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Imino‐Bridged Bisphosphaalkenes (2,4‐Diphospha‐3‐azapentadienes)
Author(s) -
Bîrzoi Roxana M.,
Bugnariu Delia,
Gimeno Rafael Guerrero,
Lungu Daniela,
Zota Vera,
Daniliuc Constantin,
Jones Peter G.,
Benkõ Zoltán,
Könczöl László,
Nyulászi László,
Bartsch Rainer,
du Mont WolfW.,
Niecke Edgar
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200903166
Subject(s) - isomerization , deprotonation , chemistry , double bond , crystallography , stereochemistry , crystal structure , nmr spectra database , ring (chemistry) , singlet state , medicinal chemistry , spectral line , catalysis , physics , polymer chemistry , organic chemistry , ion , astronomy , nuclear physics , excited state
Abstract Deprotonation of aminophosphaalkenes (RMe 2 Si) 2 CPN(H)(R′) (R=Me, i Pr; R′= t Bu, 1‐adamantyl (1‐Ada), 2,4,6‐ t Bu 3 C 6 H 2 (Mes*)) followed by reactions of the corresponding Li salts Li[(RMe 2 Si) 2 CP(M)(R′)] with one equivalent of the corresponding P ‐chlorophosphaalkenes (RMe 2 Si) 2 CPCl provides bisphosphaalkenes (2,4‐diphospha‐3‐azapentadienes) [(RMe 2 Si) 2 CP] 2 NR′. The thermally unstable tert ‐butyliminobisphosphaalkene [(Me 3 Si) 2 CP] 2 N t Bu ( 4 a ) undergoes isomerisation reactions by Me 3 Si‐group migration that lead to mixtures of four‐membered heterocyles, but in the presence of an excess amount of (Me 3 Si) 2 CPCl, 4 a furnishes an azatriphosphabicyclohexene C 3 (SiMe 3 ) 5 P 3 N t Bu ( 5 ) that gave red single crystals. Compound 5 contains a diphosphirane ring condensed with an azatriphospholene system that exhibits an endocylic PC double bond and an exocyclic ylidic P (+) C (−) (SiMe 3 ) 2 unit. Using the bulkier i PrMe 2 Si substituents at three‐coordinated carbon leads to slightly enhanced thermal stability of 2,4‐diphospha‐3‐azapentadienes [( i PrMe 2 Si) 2 CP] 2 NR′ (R′= t Bu: 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 PC sites, but 31 P NMR spectra in solution exhibit singlet signals. 31 P NMR spectra also reveal that bulky Mes* groups (Mes*=2,4,6‐ t Bu 3 C 6 H 2 ) at the central imino function lead to mixtures of symmetric and unsymmetric rotamers, thus implying hindered rotation around the PN bonds in persistent compounds [(RMe 2 Si) 2 CP] 2 NMes* ( 11 a , 11 b ). DFT calculations for the parent molecule [(H 3 Si) 2 CP] 2 NCH 3 suggest that the non‐planar distortion of compound 8 will have steric grounds.