Transition metal derivatives

Of the linear clusters, the organogermanium-substituted transition metal carbonyl compounds are the simplest. In every case, the coordination at germanium is tetrahedral, while the transition element retains the geometry of the parent carbonyl compound (50,108,119,155, 157, 181). The Ge—M bond is almost without exception shorter than the sum of the Ge—M covalent radii (Table VI), which is cited as evidence for (d — d)-n multiple bonding. 

The rhenium derivative (CH3)3GeRe(COb, can be converted into the carbene complex (CH3)2(jeRe(CO)4C G )CH ), which in solution is in equilibrium with its dimer. The dimer crystallizes preferentially, and incorporates an eight-membered GeReCO]2 heterocycle (181). 

Three linear organogermanium mercury structures have been reported (116, 117, 164). The two independent molecules in the asymmetric unit of [(C6H5)3Ge]2Hg differ in that one is centrosymmetric at mercury while the other has a Ge—Hg—Ge angle of 178.68°, with a shortening of the contiguous Ge—Hg bond from 2.543 to 2.514 A (164). 

The longest polymetallic chain known to date for any combination of metals is the nine-atom cluster (Ph3GeCd)(Ph3Ge)(i75-C5H5)Ni]2Cd 

The Ge—Co bond exocyclic to the triangular GeCo2 cluster in C6H5Ge—CO i(CO)u is longer than both of the two endocyclic Ge—Co bonds by 0.64-0.81 A (13). 

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Ziegler catalysts Complex catalysts prepared by interaction between an organometallic derivative and a transition metal derivative. A typical catalyst is the product of the interaction of TiCU and AIBU3. These catalysts polymerize olefins, particularly ethylene, to polyolefins, the polymerization generally being in a siereoregular manner. 

Chemical Properties. Higher a-olefins are exceedingly reactive because their double bond provides the reactive site for catalytic activation as well as numerous radical and ionic reactions. These olefins also participate in additional reactions, such as oxidations, hydrogenation, double-bond isomerization, complex formation with transition-metal derivatives, polymerization, and copolymerization with other olefins in the presence of Ziegler-Natta, metallocene, and cationic catalysts. All olefins readily form peroxides by exposure to air. 

A limited number of non-transition-metal derivatives of thiophene will be considered in this subsection. There are no short-range contacts between the lithium atoms originating from the (LiO)6 cores and the sulfur atoms in [Li—O—EMc2 (2-C4H3S)]6 (E = C, Si) (97OM5032), and evidence for Tr-interactions can be found in the X-ray crystal structures of these compounds. Theoretical computations show that a- (S ) Li" " interactions are weak, whereas Tr-Li" contributions are considerable, in accord with the general reasoning on the electronic characteristics of uncomplexed thiophene. 

Coordination compounds with delocalised ground states. The transition metal derivatives of dithioketones and ethylene(l,2)dithiolates (metal dithienes). G. N. Schrauzer, Acc. Chem. Res., 1969,2,72-80 (36). 

Paver MA, Russell CA, Wright DS (1995) Gallium, Indium and Thallium excluding Transition Metal Derivatives. In Abel EW, Stone FGA, Wilkinson G (eds) Comprehensive Organometallic Chemistry II. Elsevier, Oxford UK, vol 1, chap Up 503... 

The discussion of the main group 3-5 and 3-6 compounds in the previous sections was limited to examples in which the group 3 element E is three-coordinate, so that an empty p-orbital on E is available for overlap with a lone pair on the group 5 or 6 atom. For the same reason, the discussion here will focus on those compounds with three-coordination at gallium, indium, or thallium. In the case of the transition metal derivatives, it is transition metal -electrons that are available to overlap with the empty p-orbital on E to form the potential ir-bond, as illustrated in Fig. 26. 

Transition metal derivatives have been less extensively investigated. /i-2,3,5,6-Tetrafluorophenylenedisilver (I) was generated in pyridine solutions of silver tetrafluoroterephthalate [Eq. (97)] (69). Decomposition of... 

See ref. [34] for a detailed listing of reviews on carbon nanotubes and their transition-metal derivatives. 

Gallium, Indium, and Thallium, Excluding Transition Metal Derivatives... 

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