Are there any molecules with delta bonds in their ground states?

Question

When looking at excited states of molecules, $\delta$ bonds are relatively common, but I've never come across a molecule with a $\delta$ bond in its ground state.

Are there molecules with $\delta$ bonds in their ground states?

What about even higher angular momentum states ($\phi$ and $\gamma$ bonds)?

Re: phi/gamma bonds, Wikipedia says There is strong evidence to believe that no two elements in the periodic table can form a bond with greater order than 6 and links to http://onlinelibrary.wiley.com/doi/10.1002/anie.200603600/abstract. Guess it's relevant here. It may not make phi/gamma bonds impossible, but probably makes them rarer. — ManishEarth, Jul 01 '12 at 13:24

score 13 · Accepted Answer · answered Jul 03 '12 at 14:07

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Chromium(II) acetate has a Cr-Cr quadruple bond - and hence a $\delta$ bond - in its ground state. This sort of "paddlewheel" configuration, with four carboxylic acids coordinating a pair of metal ions, is reasonably common (see also copper(II) acetate, for instance), although the extent to which the metals can be considered covalently bonded varies.

answered Jul 03 '12 at 14:07

Aant

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The copper analog is another example – khaverim Mar 03 '16 at 13:15

score 7 · Answer 2 · edited Jan 13 '17 at 14:02

Metal-metal quadruple bonds have seemingly been reported for several cases, quite often by F. A. Cotton. A short search revealed a more recent report on a species with a Cr-Cr quintuple bond: Synthesis of a Stable Compound with Fivefold Bonding Between Two Chromium(I) Centers.

Admittedly, I didn't bother to read the full article, it's just not the kind of chemistry I'm interested in. However, YMMV and you might find it helpful.

score 5 · Answer 3 · edited Apr 13 '17 at 12:57

I am a bit late to the party, but I just found this question. When I did research on the φ bond for What would follow in the series sigma, pi and delta bonds? I came across some predictions about possible φ bond in the ground state.

According to Gagliardi and Roos, there should be a φ bond in the ground state of the $\ce{U2}$ molecule. That being said, it is probably incredibly tough to synthesise this molecule.

Metal-metal multiple bonds have become fairly common as my earlier answer demonstrates.
It should be clarified that a quadruple bond does not necessarily mean that a δ bond is involved. Often enough the combination of the d_z² metal orbitals lead to the formation of a second σ bond first.
It should further be explained, that a δ bond can be present, but the overall bond order could be lower than four.

Laura Gagliardi, Björn O. Roos, Nature, 2005, 433, 848-851. Available free at Archive ouverte UNIGE.

I figure you could make $\ce{U2}$ molecules by heating the metal enough so that becomes gaseous. Either find a chamber that resists temperatures of around $\mathrm{4000\ K}$ to get a decently high vapour pressure, or more likely, do some kind of ablation (plasma, laser, etc) on solid uranium, though there would probably be contamination with larger metallic clusters. — Nicolau Saker Neto, Mar 03 '16 at 09:11

Are there any molecules with delta bonds in their ground states?

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