The reaction of the sodium salts of ligands 1a,b (1a = 1,3-bis(2-(5-(3,5-xylyl)pyridyl)imino)-5,6-dimethylisoindole, 1b = 1,3-bis(2-(4-tert-butylpyridyl)imino)-5,6-dimethylisoindole) with [Ir(μ-Cl)(COD)]2 (COD = cyclooctadiene) and [Ir(μ-Cl)(C2H4)2]2 afforded the corresponding isoindolato complexes [{BPI(1a,b)}IrI(COD)] (2a,b) and [{BPI(1a,b)}IrI(C2H4)2] (3a,b), respectively. The catalytic activity of the complexes 2a,b was tested in the epoxidation of a wide range of non-electron-rich olefins, using PPO (PPO = 3-phenyl-2-(phenylsulfonyl)-1,2-oxaziridine) as oxidizing agent, giving the corresponding epoxides in moderate to high yields.

The activation of a CPh−H bond in the phenyl ring of 2-(4-bromophenyl)imidazol[1,2-a]pyridine (HC∧N) by [{Pt(η3-C4H7)(μ-Cl)}2] (η3-C4H7 = η3-2-methylallyl) renders the new cyclometalated complex [{Pt(C∧N)(μ-Cl)}2] (2) with high yield and selectivity. Complex 2 can be achieved directly in a one-pot reaction or step by step through the intermediate [Pt(η3-C4H7)Cl(HC∧N-κN)] (1). Compound 1 could be isolated and fully characterized. The X-ray structure shows the coordination of HC∧N through only the N and the existence of a weak Pt···H−C hydrogen bridging bond (Pt···H1 = 2.78 Å, Pt···C1 = 3.365(3) Å, Pt−H1−C1 = 120.9°). Hence, the formation of this intermediate could be considered the first step in the cyclometalation process. The mononuclear complexes [PtCl(C∧N)L] (L = tht (3), PPh3 (4), CN-Xyl (5), CN-tBu (6)) were obtained by cleavage of the bridging system in [{Pt(C∧N)(μ-Cl)}2] (2) by the neutral ligands, L. The resulting geometry (trans C, Cl) is that expected from the electronic preferences, taking into account the degree of transphobia (T) of pairs of trans ligands, T[C(C∧N)/L(Cl)] < T[C(C∧N)/L(S, P, C)]. Complexes [PtCl(C∧N)L] (L = CN-Xyl (5), CN-tBu (6)) containing two strong-field ligands, a CC∧N σ-bonded and an isocyanide ligand, are luminescent. TD-DFT calculations were performed for the singlet ground state, S0, as well as for the first triplet excited state of 6 in both the gas phase and solution. Calculations indicate that the lowest-lying absorption involves mainly 1IL (C∧N) mixed with a small contribution of 1MLCT/1L′LCT (L = C∧N; L′ = Cl) transitions. Complex 5 exhibits “luminescent thermochromism” in the solid state; at 77 K it shows a green phosphorescence band assigned to 3IL transitions located on the C∧N group of monomer species, while at 298 K an orange-red emission is observed, being tentatively assigned to excited states of emissive aggregates (3MMLCT/3π−π*). However complex 6 shows phosphorescence only at 77 K both in solution and in the solid state with the emissions arising from 3IL and 3L′MLCT excited states of monomer species.

The synthesis of a novel hybrid pyrazolate/phosphine anionic ligand [CH2=CHCH2B(CH2PPh2)(pz)2]- is described. Coordination of this ligand to metals in a fac tridentate fashion occurs in the complexes [CH2=CHCH2B(CH2PPh2)(pz)2M(cod)], prepared by reactions of the lithium salt of the ligand with [M(mu-Cl)(cod)]2 (M=Rh, Ir). They are pentacoordinated, with the rhodium complex showing a distorted trigonal-bipyramidal structure in the solid state, as determined by X-ray diffraction methods. Furthermore, the ligand has been linked to the periphery of a carbosilane dendrimer, resulting in the polyanionic dendrimer [Li(TMED)]4[Si{(CH2)3SiMe2(CH2)3B(CH2PPh2)(pz)2}4], which leads further to the corresponding metallodendrimer with four rhodium atoms.

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