SITE-SELECTIVE SUBSTITUTION-REACTIONS AND ISOMERIZATIONS IN TETRAHEDRAL MCO3 CARBONYL CLUSTERS (M=FE, RU) AND N, P, S, AND TE DONOR LIGANDS- CRYSTAL-STRUCTURES OF HRUCO3(CO)10(PME2PH)2 AND HRUCO3(CO)9(PME2PH)3

We report on the influence of the metals and of the ligands on site-se lective substitution reactions with various two-electron donor ligands . The reaction between the tetrahedral mixed-metal cluster HRuCo3(CO)1 1(PMe2Ph) (1) and PMe2Ph has led selectively to the disubstituted clus ter HRuCo3(CO)10(PMe2Ph)2(2a) in which the phosphines are bound to cob alt atoms [isomer Co,Co]. This cluster spontaneously transforms in CH2 Cl2 into the isomer 2b in which a phosphine is bound to ruthenium [Co, Ru]. Reaction of 2a with PMe2Ph occurs via first isomerization in 2b, which instantly yields HRuCO3(CO)9(PMe2Ph)3 [Co,Co,Ru] (3). The latter is best prepared by the reaction of 1 with 2 equiv of PMe2Ph in the p resence of Me3NO. Clusters containing different phosphine ligands have also been prepared. In contrast to the reactions of PMe2Ph with the c lusters HRuCo3(CO)11(E) (E = SMe2, SeMe2, TePh2) in which the Ru-bound chalcogenide ligand is displaced by the phosphine without formation o f a disubstituted cluster, the reaction of 1 with TeMe2 produced HRuCo 3(CO)10(PMe2Ph)(TeMe2) (4) in good yield. Reaction of 1 with SEt2 affo rded a mixture containing the disubstituted clusters HRuCo3(CO)10(PMe2 Ph)(SEt2) in the form of two isomers, [Co,Co] (5a) and [Co,Ru] (5b). I n the presence of Me3NO, mainly 5b was formed. In HRuCo3(CO)10(NMe3)(P Me2Ph) (6a), which was obtained from 1 and Me3NO, the amine ligand is readily displayed by SEt2 to give 5a selectively and in quantitative y ields. Spectroscopic IR [nu(CO)] and H-1 and Co-59 NMR data are presen ted. Comparative studies have been performed with HFeCo3(CO)11(phosphi ne): reactions with phosphine, amine, or thioether ligands afford only the [Co,Co] disubstituted clusters. Reaction from HFeCo3(CO)12-nLn (n = 0-2) never led to substitution at iron. Clusters 2b and 3 have been structurally characterized by X-ray diffraction: HRuCo3(CO)10(PMe2Ph) 2 (2b) crystallizes in the space group P2(1)/c, monoclinic, with a = 1 7.69(1) angstrom, b = 14.275(7) angstrom, c = 12.518(7), beta = 97.64( 5)-degrees, and Z = 4, and HRuCo3(CO)9(PMe2Ph)3 (3) crystallizes in th e space group P2(1)/c, monoclinic. with a = 10.927(5) angstrom. b = 21 .275(5) angstrom, c = 16.096(3), beta = 94.65(3)-degrees, and Z = 4.