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RESEARCH PRODUCT

Reaction of Rh2(μ2-O2CCH3)3[μ2-(C6H4)PMePh](HO2CCH3)2 with triphenylphosphine: rearrangement of the metalated PMePh2 ligand and formation of a compound with a diphenylphosphinomethanide group in (P,C) coordination; crystal structure of [Rh2(μ2-O2CCH3)2{μ2-(CH2)PPh2}- {μ2-(C6H4)PPh2}(PPh3)]·2CH2Cl2

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The reaction of [Rh2(μ2-O2CCH3)3{μ2-(C6H4)PMePh}] (1) in CHCl3 with one mole of PPh3 gives the two phosphine monoadducts, which are in rapid equilibrium above −40 °C. After 6 h at room temperature this mixture gives [Rh2(μ2-O2CCH32{μ2-(C6H4)PMePh}{μ2-(C6H4)PPh2}](HO2CCH3)2 (3), a doubly metalated compound with a head-to-head configuration. 1 reacts with two moles of PPh3, forming the bis-adduct 1.P2, which at 10 °C gives a mixture 3, in the form of its phosphine adduct 3.P, and [Rh2(μ2-O2CCH3)2{μ2-(CH2)PPh2}{μ2- (C6H4) PPh2}(PPh3)] (2). It is confirmed that 3.P is not the kinetic product in the reaction from 1.P2 to 2. The structure of [Rh2(μ2-O2CCH3)2{μ2-(CH2)PPh2}{μ2-(CP6H4) PPh2} (PPh3)]·2CH2Cl2 has been determined by X-ray diffraction: Mr = 1216.55, monoclinic, space group P21/c, a=19.930(8), b=15.29(2), c=16.84(2) A, β=90.14(9)°, V=5129(9) A3, Z=4, Dc=1.58 g cm−3, Mo Kα radiation (graphite monochromator, λ=0.71073 A), μ (Mo Kα)=9.80 cm−1, F(000)=2464, T=200 K. The final conventional R factor was 0.061 for 4749 ‘observed’ reflections. The compound contains an orthometalated triphenylphosphine and a diphenylphosphinomethanide group bridging the two rhodium atoms. The two ligands are in a head-to-head configuration. Two bridging acetate groups and one axial PPh3 complete the coordination around the rhodium atoms. The RhRh bond distance is 2.532(2) A.