Phosphides transition metal complexes

C. C. Cummins, Terminal, Anionic Carbide, Nitride, and Phosphide Transition-Metal Complexes as Synthetic Entries to Low-Coordinate Phosphorus Derivatives, Angew. Chem. Int. Ed. 45, 862-870 (2006). 

Cummins CC (2006) Terminal, anionic carbide, nitride, and phosphide transition-metal complexes as synthetic entries to low-coordinate phosphcnus derivatives. Angew Chem Int Ed 45 862-870... 

Phosphorus Magnetic Shielding Tensors of General Phosphide Ligands in Transition Metal Complexes... 

As described in Chapter 2, phosphines have sufficiently large barriers to inversion that phosphines with three different substituents can be resolved. In contrast, the inversion of configuration at phosphorus in metal-phosphido complexes tends to occur near room temperature. In imsaturated transition metal complexes, a vacant acceptor orbital stabilizes the planar transition state. This effect is shown by the interconversion between pyramidal structures through a planar transition state, like the one shown in Equation 4.101 and formed during inversion of related compounds. - In saturated middle and late transition metal complexes, inductive effects explained below destabilize the groimd state and lead to lower barriers to inversion. The presence of an ancillary planar phosphide or amide ligand can contribute to a low barrier by accepting the lone pair from a p)Tamidal phosphide, as in Equation 4.101. 

The bridging phosphide group in bimetallic transition metal complexes appeared to participate in a transformation, rather than behave as an inert spectator ligand. This is particularly obvious in homobimetallic iron and cobalt systems.Mays et al. showed that the reactions of iron-cobalt phosphido-bridged complex 25 with both symmetrical and unsymmetrical alkynes gave five-membered ferracycle-containing compounds, such as 26, in which a CO and an alkyne were inserted regiospecifically into a Co-P bond in 25. Subsequent decarbonylation led to a set of four-membered ferracyclic species 27-30 in low yields. 

Heterometallic alkali metal phosphide complexes with transition metals have also been reported. The complex [(Cy2P)3Hf(ju.-PCy2)2Li (DME)] results from the reaction of LiPCy2 with HfCl4(THF) (98). This complex persists in solution. Jones et al. have reported the synthesis and reactivity toward a range of electrophiles of a series of lithium di-t-butylphosphido(alkyl)cuprates [RCu(PBu2)Li] (R = Me,... 

There are only a few reported examples of olefin polymerization catalyzed by heterobimetallic complexes in these, bis(cyclopentadienyl) M (M = Zr, Ti) moieties are cormected to other transition metals via phosphide or nitrogen ligands (55). The microstructures of the polymer products can be controlled by changing the ligand envirorunent surrounding the metal centers, which in turn leads to different specificities of the separate active species. Therefore, the attractive possibility of bringing two catalytic centers into a close, constrained proximity offers the potential for significantly enhanced catalytic efficiency. 

Table 6 gives a survey on the range of M-P distances. The upper limits are uncertain because the selected distances are only compared with atomic radii and take not into account the topology (convex polyhedra procedure). The M-P coordination in sohd phosphides demonstrates both coordination and donor functions in isolated complex compounds (cf the (E15) complexes, stabihzed in the coordination sphere of transition metals). This is especially true with the polyphosphides. An extreme is CU2P3I2 (see Section 6.5.7), which is an adduct of Cul and elemental phosphorus (charge transfer complex). Chains of polycychc... 

In terms of the total number of species known, the transition metals chemistry of phosphorus is dominated by the metal phosphides and by complexes of organo-substituted phosphanes. Both are dealt with in some detail in other sections suffice to say here that transition metal phosphane complexes are of paramount importance in terms of catalytic behavior in all manner of industrial and academic-related scenarios - and as such have been extensively reviewed. 

Asymmetric Synthesis by Homogeneous Catalysis Carbonyl Complexes of the Transition Metals Carbonylation Processes by Homogeneous Catalysis Heterogeneous Catalysis by Metals Phosphides Solid-state Chemistry Polynuclear OrganometaUic Cluster Complexes Zeolites. 

Although this theory explains theoretically the experimental observations in the case of ReOj, TiO, and VO, it fails to verify the conductivity characteristics of transition metal oxides such as TiO, VO, MnO, and NiO. Band theory explains the metallic characteristics but fails to account for the electrical properties of insulators or semiconductors and metal-nonmetal transitions because of neglect of electronic correlation inherent in the one-electron approach to the problem. Although there is no universal model for description of the conductivity, magnetic and optical properties of a wide range of materials (e.g., simple and complex oxides, sulfides, phosphides), several models have been proposed (for details, see Refs. 447-453). Of these, a generally accepted one is that described by Goodenough (451). 

Transition metal carbides and phosphides have shown potential as highly active catalysts. In these compounds, the C and P sites cannot be considered as simple spectators. They moderate the reactivity of the metal centers and provide bonding sites for adsorbates. The reactivity of the C centers in MC(OOl) surfaces varies in a complex way with the position of the metal in the Periodic Table and the filling of the carbide valence band. M Cj metcars should display a catalytic performance even better than that of the well-known Mo C or MC catalysts. By introducing six pairs of groups in the structure, the system is stabilized, while the presence of four low-coordinated M sites allows a reasonably high chemical reactivity. 

Hydrophosphination of carbodiimides to yield phosphaguanidines was catalyzed by several related metal complexes. For example, after carbodiimide coordination by the calcium phosphide complex 12 (see Scheme 18 above), P-C bond formation involving a four-centered transition state and rearrangement was proposed to yield the N,N-bound intermediate 13. Addition of the P-H bond across the Ca-N bond, followed by dissociation of the product, then regenerates the phosphide intermediate (Scheme 23) [37]. Related chemistry was reported recently using the calcium phosphide complex Ca(PPh2)2(THF)4 [38]. 

Whilst almost all metals are included here in the treatment of metal phosphides (Sections 8.1 through 8.7), the treatment of metallophosphorus coordination complexes (Sections 8.9 through 8.20) deals mostly with transition metals. The discussion of metal phosphines and metal phosphites (Section 8.8) is largely confined to metals from Groups I through in while compounds with p-block metals are dealt with in Chapter 9 (Eigure 8.1). 

A few final comments should be made on the insertions of substrates containing C-C multiple bonds into the bonds between a transition metal and an electronegative heteroatom. First, insertions of olefins into related thiolate and phosphide complexes are as rare as insertions into alkoxo and amido complexes. Reactions of acrylonitrile into the metal-phosphorus bonds of palladium- and platinum-phosphido complexes to give products from formal insertions have been observed, and one example is showm in Equation 9.90. However, these reactions are more likely to occur by direct attack of the phosphorus on the electrophilic carbon of acrylonitrile than by migratory insertion. Second, the insertions of alkynes into metal-oxygen or metal-nitrogen covalent bonds are rare, even though the C-C ir-bond in an alkyne is weaker than the ir-bond in an alkene. 

Phosphide formation has been observed for many transition metal phosphine complexes [7, 8]. Upon prolonged heating and under an... 

Organogermanium phosphorous derivatives include phosphines, phosphine imines, tris(trimethylgermyl)phosphine complexes with transition metals and mixed organosilicon and organotin phosphides. The compounds listed in Table 71 are prepared by methods from the following scheme. 

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