Phosphaalkenes coordination chemistry

This research area is continuously growing. It is evident that small changes of the ligands or at the metal centers in a given transition-metal complex often lead to different products. Bearing in mind the rich coordination chemistry displayed by d-block elements, one concludes that transition-metal-assisted syntheses with phosphaalkenes and -alkynes will persist as a highly prolific research area. 

Whether the theoretically interesting results will lead to applications of the new phosphaalkenes as synthones for the class of heterocyclic compounds or, in coordination chemistry, to animate catalysis research, will be answered in the future. 

The coordination chemistry of compounds containing phosphorus-carbon multiple bonds, such as phosphaalkynes, phosphaalkenes, phos-phaallenes, phosphaalkenyls, and phosphaallyls, has been studied extensively (349,350). The chemistry is dominated by the donor properties of the phosphorus atom, and, as far as we are aware, no examples of bimetallic or trimetallic compounds with bridging ligands which link metal centers by a carbon cr bond and a C=P or C P n bond have been recorded. Once the lone pair on the phosphorus atom is involved in bonding, the unsaturated bond becomes a possible site for further coordination. 

Phosphinines are a special group of phosphaalkenes in which the P=C double bond becomes integrated into the aromatic system of benzene and related arenes. The majority of examples are based on the mono-phospha-benzenes, but di-and triphospha-benzenes in various substitution patterns have also been employed as ligands. The coordination chemistry of this class of ligands has been reviewed. ... 

A new route to phosphaalkenes is provided by treatment of dichloro-phenylphosphine with two equivalents of carbonyl-functional carbenes, resulting in a two-electron reduction of the phosphorus centre coupled with carbene oxidation. A range of amido-functional phosphaalkenes, e.g., (112), (alternatively viewed as carbene-phosphinidene adducts), was prepared using this approach, followed by full spectroscopic and structural characterisation. A related diamino-functional phosphaalkene has also been described and its coordination chemistry studied. Among other new phosphaalkene systems reported is a series of phosphaalkene-phospholes, e.g., (113), the monoanionic phos-phaalkenyl-phosphido ligand (114), alkali metal salts of the phosphaalkene radical anion (115), ° and new 1,3-diphosphacyclobutadiene... 

Phosphinidenes (R-P) differ from other low-coordinate organophosphorus compounds, such as phosphaalkynes (R-C=P), phosphaalkenes (R2C=PR), and phosphaaromatics, in that the phosphorus atom carries only a single a-bonded substituent [7-9]. They relate to carbenes, nitrenes, and silylenes and likewise can exist as singlet and triplet species. The advances that led to stable carbenes [10, 11] and silylenes [12] stimulated an exploration of the chemistry of phosphinidenes. 

Abstract Many similarities between the chemistry of carbon and phosphorus in low coordination numbers (i.e.,CN=l or 2) have been established. In particular, the parallel between the molecular chemistry of the P=C bond in phosphaalkenes and the C=C bond in olefins has attracted considerable attention. An emerging area in this field involves expanding the analogy between P=C and C=C bonds to polymer science. This review provides a background to this new area by describing the relevant synthetic methods for P=C bond formation and known phosphorus-carbon analogies in molecular chemistry. Recent advances in the addition polymerization of phosphaalkenes and the synthesis and properties of Tx-con-jugated poly(p-phenylenephosphaalkene)s will be described. 

Phosphaalkenes R. Appel on Multiple Bonds and Low Coordination in Phosphorus Chemistry , in M. Regitz and O.J. Scherer (Ed.) Houben-Weyl, Methoden der Organi-schen Chemie, G. Thieme, Stuttgart, New York, 1990, p. 157... 

Appel R (1990) Phosphaalkenes, phosphacarbaoligoenes and phosphaallenes. In Scherer OJ, Regitz M (eds) Multiple bonds and low coordination in phosphorus chemistry. Thieme Verlag, Stuttgart New York... 

This area continues to generate interest across the range of p -bonded phosphorus compounds. Whereas long-established topics such as the chemistry of diphosphenes and phosphaall nes have again received comparatively little study, the chemistry of phosphaalkenes (and related P=C=X compounds), and the less-developed groups of low coordination number phosphorus compounds, in particular phosphenium ions, phosphinidenes, and their complexes with carbenes and metal ions, has again dominated the area. 

Due to space restrictions a comprehensive review of organophosphorus chemistry cannot be included here. Instead emphasis has been placed on developments in low-coordination phosphorus chemistry. In this area a review has appeared on the chemistry of phosphaalkenes with an inverse polarisation, i.e. P=C +, to that normally seen for phosphaalkenes. Comparisons of the reactivity of these phosphaalkenes with classical phosphaalkenes were made. 

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