Structural Variability of R2C Adducts of 3a,6a‐Diaza‐1,4‐diphosphapentalene: Tuning the N→P Bonding

• Published in: Zeitschrift für anorganische und allgemeine Chemie (1950) Vol. 643; no. 19; pp. 1208 - 1214
• Main Authors: Kornev, Alexander N., Galperin, Vadim E., Panova, Yulia S., Arapova, Alla V., Baranov, Evgenii V., Fukin, Georgy K., Abakumov, Gleb A.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 17.10.2017
• Subjects: Addition reaction; Adducts; Azaphospholes; Bonding; Electronegativity; Hypervalent phosphorus; Malononitrile; Phosphorus ylides; X‐ray diffraction; Zwitterions
• ISSN: 0044-2313; 1521-3749
• DOI: 10.1002/zaac.201700223

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).