Phosphide terminal

A completely different structural motif has very recently been found in the red-brown phosphide CasPg, formed by direct fusion of Ca metal and red P in the correct atom ratio in a corundum crucible at 1000 C. The structure comprises Ca + cations and Pg anions, the latter adopting a staggered ethane conformation. (Note that P+ is isolobal with C and P with H so that C2H6 = [(P+)2(P"")6] = Ps - -) The internal P-P distance is 230.1pm and the terminal P-P distances 214.9-216.9 pm, while the internal PPP angles are 104.2-106.4° and the outer angles are 103.4-103.7°. 

More recently this same phosphide has been structurally characterized as the LiCl adduct, [(THF)LiCl (THF)2Li(PBu2)]2 (34). Again the structure takes the form of a four-rung ladder however, the central two rungs are now part of a Li2Cl2 cycle and the two terminal Li atoms are each coordinated by two molecules of THF. The ladder motif is broken down by the addition of the bidentate ligand DME The recently reported complex [Li(PBu2)(DME)]2 (DME = 1,2-dimethoxy-... 

In a similar vein, it was shown that molybdenum amido derivatives of the isolobal terminal phosphide and carbide, " and related chalcogenide atoms,could be obtained. Detailed mechanistic studies of the Mo N(R)Ar 3/N2 system involving X-ray, EXAFS, magnetic, Raman, and isotopicaUy labelled NMR spectroscopy showed that the reaction proceeded through an intermediate involving an end-on bound N2 bridging the molybdenum centres (Scheme... 

Et20 at -78 °C gives [Mo2(PBu2)4]. The molecule (Figure 5) possesses a central M02P2 butterfly and a terminal phosphide on each molybdenum completes a planar M0P3 arrangement about each metal centre.74... 

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). 

Metathesis routes have been used to prepare terminal amido, phosphide, and thiolato complexes (equations 8 10) from Cp 2AnCl2 starting materials. For the bulky bis(trimethylsilyl)phosphido ligand, only mono substitution occurs. 

For vinylacetylene the static CNDO/2 data given in Figure 6 indicate that the two internal carbons are more electrophilic than the terminal ones but terminal attack is presumably favoured because this leads to transition states which are resonance-stabilized > . The confusing issue in the additions to vinylacetylene is the variability in the point of entry with changes in nucleophile and solvent, e.g. thiols attack primarily at the terminal sp carbon - - while alkoxides, phosphides and amides prefer the terminal sp- carbon . Attack on the internal sp carbon may occur when the vinylacetylene contains special substituents , e.g. equation (36). Perhaps these matters would be clarified if equilibrium and rate studies were performed. 

The ladder structures found in 5-block amides are common structural motifs in phosphides as well. Solvent free [LiP(SiMe3)2]6 displays such an arrangement in the solid state, with four five-coordinate and two four-coordinate P atoms and four three-coordinate and two two-coordinate Li atoms the Li—P distances range from 2.38 A to 2.63 A (see Figure 52)." Li4(/X2-PR2)20 3 PR2)2(TFIF)2, formed from the reaction of P(SiMe3)3 with Bu Li in TFIF, has a fused tricyclic (LiP)4 ladder skeleton. The Li atoms are three-coordinate, with each of the two terminal lithiums bound to two P atoms and one THF, while the two internal lithiums have three phosphorus atoms as neighbors (see Figure 53)." " In solution, there is no NMR evidence for Xi- P... 

The solvent used for most of polymerizations is THF or dioxane. However, it is also possible to use toluene, benzene, or hexane with an addition of polar substances (ether, amines). In those cases, it is necessary to use mild conditions and gentle catalysts because if the dissociation of the amides of phosphides is weakened, multicenter processes, for example, have an effect. These are favored by the free electron pair on the nitrogen or phosphorus, and they lead to chain-terminating reactions. 

Mo(N[f-Bu]Ar)3 has also been demonstrated to activate white phosphorous forming the terminal phosphide P = Mo(N[f-Bu]Ar)3.122 Additional interesting molecules containing multiple bonds such as the terminal carbide (C =Mo(N[/-Bu] Ar)3 ), selenide (Se Mo(N f-Bu Ar)3), and telluride (Te=Mo(N[i-Bu]Ar)3) have also been isolated.123 Reaction with PhE-EPh complexes have also been investigated and shown to proceed by a radical mechanism.124... 

The stability of the heptaphosphanortricyclene cage is emphasized by its presence as the terminal group in trisodium henicosaphosphide Na3P21, which is preferentially silylated terminally rather than at the middle phosphide atom to give 54 (equation 53)68. 

The appearance of a bridging phosphide is seen downfield from a terminal one, and compounds with well defined P=M double bonds exhibit chemical shift values that are very significantly downfield. An example is [Cp2Mo=PMes ] at < p=799.5ppm. 

Take a glass tumbler three parts full of water, and drop into it two or three lumps of phosphuret of lime (phosphide of calcium), decomposition will take dace and phosphuretted hydrogen be produced, bubbles of which will rise to the surface and take fire immediately they burst through the surface or skin of the water, terminating in beautiful rings of smoke. 

Compounds consisting of two elements, or of an element and a radical only, binary compounds, are designated by compound names made up of the name of the more electro-positive, followed by that of the more electro-negative, in which the termination ide has been substituted for tbe terminations ine. on, ogen, ygm, orus, turn, and ur. For example the compound of potassium and chlorine is called potassium chloride, that of potassium and oxygen, potassium oxide, that of potassium and phosphorus, potassium phosphide. 

The tripalladium mixed-valence Pd3(2/3) and Pd3(4/3), Pd(II) and Pd(0) clusters may be formed with a range of phosphines, isocyanides, or carbonyls as terminal ligands and carbonyls, nitrosyls, isocyanides, sulfur dioxide, phosphides, phosphines or diphosphines, halides, thiolates as doubly or triply bridging ligands. These clusters exhibit a wide range of steric and electronic environments. 

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