Structure of transition-metal cluster compounds: Use of an additional orbital resulting from the f, g character of spd bond orbitals

Abstract

A general theory of the structure of complexes of the transition metals is developed on the basis of the enneacovalence of the metals and the requirements of the electroneutrality principle. An extra orbital may be provided through the small but not negligible amount of fand g character of spd bond orbitals, and an extra electron or electron air may be accepted in this orbital for a single metal or a c uster to neutralize the positive electric charge resulting from the partial ionic character of the bonds with ligands, suc-h as the carbonyl group. Examples of cluster compounds of cobalt, ruthenium, rhodium, osmium, and gold are discussed. The composition and structure of a great many compounds of transition metals correspond well to the assumption that transition-metal atoms can use their set of nine hybrid sp3d5 bond orbitals in forming bonds (1-4). For example, cobalt has nine outer electrons and accordingly can form nine bonds, as in the molecule hydridotetracarbonylcobalt, HCo(CO)4, in which a single bond is formed with a hydrogen atom and double bonds are formed with each of the four carbon atoms. Another example is the enneahydridorhenate anion, [ReHg]2-, in which the rhenium atom, which has increased its number of valence electrons from 7 to 9 by transfer of 2 from an electropositive metal (potassium in K2ReHg), forms single bonds with each of 9 hydrogen atoms. A few complexes are known, however, for which the composition and structure indicate that an additional stable orbital, which can serve as a bond orbital, is present. The explanation of this deviation from the predictions of the simple hybrid-orbital theory of chemical bonds has not been obvious. I have now found that consideration of the f, and to some extent the g, character of spd bond orbitals leads to the conclusion that some transition-metal atoms or clusters of them are provided with an additional bond orbital by the release of some spd character through the contribution of a small amount of f and g character by the relatively unstablef and g orbitals. Hybrid bond orbitalsIn the simple theory of hybrid bond orbitals (5, 6) the bond strength S, equal to the value of the angular part of the wave function in the bond direction, is taken as a measure of the bond-forming power of the orbital. The values of S for the best hybrid sp, spd, and spdf bond orbitals are 2, 3, and 4, respectively. The carbon atom is usually described as forming bonds in the four tetrahedral directions by using a set of four best Sp3 bond orbitals, each with strength 2. It has been pointed out, however, that the bond orbitals have some d and f character,The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact. estimated at about 4 and 2%, respectively, which increases the value of S to about 2.76, thus making the bonds significantly stronger (ref. 6, p. 126). The spectral term values for potassium, rub...

A Hypothetical Model for the Formation of Transition Metal Carbonyl Clusters Based upon 4n Series Skeletal Numbers

“…On the basis of k values, these complexes are expected to have single, Cr-Cr and W-W bonds. The existence of complexes such as HCo(CO) 4 (Co, k =4.5)and ReH 9 2-(Re, k =5.5) can easily be appreciated in terms of k values of the skeletal elements (Pauling, 1977). Let us consider the Cr 3 naked skeletal cluster.…”

The Main Group Elements, Fragments, Compounds and Clusters Obey the 4n Rule and Form 4n Series: They are Close relatives to Transition Metal Counterparts via the 14n Linkage

“…The principle ably links the concepts of organic, inorganic and organometallic chemistry (Hoffmann, 1982) by using chemical fragments. The fragments are extremely useful in explaining numerous carbonyl and borane shapes of clusters which have attracted the attention of scientists for many years ( Lipscomb, 1963, Wade, 1971,1976, Rudolph, 1976, Pauling, 1977, Jensen, 1978, Cotton, et al, 1980, Mingos,1972, 1984, Douglas, et al, 1994, King, 2002, Jemmis, 2001a, 2001b,2002, 2003,2006, 2008, Bowen, et, al, 2007, King, et al, 2009, Welch, 2013. It was recently discovered that transition metal carbonyl clusters could readily be categorized using a matrix table (Kiremire, 2016a(Kiremire, , 2016b derived from 14n-based series.…”

Carbonyl Chalcogenides Clusters Existing as Disguised Forms of Hydrocarbon Isomers

“…Arising from the unique polyhedral structures and potential applications, the clusters have continued to fascinate many scientists (Lipscomb, 1963;Wade, 1971Wade, , 1976Pauling, 1977;Mingos, 1972Mingos, , 1984Hawthorne, et al, 1999;Jemmis, 2005;Jemmis, et al, 2006;Jemmis, et al, 2008;Welch, 2013). Wade-Mingos rules have been exceedingly useful in categorizing and predicting the shapes of clusters (Wade, 1971(Wade, , 1976Mingos, 1972Mingos, , 1984Welch, 2013).…”