NEW IRON(II)-CONTAINING AND GOLD(I)-CONTAINING METALLOCENES - X-RAY STRUCTURE OF A 3-COORDINATE GOLD(I) FERROCENOPHANE-TYPE REPRESENTATIVE

The metallophosphines 1,1'-bis(diphenylphosphino)octamethylferrocene (dppomf) (5) and (1,1-octamethylferrocenediyl)phenylphosphane (4) have been synthesized by reacting FeCl2 with lithium (diphenylphosphino)tetramethylcyclopentadienide and bis(tetramethylcyclopentadienyl)phenylphosphine dilithium salt, respectively. When 5 was reacted with ClAu(tht) (tht = tetrahydrothiophene) in a 1:2 ratio, 6 was obtained in which one AuCl unit is coordinated to each phosphine group. The proportion 1:1 led to the three-coordinate gold(I) monomer complex 7, of which the X-ray structure has been established. It crystallizes in space group P2(1)/c, monoclinic, with a = 23.153(4) Angstrom, b = 9.070(4) Angstrom, c = 20.414(3) Angstrom, beta = 114.2(1)degrees, and Z = 4. The gold atom is trigonal planar, the Au-P and Au-CI bond lengths are greater than those in linear P-Au-CI complexes. The cyclopentadienyl rings are planar, parallel, and staggered by 17 degrees, and the methyl substituents deviate slightly both sides from the plane. The pseudotriplets observed in C-13 NMR for the cyclopentadienyl part are the result of long-range coupling with the two phosphorus atoms through,gold. The stability of 7 in solution is shown by finding the same spectrum again after several hours. Electrochemistry showed the formation of Fe(III) derivatives of the metallophosphine gold(I) complexes, which can also be obtained by direct reaction of the precursors with electrochemically generated [Cp(2)Fe](+). The (197)AU Mossbauer parameters for 6 and 8 are typical for linear two-coordination of gold(I), and the particularly small IS value for 7 can be explained by the strained P-Au-P angle which decreases the s-character of the P-Au bond. The reactivity of 6 and 7 was shown by the substitution of the chlorine atoms by the nucleophile C6F5- affording the fluorine-containing complexes 8 and 9, respectively. Compound 9 represents the first example of a P-Au(-P)-C tricoordinate gold(I). Complexes 5-8 have been tested in vitro against various human cancer cells. The cytotoxicity, although improved by the presence of gold, is not better than that of drugs already known.