THE REACTION OF THE P2N2 SCHIFF-BASE LIGAND EN=P-2 WITH MI(2) SALTS AND THE REACTION OF THE TETRAIODINE ADDUCT OF EN=P-2 WITH UNACTIVATED COARSE-GRAIN METAL POWDERS - A COMPARATIVE-STUDY (EN=P-2=N,N'-BIS[(O-DIPHENYLPHOSPHINO)BENZYLIDENE]ETHYLENE-DIAMINE - M=MN, CO AND NI)

The reaction of the N2P2 donor set Schiff base ligand en=P-2 with metal salts MI(2) (M = Mn, Co and Ni) produces compounds of stoichiometry M(en=P-2)I-2. Single crystal X-ray diffraction studies have shown the nickel complex to be five-coordinate [Ni(en=P-2)I]I and to have a square pyramidal structure. This complex appears to exist in a spin-crossover state, mu(eff) = 2.35 mu(B). The analogous cobalt complex has been shown by X-ray powder diffraction to be isostructural with the nickel complex, but is low spin, mu(eff) = 2.40 mu(B). Reaction of en=P-2 with two equivalents of diiodine in dry diethyl ether produces an adduct of stoichiometry (en=P-2)I-4. Solution P-31(H) NMR studies in CDCl3 indicate one phosphorous environment, delta = 53.4 ppm. Addition of two further equivalents of diiodine to this compound in CDCl3 results in no change in the P-31 chemical shift, implying that (en=P-2)I-4 exists as the ionic [(en=P-2)I-2](2+)2I(-) in CDCl3 solution. The solid state Raman spectrum of (en=P-2)I-4 shows a strong band at 154 cm(-1) which is assigned to nu(P-I). Another band is observed at 111 cm(-1), which has been tentatively assigned to nu(I-I) indicating that the compound may exist as a molecular charge transfer adduct in the solid state. This tetraiodophosphorous adduct reacts with Mn, Co and Ni coarse grain metal powders to form compounds of stoichiometry M(en=P-2)I-4. The cobalt and nickel complexes have been shown to be isostructural by X-ray powder diffraction methods. Bands in the UV-Vis spectrum at similar to 293 nm and at 364 nm indicate the presence of the I-3(-) ion, which we believe indicates that these compounds adopt a five coordinate geometry analogous to the [M(en=P-2)I]I compounds of [M(en=P-2)I]I-3. This is further supported by the room temperature magnetic moment of [Co(en=P-2)I]I-3 of 3.8 mu(B) consistent with a high spin five-coordinate cobalt(II) centre which is in complete contrast to that observed for [Co(en=P-2)I]I. This further highlights the ability of dihalogen adducts of tertiary phosphines to react with coarse grain unactivated metal powders to generate products not attainable by conventional means.