Molecular Structure of Monomeric (Pentamethylcyclopentadienyl)aluminum(I) by Gas-Phase Electron Diffraction

Haaland, Arne; Martinsen, Kjell-Gunnar; Shlykov, Sergey A.; Volden, Hans V.; Dohmeier, Carsten; Schnoeckel, Hansgeorg

doi:10.1021/om00006a065

Cited by 93 publications

(64 citation statements)

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“…Thus, these orbitals contribute to the stabilization of the occupied t 2 orbitals to a much lower extent than in alkyl or silyl derivatives. In accordance with these results, the experimentally accessible compound Al 4 Cp* 4 (Cp*=C 5 Me 5 ) dissociates in solution or in the gas phase to yield the monomeric cluster fragments Al-Cp* (Haaland et al 1995(Haaland et al , 1996.…”

Section: Physical Properties Bonding and Structuressupporting

confidence: 63%

Tetrahedral homonuclear organoelement clusters and subhalides of aluminium, gallium and indium

Uhl

2004

Naturwissenschaften

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This review is focused on the synthesis and the reactivity of tetrahedral organoelement clusters of the heavier elements of third main-group aluminium, gallium, and indium, which have been known for about a decade. They possess the elements in an unusually low oxidation state of +1 and have direct element--element interactions between their four constituents. Each cluster atom is further attached to one terminal and in most cases a bulky organic substituent, which prevents disproportionation by steric shielding. The synthesis of these compounds succeeds by different methods such as the reduction of suitable organoelement(III) halides with alkali metals and magnesium or the treatment of element(I) halides with lithium organyls. They are deeply coloured, and their bonding situation may best be described by delocalized molecular orbitals. They show a singular chemical reactivity, which results in the formation of many secondary products possessing unprecedented structures and properties. The synthesis of organoelement subhalides still containing the elements in low oxidation states is discussed in more detail in the second part of this review. These compounds are easily accessible by the careful oxidation of the clusters with halogen donors such as hexachloroethane or with AlX(3)/X(2) mixtures. They produce dimers via halogen bridges, but in certain cases monomers were observed even for the solid state. They are very effective starting compounds for secondary reactions and the generation of new products containing the elements in unusual oxidation states by salt-elimination reactions, for instance.

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Section: Physical Properties Bonding and Structuressupporting

confidence: 63%

Tetrahedral homonuclear organoelement clusters and subhalides of aluminium, gallium and indium

Uhl

2004

Naturwissenschaften

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“…These PdÀPd bond lengths are distinctly shorter than in 2 a or 2 b. Both faces of the metal triangle are capped by a m 3 -AlCp* unit (Al(1) and Al (2) [19] and are distinctly longer than the distances in the metal carbonyl complexes [(CO) 5 Cr(AlCp*)] (1.819 ) [20] and [(CO) 4 Fe(AlCp*)] (1.775 ) [21] with significantly more polarized M dÀ ÀE d + bonds. The 1 H NMR spectrum of 3 in C 6 D 6 at room temperature exhibits two distinguishable singlets at d = 2.05 and 1.97 ppm with an integral ratio of 1:2.…”

Section: Resultsmentioning

confidence: 85%

“…The three central palladium atoms are arranged with an angle Pd(3)-Pd(2)-Pd(1) of 87.13(6)8 ( Table 3). The longest PdÀPd distance of 3.619 (Pd(1) À Pd(3)) can be regarded as nonbonding, while the other two Pd À Pd bond lengths of 2.6157(18) and 2.6363 (19) are shortened due to the edge-bridging AlCp* ligands. These PdÀPd bond lengths are distinctly shorter than in 2 a or 2 b.…”

Section: Resultsmentioning

confidence: 99%

The Clusters [M_a(ECp*)_b] (M=Pd, Pt; E=Al, Ga, In): Structures, Fluxionality, and Ligand Exchange Reactions

Steinke

Gemel

Winter

et al. 2005

Chemistry A European J

102

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The synthesis and structural characterization of the novel homoleptic cluster complexes [Pd2(GaCp*)2(mu2-GaCp*)3] (1c), [Pd3(GaCp*)4(mu2-GaCp*)4] (2b) and [Pd3(AlCp*)2(mu2-AlCp*)2(mu3-AlCp*)2] (3) (Cp*=C5Me5) are presented. Furthermore, ligand exchange reactions of these cluster complexes are explored. In contrast to the electronically and sterically saturated complexes [M(ECp*)4] (M=Ni, Pd, Pt), the new unsaturated analogues [M(a)(ER)b] (E=Al, Ga, In) react with a variety of typical ligands (Cp*Al, CO, phosphines, isonitriles) to give new di- and tri-substituted compounds like [Pt2(GaCp*)2(mu2-AlCp*)3] (1d), [PdPt(GaCp*)(PPh3)(mu2-GaCp*)3] (4b), or [Pd3(PPh3)3(mu2-InCp*)(mu3-InCp*)2] (8). The trends of the reactivity of [M(a)(ER)b] as well as their fluxional behavior in solution has been elucidated by NMR spectroscopy, resulting in a mechanistic rationale for the ligand exchange reactions as well as the fluxional processes.

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“…A number of later works considered the simple Al metallocenes in the context of examining trends in a broader range of main-group metallocenes or similar organometallics. 17À20 In recent years, Huber and Schn€ ockel have performed density functional theory calculations in support of their X-ray diffraction and 27 Al NMR studies of larger aluminumÀCp-type clusters. 14,21 They proposed that the large clusters, such as Al 50 Cp 12 *, may serve as a type of barrier state that prevents the smaller compounds from spontaneously decomposing to metallic aluminum and trivalent aluminum species.…”

Section: ' Introductionmentioning

confidence: 99%

Structure, Thermodynamics, and Energy Content of Aluminum–Cyclopentadienyl Clusters

Williams

Hooper

2011

J. Phys. Chem. A

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We present quantum chemistry simulations of aluminum clusters surrounded by a surface layer of cyclopentadiene-type ligands to evaluate the potential of such complexes as novel fuels or energetic materials. Density functional theory simulations are used to examine the aluminum-ligand bonding and its variation as the size of the aluminum cluster increases. The organometallic bond at the surface layer arises mainly from ligand charge donation into the Al p orbitals balanced with repulsive polarization effects. Functionalization of the ligand and changes in Al cluster size are found to alter the relative balance of these effects, but the surface organometallic bond generally remains stronger than Al–Al bonds elsewhere in the cluster. In large clusters, such as the experimentally observed Al50Cp12*, this suggests that unimolecular thermal decomposition likely proceeds through loss of surface AlCp* units, exposing the strained interior aluminum core. The calculated heats of combustion per unit volume for these systems are high, approaching 60% that of pure aluminum. We discuss the possibility of using organometallic aluminum clusters as a means of achieving rapid combustion in propellants and fuels.

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Molecular Structure of Monomeric (Pentamethylcyclopentadienyl)aluminum(I) by Gas-Phase Electron Diffraction

Cited by 93 publications

References 1 publication

Tetrahedral homonuclear organoelement clusters and subhalides of aluminium, gallium and indium

Tetrahedral homonuclear organoelement clusters and subhalides of aluminium, gallium and indium

The Clusters [M_a(ECp*)_b] (M=Pd, Pt; E=Al, Ga, In): Structures, Fluxionality, and Ligand Exchange Reactions

Structure, Thermodynamics, and Energy Content of Aluminum–Cyclopentadienyl Clusters

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Molecular Structure of Monomeric (Pentamethylcyclopentadienyl)aluminum(I) by Gas-Phase Electron Diffraction

Cited by 93 publications

References 1 publication

Tetrahedral homonuclear organoelement clusters and subhalides of aluminium, gallium and indium

Tetrahedral homonuclear organoelement clusters and subhalides of aluminium, gallium and indium

The Clusters [Ma(ECp*)b] (M=Pd, Pt; E=Al, Ga, In): Structures, Fluxionality, and Ligand Exchange Reactions

Structure, Thermodynamics, and Energy Content of Aluminum–Cyclopentadienyl Clusters

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The Clusters [M_a(ECp*)_b] (M=Pd, Pt; E=Al, Ga, In): Structures, Fluxionality, and Ligand Exchange Reactions