| Summary: | The direct reaction of a series of R3P compounds with ICl3 has been shown to be an effective route for the synthesis of [R3PCl][ICl2] salts. Two of these salts have been structurally characterised and represent the first reported structural data for these systems. A two step route of R3P + Br2 + IBr does not yield the intended [R3PBr][IBr2] salts, instead [R3PBr][Br3] compounds are formed.The reactions of R3P with SeX4 have been studied. A redox reaction occurs, with oxidation of R3P to [R3PX]+ and reduction of SeX4 to [SeX3]–. The structures of two [R3PCl][SeCl3] salts are reported. In [(p–OCH3C6H4)3PCl][SeCl3] the anion dimerizes in the solid–state to [Se2Cl6]2– via secondary Se···Cl interactions, whilst in [(o–SCH3C6H4)3PCl][SeCl3] dimerization does not occur as there is an unusual S···Se interaction between the cation and anion.The versatile coordination chemistry of tertiary phosphine selenides (monodentate and bidentate) to group 15 centres (As, Sb, Bi) has been examined. Most Ar3PSe ligands yield 1:1 [MX3{SePAr3}] compounds which form dimers linked by M–X bridges. The asymmetry of these bridges is dependent on the nature of M and X. The aryl rings are usually located over the vacant coordination site occupied by the lone pair on the square pyramidal As, Sb or Bi atom. The weaker donor SeP(p–FC6H4)3 forms co–crystals with MX3 (M = As, Sb, Bi; X = Cl, Br) which link to form highly unusual distorted M4Se4 cuboids of high symmetry.Mixed alkyl/aryl phosphine selenides form compounds with different types of structures. The reaction of BiCl3 with SePPh2CH3 forms a tetrameric compound, [Bi4Cl12{SePPh2CH3}4] with octahedral bismuth centres. In contrast, the 1:1 [SbBr3{SePPh(CH3)2}] compound is a chain polymer with bridging phosphine selenide ligands.Polymeric chain structures are usually formed when bidentate phosphine diselenides Ph2P(Se)(CH2)n(Se)PPh2 (n = 1, 2, 6) or trans Ph2P(Se)CH=CH(Se)PPh2 complex to MX3, (M = As, Sb, Bi).
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