SYNTHESIS, CHARACTERIZATION AND REACTIVITIES OF DINUCLEAR RHODIUM(I) COMPLEXES OF A HEXADENTATE LIGAND, AKIS[2-(DIPHENYLPHOSPHINO)ETHYL]ETHANE-1,2-DIAMINE

A number of square planar dinuclear rhodium(I) complexes, [Rh(2)LX(2)] (X=Cl, I, N-3) and [Rh(2)L][ClO4](2) have been prepared with a hexade ntate ligand having N2P4 donor sites, N,N,N',N'-tetrakis[2-(diphenylph osphino) ethyl]ethane-1,2-diamine (L.). The compound [Rh(2)LCl(2)] rea dily undergo oxidative addition reactions with Cl-2, Br-2, I-2 and MeI which result in the formation of octahedral dinuclear complexes with additional ligands in axial positions. [Rh(2)LCl(2)] with NOBF4 forms a pentacoordinate complex [Rh(2)L(NO)(2)Cl-2][BF4](2). Reaction of [Rh (2)LX(2)] (X=Cl,N-3) with CO gives pentacoordinate dinuclear complexes [Rh(2)L(CO)(2)X(2)] with trigonal bipyramidal geometry. However, a CO adduct [Rh(2)L(CO)(4)I](2) is obtained when [Rh(cod)I](2) reacts with L in CO-saturated dichloromethane solution. All CO adducts react with O-2 to give octahedral carbonate complexes, [Rh(2)L(O)(4)(CO3)(2)X(2) ] (X=Cl, I, N-3) in which CO32- acts as a bidentate ligand and PPh(2) of L is oxidised to Ph(2)P=0 which coordinates to rhodium through oxyg en. The complex [Rh(2)LCl(2)] reacts with SO2 to give [Rh(2)L(SO2)(2)C l-2] which on reaction with O-2 results in the formation of the octahe dral sulphate complex [Rh(2)L(O)(4)(SO4)(2)Cl-2]. Reaction of [Rh(2)LC l(2)] with O-2 and S-8 yields [Rh(2)L(O-2)(2)Cl-2] and [Rh(2)L(S-2)(2) Cl-2], respectively, in which O-2 and S-2 are pi-bonded to rhodium. Th e complex [Rh(2)L(O)(2)Cl-2] in solution is slowly oxidised to [Rh(2)L (O)(4) Cl-2]. All complexes have been characterized and geometric aspe cts discussed on the basis of (31)p-{H-1}NMR data.