Platinum complexes carbon-donor ligands

Excitation to the LC states may also result in population of the CT-excited states, especially the LLCT states. These phenomena are frequently encountered in complexes containing both rc-acceptor (eg 1,10-phenantroline or 2,2 -bipyridyl) and 7r-donor ligands (eg aromatic thiols). Then the LC excitation can induce charge transfer between these ligands through central atom (LLCT) that leads to a photoredox reaction. Such reactions were reported in the case of heteroleptic organometallic compound [Rh CylLXCsHs)]3 [37], heteroleptic Re1 complex fac-[Re (L)(CO)3(bpy)]n+ [46] and metal-carbon-bonded platinum complexes [47]. 

The rates of substitution of the latter ligand by TU, DMTU and TMTU were followed as a function of nucleophile concentration, temperature and pressure by s.f. spectrophotometry. The reaction was first order in both platinum complex and nucleophile concentrations. From the form of the rate law and the negative entropies and volumes of activation it was concluded that the mechanism is an associ-atively activated substitution. It prevailed that substitution in the terpy parent ligand did not affect significantly the kinetic parameters. The reaction was slower when a carbon a-donor was in the cis position than when an N a-donor occupies this position, indicating a different situation from the effect of a Pt-C bond in the trans position. 

Clark and Ward (45) obtained NMR parameters for a series of phenyl-platinum(2 +) complexes rrflns-[(C6H5)Pt(As(CH3)3)2L]+PF6, (IV), where L is a neutral donor ligand. Carbon-13 NMR parameters for IV are given in Tables XXVIII and XXIX. 

PF3 is the strongest of the P-donor n acids and its ability to replace carbon monoxide in a zerovalent transition metal complex was realized in the 1940s by Chatt. However, WiUdnson was the first to isolate a homoleptic PF3 complex, viz. [Ni(PF3)4] see Homoleptic Compound), which turned out to be more thermally stable than [Ni(CO)4] subsequent research into the PF3 complexes of transition metals was carried out by Nixon. Bidentate ligands with two PF2 moieties have been prepared an example is F2P(l,2-cyclo-C6Hio)PF2. The volatility of the homoleptic PF3 transition metal species together with their relative stability has led to their use in MOCVD processes [Pt(PF3)4], for instance, has been used to deposit platinum films. ... 

Aqua ions are known but not very stable. Substitution of Pt in aqueous solution is sometimes zero-order in the added ligand, L, or can have both L-dependent and L-independent contributions to the rate, probably because intermediate formation of an unstable aqua complex is the rate-determining step for the L-independent pathway. A large number of O-donors, particularly anionic ones, give stable complexes, for example, carbonate, acetate, oxalate, acetylacetonate, and alkoxide. Tetrameric platinum(II) acetate is formed by formic acid reduction of Pt solutions in acetic acid. It does not appear to be a very useful synthetic precursor for Pt chemistry. The acetylacetonate [Pt(acac)2] is monomeric and square planar. 

Ligands with One Donor-carbon Atom. The complexes [PtCln(py)(CsH5-NCHCH2CH3)], where n = 2 in the square-planar platinum(ii) compound (62) and n = 4 in the octahedral platinum(iv) compound (63), are both... 

A new platinum(O) carbonyl complex has been prepared by the reaction of 3 equiv. of carbon monoxide with a carbene complex (Equation (1)). Not only does the carbon monoxide displace an existing ligand but coordinated GO is also attacked by the ligating nitrogens, with the siloxy group migrating to give the unusual tris-carbene carbonyl complex 1, where all the donor atoms are carbon. Yields are reported to be quantitative, and an X-ray structure has a short Pt-GO bond of 1.868(6) A with a GO stretch of 2,038 cm Further aspects of the synthesis of both 1 and its precursor are discussed in Sections 8.07.3.2.2 and 8.07.3.3. 

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