Phospholyl complexes

JOM(400)149 96BSCF33]. The complex 164 is the first known t] -phospholyl species. The tungsten atoms have a coordination number of 9, and the carbon atoms of the phospholyl ring are coplanar. The phosphorus atom deviates from the plane of carbon atoms by 0.015 nm. The basic difference between the Ti -cyclopentadienyl and ri -phospholyl complexes is the existence of a low-lying LUMO localized mainly at the phosphorus atom. 

Some other phospholyl complexes of cobalt are known (910M2631 95CCR201). 

The phosphorus atom in a r-coordinated phospholyl ligand still exhibits a lone-pair of electrons that is capable of binding a second metal atom, so that a phospholyl complex such as phosphaferrocene is—in contrast to ferrocene—itself a ligand. This special property which has no direct correspondence in the chemistry of cyclopentadienyl complexes has recently been fruitfully exploited as the underlying principle which allowed the introduction of phosphaferrocenes as effective ligands in catalytic applications [10, 13, 14]. 

The cleavage of a P-Ph bond (method (1)) has been widely used to create a variety of phospholide salts. Notably, this methodology has been employed in the synthesis of group 13 phospholyl complexes, which have come to the fore in recent years as potential single source substrates for the preparation of the corresponding metal phosphides by chemical vapor deposition (CVD). This is exemplified by the reaction of lithium 2,5-di(tert-butyl)phospholide with GaBr to afford a Ga(l) polymer 297 (Scheme 101) <1999AGE1646>. Additionally, this synthesis nicely illustrates the use of bulky substituents in the position a to phosphorus to favor -coordination. 

An excellent example of the use of method (2) for the synthesis of phospholyl complexes is given by the preparation of the Ca and Sr complexes 299 and 300. Here, insertion of either of these two metals into the P-P bond of 1,1 -biphosphole 298 occurs readily, affording the corresponding group 2 metal complexes (Scheme 102) <1999IC3207>. 

A further example of the use of this route to phospholyl complexes is given by Mathey <1996AGE1125>. Here, the P-P bonds of the macrocyclic tetraphosphole 230 are cleaved by elemental Na or K in a coordinating solvent (1,2-dimethoxyethane, DME) to afford new 2,2 -biphospholyl complexes. The exact composition of the product obtained is intimately linked to the nature of the metal and reaction stoichiometry (Scheme 103). With sodium a complex 301 is obtained in which just one of the P-P bonds has been ruptured, and the phospholyl moieties are bound in both an... 

Route (4) for the preparation of phospholyl complexes, namely insertion of diynes into metal phosphide bonds and subsequent cyclization, is the least used approach. However, an alternative synthesis of299 and 300 using this type of methodology has been demonstrated successfully (Scbeme 105) <1996AGE1125>. 

Another intriguing example of reactivity specific to phospholes and their complexes is given by the formation of 3,4-dimethyl-phenylphosphole in the coordination sphere of a metal as illustrated in Scheme 115 (see also Section 3.15.5.2.2) <2004JOMC4647>. Here, treatment of the phospholyl complex 344 with Bu Li affords the corresponding 77 -bound phosphole complex 345, which reacts with Pd(ii) to generate the bimetallic 7] -Mn cr-Pd complex 346 that has been characterized in the solid state by X-ray diffraction. Notably, the P-Mn bite angle of 65° is typical of other dimeric Pd2Cl2 complexes. The 77 -bound C4 moiety shows the expected bond localization. 

The characterisation of phospholyl complexes has continued to attract attention.The reactions of bridging diphenyl-phosphido ligands with alkynes has led to the synthesis of... 

Triphenylphosphine sulfide(Ph3PS) reacts with Tm(dtp)2 to give the sulfido-bridged binuclear complex [(dtp)2Tm]2(/r-S) (Scheme 203), whereas the samarium(ll) phospholyl complexes have been found to be unreactive towards Ph3PS.728... 

The bridged phospholyl-amido complexes shown in Scheme 737 have been synthesized. The compound is structurally similar to the well-known constrined-geometry Cp-amido compound (GsMe4SiMe2NBut)TiCl2, and preliminary ethylene polymerization data for the phospholyl complexes show indeed comparable catalyst activ-ities.1850... 

A 2,5di-(tert-butyl)phospholyl complex containing a molybdenum-molybdenum triple bond synthesis, molecular structure, and coordination chemistry of [Mo2(PC4H2Bu 2)2(CO)4] <94CC2459>. 

Use of the 2,5-bis-(tert-butyl)phospholide anion as an // -ligand stabilization of 5-phospholyl complexes of ruthenium and rhodium <94jcsii67>. 

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