The linear tetraphos ligand prP4 (1,1,4,8,11,11-hexaphenyl-1,4,8,11-tetraphosphaundecane, Ph2PCH2CH2P(Ph)CH2CH2CH2P(Ph)CH2CH2PPh2): Synthesis and characterization of cis- and trans-[Fe(NCS)2(prP4)]

The stereochemistry of prP4 (1,1,4,8,11,11-hexaphenyl-1,4,8,11-tetraphosphaundecane) and its coordination properties in mononuclear complexes are explored. The free ligand is obtained as a mixture of meso and rac diastereomers from the reaction of dilithium 1,3-bis(phenylphosphido)propane−tetrakis(tetrahydrofuran) (“Lippp”) with 2 equiv of 1-chloro-2-(diphenylphosphino)ethane. Reaction of prP4 with FeCl2 and KSCN leads to cis- and trans-[Fe(NCS)2(prP4)] complexes of the meso and the rac ligands; the composition of this mixture has been fully analyzed. The iron isothiocyanato complexes cis-α- and trans-[Fe(NCS)2(rac-prP4)] have been characterized by X-ray structure determinations. The 31P NMR spectrum of the free tetraphos ligand shows an AA‘XX‘ coupling scheme with three groups of signals centered at −20.6 and −20.7 ppm and at −12.4 ppm, which belong to the rac and meso isomers, respectively. 31P NMR spectra of the cis and trans iron isothiocyanato complexes of rac-prP4 exhibit AA‘XX‘ patterns as well, wh...