Platinum monomeric structures

Platinum-thiourea complexes have been extensively studied because of their biological activity [54], but few have been used in catalysis. Neutral thioureas are able to coordinate to metal centres through their sulfur atom (Scheme 9) [55,56] monomeric (I) and oligomeric (II) species are known for Rh [57], and an X-ray structure has also been determined for the chiral complex III [58]. In many complexes hydrogen bonding has been observed... 

Platination of the N3 position in 1-substituted uracil and thymine derivatives requires proton abstraction and usually occurs only at high pH, but the Pt-N3 bond, once formed, is thermodynamically stable (log K 9.6) [7]. Platinum binding to N3 increases the basicity of 04, which becomes an additional binding site leading to di- and trinuclear complexes. A list of X-ray structurally characterized species is given by Lippert [7]. Pt complexes of uracil and thymine can form intensely colored adducts (e.g. platinum pyrimidine blues), which show anticar-cinogenic activity analogously to the monomeric species [7]. 

Similar processes for producing conducting polymeric films of benzene and its derivatives had been studied earlier [2-4], Necessary conditions for the successful realization of these processes are the use of a platinum electrode and a polar solvent in the presence of catalysts (Lewis acids) and thermostatting of the reactor at -75°C. A poly(para)phenylene polymerizate of the linear structure H-(-C6FLr)n-H with the degree of polymerization n, which varies between 3 and 16, is formed. Forced convection of monomeric molecules facilitates the polymerization reaction in the diffusion layer near the electrode and the formation of a dense film on the electrode surface and prevents the formation of poly(para)phenylene in the bulk. 

Dibromodimethylplatinum(IV) is a yellow crystalline solid that decomposes at 180-190°. It is insoluble in water and sparingly soluble in organic solvents. Although no X-ray crystal structure data are available, the complex is expected to be polymeric if the usual six-coordination of platinum(IV) is maintained. In methanol solution it is monomeric. Its reactivity with a variety of ligands has been described.7 Sharp infrared absorption bands at 1220 (s), 1222 (w, sh), 1245 (w), and 1252 (m) cm-1 in the CH3 deformation region are characteristic of the compound. 

Polymeric derivatives of cw-diaminodichloroplatinum have been prepared240,241,242 because of the wide use of the anticancer monomeric drug cis-platinum. Polymeric platinum systems may function as medicinal agents. These polymers were prepared using diamines, substituted hydrazines, ureas, and thioureas and K2PtCl4. Structure 104 is representative of... 

Elements of this group, like metals of groups 8 and 9, form mononuclear and cluster homoleptic complexes in which metals adopt a zero oxidation state. The following homoleptic complexes of these elements are known [M(CNR)4] (M = Ni, Pd, Pt), [Ni(CNR)4], [Ni4(CNR),], [Ni4(CNR)4] , [NigiCNR). ], [Ni4(CNR)i4](C104)s, and [Ni3(CNR),i](C104)6. Linear structures were assigned for the last two compounds.Monomeric platinum and palladium compounds... 

Let us try to predict" qualitatively (without making calculations) the band structure of a stack of platinum square planar complexes - typically [Pt(CN )4 ]oo. Consider the eclipsed configuration of all the monomeric units. Let us first simplify our task. Who likes cyanides Let us throw them away and take something theoreticians really love H . This isn t just laziness. If needed, we are able to make calculations for cyanides too, but to demonstrate that we really understand the machinery, we are always recommended to make the system as simple as possible (but not simpler). We suspect that the main role of CN is just to interact electrostatically, and H does this too (being much smaller). In reality, it turns out that what decides is the Pauli exclusion principle, rather than the ligand charge." " ... 

Very few rr-bonded alkyne complexes of palladium(ll) have been reported in recent years. Except for two examples of monomeric complexes, most of them are polymetallic derivatives where a metal alkynyl acts as a liquid, as discussed above for some Pd(0) derivatives. These complexes adopt interesting stmctures that conform to the types shown below. They have been synthesized by reaction of a metal alkynyl with [PdCl(7/ -C3H5)]2 or Pd(C6Fs)2(THF)2. Platinum alkynyl complexes are the most common ligand frame used, as shown in structures 76-79, but other metal alkynyls can play the same role, such as the Rh and Ir alkynyls depicted 80 and 81. The 7 -alkyne moieties bound to palladium are rotated out of the Pd-coordination plane. The angles of the vectors and the normal to the... 

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