Intramolecular coordination complex

Meanwhile, Parkin and his co-workers have also reportedthe synthesis of a series of terminal chalcogenido complexes of germanium 66, 67, and 68 (Scheme 20).42 X-ray structural analyses of 66, 67, and 68 revealed that they have unique germa-chalcogenourea structures stabilized by the intramolecular coordination of nitrogen atoms. The central Ge-X (X = S, Se, Te) bond of 66, 67, and 68 should be represented by a resonance structure, Ge+ - X- —>- Ge=X, because their bond... 

For reactants having complex intramolecular structure, some coordinates Qk describe the intramolecular degrees of freedom. For solutions in which the motion of the molecules is not described by small vibrations, the coordinates Qk describe the effective oscillators corresponding to collective excitations in the medium. Summation rules have been derived which enable us to relate the characteristics of the effective oscillators with the dielectric properties of the fi edium.5... 

Intramolecularly coordinated A1 and In compounds (e.g., (75), (76)) transfer the Me group in cross-coupling reactions with various aryl halides, including chlorides, catalyzed by Pd and Ni complexes.16 262 265 Monoorganobismuth compounds are reactive in cross-coupling reactions only if they contain an intramolecularly coordinating residue (77),266 267... 

Examples of heavier alkali metal complexes include [ GH(SiMe3)(SiMe2OMe) M] (M = Na 59, K 60) as well as the polymeric etherate [CH(SiMe3)(SiMe2OMe)K(OEt2)]oo 61.69 All these examples demonstrate the potency of intramolecular coordination, since methoxide-metal interactions under formation of metallacycles are observed in all cases. 

The centrosymmetrical complex 154, formed by interaction of the quinolyl ligand with HgCl2, features intramolecular coordination of one of the cyclopentadiene C=C bonds to the mercury center. The resulting Hg-C(sp2) distances of 2.81 and 2.88 A are longer than typical Hg-C c-bonds but remain much shorter than the sum of the van der Waals radii. This dihapto interaction does not result in a significant lengthening of the coordinated C=C... 

Intramolecular coordination site exchange reactions in square-planar platinum(II) complexes [Pt(tbte)Cl]+ of the potentially four-donor-atom tripodal ligand tris[2-(t-butyl-thio)ethyl]amine (tbte) N,S,S-bonded occur through a trigonal bipyramidal five-coordinate intermediate... 

Naturally, the concept of intramolecular coordination in hthium chemistry via side-arm complexation is not limited to aromatic planar aryls. Like the metalation of cyclohexane... 

Dithiolene Complexes of Transition Metals 1660 Organometallic Intramolecular-Coordination Compounds. Recent Aspects in the 1661... 

Nickel(II) complexes display a variety of equilibria which involve spin state changes. Planar four-coordinate complexes are invariably diamagnetic. These can undergo an intramolecular isomerization to paramagnetic tetrahedral four-coordinate species. Alternatively, the planar complexes can coordinate additional ligands to form five- and six-coordinate paramagnetic complexes. The additional ligand molecules can be Lewis bases in solution, or solvent molecules, or, in par-... 

As noted in the introduction, in contrast to attack by nucleophiles, attack of electrophiles on saturated alkene-, polyene- or polyenyl-metal complexes creates special problems in that normally unstable 16-electron, unsaturated species are formed. To be isolated, these species must be stabilized by intramolecular coordination or via intermolecular addition of a ligand. Nevertheless, as illustrated in this chapter, reactions of significant synthetic utility can be developed with attention to these points. It is likely that this area will see considerable development in the future. In addition to refinement of electrophilic reactions of metal-diene complexes, synthetic applications may evolve from the coupling of carbon electrophiles with electron-rich transition metal complexes of alkenes, alkynes and polyenes, as well as allyl- and dienyl-metal complexes. Sequential addition of electrophiles followed by nucleophiles is also viable to rapidly assemble complex structures. 

The main methods for the synthesis of hexacoordinate silicon compounds are similar to those for pentacoordinate complexes and were outlined in a recent review6. These methods include (a) addition of nucleophiles (neutral or anionic) to tetracoordinate silanes (b) intermolecular or intramolecular coordination to an organosilane (c) substitution of a bidentate ligand in a tetrafunctional silane. The following discussion focuses mainly on new complexes, reported since the recent reviews6,7 were published. 

VI. NEUTRAL HEXACOORDINATE SILICON COMPLEXES A. Intramolecular Coordination... 

Silylene complexes with two intramolecular coordinating arms can participate in dynamic behavior, involving a flip-flop alternating coordination, illustrated in... 

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