Synthesis and characterisation of the five diastereoisomers of 4,7,13,16-tetraphenyl-1,10-dithia-4,7,13,16-tetraphosphacyclo-octadecane: crystal structure of the nickel bromide complex of the β-isomer

Abstract

The novel dithiatetraphospha-macrocycle 4,7,13,16-tetraphenyl-1,10-dithia-4,7,13,16-tetraphosphacyclo-octadecane (L²) has been synthesised in 14% yield via a one-step procedure. All of the five possible diastereoisomers were isolated, and two of them (α and β) used to form cobalt(II) and nickel(II) complexes. The compound [Ni(β-L²)]Br₂·2H₂O crystallises in a triclinic unit cell (P space group) with lattice Constants a= 9.645(3), b= 10.159(3), c= 10.869(3)Å, α= 68.07(4), β= 78.09(4), γ= 84.69(4)°, and Z= 1. Least-squares refinement gave R= 0.059 for 1 395 observed reflections. The X-ray diffraction study of this complex shows that the nickel atom is six-co-ordinated by two sulphur and four phosphorus atoms of the macrocycle forming an elongated trans-octahedral geometry. The stereochemistry of the β isomer is 4RS,7RS,13SR,16SR. The 4RS,7RS,13RS,16SR isomer (α isomer) has been identified by ³¹P n.m.r. spectroscopy.