Preparation and co-ordination properties of trans-chloro-[1-(p-methoxyphenylimino)-2-(methylimino)propyl]bis(triphenylphosphine)-platinum. Crystal and molecular structure of the ionic compound [PtCl{C(NR)CMeNMe[Rh(CO)2]}(PPh3)2][RhCl2(CO)2](R = C6H4OMe-p)

Abstract

The 1,2-bis(imino)propyl complex trans-[PtCl{[graphic omitted]MeNR′}(PPh₃)₂](2)(R = C₆H₄OMe-p, R′= Me) can be prepared by the condensation reaction of monomethylamine with the carbonyl group of [PtCl{[graphic omitted]MeO}(PPh₃)₂](1). Complex (2) reacts with MCl₂ and K[PtCl₃(CH₂CH₂)] to give the adducts [PtCl{C([graphic omitted]Cl₂)}(PPh₃)₂][ClO₄](3)(M = Cu, Zn, or Pt), and with chloro-bridged dimers [{M′CIL₂}₂] in the presence of NaClO₄(molar ratio Pt : M′= 1 : 1) to give the cationic complexes [PtCl{C([graphic omitted]L₂)}(PPh₃)₂][ClO₄](4)[M′L₂= Pd(η³-2-MeC₃H₄) or Rh(cod)(cod =η⁴-Cyclo-octa-1,5-diene)]. In the binuclear complexes (3) and (4) the 1,2-bis(imino)propyl group of (2) is σ : σ′-N,N′-chelated to the metal centres M and M′ respectively. The reaction of (2) with [{M′CIL₂}₂](molar ratio Pt : M′= 1 : 2) yields the [PtCl{C([graphic omitted]L₂)}(PPh₃)₂]-[M′Cl₂L₂](5), which are characterized in solution by conductivity measurements and ¹H and ³¹P n.m.r. spectroscopy. The ¹H n.m.r. data indicate an interaction between the cationic and the anionic species of (5) which involves breaking of one of the M′-N_imino bonds in the binuclear cation, without exchange of PPh₃ and chloride ligands between the Pt and M′ metal centres. When M′L₂= Rh(CO)₂, the reaction affords the complex [PtCl{C([graphic omitted]h(CO)₂]}(PPh₃)₂][RhCl₂(CO)₂](5c) as a red-brown microcrystalline product, which is partially associated in solution. The crystal and molecular structure of (5c) has been determined by X-ray diffraction analysis. Crystals are monoclinic, space group P2₁/a, with a= 19.521 (3), b= 17.212(7), c= 15.910(3)Å, β= 104.11 (2)°, and Z= 4. The structure has been determined by the heavy-atom method and refined to the conventional R of 0.055 for 3 892 counter reflections (up to 2θ= 43°, Mo-K_α radiation). The structure consists of discrete, well separated cationic binuclear species and distorted square-planar cis-[RhCl₂(CO)₂]^– anions. In the cation the rhodium co-ordination plane forms a dihedral angle of 81° with the platinum co-ordination plane, with bond distances in the normal range (mean values : Rh–Cl 2.342, Pt–P 2.330, Rh–N 2.07, Rh–CO 1.81, Pt–Cl 2.375, Pt–C(sp²) 1.97 Å). In the solid state there are no unusually short intermolecular contacts.