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Imino‐Bridged Bisphosphaalkenes (2,4‐Diphospha‐3‐azapentadienes)
Authors:Roxana?M Bîrzoi Dr  Delia Bugnariu Dr  Rafael Guerrero Gimeno Dr  Daniela Lungu  Vera Zota Dr  Constantin Daniliuc Dr  Peter?G Jones Prof?Dr  Zoltán Benkõ Dr  László Könczöl  László Nyulászi Prof?Dr  Rainer Bartsch Dr  Wolf‐W du?Mont Prof?Dr  Edgar Niecke Prof?Dr
Institution:1. Institut für Anorganische und Analytische Chemie, Technische Universit?t Braunschweig, Hagenring 30, 38106 Braunschweig (Germany), Fax: (+49)?531‐3915387;2. Institut für Anorganische Chemie, Universit?t Bonn, Gerhard‐Domagk‐Strasse 1, 53121 Bonn (Germany);3. Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szt Gellért tér 4, 1521 Budapest (Hungary)
Abstract:Deprotonation of aminophosphaalkenes (RMe2Si)2C?PN(H)(R′) (R=Me, iPr; R′=tBu, 1‐adamantyl (1‐Ada), 2,4,6‐tBu3C6H2 (Mes*)) followed by reactions of the corresponding Li salts Li(RMe2Si)2C?P(M)(R′)] with one equivalent of the corresponding P‐chlorophosphaalkenes (RMe2Si)2C?PCl provides bisphosphaalkenes (2,4‐diphospha‐3‐azapentadienes) (RMe2Si)2C?P]2NR′. The thermally unstable tert‐butyliminobisphosphaalkene (Me3Si)2C?P]2NtBu ( 4 a ) undergoes isomerisation reactions by Me3Si‐group migration that lead to mixtures of four‐membered heterocyles, but in the presence of an excess amount of (Me3Si)2C?PCl, 4 a furnishes an azatriphosphabicyclohexene C3(SiMe3)5P3NtBu ( 5 ) that gave red single crystals. Compound 5 contains a diphosphirane ring condensed with an azatriphospholene system that exhibits an endocylic P?C double bond and an exocyclic ylidic P(+)? C(?)(SiMe3)2 unit. Using the bulkier iPrMe2Si substituents at three‐coordinated carbon leads to slightly enhanced thermal stability of 2,4‐diphospha‐3‐azapentadienes (iPrMe2Si)2C?P]2NR′ (R′=tBu: 4 b ; R′=1‐Ada: 8 ). According to a low‐temperature crystal‐structure determination, 8 adopts a non‐planar structure with two distinctly differently oriented P?C sites, but 31P NMR spectra in solution exhibit singlet signals. 31P NMR spectra also reveal that bulky Mes* groups (Mes*=2,4,6‐tBu3C6H2) at the central imino function lead to mixtures of symmetric and unsymmetric rotamers, thus implying hindered rotation around the P? N bonds in persistent compounds (RMe2Si)2C?P]2NMes* ( 11 a , 11 b ). DFT calculations for the parent molecule (H3Si)2C?P]2NCH3 suggest that the non‐planar distortion of compound 8 will have steric grounds.
Keywords:bisphosphaalkenes  density functional calculations  heterocycles  PNP ligands  X‐ray diffraction
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