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Pechmann T, Brandt CD, Werner H: Extending the coordination capabilities of tertiary phosphines and arsines: preparation, molecular structure, and reactivity of dinuclear rhodium complexes with PR3 and AsR3 in a doubly bridging coordination mode. Dalton Trans. 2004 Mar 21;(6):959-66. Epub 2004 Feb 12.
The reactions of [Rh2 (kappa2-acac) 2 (mu-CPh2) 2 (mu-PR3)] (PR3= PMe34, PMe2Ph 7, PEt38) with an equimolar amount of Me3SiX (X = Cl, Br, I) afforded the unsymmetrical complexes [Rh2X (kappa2-acac)(mu-CPh2) 2 (mu-PR3)] 5, 9-12, which contain the phosphine in a semi-bridging coordination mode. From 4 and excess Me3SiCl, the tetranuclear complex [[Rh2Cl (mu-Cl)(mu-CPh2) 2 (mu-PMe3)] 2] 6 was obtained. In contrast, the reaction of 4 with an excess of Me3SiX (X = Br, I) yielded the dinuclear complexes [Rh2X2 (mu-CPh2) 2 (mu-PMe3)] 13, 14 in which, as shown by the X-ray crystal structure analysis of 14, the bridging phosphine is coordinated in a truly symmetrical bonding mode. While related compounds with PEt3 and PMe2Ph as bridging ligands were prepared on a similar route, the complex [Rh2Cl2 (mu-CPh2) 2 (mu-PiPr3)] 19 was obtained from the mixed-valence species [(PiPr3) Rh (mu-CPh2) 2Rh (kappa2-acac) 2] 17 and HCl. The reaction of [Rh2 (kappa2-acac) 2 (mu-CPh2) 2 (mu-SbiPr3)] 3 with AsMe3 gave the related Rh (mu-AsMe3) Rh compound 21. With Me3SiCl, the acac ligands of 21 can be replaced stepwise by chloride to give [Rh2Cl (kappa2-acac)(mu-CPh2) 2 (mu-AsMe3)] 23 and [[Rh2Cl (mu-Cl)(mu-CPh2) 2 (mu-AsMe3)] 2] 24, the latter being isomorphous to the phosphine-bridged dimer 6. |
32(0,1,1,2) |