Transition metal complexes tris

A very significant recent development in the field of catalytic hydrogenation has been the discovery that certain transition metal coordination complexes catalyze the hydrogenation of olefinic and acetylenic bonds in homogeneous solution.Of these catalysts tris-(triphenylphosphine)-chloror-hodium (131) has been studied most extensively.The mechanism of the deuteration of olefins with this catalyst is indicated by the following scheme (131 -> 135) ... 

In the transition metal polypyridyl complex group, tris(4,7-diphenylphen-antroline) ruthenium(II) (Ru(dpp)2+) is widely used as a probe for a PSP. The luminescence lifetime of Ru(dpp)2+ is long compared with the other ruthe-nium(II) polypyridyl complexes [17]. The absorption and emission maxima of Ru(dpp)2+ are 457 and 610 nm, respectively. The luminescence lifetimes under nitrogen- and air-saturated conditions are ca. 4.0 and 2.0 ps, respec-... 

This thinking applies, in particular, when planning the design of a chiral three-dimensional supramolecular host-guest system, since the mutual interaction of the two distinct complementary molecular units or coordination entities is necessary. Examples of this methodology include the above-described anionic, tris-chelated transition metal oxalato complexes [Mzl(ox)3/6 which form the host system together with the cationic, tris-chelated transition metal diimino complexes, e.g. [M(bpy)3]21/31, bpy = 2,2 -bipyridine, which play the role of the guest compounds. 

The authors have previously reported33 a new convenient method of preparing transition metal-acetylide complexes of the type cis- and frans-(PR3)2M(C=CR)2 according to Eq. 10, and have shown that the complex having tri-n-butylphosphine as the ligand is air-stable and highly soluble in a variety of organic solvents. This new M-C bond formation reaction... 

The first tris(arene)niobinm complex, [Nb(l-4-J7 -anthracene)3], prepared by the Na or K anthracene rednction of NbCL (THF)2, undergoes facile anthracene displacement in the presence of CO to afford [K(18-crown-6)(THF)2][Nb(CO)6]. Rednction of TaCls by sodinm naphthalene provides [Na(THF)][Ta(j7 -naphthalene)3], the first homoleptic naphthalene complex of a third row transition metal. This complex reacts with CO and anthracene to give [Ta(CO)6] and [Ta(l-4-jj -anthracene)3], respectively. The latter prodnct reacts with cyclooctatetraene (COT) to give [Ta(COT)3]... 

Transition metal tris(acetylacetonato) complexes have been chosen by numerous workers (265-270,282) for investigating second sphere phenomena. Cr(acac)3 with solvents (L) such as CHCI3, CH2CI2, and CgHg is involved in the equilibria (266)... 

There is much interest in transition metal polypyridyl complexes, largely due to their numerous applications in a variety of fields (247-250). In particular, ruthenium(II) tris(2,2 -bipyridyl) has been one of the most extensively studied complexes of the last decade due to its chemical stability, redox properties, excited-state reactivity, and luminescent emission (251, 252). 

Transition metal n-complexes can be used in photolabile linkers. The ir-complex 40 was formed from the chromium arene complex 39 and polymer-supported tri-phenylphosphine (38) [60] (Scheme 17.20). The complex 40 tolerated LiAlH4 reduction and acetylation, but released the product 41 in 70% yield when oxidized with air under the influence of UV irradiation. 

Preparation of Phosphines by Addition of P-H to Unsaturated Compounds. -This route has not received much attention over the past year. A stereoselective synthesis of tris(Z-styryl)phosphine is offered by the addition of phosphine to phenylacetylene in a superbasic system (HMPA-H20-K0H)." In a similar vein, the reaction of phosphine with styrene and a-methylstyrene in a superbasic medium (DMSO-KOH) provides a route to the primary phosphines, (2-phenylethyl)phosphine and (2-methyl-2-phenylethyl)phosphine, respectively. 7 Transition metal phosphine complexes have been shown to catalyse the a-hydroxylation, P-cyanoethylation, and P-alkoxycarbonylethylation of phosphine. 71 Addition of primary phosphines to acrylic esters has been used for the synthesis of the phosphines (80).7 A similar addition of diphenylphosphine to acrylic esters and amides has given a series of hydrophilic phosphines (81). 72 The bis(phosphorinanyl)ethane (82) is formed in the photochemical addition of l,2-bis(phosphino)ethane to 1,4-pentadiene. ... 

A stereospecific receptor site for tetrahedral oxometallate anions has been realized in the form of octahedral transition metal cation complexes [10]. For example, the Cu (II) tris (ethylenediamine) SAMMS (Cu-EDA SAMMS) have demonstrated excellent affinity for anions such as chromate and arsenate, and have significant potential for the sequestration of pertechnetate. With the global concerns over arsenic in drinking water, these materials can truly save lives. 

We have also determined aG values for electron attachment to a number of neutral metal complexes by charge-transfer bracketing and equilibrium experiments with organic acceptors (Figure 2). One metallocene, Cp2Ni, was known to form a stable negative ion from early studies by Beauchamp and coworkers (20). Many aG values have also been determined for electron attachment to the first row transition metal tris(acetylacetonate) (M(acac)3) and tris(hexafluoracetylacetonate)... 

Considerable efforts are now being devoted to many other bipy-type complexes with transition metals, trying to prepare new electrocrystalline materials, solve their X-ray stmctures, and measure their conductivities as a function of temperature. It is possible that some of these materials will have similar propoerties to those of the endohedral fullerenes and the cryptatium species described above. After all, they also contain metal cation centers sorrounded by highly unsaturated organic ligands that are capable of easy reduction. As such, all of these systems, if appropriately designed and manipulated, could yield novel conducting materials widi unusual properties. 

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