Keywords: Rhodium / Tridentate ligands / X-ray diffraction / Cyclic voltammetry / Density functional calculations Rh I -terpyridine complexes have been unambiguously formed for the first time. The 2,2Ј:6Ј,2ЈЈ-terpyridine (tpy), 4Ј-chloro-2,2Ј:6Ј,2ЈЈ-terpyridine (4Ј-Cl-tpy) and 4Ј-(tert-butyldimethylsilyl-ortho-carboranyl)-2,2Ј:6Ј,2ЈЈ-terpyridine (carboranyltpy) ligands were used for successful syntheses and characterisation of the corresponding Rh I complexes with halide coligands, [Rh(X)(4Ј-Y-terpyridine)] (X = Cl, Y = H, Cl, carboranyl; X = Br, Y = H). All four neutral Rh-tpy complexes are square planar, with Rh−X bonds in the plane of the 4Ј-Y-terpyridine ligands. Full characterisation of these dark blue, highly air-sensitive compounds was hampered by their poor solubility in various organic solvents. This is mainly due to the formation of π-stacked aggregates, as evidenced by the crystal structure of [Rh(Cl)(tpy)]; in addition, [Rh(Cl)(carboranyl-tpy)] merely forms discrete dimers. The (bonding) properties of the novel Rh I -terpyridine complexes have been

Oxidative addition reactions with the highly nucleophilic complex [Rh I (Cl)(4′-(4-tertbutylphenyl)-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 [Rh I (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 1 H, 13 C, 15 N, 103 Rh 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.

o-Phenylenemagnesium (1) was used to prepare the first structurally characterized intramolecularly coordinated diindacycle:  9,10-dihydro-9,10-bis[2,6-bis((dimethylamino)methyl)phenyl]-9,10-diindaanthracene (3).

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