Activation of C(sp2)−H and Reduction of CE (E = CH, N) Bonds with an Osmium-Hexahydride Complex: Influence of E on the Behavior of RCHE-py Substrates

Reactions of triosmium and triruthenium clusters with 2-ethynylpyridine: new modes for alkyne C-C bond coupling and C-H bond activation

The reaction of the trimetallic clusters [H₂Os₃(CO)₁₀] and [Ru₃(CO)₁₀L₂] (L = CO, MeCN) with 2-ethynylpyridine has been investigated. Treatment of [H₂Os₃(CO)₁₀] with excess 2-ethynylpyridine affords [HOs₃(CO)₁₀(μ-C₅H₄NCH=CH)] (1), [HOs₃(CO)₉(μ₃-C₅H₄NC Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CH₂)] (2), [HOs₃(CO)₉(μ₃-C₅H₄NCCCO₂)] (3), and [HOs₃(CO)₁₀(μ-CHCHC₅H₄N)] (4) formed through either the direct addition of the Os–H bond across the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bond or acetylenic C–H bond activation of the 2-ethynylpyridine substrate. In contrast, the dominant pathway for the reaction between [Ru₃(CO)₁₂] and 2-ethynylpyridine is C–C bond coupling of the alkyne moiety to furnish the triruthenium clusters [Ru₃(CO)₇(μ-CO){μ₃-C₅H₄NCCHC(C₅H₄N)CH}] (5) and [Ru₃(CO)₇(μ-CO){μ₃-C₅H₄NCCHC(C₅H₄N)CHCHC(C₅H₄N)}] (6). Cluster 5 contains a metalated 2-pyridyl-substituted diene while 6 exhibits a metalated 2-pyridyl-substituted triene moiety. The functionalized pyridyl ligands in 5 and 6 derive via the formal C–C bond coupling of two and three 2-ethynylpyridine molecules, respectively, and 5 and 6 provide evidence for facile alkyne insertion at ruthenium clusters. The solid-state structures of 1–3, 5, and 6 have been determined by single-crystal X-ray diffraction analyses, and the bonding in the product clusters has been investigated by DFT. In the case of 1, the computational results reveal a rare thermodynamic preference for a terminal hydride ligand as opposed to a hydride-bridged Os–Os bond (3c,2e Os–Os–H bond).

The reactivity of 2-ethynylpyridine at low-valent triosmium and triruthenium centers has been investigated.

Vinylimidazole coordination modes to Pt and Au metal centers

Reaction conditions affect the coordination modes of vinylimidazole to platinum and gold.

New molecular architectures containing low-valent cluster centres with di- and trimetalated 2-vinylpyrazine ligands: synthesis and molecular structures of Ru5(CO)15(μ5-C4H2N2CH[double bond, length as m-dash]CH)(μ-H)2 and Ru8(CO)24(μ7-C4H2N2CH[double bond, length as m-dash]C)(μ-H)3

Reaction of 2-vinylpyrazine with Ru₃(CO)₁₂ results in multiple C-H bond activations to afford penta- and octa-ruthenium clusters, Ru₅(CO)₁₅(μ₅-C₄H₂N₂CH[double bond, length as m-dash]CH)(μ-H)₂ (2) and Ru₈(CO)₂₄(μ₇-C₄H₂N₂CH[double bond, length as m-dash]C)(μ-H)₃ (3), in which a Ru₃ sub-unit is linked to Ru₂ and Ru₅ centres via di- and tri-metalated 2-vinylpyrazine ligands, exhibiting novel coordination modes including the loss of ring aromaticity in 2. The bonding of 2 and the mechanism for the fluxional behaviour of the hydrides have been examined by electronic structure calculations.

Mono- and dinuclear osmium N,N'-di- and tetraphenylbipyridyls and extended bipyridyls. Synthesis, structure and electrochemistry

The efficient synthesis of mono- and dinuclear Os(IV) bipyridyl complexes is reported. These compounds show a two-step oxidation process leading to notable structural changes, which are reflected in their emission properties. During the second oxidation process a tetracation with a hydride-dihydrogen structure (instead of a trihydride) is formed. This results in a significant bathochromic shift of the emission band, accompanied by a moderate increase in intensity.

Synthesis and characterisation of [6]-azaosmahelicenes: the first d4-heterometallahelicenes

[6]-Azaosmahelicenes, the first d(4)-heterometallahelicenes, have been synthesised and fully characterised. Their optical properties (UV-Vis absorption and luminescence) are reported.