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Enynes are important synthetic intermediates that are also found in a variety of natural products and other biologically relevant molecules. The most atom economical synthetic route to enynes is via the direct coupling of readily available terminal alkyne precursors. Towards this goal, we demonstrate the formation of 1,3-enynes from terminal alkynes facilitated by a reduced ZrIV/Co-I heterobimetallic complex. An intermediate is trapped as a tBuNC adduct, revealing that bimetallic activation of the terminal C-H bond of the alkyne is an essential mechanistic step.

A series of compounds comprised of N -heterocyclic phosphido-containing ligands bound to a Co(CO) 2 fragment are explored computationally using density functional theory (DFT). Computational methods are used to identify changes in the electronic structure and bonding in these molecules as a function of substituent and backbone modifications, with the ultimate goal of identifying the most intriguing targets for further experimental studies. A series of N, As, and Sb derivatives are also explored through computational studies to better understand the geometric and electronic effects of varying the central pnictogen atom. [ABSTRACT FROM AUTHOR]

Abstract: Addition of H2 across the cobalt–phosphorus bond of (PPP)CoPMe3 (3) is demonstrated, where PPP is a monoanionic diphosphine pincer ligand with a central N‐heterocyclic phosphido (NHP−) donor. The chlorophosphine CoII complex (PPClP)CoCl2 (2) can be generated through coordination of the chlorophosphine ligand (PPClP, 1) to CoCl2. Subsequent reduction of 2 with KC8 in the presence of PMe3 generates (PPP)CoPMe3 (3), in which both the phosphorus and cobalt centers have been reduced. The addition of 1 atm of H2 to complex 3 cleanly affords (PPHP)Co(H)PMe3 (4), in which H2 has ultimately been added across the metal–phosphorus bond. Complex 4 was characterized spectroscopically and using computational methods to predict its geometry. [ABSTRACT FROM AUTHOR]

The reactivity of the reduced ZrIIICo0 heterobimetallic complex [(thf)Zr(MesNP iPr2)3CoN2] ( 1a) towards O-H, S-H, S-S, and O-O bonds has been investigated. Complex 1a reacts readily with PhOH, EtOH, and H2O to generate the one-electron-oxidized complexes [(RO)Zr(MesNP iPr2)3CoN2] [R = Et ( 2), Ph ( 3), H ( 4)]. In contrast, PhSH and PhS-SPh react by means of overall two-electron processes to form [(η2-MesNP iPr2)Zr(μ-SPh)(MesNP iPr2)2Co(SPh)] ( 5a). Addition of stoichiometric diethyl peroxide to 1a generates 2, but further equivalents lead to the two-electron oxidized product [(EtO)Zr(MesNP iPr2)3Co(OEt)] ( 6). More sterically hindered peroxides such as dicumyl peroxide or di- tert-butyl peroxide do not react with 1a under ambient conditions, but upon photolysis, di- tert-butyl peroxide reacts with 1a to form [( tBuO)Zr(MesNP iPr2)3CoN2] ( 7). These results imply that an inner-sphere electron-transfer process is occurring at the Zr site of 1a upon treatment with these chalcogen-based substrates, and a dissociative electron-transfer mechanism is proposed. [ABSTRACT FROM AUTHOR]

A tris(phosphino)amide-ligated Zr–Co heterobimetallic complex has been shown to activate N–H bonds of hydrazine derivatives via a proton-coupled electron transfer process. Such reactivity is highly unusual for an early metal such as Zr, but is promoted by the adjacent redox active Co atom. [ABSTRACT FROM AUTHOR]

The phosphinoamide-linked Co/Hf complexes ICo(Ph2PNiPr)3HfCI (4), ICo(iPr2PNMes)3HfCI (5), and ICo(iPr2PNiPr)3HfCI (6) have been synthesized from the corresponding tris(phosphinoamide)HICI complexes (1-3) for comparison with the recently reported tris(phosphinoamide) Co/Zr complexes. Very minor structural and electronic differences between the Zr and Hf complexes were found when the N-iPr-substituted phosphinoamide ligands [Ph2PNiPr]- and [Pr2PNiPr]- were utilized. The reduction products [(THF)4Na-{(N2-Co(Ph2PNiPr)3HfCl}2]Na(THF)6 (7) and N2-Co(iPr2PNiPr)3Hf (9) are also remarkably similar to the corresponding Zr/Co analogues. In the case of Hf/Co and Zr/Co complexes linked by the N-Mes ligand [iPr2PNMes]- (Mes = 2,4,6-trimethylphenyl), however, more pronounced differences in structure, bonding, and reactivity are observed. While differences associated with S are still modest, larger variations are observed when comparing the two-electron reduction product [N2-Co(iPr2PNMes)3Hf-X] [Na(THF)5] (8) with its Zr congener. In addition to structural and spectroscopic differences, vastly different reactivity is observed, with 8 undergoing one-electron oxidation to form ClHf(MesNPiPr2)3CoN2 (II) in the presence of Mel, while a two-electron oxidative addition process occurs in a similar reaction with the Zr derivative. The activity of S toward Kumada coupling was investigated, finding significantly diminished activity in comparison to Co/Zr complexes. [ABSTRACT FROM AUTHOR]

The reactivity of the reduced heterobimetallic complex Zr(iPrNPiPr2)3CoN2 (1) toward aryl azides was examined, revealing a four-electron redox transformation to afford unusual heterobimetallic zirconium/cobalt diimido complexes. In the case of p-tolyl azide, the diamagnetic C3-symmetric bis(terminal imido) complex 3 is formed, but mesityl azide instead leads to asymmetric complex 4 featuring a bridging imido fragment. [ABSTRACT FROM AUTHOR]

The article presents a study on the ability of synthesized Cobalt (Co)-Zircon (Zr) heterobimetallic complexes for coordinative support of unsaturated species. The study synthesized Co/Zr complexes linked by three phosphinoamide ligands, wherein reduction of two-electrons were noted in the interaction. It founds involvement of electron density in Nitrogen (N2) bond to Co-Zr bond electronic structure evaluation, suggesting unsaturated species reactivity to small molecule substrate.