Heterobimetallic anions

Not unexpectedly, the [FeH(CO)4] anion aggregates with photochemi-cally generated [M(CO)s] fragments (M = Cr, Mo, or W) to give the [FeMH(CO)9] anions.5 These anions have interesting structures and reactivities, and can serve as useful precursors to the heterobimetallic anions [FeM(CO)9]2, 5. A preparation of the latter dianions, based on the reaction of Na2 [Cr(CO)5] and Fe2(CO)9, is available.6 However, problems of separation and purification are considerably alleviated in the following procedures. 

Photolytic reactions of metal carbonyl anions with metal carbonyls are also utilized to prepare heterobimetallic anions ... 

In accordance with the electropositive nature of the bridgehead atoms, all di(pyridyl) substituted anions behave like amides with the electron density accumulated at the ring nitrogen atoms rather than carbanions, phosphides or arsenides. The divalent bridging atoms (N, P, As) in the related complexes should in principle be able to coordinate either one or even two further Lewis acidic metals to form heterobimetallic derivatives. According to the mesomeric structures, (Scheme 7), it can act as a 2e- or even a 4e-donor. However, theoretical calculations, supported by experiments, have shown that while in the amides (E = N) the amido nitrogen does function as... 

Similarly, the reaction of metallic rubidium with another metal in ammonia led to the appropriate heterobimetallic amides, as in the reaction of Rb with Ca in supercritical ammonia at 573 K yielding RbCa(NH2)3. " " which consists of one-dimensional infinite face-sharing anion-octahedra occupied by calcium and connected into a three-dimensional network by the rubidium ions (Rb N contacts between 3.11 and 3.92 A). 

The assembling tendency of donorfunctionalized ligands was investigated in detail in heterobimetallic complexes derived from hydroxypyridine and the anion of 2-pyrrolidone. The diversity of structural types is controlled inter alia by solvent, kind of 6-substitution of the pyridine ring, type of additional counterions and work up procedures. LnxCuy-complexes derived from hydroxypyridine exhibit Ln Cu ratios of 1 3, 2 2, 2 4, 2 8, 4 4 and 8 12 [141-144]. The anion of 2-pyrrolidine forms polymeric macrocyclic chain structures of type LnHg2 n and Ln2Hg3 n dependent on the size of the lanthanide element [145]. 

Somewhat more loosely related to platinum antitumor drugs were EHMO calculations performed on heterobimetallic Pt-Pd complexes with a bridging methylcytosinate anion by Mealli, Randaccio, Lippert, and coworkers [31][32], The calculations served to elucidate the metal-metal and metal-ligand binding interactions, and yielded a qualitative interpretation of the 195Pt-NMR chemical shifts. 

Most importantly, the heterolytic coupling of carbonylmetal cations and anions is indicated in the treatment of tetracarbonylcobaltate(—I) with hexacarbonylrhenium(I) to afford the mixed carbonyl (65). Similarly, the treatment of Co(CO)4- with the phenanthroline-substituted tetracarbonyl-manganese(I) cation leads to the substituted heterobimetallic carbonyl (66), and the highly efficient coupling of the carbonylmanganese anion and cation yields the homodimer (67),... 

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