Synthesis of a Stable Compound with Fivefold Bonding Between Two Chromium(I) Centers

Abstract

Although in principle transition metals can form bonds with six shared electron pairs, only quadruply bonded compounds can be isolated as stable species at room temperature. Here we show that the reduction of {Cr(mu-Cl)Ar'}2 [where Ar' indicates C6H3-2,6(C6H3-2,6-Pri2)2 and Pr indicates isopropyl] with a slight excess of potassium graphite has produced a stable compound with fivefold chromium-chromium (Cr-Cr) bonding. The very air- and moisture-sensitive dark red crystals of Ar'CrCrAr' were isolated with greater than 40% yield. X-ray diffraction revealed a Cr-Cr bond length of 1.8351(4) angstroms (where the number in parentheses indicates the standard deviation) and a planar transbent core geometry. These data, the structure's temperature-independent paramagnetism, and computational studies support the sharing of five electron pairs in five bonding molecular orbitals between two 3d5 chromium(I) ions.

Contrasting the group 6 metal–metal bonding in sodium dichromate(ii) and sodium dimolybdate(ii) polymethyl complexes: synthetic, X-ray crystallographic and theoretical studies

“…hence widening the angle at C and concomitantly lengthening the metal-metal separation, whereas the bridging methyl in 7 is relatively unencumbered. There are two distinct sodium environments, with those of Na (2) and Na (3) replicating that seen in previous M2Me8 complexes, namely acting as a cap to four methyl anions. However, the formal absence of the eighth methyl group, and the subsequent slippage of C7 from a terminal to a bridging environment, leaves Na(1) capping only three methyl groups.…”

“…The Cr-Cr interaction in 6 is highly multiconfigurational giving rise to a BS (3,3) solution for a total spin ground state of S = 0. This state is a colossal 65.5 kcal mol The chemical properties of these two group 6 metals -Cr and Mo -is neatly contrasted in these dimetallic compounds.…”

Formation of unprecedented actinidecarbon triple bonds in uranium methylidyne molecules

“…Main-group and transition-metal compounds with multiple chemical bonds have always been fascinating to chemists because of their pivotal role in organic, inorganic, and organometallic chemistry, characteristic chemical and physical properties, and versatile applications in biological and material science (2)(3)(4)(5)(6). Whereas numerous organic and inorganic compounds with multiple bonds are known (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), f elements (lanthanides and actinides) with multiple bonds are relatively rare, except for early actinides. Such bonding has aroused great interest recently in the search for actinide complexes with multiple bonds between two actinide metals (18)(19)(20)(21) and between actinide (An) and main-group ligands (L) (22)(23)(24)(25)(26)(27)(28).…”

Non-traditional ligands in f-block chemistry

“…Historically speaking, major advances regarding our understanding of chemical bonding have emerged from metal-metal chemistry, as exemplified by rhenium-rhenium (Cotton et al 1964), zinc-zinc (Resa et al 2004), magnesium-magnesium (Green et al 2007), chromium-chromium (Nguyen et al 2005) and hexa-indium (Hill et al 2006) complexes. However, while metal-metal bonding in the d-and p-blocks of the periodic table is widespread and well understood, and now even known in the s-block, very little is known about metal-metal complexes where one metal is an f-element.…”