COORDINATION BEHAVIOR OF POTENTIALLY TRIDENTATE DIPHOSPHINOAMIDO LIGANDS - SYNTHESIS AND CRYSTAL-STRUCTURES OF THE COMPLEXES [CRCL(N(CH2CH2PME2)2)2], [CR2CL3(N(CH2CH2PME2)2)(CH2P(ME)CH2CH2NCH2CH2-PME2)] AND [CR2CL4(N(CH2CH2PPR(I)2)2)2]

The reaction of CrCl3.3thf (thf = tetrahydrofuran) with bis(2-dialkylphosphinoethyl)amidolithium reagents, LiN(CH2CH2PR2)2, resulted in the formation of the new compounds [CrCl{N(CH2CH2PMe2)2}2] 1, [Cr2Cl3{N(CH2CHPMe2)2}{CH2P(Me)CH2CH2NCH2CH2PMe2}] 2 and [Cr2Cl4{N(CH2CH2PPr2i)2}2] 3 depending on reaction conditions and stoichiometry. Thus, if 2 equivalents (per Cr) of LiN(CH2CH2PMe2)2 are used 1 may be isolated where chromium is bound to two amido ligands each in different co-ordination modes (bi- and tri-dentate). With 1.5 equivalents of LiN(CH2CHPMe2)2, 2 is formed which has a binuclear structure with bridging amido ligands and an unusual alpha-metallated PCH2 group. With the more bulky LiN(CH2CH2PPr2i)2, 3 may be isolated in which a binuclear structure is bridged by both bi- and tri-dentate amido ligands. All complexes have been characterised by analysis, mass spectroscopy, and single-crystal X-ray crystallography.