Cp2M + complexes, bonding

In CP2MXY complexes (M Ti, Zr, Hf), the ligands X and Y together donate a total of four electrons to the neutral fragment CP2M. When Y is a non-ff-donor, as CH3 in complex III, all ir bonding is provided by X(0R) this leads to maximum contraction of the Zr-0 distance. It was noted previously (3.) that the Ti-Cl distance in... 

Ethynylruthenocene acetylides, preparation, 6, 642 ETL, see Electron-transporting layer ET reactions, see Electron-transfer reactions Europium complexes with arenes, 4, 118-119 Cp2Ln compounds, 4, 27 CpLnX2 compounds, 4, 29-30 Cp2M compounds, 4, 63 cyclooctatetraenyl compounds, 4, 122-123 heterobimetallic compounds without direct M—M bonds,... 

Bonding. The bonding in Cp2M(H)(CO) and Cp2M(H)(C2H4) complexes has been discussed from the molecular-orbital viewpoint. It is of interest that such compounds are predicted only for those metals with two or fewer d electrons in the M(III) state (79). 

Hydrogen chloride attacks the Mn—Pb bonds to form lead chloride486. To compare the reactivity of the M—H bond with the M—Pb bond in the [(Cp2MH)2(Ai-Pb(02CMe)2] (M=Mo, W), the complexes were reacted with cyanoalkyne, HC=C—CN however, the only isolated product was Cp2M C(CN)=CH2 2515. 

Cyclopentadienide derivatives appear both as simple complexes, reminiscent of ferrocene, or as heteroleptic systems. Because ofthe primarily electrostatic bonding models attributed to alkaline earth organometallics, the range of geometries available even for simple homoleptic alkahne earth metallocenes Cp2M (M = Be Ba) is surprising. 

Since the mid-1980s the chemistry of related cationic 16-electron Cp2M(R)(L) complexes (1) and base-free 14-electron Cp2M(R) complexes (2) (M = Ti, Zr) has been developed (/O). These complexes are considerably more reactive than their neutral counterparts as a result of the increased Lewis acidity of the cationic metal center, as well as the presence of the labile ligand L in 1 and the increased unsaturation of 2. These features promote coordination and activation of olefins, acetylenes, H, C— H bonds, and other substrates, and they open reaction pathways which are unavailable to neutral 16-electron analogs. Cationic complexes 1 and 2 are thus classified as highly electrophilic metal alkyls. 

A 16-electron, d° Cp2M(R)X species contains one low-lying metal-centered LUMO localized in the equatorial plane between the Cp ligands which is utilized for substrate coordination (Fig. 1) (11). Zr—X r-bonding (X = OR, halide, etc.) utilizes this orbital and generally results in decreased reactivity (5). The electronic structure of a Cp2Zr(R)(L) complex is similar to that of neutral analogs, but the LUMO is stabilized by the metal... 

Cp2M(R)" complexes. Hlatky and Turner reported that the reaction of Cp 2Zr(CH3)2 with [HN("Bu)3][BPh4] in toluene yields the zwitterionic complex Cp 2Zr+ C6H4BPh3 via initial Zr—CH3 bond protonolysis followed by subsequent BPh4 aryl C—H bond activation [Eq. (12)] (47). An... 

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