Crystal structures document the ability of a TF3group (T=Si, Ge, Sn, Pb) situated on a naphthalene system to engage in an intramolecular tetrel bond (TB) with an amino group on the adjoining ring.
The PnF2(Pn=P,As,Sb,Bi) on a naphthalene scaffold can engage in an internal pnicogen Pn⋅⋅⋅N bond (PnB) with an NH2group placed close to it on the adjoining ring. An approaching neutral NH3molecule can engage in a second PnB with the central Pn, which tends to weaken the intramolecular bond. The presence of the latter in turn weakens the intermolecular PnB with respect to that formed in its absence. Replacement of the external NH3by a CN−anion causes a fundamental change in the bonding pattern, producing a fourth covalent bond with Pn, which rearranges into a trigonal bipyramidal motif. This addition disrupts the internal Pn⋅⋅⋅N pnicogen bond, recasting the PnF2⋅⋅⋅NH2interaction into an NH⋅⋅⋅F H‐bond.
more » « less- Award ID(s):
- 1954310
- PAR ID:
- 10445962
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemPhysChem
- Volume:
- 23
- Issue:
- 11
- ISSN:
- 1439-4235
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract Ab initio calculations evaluate the strength of this bond and evaluate whether it can influence the ability of the T atom to engage in a second, intermolecular TB with another nucleophile. A very strong CN−anionic base can approach the T either along the extension of a T−C or T−F bond and form a strong TB with an interaction energy approaching 100 kcal/mol, although this bond is weakened a bit by the presence of the internal T⋅⋅⋅N bond. The much less potent NCH base engages in a correspondingly longer and weaker TB, less than 10 kcal/mol. Such an intermolecular TB is weakened by the presence of the internal TB, to the point that it only occurs for the two heavier tetrel atoms Sn and Pb. -
Abstract In contrast to phosphine oxides and arsine oxides, which are common and exist as stable monomeric species featuring the corresponding pnictoryl functional group (Pn=O/Pn+–O−; Pn = P, As), stibine oxides are generally polymeric, and the properties of the unperturbed stiboryl group (Sb=O/Sb+–O−) remain unexplored. We now report the isolation of the monomeric stibine oxide, Dipp3SbO (where Dipp = 2,6-diisopropylphenyl). Spectroscopic, crystallographic and computational studies provide insight into the nature of the Sb=O/Sb+–O−bond. Moreover, isolation of Dipp3SbO allows the chemistry of the stiboryl group to be explored. Here we show that Dipp3SbO can act as a Brønsted base, a hydrogen-bond acceptor and a transition-metal ligand, in addition engaging in 1,2-addition, O-for-F2exchange and O-atom transfer. In all cases, the reactivity of Dipp3SbO differed from that of the lighter congeners Dipp3AsO and Dipp3PO.
-
Abstract We report a nickel complex for catalytic oxidation of ammonia to dinitrogen under ambient conditions. Using the aryloxyl radical 2,4,6‐tri‐
tert ‐butylphenoxyl (t Bu3ArO⋅) as a H atom acceptor to cleave the N−H bond of a coordinated NH3ligand up to 56 equiv of N2per Ni center can be generated. Employing theN ‐oxyl radical 2,2,6,6‐(tetramethylpiperidin‐1‐yl)oxyl (TEMPO⋅) as the H‐atom acceptor, up to 15 equiv of N2per Ni center are formed. A bridging Ni‐hydrazine product identified by isotopic nitrogen (15N) studies and supported by computational models indicates the N−N bond forming step occurs by bimetallic homocoupling of two paramagnetic [Ni]−NH2fragments. Ni‐mediated hydrazine disproportionation to N2and NH3completes the catalytic cycle. -
Abstract We report a nickel complex for catalytic oxidation of ammonia to dinitrogen under ambient conditions. Using the aryloxyl radical 2,4,6‐tri‐
tert ‐butylphenoxyl (t Bu3ArO⋅) as a H atom acceptor to cleave the N−H bond of a coordinated NH3ligand up to 56 equiv of N2per Ni center can be generated. Employing theN ‐oxyl radical 2,2,6,6‐(tetramethylpiperidin‐1‐yl)oxyl (TEMPO⋅) as the H‐atom acceptor, up to 15 equiv of N2per Ni center are formed. A bridging Ni‐hydrazine product identified by isotopic nitrogen (15N) studies and supported by computational models indicates the N−N bond forming step occurs by bimetallic homocoupling of two paramagnetic [Ni]−NH2fragments. Ni‐mediated hydrazine disproportionation to N2and NH3completes the catalytic cycle. -
Abstract The effects on the C−I⋅⋅N halogen bond between iodobenzene and NH3of placing various substituents on the phenyl ring are monitored by quantum calculations. Substituents R=N(CH3)2, NH2, CH3, OCH3, COCH3, Cl, F, COH, CN, and NO2were each placed ortho, meta, and para to the I. The depth of the σ‐hole on I is deepened as R becomes more electron‐withdrawing which is reflected in a strengthening of the halogen bond, which varied between 3.3 and 5.5 kcal mol−1. In most cases, the ortho placement yields the largest perturbation, followed by meta and then para, but this trend is not universal. Parallel to these substituent effects is a progressive lengthening of the covalent C−I bond. Formation of the halogen bond reduces the NMR chemical shielding of all three nuclei directly involved in the C−I⋅⋅N interaction. The deshielding of the electron donor N is most closely correlated with the strength of the bond, as is the coupling constant between I and N, so both have potential use as spectroscopic measures of halogen bond strength.