Hetero-Pt Clusters

The nucleophilic displacement of halide ions from M—X bonds by carbonylate anions (either mononuclear or polynuclear) is a general synthetic route to metal-metal bonded species (1,2), and numerous hetero-Pt clusters have been obtained in this way. The resulting products are not often those of expected stoichiometry, although under optimized experimental conditions this method can provide very useful syntheses, particularly of high-nuclearity clusters. Some examples are shown in Eqs. (7)—(11) (5,51-54). 

Fe5Pt(/i6-C)(CO)15(PPh3) (12) (see later, Fig. 12, for 12) (82). In all these clusters the coordination geometry about the Pt center is nonplanar, assuming nonbridged Pt-M vectors are included in the coordination sphere. Several observations about electron counts in hetero-Pt clusters can be made ... 

These three classes are not mutually exclusive, and all have been observed in hetero-Pt clusters. Whereas most examples of fluxional behavior seen in hetero-Pt clusters are common to other systems, there are several interesting examples that appear to be intimately connected with formal 16 - 18-electron conversions at Pt centers. 

It is convenient to discuss the structures and chemical reactivity of hetero-Pt clusters under the individual metals, because there is little homogeneity of structural type, particularly when the details of ligand coordination are taken into account. There are remarkably few examples common to more than one... 

These form the largest single group of hetero-Pt clusters, with more than 40 crystal structures (Table V) reported. Their chemistry, particularly with regard to triosmium-platinum species, is the most developed of any hetero-Pt clusters. 

Hetero-atomic clusters, moreover, may be derived from the binary structures mainly through the introduction of late transition or earlier post-transition elements. Examples of ternary alloys containing such structures are the alkali metal salts of centred clusters In10Me10 (Me = Ni, Pd, Pt), Tl12 Me12- (Me = Mg, Zn, Cd, Hg), etc. The crystal structure of the phase Na T Cdi x)27 (0.24 < x < 0.33)... 

A variety of routes have been employed for the synthesis of hetero-metallic clusters containing Fe(NO)S fragments, and examples of such systems have been described in which the second metal is V, Mo, Co, Ni, and Pt it seems probable, given the variety of potential synthetic approaches to such mixed metal systems, that many more examples await discovery. 

Pt Chemical Shift Data for Hetero-Platinum Clusters... 

As discussed in Sec. 1.28.3.1, the number of Ph3PAu(0) groups in the hetero-nuclear clusters of the type [M(CO)x(AuPPh3), ] is determined by the electronic demand of the transition metal M, that requires a stable 18 electron configuration. The cluster cation [Pt(dppe)(AuPPh3)4] + is an exception to this rule, since the central Pt atom only achieves 16 electrons by adding to the 10 d electrons of the Pt(0) atom the four electrons of the two Pt P bonds, and the two electrons of the... 

---