Proton Affinities of Cationic Carbone Adducts [AC(PPh₃)₂]⁺(A=Halogen, Hydrogen, Methyl) and Unusual Electronic Structures of the Cations and Dications [AC(H)(PPh₃)₂]²⁺

Abstract

This work reports the syntheses and the first crystal structures of the cationic carbone adducts [FC(PPh3 )2 ](+) and [BrC(PPh3 )2 ](+) and the protonated dication [FC(H)(PPh3 )2 ](2+) , which are derived from the carbone C(PPh3 )2 . Quantum chemical calculations and bonding analyses were carried out for the series of cations [AC(PPh3 )2 ](+) and dications [AC(H)(PPh3 )2 ](2+) , where A=H, Me, F, Cl, Br, I. The bonding analysis suggests that the cations are best described as phosphane complexes L→(CA)(+) ←L (L=PPh3 ), which are related to the neutral borylene adducts L→(BA)←L (L=cyclic carbene; A=H, aryl) that were recently isolated. The carbone adducts [AC(PPh3 )2 ](+) possess a π electron lone pair at carbon and they can easily be protonated to the dications [AC(H)(PPh3 )2 ](2+) . The calculations of the dications indicate that the molecules are best represented as complexes L→(CHA)(2+) ←L (L=PPh3 ) where a carbene dication is stabilized by the ligands. The central carbon atom in the cations and even in the dications carries a negative partial charge, which is larger than the negative charge at fluorine. There is also the peculiar situation in which the carbon-fluorine bonds in [FC(PPh3 )2 ](+) and [FC(H)(PPh3 )2 ](2+) exhibit the expected polarity with the negative end at fluorine, but the carbon atom has a larger negative charge than fluorine. Given the similarity of carbodiphosphorane C(PPh3 )2 and carbodicarbene C(NHC)2 , we expect that analogous compounds [AC(NHC)2 ](+) and [AC(H)(NHC)2 ](2+) with similar features as [AC(PPh3 )2 ](+) and [AC(H)(PPh3 )2 ](2+) can be isolated.

Ylide‐Functionalization via Metalated Ylides: Synthesis and Structural Properties

“…Accordingly, an analogous observation has been observed by Olah by means of a simple α‐fluorinated carbanion as well as by computational studies of fluorinated ylides . In contrast, the fluorinated hexaphenylcarbodiphosphorane (CDP) showed a planar geometry of the ylidic carbon atom . It is important to note, that the pyramidalization of the ylide carbon atom in 1‐F and 2‐F also results in longer P−C and C−S/C−CN distances in the ylide backbone compared to those of the other compounds.…”

Hollowing out MOFs: hierarchical micro- and mesoporous MOFs with tailorable porosity via selective acid etching

“…To further validate the size-selective acid diffusion of the etching process, sulfuric acid (H 2 SO 4 , d = 0.66 nm ( ref. 19 )), which has a comparable size to H 3 PO 4 , and hydrochloric acid (HCl, d = 0.34 nm ( ref. 20 )) were employed as etching agents.…”

Ligands Based on Phosphine‐Stabilized Aluminum(I), Boron(I), and Carbon(0)

“…Interestingly,t he interaction energy for the protonated CDP ligand (E = CH) is too low to compensate for the preparation energy,w hich results in an overall negative dissociatione nergy.T hese findings suggest that the corresponding iron complex 2c is not stable towardsF e ÀCb ond dissociation,w hich is indeed often observed upon protonation of CDP complexes. [7,17] The deformation densities in variant IV predominantly show s donation of the phosphine lone pairs to the iron-bound group E. In the case of variant IV,aninverse trend for the interaction energies (DE int )i so bserved, in comparison to that of variant III.The interaction between the phosphines andcoordinated AlH fragment is by far the weakest, followed by E = BH and E = C. Thes trongest interaction is observed for protonated CDP (E = CH). Except for the aluminum-based complex,a ttractive interactions between the fragments in variant IV are domi-nated by contributions from orbital interactions.…”

“…This is in agreement with previouse xperimentalo bservations that monodentate CDP adducts dissociate in most cases upon protonation. [7,17,30,31] Analysis of the octahedral 3d metal complexes with aformal d 6 -electronc ount reveals the impact of varying chargei nM n + , Fe 2 + ,a nd Co 3 + on different contributions to the investigated metal-ligand bond ( Table 6). For neutral ligands (E = AlH, BH, C), DE int and D e increasef rom Mn + to Co 3 + .T his is ar esult of stronger orbitala nd electrostatic interactions upon going from Mn + to Fe 2 + and Co 3 + ,w hich are compensated for to differing extentsb yt he Pauli repulsion.…”