Generation and Characterization of Diphosphene and Triphosphene Radical Anions. Computational Studies on the Structure and Stability of P3H3·-

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Inorganic Chemistry, 35 (7): 2119--2126 (1996)
DOI: 10.1021/IC950661A


Complexation of the K+ ions of slightly sol. K2tBuP2·1/2THF with 18-crown-6 or 2.2.2cryptand in THF leads to brown-red solns. which exhibit limited stability at room temp. The 31P NMR spectrum consists of two singlets (1:1) which are assigned to the trans and gauche rotamers of the dianion tBuP-PtBu2-. That dianion undergoes a protonation by the solvent forming the monoanion (tBu)(H)P-PtBu-, which was characterized by 31P NMR spectroscopy. The brown-red solns. contain a paramagnetic species, for which the EPR spectrum revealed a 1:2:1 triplet caused by the hitherto unknown diphosphene radical anion tBuP:PtBu.bul.- (giso = 2.0103). These reactions of the dianion tBuP-PtBu2- on complexation of the K+ ions occur also at -40° and can be attributed to a tendency to reduce the Coulombic repulsion between the adjacent neg. charges. The homologous triphosphene radical anion tBuP-(tBu)P-PtBu.bul.- could be generated by redn. of the cyclic triphosphine (tBuP)3 on a K mirror. The new triphosphene radical anion was identified by its EPR spectrum which showed a triplet of doublets (giso = 2.0098). Finally, redn. of the neutral valence isoelectronic cyclic diphosphirane Me2C(tBuP)2 on a K mirror yields the radical anion Me2C(tBuP)2.bul.-, which exhibits a 1:2:1 triplet in the EPR spectrum (giso = 2.0060). The triphosphene radical anion tBuP-(tBu)P-PtBu.bul.- is related to the radical anions O3.bul.-, S3.bul.- and P3.bul.4-, but in contrast to O3.bul.- and S3.bul.-, the pattern of hyperfine coupling consts. is reversed. Quantum-chem. calcns. of P3H3.bul.- suggest an open-chain structure for tBuP-(tBu)P-PtBu.bul.-. A possible explanation is given for the reversion of the hyperfine coupling pattern due to the shape of the highest occupied orbital. The adiabatic electron affinities are calcd. for two possible structures of P3H3.bul.-. on SciFinder(R)



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