Bicapped tetrahedral, trigonal prismatic, and octahedral alternatives in main and transition group six-coordination

Hoffmann, Roald; Howell, James M.; Rossi, Angelo R.

doi:10.1021/ja00425a016

Cited by 174 publications

(96 citation statements)

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“…n,, 4e-stabilize the e' metal orbitals and hence lead to TP geometry. This is not a new result and had been considered by previous workers in the field (2,8,13). Nevertheless, it provides a natural link to other "even" type unsaturated ligands that present a symmetrical empty n-acceptor orbital to the central metal atom and properly account for the TP geometry observed in tris(buta-1,3-diene)molybdenum (29), tris(ortho-xyly1)tungsten (30), and tris(methylviny1ketone)tungsten (3 1 &P importance of n back-bonding for the observed TP rather than octahedral geometry about the metal atom in tris(buta-1,3-diene)Mo/W.…”

Section: Discussionsupporting

confidence: 62%

“…This result has been corroborated by Hoffman et al (2) on the basis of extended Hiickel MO calculations.…”

Section: Introductionsupporting

confidence: 65%

“…2), and the interaction of these orbitals with the unsaturated ligands in both n-acceptor and n-donor extremes. We recall that under D3h symmetry (TP geometry) the 3nv MOs of the ligands will give rise to two group molecular orbitals of a2' and e' symmetries.…”

Section: Discussionmentioning

confidence: 99%

“…In 1965 the first observation of a discrete TP complex, Re(l ,2,-S2C2Ph2)3 (3), rekindled interest in TP geometry and since then a host of factors, such as (a) ligand constraint (4,5), (b) ligand field stabilization energy (2,4,6), (c) interdonor atom bonding (3,(7)(8)(9), (d) proper matching of ligand and metal orbital energies (1,2,(10)(11)(12), (e) the symmetry of ligand n orbitals (2,8,13), and (f) the overall charge of the complex, have been suggested as important factors influencing the formation of TP, octahedral, or intermediate geometries. From experimental work of Holm and co-workers (4) and Eatough et al (14) and theoretical work of Holm (4), Kepert ( 3 , and Wentworth (6) it appears that the two most important factors involved are probably the ligand constraint (provided by cage type 'present address: Phillips Petroleum Co., 96-G PRC, Bartlesville, OK 74004, U.S.A.…”

Section: Introductionmentioning

confidence: 99%

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Trigonal prismatic versus octahedral coordination geometry of transition metal dithiolates: Comparison between saturated and unsaturated early transition metal tris(1,2-dithiolate) complexes

Martin¹,

Takats²

1989

Can. J. Chem.

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Reaction of a stoichiometric amount of Hzedt/NaHedt (edt = ethane-l,2-dithiolate) with the appropriate metal amide, followed by cation exchange, gave the complexes [NEt412 [M(edt),] (M = Ti, 1; Hf, 2) and [AsPh,] [Nb(edt),].CH,CN, 3. The structure of 3 has been determined crystallographically (space group; cell dimensions; Z; unique data (I 2 3u (I); R/R,): p i ; a = 9.095(1), b = 14.609(3), c = 15.639(3) A and a = 60.09(2), P = 80.07(3), y = 89.89(2)"; z = 2; 1488; 4.3/4.5. The coordination geometry of 3 is severely distorted from the trigonal prismatic (TP) structure found in the analogous Nb(1,2-S2C6H4)3-r which contains an unsaturated 1,2-dithiolate ligand system. The average twist angle between triangular faces is 33.3". However, on the basis of VT 'H NMR spectroscopy it is argued that the TP form is at most 9-10 kcal mol-' less stable than the observed geometry. A comparison between the structures of tris-chelate complexes of the early transition metals containing saturated and unsaturated 1,2-dithiolates and related ligands is made, and the factors thought to be responsible for TP vs. octahedral geometry are reviewed and their relative importance assessed.Key words: structure, trigonal prismatic, 1,2-dithiolate, early transition metals. . La gComCtrie de coordination du composC 3 est fortement deformCe par rapport a la structure prismatique trigonale (PT) qui a kt6 observCe antkrieurement avec I'analogue Nb(l,2-SZC6H4)3-qui contient un ligand 1,2-dithiolate insaturk. L'angle moyen de dCviation entre les faces triangulaires est de 33,3". Toutefois, sur la base de la RMN du 'H a tempkrature variable, on suggkre que la difference de stabilitk entre la forme PT et la gComCtrie observke ne favorise cette dernikre que par 9-10 kcal mol-I. On a comparC les structures des complexes tris chClates des mCtaux de transition du debut contenant des ligands 1,2-dithiolates saturts et insaturks ainsi que d'autres ligands apparentis; on passe en revue les facteurs que I'on croit responsable des structures PT vs. les gComCtries octaCdriques et on Cvalue leurs importances relatives. Mots clis : structure, prismatique trigonal, 1,2-dithiolate, mCtaux de transition du dCbut.[Traduit par la revue] Introduction The possibility of trigonal prismatic (TP) geometry in highly covalent do transition metal complexes was predicted as early as 1932 by Hultgren (I), based on the concept of metal orbital hybridization presenting a more favorable bonding picture for TP than for octahedral geometry. This result has been corroborated by Hoffman et al. (2) on the basis of extended Hiickel MO calculations.In 1965 the first observation of a discrete TP complex, Re(l ,2,-S2C2Ph2)3 (3), rekindled interest in TP geometry and since then a host of factors, such as (a) ligand constraint (4, 5), (b) ligand field stabilization energy (2,4,6), (c) interdonor atom bonding (3, 7-9), (d) proper matching of ligand and metal orbital energies (1, 2, 10-12), (e) the symmetry of ligand n orbitals (2, 8, 13), and (f) the overall charge of the complex, have bee...

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Section: Discussionsupporting

confidence: 62%

“…This result has been corroborated by Hoffman et al (2) on the basis of extended Hiickel MO calculations.…”

Section: Introductionsupporting

confidence: 65%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Trigonal prismatic versus octahedral coordination geometry of transition metal dithiolates: Comparison between saturated and unsaturated early transition metal tris(1,2-dithiolate) complexes

Martin¹,

Takats²

1989

Can. J. Chem.

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show abstract

“…Indeed, an octahedral arrangement of the chalcogenide ions creates a staggered intralayer AB close-packing that would intuitively have lower energy than the AA layer stacking in the trigonal prism. Madelung calculations of the different structures would appear to support this notion [49]. Kertesz and Hoffmann argue that octahedral geometries of do configurations are also more stable electronically, but the differences in the two geometries are quite small [48].…”

Section: Bonding Forcesmentioning

confidence: 97%