Cycloosmathioborane Compounds: Other Manifestations of the Hückel Aromaticity

Esteruelas, Miguel A.; Fernández, Israel; García‐Yebra, Cristina; Martín, Jaime; Oñate, Enrique

doi:10.1021/acs.inorgchem.8b03366

“…The aromatic characteristics of metallaaromatics have become a topic of intense debate. ,,− It has been shown that studying the aromaticity in these systems is not a trivial task, and many new phenomena, which have not been previously detected in analogous organic compounds, appear. ,,, For instance, aromaticity of monocyclic conjugated hydrocarbons and their heteroatom derivatives can be rationalized by several electron counting aromaticity rules . On the other hand, even in the most simple monocyclic metallaaromatics, there is an ongoing debate on how many electrons are involved in cyclic conjugation.…”

Section: Introductionmentioning

confidence: 99%

Aromaticity of Osmaacenes in Their Lowest-Lying Singlet and Triplet States

Radenković

¹

,

Solà

²

2023

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The aromatic character of a series of osmaacenes in their lowest-lying singlet and triplet states was thoroughly examined by means of the magnetically induced current densities and multicentre delocalization indices (MCIs). Both employed approaches agree that the osmabenzene molecule (OsB) in the S0 state exhibits dominant π-Hückel-type aromatic character, with a small but nonnegligible amount of π-Craig–Möbius aromaticity. Contrary to benzene, which is antiaromatic in the T1 state, OsB preserves some of its aromaticity in the T1 state. In higher members of the osmaacene series in the S0 and T1 states, the central Os-containing ring becomes nonaromatic, acting as a barrier between the two side polyacenic units which, on the other hand, exhibit a significant extent of π-electron delocalization.

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“…According to such ability, xant(P i Pr 2 ) 2 is adapted to the requirements of the reactions in which its complexes participate, enabling the necessary geometrical transformations on the metal coordination sphere through changes in its coordination mode . As proof-of-concept validation, besides species bearing the diphosphine κ 3 - P , O , P - mer coordinated, complexes with the ligand in fashions κ 3 - P , O , P - fac , κ 2 - P , P - cis , and κ 2 - P , P - trans , have been also isolated. This is allowing to perform reactions and to isolate compounds initially forbidden, and as result, interesting catalysts for a wide range of processes are being discovered. ,,, The proved flexibility and great coordinative versatility of xant(P i Pr 2 ) 2 inspired us to use it to address the preparation of a neutral hydride-osmium(II)-allenylidene complex.…”

Section: Introductionmentioning

confidence: 99%

Repercussion of a 1,3-Hydrogen Shift in a Hydride-Osmium-Allenylidene Complex

Esteruelas

¹

,

Oñate

²

,

Paz

³

et al. 2021

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An unusual 1,3-hydrogen shift from the metal center to the C β atom of the C 3 -chain of the allenylidene ligand in a hydride-osmium(II)-allenylidene complex is the beginning of several interesting transformations in the cumulene. The hydride-osmium(II)-allenylidene complex was prepared in two steps, starting from the tetrahydride dimer [(Os(H···H){κ 3 - P , O , P -[xant(P i Pr 2 ) 2 ]}) 2 (μ-Cl) 2 ][BF 4 ] 2 ( 1 ). Complex 1 reacts with 1,1-diphenyl-2-propyn-1-ol to give the hydride-osmium(II)-alkenylcarbyne [OsHCl(≡CCH=CPh 2 ){κ 3 - P , O , P -[xant(P i Pr 2 ) 2 ]}]BF 4 ( 2 ), which yields OsHCl(=C=C=CPh 2 ){κ 3 - P , O , P -[xant(P i Pr 2 ) 2 ]} ( 3 ) by selective abstraction of the C β –H hydrogen atom of the alkenylcarbyne ligand with K t BuO. Complex 3 is metastable. According to results of DFT calculations, the migration of the hydride ligand to the C β atom of the cumulene has an activation energy too high to occur in a concerted manner. However, the migration can be catalyzed by water, alcohols, and aldehydes. The resulting alkenylcarbyne-osmium(0) intermediate is unstable and evolves into a 7:3 mixture of the hydride-osmium(II)-indenylidene OsHCl(=C IndPh ){κ 3 - P , O , P -[xant(P i Pr 2 ) 2 ]} ( 4 ) and the osmanaphthalene OsCl(C 9 H 6 Ph){κ 3 - P , O , P -[xant(P i Pr 2 ) 2 ]} ( 5 ). Protonation of 4 with HBF 4 leads to the elongated dihydrogen complex [OsCl(η 2 -H 2 )(=C IndPh ){κ 3 - P , O , P -[xant(P i Pr 2 ) 2 ...

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“…Osmapentalenes and osmapentalynes are known. , However, pincer complexes of this element are scarce in comparison with the number of known compounds for the rest of the platinum-group metals. The pincer ligands coordinated to this element mainly involve neutral or monoanionic , moieties, which result from the simple coordination of tridentate molecules or the coordination of bidentate groups along with the σ-bond activation of one of their substituents, whereas osmium complexes bearing dianionic pincer ligands are very rare. Examples include C,C′,N-donors, which are generated by coordination of a 2e-donor N atom and two σ-bond activations at the molecule skeleton, or O,N,O-, C,C′,C-, and C,N,C-donors, which are formed as a consequence of the coordination of a 2e-donor atom and a σ-bond activation at two substituents of the molecular core. − …”

Section: Introductionmentioning

confidence: 99%

Assembly of a Dihydrideborate and Two Aryl Nitriles to Form a C,N,N′-Pincer Ligand Coordinated to Osmium

Babón

¹

,

Esteruelas

²

,

Fernández

³

et al. 2021

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The C,N,N'-donor aryl-diimineborate pincer ligand of complexes OsH2{κ 3 -C,N,N-[C6H3RCH=NB(cat)N=CHC6H4R]}(P i Pr3)2 (R = H, Me) has been generated in a one-pot procedure, by the reaction of the hexahydride OsH6(P i Pr3)2 with catecholborane (catBH) and two molecules of the corresponding aryl nitrile. The osmium-pincer bonding situation has been analyzed by means of Atoms In Molecules (AIM), Natural Bond Orbital (NBO), and Energy Decomposition Analysis coupled with the Natural Orbitals for Chemical Valence (EDA−NOCV) methods. According to the results, it exhibits a rather strong electron-sharing Os-C bond, two weaker donor-acceptor N-to-Os bonds, and two π-backdonations from the transition metal to vacant π* orbitals of the formed metallacycles. In addition, spectroscopic findings and DFT calculations reveal that the donor units of the pincer are incorporated in a sequential manner. Firstly, the central Os-N bond is formed, by the reaction of the dihydrideborate ligand of intermediate OsH3{κ 2 -H,H-(H2Bcat)}(P i Pr3)2 with one of the aryl nitriles. The subsequent oxidative addition of the ortho-C-H bond of the aryl substituent of the resulting κ 1 -N-(N-boryl-arylaldimine) affords the Os-C bond. Lastly, the second Os-N bond is generated from a hydride, an orthometalated Nboryl-arylaldimine and the second aryl nitrile.

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Cycloosmathioborane Compounds: Other Manifestations of the Hückel Aromaticity

Cited by 17 publications

References 47 publications

Aromaticity of Osmaacenes in Their Lowest-Lying Singlet and Triplet States

Aromaticity of Osmaacenes in Their Lowest-Lying Singlet and Triplet States

Repercussion of a 1,3-Hydrogen Shift in a Hydride-Osmium-Allenylidene Complex

Assembly of a Dihydrideborate and Two Aryl Nitriles to Form a C,N,N′-Pincer Ligand Coordinated to Osmium

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