Unequivocal Characterization of an Osmium Complex with a Terminal Sulfide Ligand and Its Transformation into Hydrosulfide and Methylsulfide

Deprotonation of the thioamidate group of [OsH{κ2-N,S-[NHC(CH3)S]}(≡CPh)(IPr)(PiPr3)]OTf [1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolylidene; OTf = CF3SO3] results in the release of acetonitrile and formation of the terminal sulfide complex OsH(S)(≡CPh)(IPr)(PiPr3) (2), which has been transformed into the hydrosulfide [OsH(SH)(≡CPh)(IPr)(PiPr3)]OTf (3) and the methylsulfide [OsH(SMe)(≡CPh)(IPr)(PiPr3)]OTf (4) through protonation and methylation reactions, respectively. The structure, spectroscopic characteristics, and reactivity of these compounds are compared. Reactions of 3 and 4 with 2-hydroxypyridine and 2-mercaptopyridine afford [OsH{κ2-X,N-[X-py]}(≡CPh)(IPr)(PiPr3)]OTf [X = O (5), S(6)].

A stable ring-expanded NHC-supported copper boryl and its reactivity towards heterocumulenes

Reaction of bis(pinacolato)diboron with (6-Dipp)CuO^tBu generates a ring-expanded N-heterocyclic carbene supported copper(I) boryl, (6-Dipp)CuBpin. This compound showed remarkable stability and was characterised by NMR spectroscopy and X-ray crystallography. (6-Dipp)CuBpin readily dechalcogenated a range of heterocumulenes such as CO₂, isocyanates and isothiocyanates to yield (6-Dipp)CuXBpin (X = O, S). In the case of CO₂ catalytic reduction to CO is viable in the presence of excess bis(pinacolato)diboron. In contrast, in the case of iso(thio)cyanates, the isocyanide byproduct of dechalcogenation reacted with (6-Dipp)CuBpin to generate a copper(I) borylimidinate, (6-Dipp)CuC(NR)Bpin, which went on to react with heterocumulenes. This off-cycle reactivity gives selective access to a range of novel boron-containing heterocycles bonded to copper, but precludes catalytic reactivity.

Preparation and Degradation of Rhodium and Iridium Diolefin Catalysts for the Acceptorless and Base-Free Dehydrogenation of Secondary Alcohols

Rhodium and iridium diolefin catalysts for the acceptorless and base-free dehydrogenation of secondary alcohols have been prepared, and their degradation has been investigated, during the study of the reactivity of the dimers [M(μ-Cl)(η⁴-C₈H₁₂)]₂ (M = Rh (1), Ir (2)) and [M(μ-OH)(η⁴-C₈H₁₂)]₂ (M = Rh (3), Ir (4)) with 1,3-bis(6′-methyl-2′-pyridylimino)isoindoline (HBMePHI). Complex 1 reacts with HBMePHI, in dichloromethane, to afford equilibrium mixtures of 1, the mononuclear derivative RhCl(η⁴-C₈H₁₂){κ¹-N_py-(HBMePHI)} (5), and the binuclear species [RhCl(η⁴-C₈H₁₂)]₂{μ-N_py,N_py-(HBMePHI)} (6). Under the same conditions, complex 2 affords the iridium counterparts IrCl(η⁴-C₈H₁₂){κ¹-N_py-(HBMePHI)} (7) and [IrCl(η⁴-C₈H₁₂)]₂{μ-N_py,N_py-(HBMePHI)} (8). In contrast to chloride, one of the hydroxide groups of 3 and 4 promotes the deprotonation of HBMePHI to give [M(η⁴-C₈H₁₂)]₂(μ-OH){μ-N_py,N_iso-(BMePHI)} (M = Rh (9), Ir (10)), which are efficient precatalysts for the acceptorless and base-free dehydrogenation of secondary alcohols. In the presence of KO^tBu, the [BMePHI]⁻ ligand undergoes three different degradations: alcoholysis of an exocyclic isoindoline-N double bond, alcoholysis of a pyridyl-N bond, and opening of the five-membered ring of the isoindoline core.

Hydrosulfide complexes of the transition elements: diverse roles in bioinorganic, cluster, coordination, and organometallic chemistry

Molecules containing transition metal hydrosulfide linkages are diverse, spanning a variety of elements, coordination environments, and redox states, and carrying out multiple roles across several fields of chemistry.

Cycloosmathioborane Compounds: Other Manifestations of the Hückel Aromaticity

The discovery of cycloosmathioborane compounds is reported. These species, which are prepared by the simultaneous dehydrogenation of a trihydride hydrogensulfide osmium(IV) complex and a BH₃NHR₂ amine-borane, bear an Os-S-B three-membered ring, being a manifestation of the 4 n + 2 Hückel aromaticity in which n = 0 and where the two π electrons of the ring are provided by the S atom.

The Reactivity of Mercapto Groups against Boron Hydrides in Pincer Ligated Nickel Mercapto Complexes

Several pincer ligated nickel mercapto complexes, [2,6-(R₂ PCH₂ )₂ C₆ H₃ ]NiSH (R=tBu, 1 a; iPr, 1 b), [2,6-(R₂ PO)₂ C₆ H₃ ]NiSH (R=tBu, 2 a; iPr, 2 b) and [4-MeOCO-2,6-(tBu₂ PO)₂ C₆ H₂ ]NiSH (3 a), were synthesized and fully characterized. The reactivity of the mercapto groups against boron hydrides and organic bases was investigated. It was found that the mercapto groups are difficult to be deprotonated by boron hydrides or organic bases. The treatment of complex 2 a or 2 b with an excess amount of catecholborane (HBcat) afforded the corresponding pincer ligated nickel borohydride complexes and the HBcat degradation product. The treatment of complex 1 a, 2 a or 2 b with an excess amount of BH₃ ⋅THF produced the corresponding nickel borohydride species and the S-bridged triborane species THF⋅BH₂ -μ₂ -S(B₂ H₅ ) (5). No reactions between these complexes and organic bases were observed. DFT calculations were carried out to understand this reactivity and get mechanistic insights into the reactions.

Remarkable reactivity of a rhodium(i) boryl complex towards CO2 and CS2: isolation of a carbido complex

The activation of CO₂, CS₂ as well as of PhNCO at [Rh(Bpin)(PEt₃)₃] (pin = pinacolato) by CX bond cleavage is reported. With CS₂ a unique binuclear μ-carbido complex was generated.