Coordinative Flexibility of a Thiophenolate Oxazoline Ligand in Nickel(II), Palladium(II), and Platinum(II) Complexes

Synthesis and structure of two isomers of a molybdenum(II) 2-butyne complex stabilized by bioinspired S,N-bidentate ligands

The synthesis and structural determination of two isomers of the molybdenum(II) complex (η2-but-2-yne)carbonylbis[2-(4,4-dimethyl-4,5-dihydro-1,3-oxazol-2-yl)benzenethiolato-κ2N,S]molybdenum(II), [Mo(C11H12NOS)2(C4H6)(CO)] or Mo(CO)(C2Me2)(S-Phoz)2, are presented. The N,N-cis-S,S-trans isomer 1 shows quite different bond lengths to the metal atom [Mo-N = 2.4715 (10) versus 2.3404 (11) Å; Mo-S = 2.4673 (3) versus 2.3665 (3) Å]. In the N,N-trans-S,S-cis isomer 2, which is isotypic with the corresponding W complex, the Mo-N bond lengths [2.236 (2) and 2.203 (2) Å], as well as the Mo-S bond lengths [2.5254 (8) and 2.5297 (8) Å], are almost the same.

Activation and Photoinduced Release of Alkynes on a Biomimetic Tungsten Center: The Photochemical Behavior of the W-S-Phoz System

The synthesis and structural determination of four tungsten alkyne complexes coordinated by the bio-inspired S,N-donor ligand 2-(4',4'-dimethyloxazoline-2'-yl)thiophenolate (S-Phoz) is presented. A previously established protocol that involved the reaction of the respective alkyne with the bis-carbonyl precursor [W(CO)2 (S-Phoz)2 ] was used for the complexes [W(CO)(C2 R2 )(S-Phoz)2 ] (R=H, 1 a; Me, 1 b; Ph, 1 c). Oxidation with pyridine-N-oxide gave the corresponding W-oxo species [WO(C2 R2 )(S-Phoz)2 ] (R=H, 2 a; Me, 2 b; Ph, 2 c). All W-oxo-alkyne complexes (2 a, b, c) were found to be capable of alkyne release upon light irradiation to afford five-coordinate [WO(S-Phoz)2 ] (3). The photoinduced release of the alkyne ligand was studied in detail by in situ 1 H NMR measurements, which revealed correlation of the photodissociation rate constant (2 b>2 a>2 c) with the elongation of the alkyne C≡C bond in the molecular structures. Oxidation of [WO(S-Phoz)2 ] (3) with pyridine-N-oxide yielded [WO2 (S-Phoz)2 ] (4), which shows highly fluxional behavior in solution. Variable-temperature 1 H NMR spectroscopy revealed three isomeric forms with respect to the ligand arrangement versus each other. Furthermore, compound 4 rearranges to tetranuclear oxo compound [W4 O4 (μ-O)6 (S-Phoz)4 ] (5) and dinuclear [{WO(μ-O)(S-Phoz)}2 ] (6) over time. The latter two were identified by single-crystal X-ray diffraction analyses.

Synthesis and characterisation of κ2-N,O-oxazoline-enolate complexes of nickel(ii): explorations in coordination chemistry and metal-mediated polymerisation

The synthesis and characterisation (UV-Vis, IR, X-ray diffraction, etc.) of a series of Ni(ii) complexes derived from both known and novel 2-acylmethyl-2-oxazolines (2a-g: i.e., (Z)-1-R-2-(4,4'-dimethyl-2'-oxazolin-2'-yl)eth-1-en-1-ol; R = -Ph, -2-furanyl, -p-NO2-Ph, -t-Bu, -2-thiofuranyl, p-NC-Ph, -CF3) is reported. These Ni materials (3a-g) represent the first group 10 metal complexes of this ligand class. All derivatives reported are paramagnetic (S = 1) compounds of formulae Ni(κ2-N,O-L)2 where L represents an enolate of structure (Z)-1-R-2-(4',4'-dimethyl-2'-oxazolin-2'-yl)eth-1-en-1-ate formed via proton loss from 2. The air- and moisture-stable metal complexes feature a less typical distorted seesaw-shaped disposition of binding atoms around the metal centre for six structurally characterised (X-ray) examples. Preliminary investigations indicate that 3a (R = -Ph) is a useful catalysts for olefin polymerisation in the presence of alkylaluminum reagents.

Towards Structural-Functional Mimics of Acetylene Hydratase: Reversible Activation of Acetylene using a Biomimetic Tungsten Complex

The synthesis and characterization of a biomimetic system that can reversibly bind acetylene (ethyne) is reported. The system has been designed to mimic catalytic intermediates of the tungstoenzyme acetylene hydratase. The thiophenyloxazoline ligand S-Phoz (2-(4',4'-dimethyloxazolin-2'-yl)thiophenolate) is used to generate a bioinspired donor environment around the W center, facilitating the stabilization of W-acetylene adducts. The featured complexes [W(C2 H2 )(CO)(S-Phoz)2 ] (2) and [WO(C2 H2 )(S-Phoz)2 ] (3) are extremely rare from a synthetic and structural point of view as very little is known about W-C2 H2 adducts. Upon exposure to visible light, 3 can release C2 H2 from its coordination sphere to yield the 14-electron species [WO(S-Phoz)2 ] (4). Under light-exclusion 4 re-activates C2 H2 making this the first fully characterized system for the reversible activation of acetylene.