Mono‐Phosphazenyl Phosphines (R2N)3P=N–P(NR2)2 – Strong P‐Bases, P‐Donors, and P‐Nucleophiles for the Construction of Chelates. Issue 13 (27th May 2020)

• Record Type: Journal Article
• Authors: Kögel, Julius F.; Ullrich, Sebastian; Kovačević, Borislav; Wagner, Sebastian; Sundermeyer, Jörg
• Is Part Of: Zeitschrift für anorganische und allgemeine Chemie. Volume 646:Issue 13(2020)
• Page Start: 923
• Page End: 932
• Publication Date: 2020-05-27
• Subjects: Basicity -- Phosphines -- Phosphazenes -- Density functional calculations -- Tolman electronic parameter; Chemistry, Inorganic -- Periodicals; Chemistry -- Periodicals; 540
• DOI: 10.1002/zaac.202000108
• Languages: English
• ISSNs: 0044-2313

Abstract

Abstract : We present a convenient three‐step synthesis of amino substituted phosphazenyl phosphines of the general formula (R2 N)3 P=N–P(NR2 )2 [NR2 = N(CH2 )4, N(CH2 )5, N(CH2 )6 ]. These easily accessible mixed valent compounds display a surprisingly high proton affinity and basicity in the same range as the corresponding Schwesinger diphosphazene (Me2 N)3 P=N–P=NEt(NMe2 )2 (Et‐P2 ) and Verkade's proazaphosphatrane superbases. Within the central [P III –N=P V ] scaffold, the phosphine P III and not the phosphazene N III atom is the center of highest proton affinity, basicity and donor strength. As P‐bases, the title compounds display calculated proton affinities between 265.8 (NR2 = NMe2 ) and 274.7 kcal· mol –1 [NR2 = N(CH2 )4 ] and p K BH + values between 26.4 (NR2 = NMe2 ) and 31.5 [NR2 = N(CH2 )4 ] on the acetonitrile scale. As P‐nucleophiles, they are key intermediates in the synthesis of hyperbasic bis(diphosphazene) proton sponges, chiral bis(diphosphazene) proton pincers, bisphosphazides, and superbasic P2 ‐bisylides. Their Staudinger reactions as nucleophile towards 1, 8‐diazidonaphthalene leading to 1, 8‐naphthalene‐bisphosphazides is described in detail. The donor strength of the title compounds towards fragments [Se] and [Ni(CO)3 ] is in the same range as that of N‐heterocyclic carbenes. Abstract :