Synthesis and Reactivity of Fluoro Complexes:  Part 2. Rhodium(I) Fluoro Complexes with Alkene and Phosphine Ligands. Synthesis of the First Isolated Rhodium(I) Bifluoride Complexes. Structure of [Rh₃(μ₃-OH)₂(COD)₃](HF₂) by X-ray Powder Diffraction

The reaction between [Rh(μ-OH)(COD)]₂ (COD = 1,5-cyclooctadiene) and 73% HF in THF gives [Rh₃(μ₃-OH)₂(COD)₃](HF₂) (1). Its crystal structure, determined by ab initio X-ray powder diffraction methods (from conventional laboratory data), contains complex trimetallic cations linked together in 1D chains by a μ₃-OH···F−H−F···HO-μ₃ sequence of strong hydrogen bonds. The complex [Rh(μ-F)(COE)₂]₂ (COE = cyclooctene; 2), prepared by reacting [Rh(μ-OH)(COE)₂]₂ with NEt₃·3HF (3:2), has been characterized. Complex 1 reacts with PR₃ (1:3) to give [RhF(COD)(PR₃)] [R = Ph (3), C₆H₄OMe-4 (4), ⁱPr (5), Cy (6)] that can be prepared directly by reacting [Rh(μ-OH)(COD)]₂ with 73% HF and PR₃ (1:2:2). The reactions of 1 with PPh₃ or Et₃P have been studied by NMR spectroscopy at different molar ratios. Complexes [RhF(PEt₃)₃] (7), [RhF(COD)(PEt₃)] (8), and [RhF(PPh₃)₃] (9) have been detected. The complex [Rh(F)(NBD)(ⁱPr₃P)] (NBD = norbornadiene; 10) was prepared by the sequential treatment of [Rh(μ-OMe)(NBD)]₂ with 1 equiv of NEt₃·3HF and ⁱPr₃P. The first isolated bifluoride rhodium(I) complexes [Rh(FHF)(COD)(PR₃)] [R = Ph (11), ⁱPr (12), Cy (13)], obtained by reacting fluoro complexes 3, 5, and 6 with NEt₃·3HF (3:1), have been characterized. The crystal structures of 3 and 11 have been determined.