Mono- and dinuclear rhodium and iridium complexes with chiral phospholanes as ligands

The 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 [RhlI(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 H-2 to 1 (L = isophos) and [RhCl(PiPr(2)Ph)(2)](2) (10) affords the mononuclear dihydrido complexes [RhH2Cl(L)(2)] (13) and [RhH2Cl(PiPr(2)Ph)(2)] (14), respectively, via the unsymmetrical compounds [RhH2(L)(2)(mu-Cl)(2)Rh(L)(2)] (11) and [RhH2(PiPr(2)Ph)(2)(mu-Cl)(2)Rh(PiPr(2)Ph)(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 eta(3)-allyl and eta(3)-benzyl complexes [(eta(3)-2RC(3)H(4))Rh(L)(2)] (16-18) and [(eta(3)-CH2Ph)Rh(L)(2)] (19, 20), which were prepared from 1 or 2 and the corresponding Grignard reagent, leads to the dinuclear (RhRhI)-Rh-III products [RhH2(L)(2)(mu-H)(2)Rh(L)(2)] (21, 22), which are structurally related to the dichloro(dihydrido) derivatives 11 and 12. Compound 21 {L = lsophos} 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 eta(2)-alkyne and alkynyl(hydrido) intermediates, the reaction of 2 with PhCequivalent toCH affords the labile enyne compound trans-[RhCl{eta(2)-(E)-PhCequivalent toCCH=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)(SbiPr(3))(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. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.