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 = (Et2PCH 2CH2)(Ph)PCH2P(Ph)CH2CH2PEt2) with 2 equiv of NiCl2. 6H(2)O in EtOH produce s soluble rac-Ni2Cl4(et,ph-P4) and precipitates meso-Ni2Cl4(et,ph-P4), allo wing facile isolation of each bimetallic complex. Subsequent reaction with more than 250 equiv of NaCN in H2O/MeOH releases the et,ph-P4 liganden char ac and [Ni(CN)(4)](2-). The rac,trans- and meso,trans-Ni(CN)(2)(eta (2,5)-e t,ph-P4) form as intermediates in the cyanolysis of rac- and meso-Ni2Cl4(et ,ph-P4). These have beterized by X-ray crystallography. The unusual partial isomerization of the meso- to rac-et,ph-P4 ligand via the monometallic tra ns-Ni(CN)(2)(eta (2,5)-et,ph-P4) intermediate complex is discussed.