Metal phosphine clusters

Because of possible catalytic and biological relevance of metal-sulfur clusters, several such compounds of cobalt have been prepared. The action of H2S or M2S (M = alkali metal) on a non-aqueous solution of a convenient cobalt compound (often containing, or in the presence of, a phosphine) is a typical route. Diamagnetic [Co6Ss(PR3)6] (R = Et, Ph) comprise an octahedral array of metal atoms (Co-Co in the range 281.7 to 289.4pm), all faces capped by atoms,and show facile redox behaviour... 

In a series of papers, metal sulfide cluster anions of first-row transition metals, principally copper, have been reacted with a variety of reagents including thiols, sulfur, phosphorus, and phosphines (99, 145, 256, 257). 

Both alkyl and aryl tellurosilanes act as a good source of Rib and Te2 ligands, forming transition metal-tellurium clusters with cobalt(II) and copper(I) salts. The nuclearity of the cluster is determined primarily by the phosphine present, but also by... 

For practical purposes the field of metal-metal bonds and metal atom clusters can be divided into two broad areas. (1) Those compounds with the metal atoms in formal oxidation states of zero or close to it, including negative ones. For the most part these are polynuclear metal carbonyls, or very similar compounds. In these compounds the M-M bonds are usually long, weak and of order one. (2) Compounds with the metal atoms in low to medium positive oxidation states, and ligands of the same kinds normally found in classical Werner complexes, e.g., halide, sulfate, phosphate, carboxylate or thiocyanate ions, water, amines and phosphines. Compounds of this type include metal-metal bonds of orders ranging from about 1/2 to 4.0. 

Finally, the 64-branch phosphine DAB-t e r-G4-[N(CH2PPh2)2]32 analogously reacts with [Ru3(CO)i2] and 1 % [Fe Cp( -C6Me6)] (20°C, THF, 20 min) to give the dark-red 192-Ru dendrimer. Characterization of the purity of these dendrimer-cluster assemblies is conveniently monitored by P NMR. This application should find extension to other metal-carbonyl clusters and other families of phosphine dendrimers. 

Reduction of [Mo CIg] and [Mo ClgX ] anions (X = Cl, Br, or I) by certain tertiary phosphines gave complexes of stoicheiometry MOgClgX3(PR3)3, which are formulated to have an ionic structure [MOgCl8(PR3)g] [Mo Clg]X in which the cation is a derivative of the previously unknown [Mo Clg] cluster. The use of photoelectron spectroscopy to determine structures of metal halide clusters has been reviewed. " A detailed study of the force fields for MojXg anions (X = Cr or Br) has indicated that 6 bonds do not play a significant part in the M—M bond strength of molybdenum halides. ... 

The system was very sensitive to the transition metal ion added to the platinum. When it was nickel, hydrocin-namaldehyde was obtained in 97% selectivity.75 The intermediates in these reductions are probably metal hydride clusters. When the colloidal platinum is supported on magnesium oxide, without another transition metal, the reduction produces the unsaturated alcohol with 97% selectivity.76 A rhodium colloid stabilized by the same polymer was used with a water-soluble phosphine in the hydro-formylation of propylene to produce 1 1 mixture of /r-bu-tyraldehyde and isobutyraldehyde in 99% yield.77 It could be used at least seven times, as long as it was not exposed to air. 

Joseph Chatt s interests in organometallic chemistry were wide-ranging, from bonding theories to nitrogen fixation. While these areas may not seem of immediate relevance to either carbonyl cluster chemistry or to electrospray mass spectrometry (both of which play a major role in the work described herein), the chemistry that is discussed broadly overlaps with Chatt s contributions in metal hydride, metal phosphine and low-oxidation-state chemistry. 

A large number of clusters of Group VIII and Group IB metals have been prepared in which a variety of phosphines are the principal ligands. These clusters are listed in Table IX. The phosphine clusters have been prepared by a wide variety of methods as can be seen from Table IX, and no general methods of preparation can be designated for these compounds. Most of them involve either the reaction of a zero-valent phosphine metal compound, or reduction of a higher valent compound. The phosphine clusters listed in Table IX have all been reported since 1966, and the structure of only one of these compounds has been... 

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