Phosphoranes metal complexes

An account has appeared on the preparation, structure and reactivity of a series of metallaphosphoranes. For example, the transition metal complex (2) reacts with (3ab) to form (4ab). X-ray crystallographic analysis and spectroscopic data for these metallaphosphoranes reveal that the transition metal fragment serves as a strong n donor towards the phosphorane fragment. The account also reports the activation parameters for pseudorotation about phosphorus in several metallaphosphoranes with values ranging from 67.8 to 89.7 kJmoP dependent upon the metal centre (Co, Ru or Fe) and the substituents in the Cp ring. 

In some cases, a second product was also formed in the synthesis. This was identified as a CH activated or ortho-metalated complex (N,0)Ni-(o-Ph)PPh2= CH2, where an ortho C-H bond of a phosphorane phenyl group was deprotonated by the Ni-Me moiety with concomitant formation of methane. Fig. 3.10 shows the molecular structure of complex 132 obtained from ligand 114. The central square planar Ni atom is part of two five-membered metallacycles. 

Phosphoranide 1 forms phosphoranes 5 and 6 when treated with the transition metal complexes AuBrPEt3 and Fe(CO)2CpI respectively (Scheme 2). This has been found to work with a large number of metals, providing the lO-P-5 species like 5 and 6. 

The year has been largely one of consolidation, with emphasis on the synthesis, structure, and properties of phosphoranes containing small (four- and five-membered) rings, especially the relatively stable compounds afforded by bi- and tri-cyclic structures. A new departure, however, has led to the first reports of five-co-ordinate phosphorus bound to transition-metal complexes vide infra) and these novel compounds may be the precursors of a new wave of chemistry in this area. 

The extrusion of disulfide from spirophosphazene (24 X = S, Y = (CH2)3) provides a useful route to two coordinate triazaphosphole (102) <76T2039>. The related extrusion reaction of (103) includes the loss of dimethylamine (Equation (1)) <80TL1307>. In some cases there is an equilibrium between the phosphorane, for example (57) and the phospholan plus disulfide <83JOC38i5>. Spirophosphonium ylide (11) can be converted to its lithium diylide which forms a nickel complex <8lCB3l6l>. Spirophosphoranide (31 Y = CF3) has also been converted to a series of metal complexes <93PS(76)87>. 

The controlled thermal decomposition of azido complexes has been used for the synthesis of metal nitrogen compounds such as nitrido, N-halogenoimido or phosphorane iminato complexes. This type of decomposition, which presumably proceeds with a cleavage of the bond of the coordinated azido ligand, could... 

The phosphoranes p-XCgH CH PPhj (X = H, Me, or OMe) react with iron carbonyls to form stilbenes, Fe(CO) PPha, Ph,PO, and unstable organo-metallic complexes. Similar reactions with alkyl CH=PPh3 also give... 

Phosphoranes have attracted attention as ligands for reactive metal complexes.Riess and coworkers have focused on the distinctive coordination chemistry of the bicyclophosphorane Ph(H)P(OCH2CH2)2N(phoran) which can, in principle, exist in different tautomeric forms (Figure 7.8). The novelty associated with this ligand system concerns its ability to... 

In the proposed mechanism, the iron porphyrin serves to catalytically convert the diazo reagent and phosphine to the corresponding phosphorane. Then, the phosphorane produces a new olefin and phosphine oxide on reaction with aldehyde [196]. Although other metal complexes can catalyze this reaction [ 197,198] the iron system seems to be especially efficient. 

Only the nitrogen is directly coordinated to metal atoms in the now established phosphorane iminato complexes. 

The reaction of 34 with triethylethylidenephosphorane is more complex. According to the multinuclear NMR data, the reaction occurs at the 1 2 ratio of the reactants. The Sn-O bond is cleaved to give phosphonium phenoxide (38) and stannylene (37) in which the tin atom is also bound to the ylide carbon atom of phosphorane (Scheme 17).61 Metallation reactions of this type are well known.61,75... 

Organometallics. Methylenetriphenylphosphoranes form stable 2 1 complexes (38)40 and 1 1 complexes (39)41 when treated with copper(i) or silver(i) chlorides. Stable adducts (40) can also be obtained from the reaction of methylenetrimethyl-phosphorane and metal trialkyls.42... 

Metal-phosphine complexes are ubiquitous in orgenometalljc chemistry. There are also metalhted phosphoranes (L M—PR ), phosphides (L M—PR2), end phosphimdenes (l. M—PR). Give specific examples of each. 

The metathetical reaction of C02 with metal (Ti(IV), U(V)) arylimido-complexes led to an arylisocyanate and a metal-oxo species [4g, 115a]. In these processes, which take place under very mild conditions (ambient temperature and pressure), the metal center acts as the sink for unrequired oxygen. A common feature which characterizes these transformations from a mechanistic point of view is the intermediate formation of a metal carbimato-species through the [2+2] cycloaddition of C02 with the metal-imido complex (Scheme 6.23). By cycloreversion, the four-membered aza-metalla-cycle then converts into isocyanate and a stable metal-oxo complex. These processes, at least formally, are reminiscent of the reaction of imino-phosphoranes with C02 to give isocyanates and carbodiimides [115b,c]. 

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