Disulfur and diselenium complexes of rhodium and iridium

A. P. Ginsberg, W. E. Lindsell, C. R. Sprinkle, K. W. West, R. L. Cohen

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Coordinatively unsaturated low-valent rhodium and iridium complexes cleave S8 and Se8 rings and form complexes with the fragments. With square-planar [M(L-L)2]Cl (M = Rh, Ir; L-L = (C6H5)2PCH2CH2P(C 6H5)2 (dppe), (CH3)2PC-H2CH2P(CH3) 2 (dmpe)) this reaction affords the monomeric electrolytes [M(Y2)(L-L)2]Cl (Y2 = S2, Se2). Oligomeric compounds are obtained from the reactions with IrX(CO)(EPh3)2 and RhX(EPh3)3 (X = Cl, Br; E = P, As); the products are [{Ir(Se2)X(CO)(PPh3)}3], [{Ir(Se2)Cl(CO)(AsPh3}3], [{IrS6Cl(CO)(PPh3)2}n], [{RhS3X(PPh3)4}], [{RhSe3Cl(PPh3)}4], and [{RhY2Cl(AsPh3)}n] (Y2 = S2, Se2). In the compounds [M(Y2)(L-L)2]Cl, disulfur and diselenium are side-on bonded to the metal at equatorial positions of a distorted octahedron. An X-ray structure determination of the diselenium complex [Ir(Se2)(dppe)2]Cl·H2O·0.5C 6H6 shows the cation to be very similar to its dioxygen and disulfur analogues. The Se-Se distance is 2.312 (3) Å, about the same as the bond length in Se8 and 0.16 Å longer than the Se-Se bond in the free Se2 molecule. [M(Y2)(L-L)2]+ complexes have ?(S-S) at 510-550 cm-1 and ?(Se-Se) at 300-310 cm-1. The lowest energy feature of their electronic absorption spectra is a weak (e 40-100 M-1 cm-1) band assigned as an a2p?* ? b1 intraligand transition. 193Ir(1/2+ ? 3/2 +) Mössbauer spectra of [Ir(Y2)(dppe)2]Cl give isomer shifts that decrease along the series Y2 = O2, S2, Se2, in parallel with decreasing Y2 electronegativity. The disulfur or diselenium group in [M(Y2)(L-L)2]+ is readily reduced: mercury and tertiary phosphines strip sulfur or selenium from the complex with formation of HgS or HgSe and R3PS or R3PSe; the rate is very sensitive to the electronic environment of the disulfur or diselenium group and to the basicity of the phosphine. Low-valent group 8 metal complexes undergo oxidative addition across the S-S or Se-Se bond, allowing synthesis of the heterometallic (µ-S)2 dimers [(dppe)2Ir(µ-S)2PtL2]X (L = PPh3, X = Cl; L = PEtPh2, X = PF6) and [(dmpe)2Rh(µ-S)2Pt(PPh3)2]Cl, as well as the asymmetric dimer [(dppe)2Ir(µ-Se)2IrCl(CO)(PEt2Ph) 2]Cl. Oxidative addition together with displacement of [M(L-L)2]+ by excess of the addend complex also occurs, giving homometallic (µ-S)2 or (µ-Se)2 dimers such as [{Ir(µ-Se)Cl(CO)(PEt2Ph)2}2]. Iodine adds across the S-S bond of [Ir(S2)(dppe)2]Cl to form the novel cis-octahedral complex [Ir(SI)2(dppe)2]Cl. © 1982 American Chemical Society.

Original languageEnglish
Pages (from-to)3666-3681
Number of pages16
JournalInorganic Chemistry
Issue number10
Publication statusPublished - 1982


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