An official website of the United States government
Abstract Multiple bonds between boron and transition metals are known in many borylene (:BR) complexes via metal dπ→BR back‐donation, despite the electron deficiency of boron. An electron‐precise metal–boron triple bond was first observed in BiB2O−[Bi≡B−B≡O]−in which both boron atoms can be viewed as sp‐hybridized and the [B−BO]−fragment is isoelectronic to a carbyne (CR). To search for the first electron‐precise transition‐metal‐boron triple‐bond species, we have produced IrB2O−and ReB2O−and investigated them by photoelectron spectroscopy and quantum‐chemical calculations. The results allow to elucidate the structures and bonding in the two clusters. We find IrB2O−has a closed‐shell bent structure (Cs,1A′) with BO−coordinated to an Ir≡B unit, (−OB)Ir≡B, whereas ReB2O−is linear (C∞v,3Σ−) with an electron‐precise Re≡B triple bond, [Re≡B−B≡O]−. The results suggest the intriguing possibility of synthesizing compounds with electron‐precise M≡B triple bonds analogous to classical carbyne systems.
more »
« less
On the remarkable resistance to oxidation by the Bi 18 − cluster
The reactivity of Bin−clusters (n= 2 to 30) with O2is found to display even-odd alternations. The open-shell even-sized Bin−clusters are more reactive than the closed-shell odd-sized clusters, except Bi18−, which exhibits no observable reactivity toward O2. We have investigated the structure and bonding of Bi18−to understand its remarkable resistance to oxidation. We find that the most stable structure of Bi18−consists of two Bi8cages linked by a Bi2dimer, where each atom is bonded to three neighboring atoms. Chemical bonding analyses reveal that each Bi uses its three 6pelectrons to form three covalent bonds with its neighbors, resulting in a Bi18−cluster without any dangling bonds. We find that the robust Bi18framework along with the totally delocalized unpaired electron is responsible for the surprising inertness of Bi18−toward O2. The Bi18framework is similar to that in Hittorf’s phosphorus, suggesting the possibility to create bismuth nanoclusters with interesting structures and properties.
more »
« less
- Award ID(s):
- 2403841
- PAR ID:
- 10565883
- Publisher / Repository:
- AAAS
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 10
- Issue:
- 44
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Organofunctionalized tetranuclear clusters [(MIICl)2(VIVO)2{((HOCH2CH2)(H)N(CH2CH2O))(HN(CH2CH2O)2)}2] (1, M=Co,2: M=Zn) containing an unprecedented oxometallacyclic {M2V2Cl2N4O8} (M=Co, Zn) framework have been prepared by solvothermal reactions. The new oxo‐alkoxide compounds were fully characterized by spectroscopic methods, magnetic susceptibility measurement, DFT and ab initio computational methods, and complete single‐crystal X‐ray diffraction structure analysis. The isostructural clusters are formed of edge‐sharing octahedral {VO5N} and trigonal bipyramidal {MO3NCl} units. Diethanolamine ligates the bimetallic lacunary double cubane core of1and2in an unusual two‐mode fashion, unobserved previously. In the crystalline state, the clusters of1and2are joined by hydrogen bonds to form a three‐dimensional network structure. Magnetic susceptibility data indicate weakly antiferromagnetic interactions between the vanadium centers [Jiso(VIV−VIV)=−5.4(1); −3.9(2) cm−1], and inequivalent antiferromagnetic interactions between the cobalt and vanadium centers [Jiso(VIV−CoII)=−12.6 and −7.5 cm−1] contained in1.more » « less
-
The hydroxylation of C–H bonds can be carried out by the high-valent CoIII,IV2(µ-O)2complex2asupported by the tetradentate tris(2-pyridylmethyl)amine ligand via a CoIII2(µ-O)(µ-OH) intermediate (3a). Complex3acan be independently generated either by H-atom transfer (HAT) in the reaction of2awith phenols as the H-atom donor or protonation of its conjugate base, the CoIII2(µ-O)2complex1a. Resonance Raman spectra of these three complexes reveal oxygen-isotope-sensitive vibrations at 560 to 590 cm−1associated with the symmetric Co–O–Co stretching mode of the Co2O2diamond core. Together with a Co•••Co distance of 2.78(2) Å previously identified for1aand2aby Extended X-ray Absorption Fine Structure (EXAFS) analysis, these results provide solid evidence for their “diamond core” structural assignments. The independent generation of3aallows us to investigate HAT reactions of2awith phenols in detail, measure the redox potential and pKaof the system, and calculate the O–H bond strength (DO–H) of3ato shed light on the C–H bond activation reactivity of2a. Complex3ais found to be able to transfer its hydroxyl ligand onto the trityl radical to form the hydroxylated product, representing a direct experimental observation of such a reaction by a dinuclear cobalt complex. Surprisingly, reactivity comparisons reveal2ato be 106-fold more reactive in oxidizing hydrocarbon C–H bonds than corresponding FeIII,IV2(µ-O)2and MnIII,IV2(µ-O)2analogs, an unexpected outcome that raises the prospects for using CoIII,IV2(µ-O)2species to oxidize alkane C–H bonds.more » « less
-
The 1:1 cocrystal of 5-fluorocytosine (5FC) and 4-hydroxybenzaldehyde (4HB), C4H4FN3O·C7H6O2has been synthesized and its structure characterized by single-crystal X-ray diffraction and Hirshfeld surface analysis. The compound crystallizes in the monoclinicP21/cspace group. A robust supramolecular architecture is stabilized by N—H...O, N—H...N, C—H...O and C—H...F hydrogen bonds, formingR22(8),R44(22),R66(32), andR88(34) ring motifs. The N—H...O and N—H...N hydrogen bonds form strong directional interactions, contributing to theR22(8) andR88(34) motifs through dimeric and extended ring structures. O—H...O interactions link 5FC and 4HB molecules, generating anR66(32) ring that enhances the packing. Weaker C—H...F bonds help form theR44(22) tetrameric motif, supporting the overall three-dimensional supramolecular framework. Additionally, C—F...π interactions between the fluorine atom and the aromatic ring add further to the crystal cohesion. Hirshfeld surface analysis and two-dimensional fingerprint plots confirm that O...H/H...O contacts are the most significant, highlighting the central role of hydrogen bonding in the stability and organization of the crystal structure.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/sciadv.ads4724
