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Syntheses and Molecular Structures of an Isoelectronic Series of (2‐Hetero‐)1,3‐Diphosphabenzenes
Author(s) -
Schmidbaur Hubert,
Gamper Siegfried,
Paschalidis Christos,
Steigelmann Oliver,
Müller Gerhard
Publication year - 1991
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19911240708
Subject(s) - chemistry , ring (chemistry) , deprotonation , molecule , crystallography , double bond , stereochemistry , base (topology) , carbon fibers , nmr spectra database , spectral line , ion , polymer chemistry , organic chemistry , mathematical analysis , materials science , physics , mathematics , astronomy , composite number , composite material
Syntheses, NMR spectra, and X‐ray molecular structures of three (2‐hetero‐)1,3‐diphosphabenzenes are reported which constitute an isoelectronic triade of compounds with BH 2 , CH, and N bridging units between the two phosphorus atoms. The remaining three carbon atoms of the rings are part of a 2‐methallylic system. The 2‐borataheterocycle 3 has been prepared by the reaction of CH 2 = C(CH 2 )PPh 2 ) 2 ( 1 ) with Me 2 SBH 2 Br to give an intermediate 2 still containing the exocyclic olefinic bond. Treatment of 2 with a base, deprotonation of one ring CH 2 group, and proton migration from the other one to the olefinic CH 2 group afford the 5‐methyl‐1λ 5 ‐phospha‐3‐phosphonia‐2‐boratabenzene 3 . The PBP unit is tilted by 144.0(2)° against the planar C 3 P 2 part of the ring. A heterocyclic precursor 4 for the carbon analog is generated from 1 and CH 2 I 2 , which on reaction with a strong base yields the diphosphabenzene 5 with a fully planar ring skeleton. For the synthesis of the aza analog 7 , CH 2 =C(CH 2 Cl) 2 is treated with HN(PPh 2 ) 2 to give the precursor 6 , which can be deprotonatad at nitrogen and carbon with a base. In the crystals of 7 , two independent molecules of very similar structure are present. The molecules show planar heterocycles.