Clusters phosphorus ligands

The structures of 13 (33), 14 (34), and 15 (35) are shown in Figs. 13, 14, and 15. Each of the products is a 76-electron five-vertex cluster in 13 the phosphorus ligand donates three electrons to the cluster, 14 is the trimethyl-phosphite substitution product of 13, and in 15 the phosphorus ligand contributes five electrons to the cluster. As with the isoelectronic [Os5C(CO)l5I]-, the Os5C cores take open structures based on a pentagonal bipyramid in which only three of the equatorial vertices are present. The structures of the Os5C cores are very similar for 13,14, and 15. Mean Os-Os distances are 2.90 0.06 A for all three, and the carbido carbon atom is... 

The unusual phosphole ring C FejP was synthesized by Huttner and co-workers (Scheme 12). In terms of Wade s rules (b) is an arachno system which can be converted into a nido cluster, (c), upon decarbonylation. The latter can form directly in the photochemical reaction of (a) with alkynes. The hve-membered organometallic heterocycle (c) is planar (deviation < 0.07 A) indicating delocalized bonding (structure 39). Signihcant developments may be expected from this new class of compounds. New types of heterocyclic phosphorus ligands are continuing to be synthesized, e.g. a 1,3,5-triphosphabenzene derivative, l,l,3,3-tetrakis(dimethylamino)-4-r-butyl-U 3x 5A -tri-phosphabenzene (40). 

Sometimes, also polynuclear clusters such as Rh4(CO)j2 or Rh6(CO)26 were submitted to the formation of rhodium catalysts [18]. Metallic rhodium embedded in inorganic materials (carbon, AI2O3) was tested for mini-plant manufacturing. In this context, the frequently phosphorus ligands [PPhj, P(OPh)3] were added with the intention to detach rhodium from the heterogeneous layer (activated rhodium catalyst = ARC) [19, 20] More recently, ligand (Xantphos, PPhj, BIPHEPHOS)-modified or unmodified rhodium(O) nanoparticles were used as catalyst precursors for solventless hydroformylation [21]. It is assumed that under the reaction conditions these metal nanoparticles decompose and merge into soluble mononuclear Rh species, which in turn catalyze the hydroformylation. 

Phosphorus donor ligands have also been used to activate Ru3(CO)i2 in the catalytic reduction of nitrobenzene by CO/H2O in the presence of sodium hydroxide [32], Reaction conditions are mild (room temperature and one atmosphere of CO). In a three hours reaction, a turnover of 95 was observed by adding l,2-bis(diphenylphosphino)ethane (DPPE) to Ru3(CO)i2 in a 0.5 molar ratio. By adding PPh3 or in the absence of any phosphorus ligand, the observed turnover was 43 and 51 respectively. However, better results have been obtained with rhodium catalysts (see later) [32]. Preformed phosphine-substituted clusters of the type Ru3(CO)9L3 (L = arylphosphine) have also been used as catalysts for the same reaction [33] and the same complex was also supported on a polystyrene-divinylbenzene copolymer. 

As with previous publications (GOMG (1982) and GOMG (1995)), phosphorus ligands feature heavily in the chemistry of ruthenium and osmium. In many instances the focus of the publications is such that the phosphorus-containing species are peripheral to the specific reactivity that a publication might be dealing with. For this reason, phosphorus ligands are somewhat ubiquitous within cluster chemistry. Here, an attempt has been made to focus on the phosphorus and its interaction with the cluster. 

Ruthenium clusters containing oxygenated diphosphine ligands Triruthenium and triosmium clusters obtained through orthometallation reactions Triruthenium complexes isolated during catalytic experiments Addition of phosphorus ligands to cationic triosmium complexes Miscellaneous oomplexes... 

Reaction of diphenyl-2-thienylphosphine with Ru3(CO)l2 gives the tiVp) ti Ti C) coordinated species, 144, along with cluster 145 where two ligand molecules participate in coordination, one via the phosphorus atom and the C=C bond of the heteroring, and the other via the phosphorus atom only. P-Coordination in the products of such an interaction is known [95JOM(488)85]. Complex 144, the main product, interacts with carbon monoxide to yield the P-coordinated cluster, 146,... 

A cluster with five Au atoms exists in Au5(dppm)3[(Ph2P)2CH]KN03)2. This cluster has a AU4 core, with an additional Au incorporated in the phosphine ligand, linearly coordinated between a phosphorus and a carbon from the methanido bridge (IV) ... 

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