Photochemical ligand rearrangement in dirhodium(II) compounds. Structure of Rh 2(O 2CCH 3) 2( η2-O 2CCH 3)[(C 6H 4)PPh 2] ( η2-PCCl)(PCClP-ClC 6H 4)Ph 2

Abstract

The photochemical reaction of the adducts Rh 2(O 2CCH 3) 3[(C 6H 4)P( o-ClC 6H 4)Ph]· (P( p-XC 6H 4) 3) (X=H, Me, Cl), yield the compounds Rh 2(O 2CCH 3) 2( η 2-O 2CCH 3)[( p-XC 6H 3)P ( p-XC 6H 4) 2]( η 2-PCCl), (PCCl=P( o-ClC 6H 4)Ph 2) in a ligand rearrangement reaction that involves activation of CH and RhC bonds. The factors that favour this process are studied by carrying out photochemical reactions with different phosphines. The structures of Rh 2(O 2CCH 3) 2( η 2-O 2CCH 3) [(C 6H 4)PPh 2]( η 2-PCCl) has been determined by X-ray diffraction. M r=1321.1, orthorhombic, space group Pbcn, a=20.339(8), b=20.07(6), c=23.07(3) A ̊ , V=9413(3) A ̊ 3, Z=8, D x =1.86 g cm −3 . Mo Kα radiation (graphite crystal monochromator, λ=0.071073 A ̊ ), μ(Mo K α) = 13.83 cm −1, F(000)=5280, T=293 K. Final conventional R factor=0.062 for 4889 ‘observed’ reflections and 500 variables. The compound contains three bridging ligands, two acetates and one metalated triphenylphosphine, and two chelating ligands, one acetate and one PCCl that acts as a P,Cl ligand, taking one equatorial (P) and one axial (Cl) coordination site. The axial RhCl bond distance is 2.573(4) Å.