Separating the racemic and meso diastereomers of a binucleating tetraphosphine ligand system through the use of nickel chloride.
The reaction of a 1:1 mixture of rac- and meso-et,ph-P4 (et,ph-P4 = (Et(2)PCH(2)CH(2))(Ph)PCH(2)P(Ph)CH(2)CH(2)PEt(2)) with 2 equiv of NiCl(2).6H(2)O in EtOH produces soluble rac-Ni(2)Cl(4)(et,ph-P4) and precipitates meso-Ni(2)Cl(4)(et,ph-P4), allowing facile isolation of each bimetallic complex. Subsequent reaction with more than 250 equiv of NaCN in H(2)O/MeOH releases the et,ph-P4 ligand and [Ni(CN)(4)](2-). The rac,trans- and meso,trans-Ni(CN)(2)(eta(2.5)-et,ph-P4) form as intermediates in the cyanolysis of rac- and meso-Ni(2)Cl(4)(et,ph-P4). These have been characterized by X-ray crystallography. The unusual partial isomerization of the meso- to rac-et,ph-P4 ligand via the monometallic trans-Ni(CN)(2)(eta(2.5)-et,ph-P4) intermediate complex is discussed.
Aubry
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DA
Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, USA.
Laneman
S A
SA
Fronczek
F R
FR
Stanley
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GG