Stereo- and regiospecific conversions of rhodium halo phosphines Rh2X6(PR3)3 molecules to Rh2X6(PR3)4 and RhX3(PR3)3 molecules

Abstract

Studies by 3,P NMR spectroscopy have shown that the face-sharing bioctahedral molecules Rh2X6(PR3)3 (X = Cl, Br; PR3 = PEt3, PPr3, PBu3) exist exclusively as the 1,2,6-isomers and are converted by addition of 1 molar equiv of PR'3 (R' may be R) exclusively to the l,3,6,8-Rh2X6(PR3)3(PR'3) isomer, with the entering PR'3 occupying the 6-(or 8-) position. Moreover, the edge-sharing 1,3,6,8-Rh2X6(PR3)4 type molecules react further with trialkylphosphine to produce exclusively mer-RhX3(PR3)3 products, even though, as is also demonstrated, the/ac-RhX3(PR3)3 isomers are thermodynamically preferred.

Synthesis of 1,4-Dichloro-1,3-butadienes by Rhodium Complex Catalyzed Reaction of Terminal Alkynes with Trichloroacetyl Chloride

“…The other lability we encountered is facile formation of a dinuclear rhodium complex. Upon recrystallization in a dichloromethane/hexane mixture, fac , cis -5 and mer , trans -5 were converted near quantitatively to known dimeric rhodium complex [Rh(μ-Cl)Cl 2 (PMe 3 ) 2 ] 2 ( 6 ), the structure of which is interesting in that one rhodium has two mutually cis phosphines and the other trans , as verified unequivocally by X-ray diffraction as illustrated in Figure although it displays a disorder at PMe 3 ligands …”