Extended Hiickel molecular orbital complexes

The Dotz reaction mechanism has received further support from kinetic and theoretical studies. An early kinetic investigation [37] and the observation that the reaction of the metal carbene with the alkyne is supressed in the presence of external carbon monoxide [38] indicated that the rate-determining step is a reversible decarbonylation of the original carbene complex. Additional evidence for the Dotz mechanistic hyphotesis has been provided by extended Hiickel molecular orbital [23, 24] and quantum chemical calculations [25],... 

From iterative extended Hiickel molecular orbital (EHMO) calculations, [VX]"+ (X = S, Se n = 0, 1, 2) ions and their tetrachloro complexes [VXCl4]m- (m = 4, 3, 2) decrease in stability 0>S>Se and with increasing charge of the anion.695 The [VXC14]2- and [VXCI4]4-complexes are expected to be S = systems while [VXC14]3- species are expected to be diamagnetic.695... 

It has been found that whereas Cu11 porphyrins luminesce, the Ag" complexes do not. By an examination of electronic absorption spectra, emission spectra, redox potentials and near-IR absorption data, it was proposed that this could be rationalized on the basis of the energy of the big (dx2 yi) orbital. Extended Hiickel molecular orbital calculations predicted that the d-n transition would be above the lowest (n, jt ) levels for Cu11 but below them in the Agn complexes. The near-IR absorptions found for Ag11 were attributed to CT transitions.554... 

Silvestre and Hoffmann have considered the conversion of ruthenium acetylide complexes to the corresponding vinylidene species using extended Hiickel molecular orbital calculations (69). Although the rearrangement of free acetylene to its vinylidene isomer is thermodynamically disfavored, their results indicate that the transformation becomes thermodynamically... 

An extended Hiickel molecular orbital analysis on both of these complexes revealed that this structural difference between the chloride and the iodide can be traced to a second-order Jahn-Teller distortion, which is predicted to occur more readily for the chloride. Specifically,... 

Concerted two-electron transfer and reversible metal-metal bond cleavage in phosphine-bridged dimers have been investigated, and extended Hiickel molecular orbital calculations have shown that the redox-active orbital is a metal-metal antibonding orbital. A Ru-Ru-bonded dimeric cation [Ru(Cp)2]2++ has been prepared and characterized electrochemically. The electrochemistry of these dimers may give insight into more complex clusters and polymeric metals. 

The reactivity of pyrylium ions with azides has been discussed theoretically on the basis of extended Hiickel molecular orbital (EHMO) calculations (84T3549). As long as the pyrylium ring is hindered, the most favorable approach of the reactants corresponds to a reaction coordinate yielding azidopyrans. However, when the ring approach is free, the system can assume a geometry that allows the formation of a stable complex. 

Puddephatt etal. [41] have studied the C-H or C-C bond activation in the alkane complexes [PtMe(CH4)L2] or [PtMe(CHjCH3)L2] (L = NH3 or PH3) as well as the reductive elimination of methane or ethane from the five-coordinate model complexes [PtHMe2L2] or [PtMesLi], respectively, by carrying out extended Hiickel molecular orbital calculations and density functional theory. The oxidative addition and reductive elimination reactions occur by a concerted mechanism, probably with a pinched trigonal-bipyramidal complex on the... 

Efficient 1,3-asymmetric induction occurs during the reaction of chiral vinylrhenium complexes of type (51) in equation (20). Extended-Hiickel molecular orbital calculations and stereochemical results are consistent with a mechanism... 

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