Making Sense of the Shapes of Simple Metal Hydrides

Landis, Clark R.; Cleveland, T.K.; Firman, Timothy K.

doi:10.1021/ja00111a036

Cited by 113 publications

(140 citation statements)

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“…Recently, independent quantum chemical [1] and low-temperature X-ray diffraction [2] studies have conclusively shown that the equilibrium structure of hexamethyltungsten, [W(CH 3 ) 6 ], is a distorted trigonal prism (the WC 6 skeleton has C 3v symmetry, the overall computed symmetry is only C 3 [1] , see also ref. [3]).…”

Section: Introductionmentioning

confidence: 99%

The Nonoctahedral Structures of d0, d1, and d2 Hexamethyl Complexes

Kaupp

1998

Chem. Eur. J.

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Section: Introductionmentioning

confidence: 99%

The Nonoctahedral Structures of d0, d1, and d2 Hexamethyl Complexes

Kaupp

1998

Chem. Eur. J.

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“…Examples range from the famous bent dihalides of some heavy alkaline earth metals [1] to nonoctahedral structures of six-coordinate organometallic complexes [2,3,4] 2À (a more general overview on ªnon-VSEPR structuresº for d 0 complexes will be given elsewhere [5] ). It has been demonstrated that the d-orbital participation in covalent s-bonding contributions (enhanced by core polarization, at least for the earlier metals [6] ) favors such distorted ªnon-VSEPR structuresº.…”

Section: Introductionmentioning

confidence: 99%

On the Relation between π Bonding, Electronegativity, and Bond Angles in High-Valent Transition Metal Complexes

Kaupp

1999

Chem. Eur. J.

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Ligand-to-metal p bonding is important for the understanding of bond angles in d 0 transition metal complexes. This is demonstrated by density functional calculations on a number of model complexes, combined with natural bond orbital and natural localized molecular orbital analyses. Analyses of the simple model systems ScF 2 and ZrO 2 indicate a complicated dependence of p bonding on bond angle. In particular, in-plane p bonding exhibits a nonuniform dependence, whereas outof-plane p bonding shows a more regular behavior. This may be understood from the nodal properties of the relevant metal d orbitals. The net p bonding behavior then depends sensitively on the donor properties of the ligands. While p bonding appears to favor the bent equilibrium structure for the ªstrong pdonor caseº ZrO 2 , it is more efficient at a linear structure for the ªweak pdonor caseº ScF 2. Similar considerations come into play for more complicated species, exemplified by MX 2 Y 2 model complexes. Thus, the ªinverse Bents rule structuresº of TiCl 2 (CH 3 ) 2 and TiCl 2 H 2 are related to the improved in-plane p(Ti ± Cl) bonding at larger ClTi-Cl angles. In contrast, for CrO 2 F 2 or MoO 2 F 2 , the angular dependences of the strong in-plane and out-of-plane components of p(M ± O) bonding compensate each other partially, and the O-M-O angles appear to be dominated by the s-bonding framework. When introducing a strong s-bonding ancillary ligand, as in CrO 2 H 2 , the net p bonding does again seem to favor larger angles. Electronegativity effects on bond angles have been probed by studying heteroleptic complexes without significant p bonding. ªInverse structuresº are found for complexes like TiH 2 (CF 3 ) 2 or Ti-(SiH 3 ) 2 (CH 3 ) 2 , that is the smaller angles are those between the less electronegative ligands. Hybridization analyses indicate less d character for these bonds. The interpretation is complicated by the fact that even the structure for the silicon analogon of the latter complex violates Bents rule. In general, Bents rule appears to be less useful for d 0 transition metal complexes than for main group compounds, in part due to the much larger importance of p bonding for the former.

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“…For instance, it has been found that the structure of unsaturated species cannot be always predicted by the valence shell electron pair repulsion (VSEPR) theory 1 or by a simple ionic model. WMe 6 and WH 6 are notable cases for the failure of the VSEPR theory since they have distorted trigonal prismatic structures with C 3v symmetry 2 while VSEPR would have predicted an octahedral coordination. The VSEPR also fails to predict the bent structure of molecular dihalides of the heavy alkaline earth metals (Ca, Sr, and Ba) and the pyramidal structure of trihydrido complexes such as ScH 3 , LaH 3 , TiH 3 + , ZrH 3 + , and their alkyl analogues.…”

Section: ■ Introductionmentioning

confidence: 99%

“…3 The main feature that emerges from the studies is that distortion away from the structure predicted by VSEPR is prevalent for complexes with hydride or alkyl ligands, which have no π-donor capability, while the presence of π-donor ligand like halide lead more often to structures that follow the VSEPR rule. For instance, WCl 6 is octahedral 4 while WMe 6 and WH 6 are not. Analysis of the metal−ligand bonding within such complexes shows that the electron delocalization between the π-donor ligand and the formally empty metal d orbital increases the electron density at the metal which, in turn, becomes less unsaturated.…”

Section: ■ Introductionmentioning

confidence: 99%

“…5 Landis et al have shown that valence bond concepts can be used for describing the shape of a variety of hydride and alkyl systems. 6 A primary feature of their studies is that the valence empty (n + 1)p orbitals of a nd metal do not contribute to the metal−ligand bonds, which are constructed from the (n + 1)s and available nd orbitals. 7 Consequently, the shape of the hydride complex, where the metal has λ nonbonding electron pairs, is determined by the optimal spatial distribution of the sd ω (ω = 5 − λ) hybrids set, that is, the spatial distribution that minimizes the interactions between the hybrid orbitals.…”

Section: ■ Introductionmentioning

confidence: 99%

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