New bis(phosphines) derived from N,N '-substituted ethylenediamine derivatives. Synthesis and transition metal chemistry of X2PN(R)CH2CH2(R)NPX2 (R = CH2Ph or Ph, X = Ph; R = CH2Ph, X2 = O2C6H4). The crystal and molecular structure of Ph2PN(CH2Ph)CH2CH2(CH2Ph)NPPh2 and cis-[{PtCl2Ph2PN(CH2Ph)CH2CH2(CH2Ph)NPPh2}]

Abstract

The bis(phosphines) of the type X₂PN(R)CH₂CH₂(R)NPX₂ (R = Ph or CH₂Ph, X = Ph; R = CH₂Ph, X₂ = O₂C₆H₄) with the ethylenediamine framework were prepared by reaction of X₂PCl with the corresponding N,N '-substituted ethylenediamine derivatives. These ligands readily formed complexes with Group 6 metals and Ru^II, Ni^II, Pd^II and Pt^II. All complexes were characterised by elemental analysis, IR and NMR spectroscopic methods of which ³¹P-{¹H} is most valuable. The structures of the bis(phosphine) ligand Ph₂PN(CH₂Ph)CH₂CH₂(CH₂Ph)NPPh₂ and its platinum(II) complex cis-[PtCl₂{PPh₂N(CH₂Ph)CH₂CH₂(CH₂Ph)NPPh₂}] were determined by X-ray crystallography. The ligand crystallises in the extended conformation with both the nitrogen atoms nearly planar and the bond angles around them close to 120°. The P-N distances are shorter than normally accepted P-N single bond lengths (ca. 1.77 Ä) suggesting some degree of P-N bonding. The seven-membered chelate ring in the platinum complex is non-planar but the metal atom is in a typical square planar environment with two phosphorus atoms and two chlorine atoms in a mutually cis disposition and the ethylenediamine bridge is folded with respect to the plane in an "open envelope" fashion.