Structural Variability of R ₂ C Adducts of 3a,6a-Diaza-1,4-diphosphapentalene: Tuning the N→P Bonding

Abstract

3a,6a‐Diaza‐1,4‐diphosphapentalene (DDP) reacts with hexachlorocyclopentadiene to form a stable adduct (ClC)4C=DDP (4). The phosphorus atom involved into coordination has a pyramidal arrangement but retains partial double bonding with carbon [1.752(3) Å]. At the same time, the P–N bond remains covalent [1.824(3) Å]. The adduct 4 is better described as a zwitterionic compound with strongly delocalized positive and negative charges. A similar zwitterionic adduct DDP=C(CN)2 was prepared by the reactions of dichloro‐DDP (7) with malononitrile in the presence of Et3N. DFT calculations showed that related structures are formed in the case of the substituents (ClC)4C=, (HC)4C=, (NC)2C=, and (MeCO)2C=, possessing electron‐delocalizing properties. Compounds with other R2C groups (R = Ph, Me, C6F5, Cl), possessing electronegative properties as well, but insufficient e‐delocalization, demonstrate the noncovalent P–N bonding and a little shorter R2C–P bond lengths (ca. 1.70 Å).

Dual Reactivity of 3a,6a-Diaza-1,4-diphosphapentalene: π-Donor versus n-Donor

“…Indeed, most of the chemical properties of a DDP can be explained by considering it as stabilized singlet phosphinidene, possessing nucleophilic properties. Oxidative addition to the phosphorus atom − of DDP proceeds very easily (Scheme ), whereas for the usual aromatic azaphospholes such reactions are unknown.…”

Unique Interaction between Layered Black Phosphorus and Nitrogen Dioxide

“…In the most stable adsorption configurations of the adsorption complex of each d-SLBP, the N atom of NO is near d-SLBP at a distance of 1.78-1.98 Å (Figure 4b). This distance is close to (in the case of SV, DV3, EGa2) or slightly larger (in the case of EGz1) than the length of a typical P-N single bond (commonly accepted value is 1.89 Å [50,51]), but much smaller than the distance (2.47 Å) between NO and SLBP (Table 1), which implies that there is a strong chemisorption between NO and unsaturated d-SLBP. The difference is that d-SLBP binds NO by forming a weak P-N bond but reacts with NO 2 by abstracting one O atom in redox reactions.…”

“…The small E ad values (−0.310 to -0.138 eV), low charge transfer amounts (−0.15 to 0.04 e) and large distances to the SLBP plane (2.47-3.44 Å) indicate weak interaction between gas molecules and SLBP (Table 1). The distance of the N atom in NO to SLBP (2.47 Å) is the shortest in the most stable adsorption configurations of the six gas molecules, but is still much longer than a P-N covalent bond length (1.89 Å [50,51]). The adsorption of gas molecules on perfect SLBP plane is dominated by vdW forces, as indicated by the ratio of 57-82% relative to E ad .…”

Synthesis of 3a,6a-diaza-1,4-diphosphapentalenes and their halogen derivatives. Specific features of the structure and behavior in solutions

“…The fi rst type includes reactions of the heterocyclic system (formation of π-complexes with organic π-acceptors, 3 cycloaddition reactions 4 ). The second type are reactions of stabilized singlet phosphinidene (oligomerization, 1 complexation with metal salts and Lewis acids, 5,6 oxidative addition reactions, 7-10 formation of adducts with carbenes 11,12 ). To date, we have described only two 3a,6a-diaza-1,4-diphosphapentalenes synthesized from azines of cyclohexanone 13 and tetralone.…”