Phosphido complexes reactivity

The phosphido complex, Th(PPP)4 [143329-04-0], where PPP = P(CH2CH2P(CH2)2)2) has been prepared and fully characterized (35) and represents the first actinide complex containing exclusively metal—phosphoms bonds. The x-ray stmctural analysis indicated 3-3-electron donor phosphides and 1-1-electron phosphide, suggesting that the complex is formally 22-electron. Similar to the amido system, this phosphido compound is also reactive toward insertion reactions, especially with CO, which undergoes a double insertion (35,36). 

Fig. 3) show n orbitals to be the HOMO orbitals. Thus, the primary reactivity pattern should be the side-on reactivity. However, this reactivity is generally not allowed in the phosphido complexes with tris-amido ligand sets due to their kinetic stabilization by bulky substituents. Therefore, experimentally, only the less crowded and more flexible alkoxide complexes 18 and 21 show the anticipated side-on access to the triple bond. 

Scheme L Phosphido-bridged complexes reactivity at other sites.

Relatively few phosphido complexes of the transition metals are known that have an alkyl or aryl group (R) in addition to hydrogen attached to phosphorus [i.e., R(H)P"]. The reactivity of the P—unit has been studied in only a few cases. The syntheses described here are for dinuclear Rh( +1) or Ni( +1) complexes that have two t-BuP(H)" bridges. In both complexes the metals have pseudotetrahedral geometries. Of added interest for the rhodium complex is the presence of a Rh=Rh double bond. ... 

Metallacycle fomiation has also been observed in bis-Cp complexes. Heating Cp 2UR[P(Si(CH2)2)2] (R = Cl [146840-37-17, CH [146840-39-3]) results in the metaHation of the phosphido ligand. These complexes are stmcturaHy similar to the group 4 and 6 transition-metal metallacycle complexes, but show a dramatically reduced reactivity. 

Bun, Bus, Bu1) (99). The complex with R = Me crystallizes as the THF solvate [MeCu(PBu2)Li(THF)3] in which the phosphide ligand bridges the two-coordinate Cu and four-coordinate Li centers. These cuprates were found to be more thermally stable than other phosphido(alkyl)-cuprates but less reactive toward electrophiles than related cyanocu-prates. 

Trialkoxy complexes of tungsten with terminal phosphido ligands could not yet be isolated. They were postulated to be very reactive intermediates in different transformation reactions, e.g., during the metathesis reaction of [W2(0R)6] with phosphaalkynes [6, 14]. However, we were able to characterize the complex [(t-BuO)3W=P] (3c) by P-NMR spectroscopy by monitoring the metathesis reaction of [W2(Ot-Bu)6] with MesC=P in the tempera-... 

Reactivity of Asymmetrically Bridged Phosphido Ligand Complexes... 

It is also pertinent to mention the occurrence of bridging phosphido and arsenido selenide ligands (Scheme 4).32 The phosphido selenide complexes (1 Scheme 4) were found to be very reactive and readily gave the six-membered heterocyclic complexes (3). In contrast the arsenido selenide systems gave both the four-membered ring intermediates (1 M = Mn, Re) and the six-membered heterocycles (3). 

Varieties of dinuclear cobalt complexes are known with two phosphido bridges. Those so far reported with the di-terf-butylphosphido ligand have two pseudotetrahedral 18-electron Co atoms linked by a metal-metal bond formally of order 2. Tetracarbonylbis(ii-di-terf-butylphosphido)-dicobalt( -t-1) can be prepared from the reaction of Co(CO)4l (generated in situ) with Li(r-Bu2P) in THE We describe here a simplified, high yield synthesis of this dimer via the interaction of Co2(CO)g with r-Bu2PH in toluene. The complex should prove to be a useful starting material for further reactivity studies. 

The synthesis, structures, and reactivity of the related silylene-linked cyclopentadienyl-phosphido lanthanide complexes has been studied. Scheme 37 illustrates the synthesis of the ligand precursors and the corresponding lanthanide(n) derivatives as well as reactions of the latter with 1,2-diiodoethane and benzophenone, which lead to binuclear lanthanide(m) species.196... 

The platinum silanoate 82 reacts smoothly with secondary phosphine 72 to regenerate catalyst 73. The reader may have notieed the difference in reactivity of Pt complex 80 compared to the similar Pd complex 50 (Section 6.2.3.1, Scheme 6.24). Formation of analogous Pd and Pt phosphido (54 and 73) complexes is summarised in Scheme 6.39. 

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