ANIONS [FE2(CO)8]2- AND [FE2(CO)6(MU-CO) (MU-PPH2)]- AS BUILDING-BLOCKS FOR THE SYNTHESIS OF MIXED-METAL CLUSTERS - CRYSTAL-STRUCTURE OF [FE2(CO)6(MU-CO)(MU-PPH2)(MU-CU(PPH3))]

Treatment of the salt [NEt4]2[Fe2(CO)8] with a tetrahydrofuran solution of the complex [Cul(PPh3)] gives an anionic orange-red cluster [NEt4][Fe2(CO)6(mu-m-CO)2 {mu-m-Cu(PPh3){] 1 which is air - and thermally unstable. When [NEt4][Fe2(CO)6(mu-m-CO) (mu-m PPh2)] and [MX(PPh3)] (M = Cu, Ag or Au) are allowed to react in the presence of TIBF4, the new neutral clusters [Fe2(CO)6(mu-CO) (mu-m-PPh2)-{mu-m-M (PPh3){] (M = Cu, 2; Ag, 3; or Au, 4) are obtained in ca. 80% yield. These relatively air-stable clusters have been characterized by IR and 31P NMR spectroscopy and the structure of 2 has been established by single-crystal X-ray diffraction studies: triclinic, space group P1BAR, with a = 11.081 (3), b = 12.190(3), c = 15.808(4) angstrom, alpha = 76.41(2), beta = 87.03(2), gamma = 80.48(2)-degrees, Z = 2 and R = 0.05. The basic skeleton consists of the first example of a Fe2Cu triangle. In this, the iron-iron bond is bridged by a phosphido and a carbonyl group.