AbstractThe dinuclear complexes [RhCl(L)2]2 (1, 2) with L = 1‐isopropyl‐(2S,5S)‐2,5‐dimethylphospholane (Isophos) and (2S,5S)‐2,5‐dimethyl‐1‐phenylphospholane (Phephos), respectively, prepared from [RhCl(C8H14)2]2 and four equivalents of L, react with Lewis bases such as L, CO, ethene and diphenylacetylene by cleavage of the chloride bridges. Mononuclear compounds of the general composition [RhCl(L)3] (3, 4) and trans‐[RhCl(L′)(L)2] (5−9; L′ = CO, C2H4, C2Ph2) were obtained, of which 4 (L = Phephos) and 8 (L′ = C2H4; L = Phephos) are in equilibrium with the precursors. Oxidative addition of H2 to 1 (L = Isophos) and [RhCl(PiPr2Ph)2]2 (10) affords the mononuclear dihydrido complexes [RhH2Cl(L)2] (13) and [RhH2Cl(PiPr2Ph)2] (14), respectively, via the unsymmetrical compounds [RhH2(L)2(μ‐Cl)2Rh(L)2] (11) and [RhH2(PiPr2Ph)2(μ‐Cl)2Rh(PiPr2Ph)2] (12) as intermediates. These intermediates can be isolated by treatment of 13 and 14 with one half equivalent of 1 or 10, respectively. The hydrogenation of the η3‐allyl and η3‐benzyl complexes [(η3‐2‐RC3H4)Rh(L)2] (16−18) and [(η3‐CH2Ph)Rh(L)2] (19, 20), which were prepared from 1 or 2 and the corresponding Grignard reagent, leads to the dinuclear RhIIIRhI products [RhH2(L)2(μ‐H)2Rh(L)2] (21, 22), which are structurally related to the dichloro(dihydrido) derivatives 11 and 12. Compound 21 (L = Isophos) reacts with CO to give trans‐[RhH(CO)(L)2] (23). While treatment of 1 with phenylacetylene yields the vinylidene complex trans‐[RhCl(=C=CHPh)(Isophos)2] (26), via η2‐alkyne and alkynyl(hydrido) intermediates, the reaction of 2 with PhC≡CH affords the labile enyne compound trans‐[RhCl{η2‐(E)‐PhC≡CCH=CHPh}(Phephos)2] (27). Reaction of 27 with CO gives 6 and the free enyne. The carbene complexes trans‐[RhCl(=CPh2)(L)2] (30, 31), obtained from trans‐[RhCl(=CPh2)(SbiPr3)2] (29) and L, react with ethene not by olefin metathesis but by formation of the isomeric olefins Ph2C=CHCH3 (32) and CH2=CHCHPh2 (33) in different ratios. With iridium as the metal center, carbonyl, dihydrido, and dihydrido(carbonyl) compounds with [IrCl(Isophos)2] as the building block have been prepared. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)