Complexes of group 10 Ni, Pd, Pt

Substanee Generation / Matrix or Solvent/Method/r[K] g-Faetor / a-Value [mX] Ref/ add. Ref 

DFT ealeulations eleetrolysis diehloro ethane ESR/298 diehloro ethane ESR / no 

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M(dmit)2 complexes (dmit = C3S52- = l,3-dithiole-2-thione-4,5-dithio-late) constitute one of the most important subclasses. The most studied metal complexes are those of group 10 (Ni, Pd, Pt), which possess a square-planar geometry see for instance the molecular structure of the monoanion [Ni(dmit)2], Figure 42.73... 

Chiral discrimination in binuclear homo- and heterochiral complexes formed by hydrazine (Fig. 3.23), a metal atom of group 10 (Ni, Pd, Pt), and halogen atoms (F, Cl, Br, I), depends on the electronic properties arising from the metal atoms and the ligand atoms attached to them [36]. The complexes were studied by quantum chemical methods by applying DFT methods at the B3LYP/LANL2DZ level of theory. 

Zr, Hf), group 6 (Cr, Mo, W), and group 10 (Ni, Pd, Pt). (Note that CrH6 was optimized with MoH -like angular geometry to prevent formation of the Cr(H2)3 dihydrogen complex.)... 

The major route to -cyclopropenylium complexes L M(C3R3) (metallatetrahedranes) is by oxidative addition reactions of cyclopropenylium salts to transition metal complexes of groups 5 (V), 6 (Mo, W), 8 (Fe, Ru), 9 (Co, Rh, Ir) and 10 (Ni, Pd, Pt). The addition is frequently accompanied by loss of one or more carbonyl, olefin or halogen auxiliary ligand. Concurrent formation of oxocyclobutenyl complexes by carbonyl insertion into the cyclopropenyl ring is often observed in reactions with group 9 cobalt triad and early transition metal complexes. 

In square-planar, 16-electron complexes (i.e. coordinatively unsaturated) as found for many group 9 (Co, Rh, Ir) and 10 (Ni, Pd, Pt) metals, the associative process is most common. The trans effect and trans influence ligand series [19-23] are also useful measures in the study of homogeneous catalysis. Apart from very small ligands, such as CO, H2, and NO, steric repulsion between ligands, as well as complexes and incoming substrates, plays a dominant role in determining the kind of intermediates and complexes formed and their equilibria in solution. 

Similar structural characteristics of the quadruply bridged dinuclear complexes of Pt(II), Pd(II), and Ni(II) indicate that the mixed-metal dinuclear complexes of these metal ions should be stable. However, probably because of the synthetic difficulties, only a few mixed-metal complexes of group 10 elements with such a structure have been prepared so far, although there are a number of examples having a doubly bridged structure (98, 99). For other metals, quadruply bridged mixed-metal complexes are known with the group 6 metal ions Cr, Mo, and W (1, 100, 101). 

Poly-yne complexes of Group 10 metals (Ni, Pd, Pt) were first synthesized by Hagiwara and co-workers in 1978-82 using condensation reactions of traits-(PBu3)2MCl2 and ran5 -(PBu3)2M(C=CR)2 in amine... 

Table 7.6 lists the theoretical BDEs of the M-L bonds in the group-10 Ni(CO)3L, Pd(CO)3L and Pt(CO)3L complexes calculated at the MP2/II and CCSD(T)/II levels of theory [49, 50], The only experimental value known for those compounds is an estimate of ca. 10 kcal/mol obtained for the (CO)3Ni-N2 bond energy at 298 K [59], This estimate is based on kinetic measurements of nitrogen extrusion from the complex. Thermal corrections to the CCSD(T)/II value of D0 = 4.6 kcal/mol yield a theoretical prediction of 6.7 kcal/mol, which is in a reasonable agreement with experiment [49]. The MP2/II BDEs listed in... 

As already described, complexations with metals of the platinum group (Ni, P d, Pt) and of other metals mostly lead selectively to rj -monoaddition. However, with platinum metals the reactions can be driven to the formation of air-sensitive hexaadducts [(Et3P)2M]5C5Q by using a 10-fold excess of the metal reagent M(PEt3)4 (M = Ni, Pd, Pt) [2, 3, 10], Each compound exists as a single structural isomer. 

The coordination geometry of silver and gold complexes is often linear. When we go to group 10 metal complexes, however, we would expect square planar (Ni, Pd, Pt) or tetrahedral (Ni) geometries [20]. 

The EDA results of the group-10 homoleptic complexes TM(EMe)4 (E = B-Tl, TM = Ni, Pd, Pt) are given in Table 13.23. The data indicate that the statement concerning significant Fe ER Tr-backdonation holds also true for other transition metals. In TM(EMe)4 (TM = Ni, Pd, Pt), the contribution of TM —> EMe ir-backdonation is between 33-49% of the covalent term However, the bonding... 

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