Platinum neutral complexes

The application of this principle is shown in Table 15.1, where we list the formulas of several complexes formed by platinum(II), which shows a coordination number of 4. Notice that one of the species, Pt(NH3)2Cl2, is a neutral complex rather than a complex ion the charges of the two Cl- ions just cancel that of the central Pt2+ ion. 

Platinum ammine complexes have been a fertile area for studying transinfluence. Table 3.21 lists data for a range of ammines showing how /(195Pt-15N) depends upon the trans-atom [153]. (A further selection of data can be found in R.V. Parish, NMR, NQR, EPR and Mossbauer Spectroscopy in Inorganic Chemistry, Ellis-Horwood, Chichester, 1991, pp. 76, 87.) Possibly the most detailed study (of complexes of tribenzylphosphine) examined over a hundred neutral and cationic complexes [154] (Table 3.22). 

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... 

An extremely rare example of a six-coordinate platinum(II) complex has been prepared by the reaction of [Pt(dmpe)2]2+ with three equivalents of I2 in H20/EtOH solution which affords black crystals of [PtI(dmpe)2(K-I2)]I3 (102). X-ray crystallography reveals a neutral I2 ligand that is coordinated to the metal center through one of the iodine atoms.278 XPS (X-ray photoelectron spectroscopy) measurements are consistent with the platinum center having a +2 oxidation state. 

Two examples of aquation/anation studies of chloro-platinum(II) complexes of possible medical relevance appeared in subsection 1 above 202,207). Aquation of cisplatin is slower in the presence of DNA but not in the presence of phosphate 220). DNA also inhibits substitution in [Pt(terpy)(py)]2+ and related complexes. For reaction of these charged complexes with iodide ion inhibition is attributable to electrostatic interactions - the complex is concentrated on the double helix and thus separated from the iodide, which distances itself from the helix. Intercalation of these complexes within the helix also serves to make nucleophilic approach by neutral reagents such as thiourea more difficult 221). 

Using metathetical replacement, cis- and frans-hydridocarborane complexes PtH(o-carborane) [L = PEt3, PPh3, PPh2Me, PPhMe2 carborane = 2-R-l,2- or 7-R-1,7-B10C2Hm (R = H, Me, Ph)] have been prepared.101 The cis complexes are the first examples of neutral as-monohydrido platinum(II) complexes with a Pt—C o bond. 

Divalent and tetravalent Pt probably form as many complexes as any other metal. The platinum(II) complexes are numerous with IV. S, halogens, and C. The letranitritoplatinum complexes are soluble in basic solution. Tetranitntoplatinum(II) ion is formed when a solution of plat-inum(II) chloride is boiled, at about neutral pH, with an excess of NaNO f. The ammonium salt may explode when heated. Generally, platinum-metal nitrites should be destroyed in solution. They never should be heated in the dry form. Pladnum(II) complexes most often have a coordination number of 4. Many compounds have been prepared with olefins, cyanides, nitriles, halides, isonitnles, amines, phosphines, arsines, and nitro compounds. 

A number of planar platinum(II) complexes, [Pt(oxime)2(NH3)2]Cl2 and [Pt(oxime)4]Cl2, have been isolated,27 28 which have been shown to function as stronger protonic acids than the corresponding free oximes in some cases neutralized species such as [Pt(Hato)(ato)2] can be readily obtained.29... 

Dipole moment studies85 substantiate the suggestion that the M—H bond tends not to be strongly polar, at least for neutral complexes of the platinum metals. 

R. Gillard and his co-workers at Kent University have extended these studies, and shown that organic complexes of rhodium produce similar effects. G. Gale and his associates at the Medical University of South Carolina developed a parallel story of the photochemical transformations and fi-lamentation of bacteria by the cA-isomer of the neutral complex with iridium instead of platinum. Thus, the experience now accumulated suggests a... 

In a separate fluorescence microscopy smdy, the distribution of a mononuclear neutral platinum-anthraquinone complex, Pt-1 C3 (1), was examined in human colon adenocarcinoma cells... 

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