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Syntheses and Molecular Structures of an Isoelectronic Series of (2-Hetero-)1,3-Diphosphabenzenes
Schmidbaur, Hubert,Gamper, Siegfried,Paschalidis, Christos,Steigelmann, Oliver,Mueller, Gerhard
, p. 1525 - 1530 (2007/10/02)
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 BH2, 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 CH2=C(CH2PPh2)2 (1) with Me2S-BH2Br to give an intermediate 2 still containing the exocyclic olefinic bond.Treatment of 2 with a base, deprotonation of one ring CH2 group, and proton migration from the other one to the olefinic CH2 group afford the 5-methyl-1λ5-phospha-3-phosphonia-2-boratabenzene 3.The PBP unit is tilted by 144.0(2) deg against the planar C3P2 part of the ring.A heterocyclic precursor 4 for the carbon analog is generated from 1 and CH2I2, which on reaction with a strong base yields the diphosphabenzene 5 with fully planar ring skeleton.For the synthesis of the aza analog 7, CH2=C(CH2Cl)2 is treated with HN(Ph2)2 to give the precursor 6, which can be deprotonated 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. Key Word: 1,3-Diphosphabenzene derivatives
