Joanne M. Sheffield

An X-ray crystallorgraphic study of the reagent Ph3PCl2; not charge-transfer, R3P–Cl–Cl, trigonal bipyramidal or [R3PCl]Cl but an unusual dinuclear ionic species, [Ph3PCl+⋯Cl–⋯+CIPPH3]Cl containing long Cl–Cl contacts

An X-ray crystallographic study of the reagent Ph3PCl2 reveals it to be [Ph3PCl+⋯Cl–⋯+ClPPh3]Cl and not trigonal bipyramidal, molecular charge-transfer Ph3P–Cl–Cl or the simple ionic species [Ph3PCl]Cl; this contrasts with the conclusions from all previous spectroscopic data recorded on compounds of stoichiometry R3PCl2 by earlier workers, and represents the first compound of this formula to be crystallographically characterised.

The reaction of triorganophosphorus diiodides, R3PI2, with zinc metal powder; dependency of product on R; the X-ray crystal structures of dimeric {ZnI2[P(NMe2)3]}2 and monomeric ZnI2(PPh2Me)2

Abstract Seventeen zinc(II) tertiary phosphine complexes have been synthesised directly from elemental zinc by reaction with the reagents R 3 PI 2 . The complexes have been characterised by elemental analysis and 31 P{H} NMR spectroscopy. The present work represents the first comprehensive study of a wide variety of zinc(II) tertiary phosphine complexes containing different parent tertiary phosphines and the majority of the complexes are reported for the first time. In most cases, reaction of R 3 PI 2 with zinc metal powder in diethyl ether in a 1:1 stoichiometric ratio, produces the dimeric complexes [ZnI 2 (PR 3 )] 2 , analogous to the previously reported [ZnI 2 (PEt 3 )] 2 . In contrast, reaction of R 3 PI 2 (R=Ph 3 , Ph 2 Et, Ph 2 Me) with zinc metal powder produces the monomeric bis complexes ZnI 2 (PR 3 ) 2 and an equimolar quantity of zinc(II) iodide, the latter product being identified by X-ray powder diffraction. The X-ray crystal structures of dimeric {ZnI 2 [P(NMe 2 ) 3 ]} 2 and monomeric ZnI 2 (PPh 2 Me) 2 are also described. The formation of the bis complexes ZnI 2 (PR 3 ) 2 (R 3 =Ph 3 , Ph 2 Me, Ph 2 Et) is surprising and cannot be due to steric factors since complexes containing less bulky tertiary phosphines are shown to be dimeric and the adoption of a monomeric zinc(II) centre increases steric crowding at the metal atom. The existence of the bis complexes is therefore reasoned to be due to favourable Π–Π interactions on the ligands and crystal packing forces.

Structural dependence of the reagent Ph3PCl2 on the nature of the solvent, both in the solid state and in solution; X-ray crystal structure of trigonal bipyramidal Ph3PCl2, the first structurally characterised five-coordinate R3PCl2 compound

The very delicate structural balance of Ph3PCl2 when prepared in diethyl ether solution is illustrated by its X-ray crystallographic study; unlike the ionic species, [Ph3PCl+···Cl–···+ClPPh3]Cl, which prevails in dichloromethane solution, the non-solvated molecular species Ph3PCl2 is formed in diethyl ether which is the first example of a trigonal bipyramidal R3PCl2 compound to be structurally characterised, and this may have an effect on the chlorinating ability of the reagent.

The structural characterisation of Ph3PSe(Ph)I. The first charge transfer (CT) complex of a tertiary phosphine containing a pseudohalogen

The reaction of 2 mol equivalents of triphenylphosphine with diphenyldiselenyldiiodine (Ph2Se2I2) produces the charge transfer (CT) complex Ph3PSe(Ph)I in quantitative yield; this compound represents the first report of a CT complex of a tertiary phosphine that contains a pseudohalogen.

Reaction of R3AsI2(R = Me or Et) with zinc metal powder to produce ZnI2(AsMe3)2 and [ZnI2(AsEt3)]2, the first tertiary arsine complexes of zinc(II)

The reaction of Et3AsI2 with zinc metal powder produced the dimeric complex [ZnI2(AsEt3)]2, whereas that of Me3AsI2 gave equimolar quantities of ZnI2(AsMe3)2 and ZnI2, the latter being identified by X-ray powder diffraction. Both arsine complexes have been structurally characterised and as such represent the only examples for zinc(II). A structural change is thus seen on changing the R groups on the R3AsI2 compound. The complex ZnI2(AsMe3)2 represents the sole example of a bis(ligand) complex of zinc(II) containing a Group 15 donor atom. Both complexes contain the zinc atoms in essentially tetrahedral geometry but significant distortion is noted for ZnI2(AsMe3)2, which may be the result of unfavourable steric interactions.