ABSTRACT The articles which report on the crystal structures of compounds which contain at least a Rh-Sb covalent linkage are critically reviewed and analyzed as regard as preparative strategies and structural characteristics. The compounds are presented in the order of their publication date, unless comparative reasons required a different order. The number of coordination compounds in which Sb atoms act as donors to Rh are quite scarce when compared to the legions of complexes which have lighter Group 15 donors (i.e. N, P, As) and the total of crystallographically investigated structures is around twenty. The reported compounds contains either Rh(I), Rh(II), or Rh(III) centers. Mixed-valence poly-nuclear species have not been reported, so far. The Sb atoms of the free ligands are usually trivalent and SbR3 (R=Ph, iPr) are the most frequent bases. The analysis reveals that new and unexpected Rh-C types of bonds form at least when [Rh1Cl(SbPh3)3] reacts with (CF3)C ΞC(CF3) to produce [RhIIICl {κ2-C2,C5- CF3CC(CF3)C(CF3)C(CF3)}(SbPh3)2]; when [Rh1(DPD)(CO)2] (see the list of abbreviations) reacts with SbPh3 in methanol to produce [Rh1(CO){C(O)CH3} (Sbph3)3 ]and in hexane to produce[RhIII(κ2-O, O-DPD) (η1-Ph)2(SbPh3)2 ]•2C6H6; when [Rh1Cl(CO)(SbPh3)3] reacts with HC ΞCCH2Cl to produce [RhIII Cl {κ2-C1,C4-C(=O)CH=C(Cl)CH2}(SbPh3)3]; and when RhCl3•3H2O reacts with SbPh3 to produce [RhIIICl2(Ph)(SbPh3)3]. The latter compound proved to be a versatile starting compound for preparing a variety of new complexes such as [RhIIICl2(Ph)(PY)3], [RhIIICl2(Ph)(PY)2(MePYM)], [RhIIICl2(Ph)(PYR)2(SbPh3)], and the triphenylphosphine derivatives [RhIIICl2(Ph)(PPh3)2] and [Rh(Ph)(H2TP)2(PPh3)] [Rh(Ph)(H2TP)(HTP)(PPh3)]Cl3•HCl•6H2O. The detailed reaction mechanisms which bring to the formation of such organometallic linkages are mostly unknown. The Rh(I)-Sb complexes were made from the reaction of Rh(I)-complexes as starting materials. η2 –C2H4 is replaced by carbene CPh2, when [RhICl(η2-C2H4)(SbiPr3)2] reacts with CPh2N2 in pentane and [RhICl(=CPh2)(SbiPr3)2] is then formed. On heating the latter compound at 600C in benzene for 4h the binuclear compound [RhI2Cl2(μ-CPh2)2 (μ-SbiPr3)] forms; it is stabilized by a metal-metal linking interaction, and most interestingly, by an unusual bridging SbiPr3 ligand. This bridge can then be removed by phosphine ligands. The Rh(II)-Sb complexes(three over a total of twenty-two) have the common binuclear structure with four bridging chelating ligands; they were prepared by starting from analogous binuclear Rh(II) compounds by displacing the apical ligands with SbPh3. The Rh(III)-Sb complexes were prepared from Rh(III)-complexes by substitution reactions (see for instance, the preparation of [RhIIICl2(S6,N7-H2TP)(Ph)(SbPh3)] from [RhIIICl2(Ph)(SbPh3)3] or from Rh(I)-complexes via complicate oxidative-addition reactions (see for instance, the preparation of [RhIII(η5-C5H5) {κ2–C1,C3-C(=NCH3)C(Ph)=C(Ph)}(SbiPr3)] from [Rh1(η5- C5H5)(η2-PhCΞCPh)SbiPr3)] and CNCH3, in pentane). The coordination arrangements around the Rh(I) centers for the mononuclear species [RhI(CO){C(O)CH3}(SbPh3)3] is trigonal bipyramidal with the Sb atoms in the equatorial plane (Rh-Sb,2.568(2) Å, average); where as for the mononuclear complexes [RhICl(=CPh2)(SbiPr3)2] and [RhICl(CNCH3)(SbiPr3)2] it is square planar with the Sb atoms trans each other (Rh-Sb, 2.5738(5) and 2.5372(6) Å, respectively). The R(I)-centers of the binuclear species [RhI2Cl2(μ-Cph2)2 (μ-SbiPr3)] are both five coordinate by a terminal chloride donor, two bridging CPh2 groups , a bridging SbiPr3 ligand and by the twin Rh atom . The Rh(I)-centers of the binuclear molecule [RhI2(η4-COD)2(μ, κ2-Sb1,Sb2-Sb2Ph4){μ-Sb1,μ-Sb2-(SbPh2)2}] are both five-coordinate when the centroids of each C=C bond from COD are taken into account, the other three linkages being with three Sb atoms. The Rh(I)-centers of the binuclear molecule [ClRhI(μ-CPh2)2 (μ-SbiPr3)RhI(ACAC)]are very asymmetrically coordinated. One of them is linked to two oxygen atoms from ACAC-, to two bridging CPh2 groups and to a bridging Sb atom. The second metal atom is linked to a terminal chloride donor, to two bridging carbene groups and (much weakly) to the bridging Sb. The coordination geometry around the metal centers in the Rh(III) complexes is usually pseudo-octahedral, as expected. The only exception is [RhIIIC1{κ2-C2,C5-CF3CC(CF3)C(CF3)C(CF3)}(SbPh3)2] for which the metal is five-coordinate (trigonal pyramidal arrangement) being linked to a chloride anion, to two carbon atoms, and to two Sb atoms (at the apical positions).
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