Group 6 metal oxide fluoride molecules in the form of OMF and OMF (M = Cr, Mo, W) were prepared via the reactions of laser-ablated metal atoms and OF in excess argon. Product identifications were performed by using infrared spectroscopy, OF samples, and electronic structure calculations. Reactions of group 6 metal atoms and OF resulted in the formation of ternary OCrF, OMoF, and OWF molecules with C symmetry in which the tetravalent metal center is coordinated by one oxygen and two fluorine atoms. Both OCrF and OMoF are computed to possess triplet ground states, and a closed shell singlet is the ground state for OWF. Triatomic OCrF, OMoF, and OWF molecules were also observed during sample deposition. All three molecules were computed to have a bent geometry and quartet ground state. A bonding analysis showed that the OMF molecules have highly ionic M-F bonds. OCrF and OMoF have an M-O double bond composed of a σ bond and a π bond. OWF has an M-O triple bond consisting of a σ bond, a π bond, and a highly delocalized O lone pair forming the other π bond. The M-O bonds in the OMF compounds have triple-bond character for all three metals.

The SO2 complexes of scandium, yttrium, and lanthanum difluorides [MF2(O2S)] were prepared via the reactions of laser-ablated metal atoms and SO2F2 upon UV–vis irradiation in cryogenic matrixes. The presence of bidentate SO2 ligand in the products was demonstrated by the characteristic infrared absorptions as well as isotopic frequency ratios from both S18O2F2 and 34SO2F2 experiments and is further supported by DFT calculations. All three product molecules were predicted to have nonplanar C 2v symmetry with the SO2 ligand bound to the metal center through both oxygens. The computed S–O bond length and stretching frequencies of ligated SO2 approach those of SO2 – as a result of electron transfer from metal center to the 1π* orbital of SO2, in agreement with the results from bonding analysis. On the basis of DFT calculations, fluorine transfer from SO2F2 to the metal center to form the MF2(O2S) complexes is highly exothermic. Although a proposed intermediate in the form of MF­(O2SF) was predicted to be stable, it was not observed in the experiments, presumably because of the low energy barrier for further isomerization to MF2(O2S).

BN/CC isosterism can give rise to attractive molecules with unique physical or chemical properties. We report here the synthesis, characterization, and reactivities of the boraiminolithium species 2, a room-temperature-stable crystalline solid accessible through a facile dehydrohalogenation/deprotonation reaction. This species, bearing a polarized BN triple bond and an anionic N center, is the first example of a BN analogue to the well-known alkynyllithium molecules (lithium acetylides). It has demonstrated a remarkable ability for iminoborane-transfer reactions, which allows for the isolation of a series of unprecedented Nfunctionalized iminoboranes as well as novel main-group heterocycles. Stable boraiminolithium reagents may become powerful tools in the exploration of new BN-containing building blocks for synthetic chemistry and materials science.

We report herein a facile and highly modular access to an intriguing class of free Au-substituted phosphines (AuPhos), namely (LAu) n PR 3À n (L = singlet carbene ligand; R = H, aryl, alkyl, silyl) (n = 1-3). The Tolman electronic parameter (TEP) values coupled with theoretical investigations showcase that Au-substitution can boost the electron-releasing ability of AuPhos, thus leading to an electronically and sterically tunable, extremely electron-rich phosphorus center. The high basicity of AuPhos is attributed to the d-p lone pair πrepulsion arising from interaction between Au substituents and the lone pair at P. A series of multi-nuclear transition metal complexes (i.e. Rh, Ir, Pd, Au, W, Mn) ligated by AuPhos are readily prepared via a straightforward process. Preliminary catalytic results reveal the facilitation of Pd-catalyzed CÀ N coupling reactions and Ir-catalyzed decarbonylation reactions via AuPhos. This work provides insights for future development of electron-rich ligands.

Side-on sulfur monoxide complexes of tantalum, niobium, and vanadium oxyfluorides OMF 2 (η 2 -SO) were prepared via the reactions of metal atoms and SO 2 F 2 upon UV−vis irradiation in a cryogenic matrix. The product structures were identified by the characteristic infrared absorptions and isotopic frequency ratios of terminal M−O, F−M−F, and M−(SO) stretches, which were further supported by density functional theory calculations at the B3LYP level. All of the three complexes were predicted to have doublet ground states with the S−O bond nearly perpendicular to the terminal metal−oxygen bond. Although end-on bonded isomers with either M−OS or M−SO geometry are stable as well, they are higher in energy than the side-on isomers, and their vibrational frequencies do not match the experimental values. For the OMF 2 (η 2 -SO) complexes, the S−O bond length approaches that of SO − , but it is longer than that of neutral SO due to the electron transfer from the metal d orbital to the in-plane π* orbital of SO. The metal−SO bonding in the side-on complex is mainly ionic, but covalent interactions play some role between the two parts. On the basis of the calculation results, the OMF 2 (η 2 -SO) complexes can be considered as (OMF 2 ) + (SO) − in which the unpaired electron is mainly located in the out-ofplane π* orbital of SO. In addition to the complexes containing SO ligand, a series of other stable isomers were obtained by the B3LYP calculations, and they were proposed as intermediates involved in the formation of the OMF 2 (η 2 -SO) products via fluorine and oxygen transfer reactions between metal atoms and SO 2 F 2 under UV−vis irradiation.

Site-specific conjugation of small molecules to antibody molecules is a promising strategy for generation of antibody-drug conjugates. In this report, we describe the successful synthesis of a novel bifunctional molecule, 6-(azidomethyl)-2-pyridinecarboxyaldehyde (6-AM-2-PCA), which was used for conjugation of small molecules to peptides and antibodies. We demonstrated that 6-AM-2-PCA selectively reacted with N-terminal amino groups of peptides and antibodies. In addition, the azide group of 6-AM-2-PCA enabled copper-free click chemistry coupling with dibenzocyclooctyne-containing reagents. Bifunctional 6-AM-2-PCA mediated site-specific conjugation without requiring genetic engineering of peptides or antibodies. A key advantage of 6-AM-2-PCA as a conjugation reagent is its ability to modify proteins in a single step under physiological conditions that are sufficiently moderate to retain protein function. Therefore, this new click chemistry-based method could be a useful complement to other conjugation methods.

A (phosphino)diazomethyl anion salt 1 ([[P]−CN2][K(18-C-6)(THF)]) ([P] = [(CH2)(NDipp)]2P; 18-C-6 = 18-crown-6) behaves as a (phosphino)carbyne anion-dinitrogen adduct ([P]−C − ←:N2). Under an atmosphere of carbon monoxide (CO), 1 undergoes a facile N2/CO ligand exchange reaction giving (phosphino)ketenyl anion salt [[P]−CCO][K(18-C-6)] 2. Oxidation of 2 with elemental Se affords (selenophosphoryl)ketenyl anion salt ([P](Se)−CCO][K(18-C-6)]) 3.These ketenyl anions feature a strongly bent geometry at the P-bound carbon and this carbon atom is highly nucleophilic. The electronic structure of 2 is examined by theoretical studies. Reactivity investigations demonstrate 2 as a versatile synthon for derivatives of ketene, enolate, acrylate and acrylimidate moieties.Ketenes of the general formula R 1 R 2 C=C=O are widely used reagents in synthetic chemistry. Due to their polarized cumulated double bonds, ketenes are usually generated in situ as very reactive intermediates, which then ensue (cyclo)additions to provide access to carboxylic derivatives (i.e. acids, esters, anhydrides, amides), cyclobutenones, β-lactams and β-lactones. [1] Despite such utility, synthetic methods toward ketenes are limited and largely rely on transition metal (TM) reagents (e.g. metal carbenes). [2] The development of ketenyl anions/ynolates [RCCO] − (Figure 1a) represents an alternative available material leading to ketenes; however, these anions are generally unstable as well, generated at low temperatures (proposed as ynolates) and consumed as soon as they are produced in chemical syntheses. [3] Recently, low-temperature spectroscopic characterization of Me3Si−C ≡ C−OK has been achieved. [4] Additionally, the group of Stephan spectroscopically characterized Ph2P(S)C(Li(THF)2)CO (A) at room temperature in a reaction mixture of dilithiomethandiide with CO and N2O (Figure 1b). [5] During the preparation of this manuscript, Gessner showed an isolable ketenyl anion Ph2P(S)C(K(18-C-6))CO (B) (18-C-6 = 18-crown-6) via an unprecedented phosphine/CO replacement reaction. [6] This breakthrough allowed the isolation of a series of ketene derivatives via facile ketenylations.

A collection of 3d transition metal (V, Mn, Fe, Co, and Ni) oxyfluorides were prepared via the reactions of laser-ablated metal atoms and OF2 in an argon matrix, and the products were identified by infrared spectroscopy together with 18OF2 substitution. OMF2 is the major product from the reactions of metal atoms and OF2. The tetravalent metal center is coordinated to two fluorine atoms and one oxygen atom. Triatomic OMF molecules were observed in the reactions of V, Mn, Fe, and Co with OF2. In addition to OMF and OMF2, OMnF3 and OFeF3 were also formed presumably via the reactions of OMnF and OFeF with F2 resulting from photodecomposition of OF2. The seldom observed OF radical was produced in all of these experiments. Electronic structure calculations at the density functional theory and molecular orbital theory including electron correlation effects (CCSD­(T) and CASPT2) levels are used to aid in the assignment of the structures. For OMF (M = Sc–Mn), the structures are bent and those for M = Fe–Cu are linear. The OMF2 molecules are optimized to be C 2v structures. Both OMF and OMF2 have a high spin ground state, with the exception of OCoF2 in which the ground state quartet is the lower energy structure. The M–O stretching frequency is a sensitive measure of the computational method in terms of the bond angle, the coupling of the M–O and M–F stretches, and the amount of spin on the oxygen. A bonding analysis in terms of the CAS orbitals shows that a number of the structures have a multireference character after M = Cr. Oxidation states of the metal are given based on the CASPT2 results. Heats of formation for the OMF and OMF2 are reported.