Bioinspired Nucleophilic Attack on a Tungsten-Bound Acetylene: Formation of Cationic Carbyne and Alkenyl Complexes.

Inspired by the proposed inner-sphere mechanism of the tungstoenzyme acetylene hydratase, we have designed tungsten acetylene complexes and investigated their reactivity. Here, we report the first intermolecular nucleophilic attack on a tungsten-bound acetylene (CH) in bioinspired complexes employing 6-methylpyridine-2-thiolate ligands. By using PMe as a nucleophile, we isolated cationic carbyne and alkenyl complexes.

Vapochromism and Magnetochemical Switching of a Nickel(II) Paddlewheel Complex by Reversible NH Uptake and Release.

Reaction of [NiCl (PnH) ] (1) (PnH=6-tert-butyl-pyridazine-3-thione) with NiCl affords the binuclear paddlewheel (PW) complex [Ni (Pn) ] (2). Diamagnetic complex 2 is the first example of a PW complex capable of reversibly binding and releasing NH . The NH ligand in [Ni (Pn) (NH )] (2⋅NH ) enforces major spectroscopic and magnetic susceptibility changes, thus displaying vapochromic properties (λ (2)=532 nm, λ (2⋅NH )=518 nm) and magnetochemical switching (2: S=0; 2⋅NH : S=1).

Structural Mimics of Acetylene Hydratase: Tungsten Complexes Capable of Intramolecular Nucleophilic Attack on Acetylene.

Bioinspired complexes employing the ligands 6-tert-butylpyridazine-3-thione (SPn) and pyridine-2-thione (SPy) were synthesized and fully characterized to mimic the tungstoenzyme acetylene hydratase (AH). The complexes [W(CO)(C H )(CHCH-SPy)(SPy)] (4) and [W(CO)(C H )(CHCH-SPn)(SPn)] (5) were formed by intramolecular nucleophilic attack of the nitrogen donors of the ligand on the coordinated C H molecule. Labelling experiments using C D with the SPy system revealed the insertion reaction proceeding via a bis-acetylene intermediate.

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) (S-Phoz) ] was used for the complexes [W(CO)(C R )(S-Phoz) ] (R=H, 1 a; Me, 1 b; Ph, 1 c). Oxidation with pyridine-N-oxide gave the corresponding W-oxo species [WO(C R )(S-Phoz) ] (R=H, 2 a; Me, 2 b; Ph, 2 c).

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.

Oxorhenium(V) complexes with phenolate-oxazoline ligands: influence of the isomeric form on the O-atom-transfer reactivity.

The bidentate phenolate-oxazoline ligands 2-(2'-hydroxyphenyl)-2-oxazoline (1a, Hoz) and 2-(4',4'-dimethyl-3',4'-dihydrooxazol-2'-yl)phenol (1b, Hdmoz) were used to synthesize two sets of oxorhenium(V) complexes, namely, [ReOCl2(L)(PPh3)] [L = oz (2a) and dmoz (2b)] and [ReOX(L)2] [X = Cl, L = oz (3a or 3a'); X = Cl, L = dmoz (3b); X = OMe, L = dmoz (4)]. Complex 3a' is a coordination isomer (N,N-cis isomer) with respect to the orientation of the phenolate-oxazoline ligands of the previously published complex 3a (N,N-trans isomer). The reaction of 3a' with silver triflate in acetonitrile led to the cationic compound [ReO(oz)2(NCCH3)](OTf) ([3a'](OTf)).