Synthesis and structural studies of platinum complexes containing monodentate, bridging, and chelating formamidine ligands

The reactions of K2PtCl4 with N,N-diphmylformamidine (HDPhF) and N,N'-di-p-tolylformamidine (HDTolF) produce the trans square-planar compounds PtCl2(HDPhF)(2), 1a, and PtCl2(HDTolF)(2), 1b. Compound 1a crystallizes as yellow parallelepipeds in the space group P2(1)/c with two independent molecules in the asymmetric unit and unit cell dimensions a = 23.427(7) Angstrom, b = 16.677(6) Angstrom, c = 12.980(4) Angstrom, and beta 96.10(2)degrees. These compounds are soluble in common organic solvents and have been used as starting materials for the preparation of diplatinum compounds. Treatment of la and Ib with NaOMe and the halide abstraction reagent T1PF(6) produces the compounds Pt-2(mu-DArF)(2)(eta(2)-DArF)(2), Ar = Ph (2a) and Tol (2b), respectively. Compound 2a crystallizes as yellow rods in the spare group P (1) over bar with unit cell dimensions a 12.296(3) Angstrom, b = 12.310(4) Angstrom, c = 15.374(4) Angstrom, alpha = 90.75(2)degrees, beta = 91.02(2)degrees, and gamma 110.20(2)degrees. Compound 2b crystallizes with a molecule of THF, as yellow rods in the space group P2(1)/c with a 17.883(3) Angstrom, b = 14.517(3) Angstrom, c = 22.581(3) Angstrom, and beta = 98.17(1)degrees. These compounds contain two cis bridging formamidinato ligands and two formamidinato ligands that are chelated to separate Pt centers, Upon heating, they further react to give the tetrabridged compounds Pt-2(mu-DArF)(4), Ar = Ph (3a), Tol (3b). Compound 39 crystallizes as orange cubes in the cubic space group I432 with a 19.671(1) Angstrom. On going from the bis-bridged, bis-chelate structure in 2a to the tetrabridged structure in 3a, the metal-metal separation decreases from 2.910(1) to 2.649(1) Angstrom. Both 2b and 3b have been oxidized to give the Pt-II-Pt-II compound Pt-2(mu-DTolF)(4)(PFt(6)), 4. Compound 4 crystallizes as cubes in the tetragonal space group P4/nnc with a 14.392(1)A and c = 14.336(1) Angstrom. The Pt-Pt distance in 4 is 2,5304(6) Angstrom.