Platinum group metals, coordination

There are several exceUent sources of information about the platinum-group metals. The exceUent reference work G. Wilkinson, R. D. GiUard, and J. A. McCleverty, eds.. Comprehensive Coordination Chemistry Pergamon Press, Oxford, U.K., 1987, contains iadividual chapters devoted to descriptive chemistry of each element. 

N3-coordinated complexes containing platinum group metal ions have also been synthesized and studied (56,60,61). Steric hindrance has been used to direct binding to N3 in a series of Pd- and Pt-containing complexes of 6,6,9-trimethyladenine (60). Platinum modification was found to have a pronounced effect on the basicity of the adenine moiety. The protonation constants (log Kh values) for the twofold protonation of 6,6,9-trimethyladenine are 4.15 and -0.75, with the initial protonation occurring at N1 followed by N7. The equivalent values for the formation of [Pt(dien)TMA-A3)H]3+ and [Pt(dien)TMA-2V3)H2]4+ are 0.3 and —1.2, respectively. Moreover, the site of initial protonation was found to be N7 (Fig. 19). These observations are supported by theoretical studies (62). 

Koch, K. R. Sacht, C. Grimmbacher, T. Bourne, S. New Ligands for the platinum-group metals deceptively simple coordination chemistry of N-acyl-N -alkyl and N-acyl-N, N -dialkyl-thioureas. S. Afr. J. Chem. 1995, 48, 71-77. 

The coordination chemistry of sulfoxides with transition metals is a much-studied topic.87 Academic interest has often centred on their ambidentate donor ability, while dimethyl sulfoxide (DMSO) is of intrinsic importance as one of the most effective aprotic solvents known. Higher sulfoxides have found application in the extraction of metals during refining processes and some potential in the separation of platinum group metals has been noted.88... 

Hydroformylation - [CARBON MONOXIDE] (Vol 5) - [OXO PROCESS] (Vol 17) -of allyl alcohol [ALLYL ALCOHOL AND MONOALLYL DERIVATIVES] (Vol 2) -catalysts for [CATALYSIS] (Vol 5) -C-19 dicarboxylic acids from [DICARBOXYLIC ACIDS] (Vol 8) -of ethylene [ETHYLENE] (Vol 9) -of ethylene [PROPYL ALCOHOLS - N-PROPYLALCOLHOL] (Vol 20) -of maleate and fumarate esters [MALEIC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15) -phosphine catalyst [PHOSPHORUS COMPOUNDS] (Vol 18) -platinum-group metal catalysts for [PLATINUM-GROUP METALS] (Vol 19) -rhodium catalysis [PLATINUM-GROUP METALS, COMPOUNDS] (Vol 19) -ruthenium cmpds or catalyst [PLATINUM-GROUP METALS, COMPOUNDS] (Vol 19) -use of coordination compounds [COORDINATION COMPOUNDS] (Vol 7)... 

Tphe bright colors of the coordination complexes of transition metal elements, including the platinum group metals, were of great assistance to pioneer workers with these materials. Thus, chemical changes could be followed visually it was frequently very easy from their colors to demonstrate the existence of isomers upon which Alfred Werner was able to base his monumental theory of coordination. Such early studies were limited to a simple qualitative visual evaluation of the color. 

The first applications of NMR to the study of dynamic systems of the platinum group metals appear to have been studies on the rotation about the metal-olefin bond of coordinated olefins, and this process has been investigated by many workers. There are two reasonable orientations of an olefin with respect to the rest of a square planar complex, XXIV and XXV. 

Transition metal complexes containing catecholate and semiquinone ligands have been reviewed by Pierpont and Buchanan.336 The syntheses of catecholate adducts of platinum group metals by oxidative addition of benzoquinone (BQ) have been reported (reaction 92).337 The coordinated catechol can then be oxidized to the semiquinone with silver ion (reaction 93). In reactions (92) and (93), L M = lr(Cl)(CO)(PPh3)2] and the benzoquinones (BQ) are shown in (146). The oxidative addition of phenanthrenequinone to [Ir(Cl)(CO)(PPh3)2] has also been cited.338... 

Mixed donor didentate ligands containing selenium are less well known than their sulfur analogues. A typical example of an Se,N donor is (41), which coordinates as a didentate chelate another is (42), a selective analytical reagent for platinum group metals. The monoanionic (43) forms neutral ML2 complexes (M = Zn, Cd, Hg) with an overall N2Sc2 donor set, with the imine N selected as a much better donor than the alternate ether However, Se,0 donor chelation is displayed by the butane-2,4-dionate analogue... 

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