Insights into the κ-P,N Coordination of 1,3,5-Triaza-7-phosphaadamantane and Derivatives: κ-P,N-Heterometallic Complexes and a 15N Nuclear Magnetic Resonance Survey

Complexes {[(PTA)₂CpRu-μ-CN-1κC:2κ²N-RuCp(PTA)₂-ZnCl₃]}·2DMSO (13) {[ZnCl₂(H₂O)]-(PTA-1κP:2κ²N)(PTA)CpRu-μ-CN-1κC:2κ²N-RuCp(PTA)(PTA-1κP:2κ²N)-[ZnCl₂(H₂O)]}Cl (14), [RuCp(HdmoPTA)(PPh₃)(PTA)](CF₃SO₃)₂ (20), [RuCp(HdmoPTA)(HPTA)(PPh₃)](CF₃SO₃)₃ (21), and [RuCp(dmoPTA)(PPh₃)(PTA)](CF₃SO₃) (22) were obtained and characterized, and their crystal structure together with that of the previously published complex 18 is reported. The behavior of the 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane (PTA) and 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (dmoPTA) ligands against protonation and κN-coordination is discussed, on the basis of ¹⁵N nuclear magnetic resonance data collected on 22 different compounds, including PTA (1), HdmoPTA (7H), and some common derivatives as free ligands (2–6 and 8), along with mono- and polymetallic complexes containing PTA and/or HdmoPTA (9–22). ¹⁵N detection via ¹H–¹⁵N heteronuclear multiple bond correlation allowed the construction of a small library of ¹⁵N chemical shifts that shed light on important features regarding κN-coordination in PTA and its derivatives.

To shed light on the behavior of the triazaphosphines 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane (PTA) and 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (dmoPTA) upon κN coordination and N protonation, the ¹⁵N chemical shifts of 22 compounds, including PTA and a representative variety of its derivatives, piano-stool complexes, were collected by ¹H−¹⁵N heteronuclear multiple bond correlation nuclear magnetic resonance. New heterometallic complexes containing PTA were also synthesized and fully characterized.

Crystal structure and magnetic study of the complex salt [RuCp(PTA)2-μ-CN-1κC:2κN-RuCp(PTA)2][Re(NO)Br4(EtOH)0.5(MeOH)0.5]

A new RuII-ReII complex salt, μ-cyanido-κ2 C:N-bis-[(η5-cyclo-penta-dien-yl)bis(3,5,7-tri-aza-phosphaadamantane-κP)ruthenium(II)] tetra-bromido-(ethanol/methanol-κO)nitrosylrhenate(II), [Ru(CN)(C5H5)2(C6H12N3P)4][ReBr4(NO)(CH4O)0.5(C2H6O)0.5] or [RuCp(PTA)2-μ-CN-1κC:2κ2 N-RuCp(PTA)2][Re(NO)Br4(EtOH)0.5(MeOH)0.5] (PTA = 3,5,7-tri-aza-phosphaadaman-tane) was obtained and characterized by single-crystal X-ray diffraction, elemental analysis and infrared spectroscopy. The title salt was obtained by liquid-liquid diffusion of methanol/DMSO solutions of (NBu4)[Re(NO)Br4(EtOH)] and [(PTA)2CpRu-μ-CN-1κC:2κ2 N-RuCp(PTA)2](CF3SO3). The RuII and ReII independent moieties correspond to a binuclear and mononuclear complex ion, respectively. A deep geometrical parameter analysis was performed, and no significant differences were found with earlier reports containing similar mol-ecules. The magnetic properties were investigated in the temperature range 2.0-300 K, and the complex behaves as a quasi-magnetically isolated spin doublet with weak anti-ferromagnetic inter-actions.

Neutron Scattering Techniques for Studying Metal Complexes in Aqueous Solution

Neutron scattering combined with ab initio calculations provides a powerful tool for studying metal complexes in different solvents and, particularly, in water. The majority of traditional characterization techniques in catalysis provide only limited information on homogeneous catalytic processes. Neutron scattering, on the other hand, thanks to its sensitivity to hydrogen atoms, and therefore water molecules, can be used to build detailed models of reaction paths and to observe, at a molecular level, the influence of solvent molecules on a catalytic process. In this Mini-Review we describe several examples on how neutron scattering combined with ab initio calculations can be used to examine the nature of the interaction of water molecules with catalytically active metal complexes in solution.

First exfoliated Ru-Ru-Au organometallic polymer with layered structure

A new water soluble heterometallic polymeric complex [{(PTA)2CpRu-μ-CN-1κC:2κ2N-RuCp(PTA)2}-μ-{Au(CN)4}4]n·2H2O (1) is synthesized and characterized by single crystal X-ray diffraction. This complex self-assembles forming 3D polymeric structures with large scale hexagonal conformation. They also organize as 3D stacks of polymer sandwiches that can be exfoliated providing mono heterometallic-3D layers, as shown by electron microscopy. Regarding the polymer dynamics, quasi-elastic neutron scattering shows a transition from vibrational Debye-Waller behaviour to a more dynamically active state as a result of the loss of structural water molecules.

Investigating the reactivity of neutral water-soluble Ru(ii)–PTA carbonyls towards the model imine ligands pyridine and 2,2′-bipyridine

The reactivity of selected Ru(ii)-PTA carbonyls with potentially labile ligands (i.e. H₂O, dmso and/or Cl) towards the model imine ligands pyridine and 2,2′-bipyridine was investigated, yielding several neutral and cationic water-soluble derivatives.

Novel Ruthenium-Silver PTA-Based Polymers and Their Behavior in Water

New coordination polymers based on two metal-containing moieties Ru–Ag are synthesized: Na[RuCpX(PTA)-μ-(PTA)-1κP:2κ²N-AgX₂]_∞ (X = Cl (1), Br (2), I (3)). Characterization is performed by NMR, UV-visible and FT-IR spectroscopy, optical-electron microscopy, and elemental analyses (C, H, N, S). Light scattering is employed to characterize the colloidal particles growth by polymer self-assembling. These structures are stable over a broad range of pH and exhibit thermally-driven swelling, thus resembling a typical thermosensitive hydrogel.

Good isomerization of 2-cyclohexenol by two Ru(ii) complexes, synthesis and characterization of a reaction intermediate

The catalytic activities of [RuClCp(PTA)2] (1) and [RuCp(PTA)2(H2O-κO)]OTf (2) were assessed for the redox isomerization of the cyclic allylic alcohol 2-cyclohexenol into cyclohexanone in water and biphasic media. Complex 2 showed unprecedented good TONs for the studied conversion both in water (TON = 647) and in the biphase of cyclohexene/H2O (TON = 3420) while 1 showed a lower but also good activity (water TON = 95, biphasic TON = 100). The catalytic reaction intermediate [RuCp(PTA)2(η2-C6H9OH)]CF3SO3 (3) was synthesized and characterized using NMR.

Water soluble derivatives of platinum carbonyl Chini clusters: synthesis, molecular structures and cytotoxicity of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2-

The reactions of [Pt3n(CO)6n]2- (n = 2-5) homoleptic Chini-type clusters with increasing amounts of 1,3,5-triaza-7-phosphaadamantane (PTA) result in the stepwise substitution of one terminal CO ligand per Pt3 triangular unit up to the formation of [Pt3n(CO)5n(PTA)n]2- (n = 2-5). Competition between the nonredox substitution with retention of the nuclearity and the redox fragmentation to afford lower nuclearity heteroleptic Chini-type clusters is observed as a function of the amount of PTA and the nuclearity of the starting cluster. Because of this, [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- are more conveniently obtained via the oxidation of [Pt9(CO)15(PTA)3]2-. All the new species were spectroscopically characterized, and the structures of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- were determined by single-crystal X-ray diffraction. These clusters may be viewed as heteroleptic Chini-type clusters composed of stacks of four and five Pt3(μ-CO)3(CO)2(PTA) units, respectively. The solubility in water of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- has been determined and their cytotoxicity towards human ovarian (A2780) cancer cells and their cisplatin-resistant strain (A2780cisR) has been evaluated.