, on the basis of our findings, no single mechanism for this oxidative addition reaction can be suggested.