Complexes Tp tolRh(C 2H 4) 2 ( 1a) and Tp tolRh(CH 2 C(Me)C(Me) CH 2) ( 1b) have been prepared by reaction of KTp tol with the appropriate [RhCl(olefin) 2] 2 dimer (Tp tol means hydrotris(3- p-tolylpyrazol-1-yl)borate). The two complexes show a dynamic behaviour that involves exchange between κ 2 and κ 3 coordination modes of the Tp tol ligand. The iridium analogue, Tp tolIr(CH 2 C(Me)CH CH 2) ( 2) has also been synthesized, and has been converted into the Ir(III) dinitrogen complex [( κ 4 -N, N’, N’’, C-Tp tol)Ir(Ph)(N 2) ( 3) by irradiation with UV light under a dinitrogen atmosphere. Compound 3 constitutes a rare example of Ir(III)–N 2 complex structurally characterized by X-ray crystallography. Its N 2 ligand can be easily substituted by acetonitrile or ethylene upon heating and denticity changes in the Tp tol ligand, from κ 4 -N, N’, N’’, C (monometallated Tp tol, from now on represented as Tp tol′) to κ 5-N , N′, N″, C, C″ (dimetallated Tp tol ligand, represented as Tp tol ″ ) have been observed. When complex 3 is heated in the presence of acetylene, dimerization of the alkyne takes place to yield the enyne complex [( κ 5 -N, N′, N′′, C, C′-Tp tol)Ir(CH 2 CHC CH), 7¸ in which the unsaturated organic moiety is bonded to iridium through the carbon–carbon double bond.