Complexes Tp tol Rh(C 2 H 4 ) 2 (1a) and Tp tol Rh(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 tol Ir(CH 2 C(Me)CHCH 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 CHCCH), 7¸ in which the unsaturated organic moiety is bonded to iridium through the carbon–carbon double bond.