Reactivity of mononuclear Pd(ii) and Pt(ii) complexes containing the primary phosphane (ferrocenylmethyl)phosphane towards metal chlorides and PPh(3).

The reaction of the primary phosphane (ferrocenylmethyl)phosphane [PH(2)CH(2)Fc, ] with an equimolar amount of [M(cod)Cl(2)] (cod = 1,5-cyclooctadiene, M = Pd, Pt) gave the unusual monobridged M(ii) dinuclear complexes of formula [(cod)ClM(micro-PHCH(2)Fc)M(PH(2)CH(2)Fc)Cl(2)] [M = Pt, ; M = Pd, ]. The mechanism leading to and involves the preliminary formation of cis-[M(PH(2)CH(2)Fc)(2)Cl(2)] which further reacts with free [M(cod)Cl(2)] before undergoing dehydrochlorination. The reaction of with PPh(3) led to the unexpected formation of the cyclic trinuclear complex [Pd(3)(micro-PHCH(2)Fc)(3)(PPh(3))(2)(PH(2)CH(2)Fc)Cl(3)] (). Further reaction of with PPh(3) led to the substitution of the tertiary phosphane for the primary one with formation of two geometric isomers and of formula [Pd(micro-PHCH(2)Fc)(PPh(3))Cl](3) differing only for the position of the PPh(3) group replacing the PH(2)CH(2)Fc ligand. In complex each micro-PHCH(2)Fc group bridging two palladium atoms has a terminal PPh(3) ligand in trans position with respect to the first Pd (the cis position being occupied by a chlorine) and a chlorine ligand trans to the other Pd (the cis position being occupied by a terminal PPh(3) ligand) thus rendering chemically equivalent the three PPh(3) (and the three phosphides). In complex the three terminal PPh(3) as well as the three bridging phosphido ligands are chemically inequivalent. Complexes and coexist in equilibrium in solution, but only precipitates from CH(2)Cl(2)-n-hexane yielding crystals suitable for X-ray analyses. These crystals are water/n-hexane solvates and belong to the monoclinic space P2(1)/c with a = 25.063(6) A, b = 15.564(4) A, c = 26.089(5) A, beta = 120.017(16) degrees . They contain two identical couples of enantiomers of . The peculiar arrangement of three metals and three phosphorus atoms of the bridging ligands ascertained for trimers , and has no precedent in the rich class of palladium and platinum phosphido chemistry.