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On the Reactivity of Rhodium(I) Complexes with κP-Coordinated γ-Phosphino-Functionalized Propyl Phenyl Sulfide Ligands: Routes to Cyclic Rhodium Complexes with κCP- and κPS-Coordinated Ligands as Well as Bis(diphenylphosphino)methanide Ligands

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journal contribution
posted on 27.12.2010, 00:00 by Michael Block, Tim Kluge, Martin Bette, Jürgen Schmidt, Dirk Steinborn
Reactions of dinuclear μ-chlorido rhodium(I) complexes [(RhL2)2(μ-Cl)2] (L2 = cycloocta-1,5-diene, cod, 3; L2 = P∧P: Ph2PCH2PPh2, dppm, 4a; Ph2P(CH2)2PPh2, dppe, 4b; Ph2P(CH2)3PPh2, dppp, 4c; Me2P(CH2)2PMe2, dmpe, 4d) with γ-phosphino-functionalized propyl phenyl sulfides PhSCH2CH2CH2PR2 (R = Ph, 1; Cy, 2) afforded mononuclear rhodium(I) complexes of the type [RhCl(R2PCH2CH2CH2SPh-κP)L2] ] (R = Ph/L2 = P∧P, 5ac; R = Ph/L2 = cod, 6; R = Cy/L2 = P∧P, 7ad; R = Cy/L2 = cod, 8). Single-crystal X-ray diffraction analysis of 7b·C6H6 exhibited the expected square-planar coordination of the rhodium atom having coordinated dppe-κ2P,P′, Cy2PCH2CH2CH2SPh-κP, and a chlorido ligand. Deprotonation of complexes 5b/c, 6, 7b/c, and 8 with lithium diisopropyl amide (LDA) yielded, with a selective deprotonation of the CH2 group next to the sulfur atom (α-CH2 group), complexes of the type [Rh{CH(SPh)CH2CH2PR2CP}L2] (13b/c, 14, 15b/c, 16), thus being organorhodium intramolecular coordination compounds. Unexpectedly, reactions of the dppm complexes 5a and 7a with LDA led to deprotonation of the CH2 group of the dppm ligand, resulting in formation of mononuclear rhodium complexes with a bis(diphenylphosphino)methanide-κ2P,P′ ligand and a R2P∧SPh-κPS ligand, as well (17, 18). Single-crystal X-ray diffraction analysis of [Rh(dppm−H2P,P′)(Cy2PCH2CH2CH2SPh-κPS)]·THF (18·THF) shows the rhodium atom located in the center of a distorted square-planar environment having bound the P∧S-κPS ligand and the anionic dppm−H2P,P′ ligand with a very small P2−Rh−P3 angle (68.8(2)°) reflecting the small bite of that ligand. Addition of Tl[PF6] to complexes 58 afforded cationic rhodium(I) complexes of the type [Rh(R2PCH2CH2CH2SPh-κPS)L2][PF6] (912) bearing bidentately coordinated neutral co-ligands (P∧P: 9, 11; cod, 10, 12) and κPS-coordinated γ-phosphino-functionalized propyl phenyl sulfide ligands, as well. Single-crystal X-ray diffraction analysis of 10 reveals that the rhodium atom adopts a slightly distorted square-planar conformation. Complexes 9ac and 11ad were found to react with carbon monoxide, yielding cationic rhodium carbonyl complexes [Rh(CO)(R2PCH2CH2CH2SPh-κPS)(P∧P-κ2P,P′)]+ (19, 20), being in a dynamic equilibrium between two diastereomers each at room temperature, which was additionally verified by DFT calculations.

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