Rhodium(I) acetylacetonato complexes of the formula [Rh(acac)(CO)(PR₃)] [acac = acetylacetonate, PR₃ = PPh₃1, PCyPh₂2, PCy₂Ph 3, PCy₃4] were synthesized and the iodomethane oxidative addition to these complexes were studied. Spectroscopic and low temperature (100 K) single crystal X-ray crystallographic data of the rhodium complexes (1–4) indicate a systematic increase in both steric and electronic parameters of the phosphine ligands as phenyl groups on the tertiary phosphine are progressively replaced by cyclohexyl groups in the series. Second order rate constants for the alkyl formation in the oxidative addition of iodomethane in dichloromethane at 25 °C vary with approximately one order-of-magnitude from 6.98(6) × 10⁻³ M⁻¹s⁻¹ (PCyPh₂2) to 55(1) × 10⁻³ M⁻¹ s⁻¹ (PCy₂Ph 3) and do not follow the expected electronic pattern from 1 to 4, which indicates a flexibility of the cyclohexyl group, significantly influencing the reactivity. Activation parameters for the reactions range from 35(3) to 44(1) kJ mol⁻¹ for ΔH^≠ and −140(5) to −154(9) J K⁻¹ mol⁻¹ for ΔS^≠ , and are supporting evidence for an associative activation for the oxidative addition step.

Three types of N(H)-nucleophiles, viz. hydrazine, acetyl hydrazide, and a set of hydrazones, were used to study the nucleophilic addition to the CN group of the 2-propanenitrilium closo-decaborate cluster (Ph₃PCH₂Ph)[B₁₀H₉NCEt], giving N-closo-decaborato amidrazones. A systematic mechanistic study of the nucleophilic addition is provided and included detailed synthetic, crystallographic, computational and kinetic work. As a result, two possible mechanisms have been proposed, which consist of firstly a consecutive incorporation of two Nu(H) nucleophiles, with the second responsible for a subsequent rapid proton exchange. The second possible mechanism assumes a pre-formation of a dinuclear [Nu(H)]₂ species which subsequently proceeds with the nucleophilic attack on the boron cluster. The activation parameters for hydrazones indicate a small dependence on bond formation [ΔH^‡ = 6.8–15 kJ mol⁻¹], but significantly negative entropies of activation [ΔS^‡ ranges from −139 to −164 J K⁻¹ mol⁻¹] with the latter contributing some 70–80% of the total Gibbs free energy of activation, ΔG^‡. In the X-ray structure of (Z)-(Ph₃PCH₂Ph)[B₁₀H₉N(H)C(Et)NHNCPh₂], very rare intramolecular non-covalent B–H⋯π(Ph) interactions were detected and studied by DFT calculations (M06-2x/6-311++G** level of theory) and topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method). The estimated strength of these non-covalent interactions is 0.8–1.4 kcal mol⁻¹.

Two rhenium(I) complexes of the form fac-[Re(L–L′)(CO)₃(S)] were synthesized (L–L′ = N–O salen-type bidentate ligand, S = coordinating methanol or pyridine) and the crystal structures of fac-[tricarbonylmethanol-(2-(3-methylbutyliminomethyl)phenolato)rhenium(I)] and fac-[tricarbonyl-(2-(3-methylbutyliminomethyl)phenolato)pyridinerhenium(I)] are reported. The influence of the coordinating neutral monodentate ligand in these fac-[tricarbonyl(N,O-salen)rhenium(I)] complexes was investigated both in solid state and at theoretical level using X-ray diffraction, IR, NMR, and DFT calculations.