Cyclopentadienylindium(I)

Names
Other names indium cyclopentadienyl, cyclopentadienyl indium
Identifiers
CAS Number	34822-89-4
3D model (JSmol)	Interactive image
ChemSpider	9270356
ECHA InfoCard	100.222.670
PubChem CID	85397242
InChI InChI=1S/C5H5.In/c1-2-4-5-3-1;/h1-5H; Key: JZPXQBRKWFVPAE-UHFFFAOYSA-N
SMILES [In+].c1[cH-]ccc1
Properties
Chemical formula	C5H5In
Molar mass	179.913 g/mol
Appearance	off-white solid
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H228, H302, H315, H319, H335
Precautionary statements	P210, P240, P241, P261, P264, P270, P271, P280, P301+P312, P302+P352, P304+P340, P305+P351+P338, P312, P321, P330, P332+P313, P337+P313, P362, P370+P378, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Cyclopentadienylindium(I), C₅H₅In, is an organoindium compound containing indium in the +1 oxidation state. Commonly abbreviated to CpIn, it is a cyclopentadienyl complex with a half-sandwich structure. It was the first (1957^[1]) low-valent organoindium compound reported.

Preparation and chemistry

CpIn can be readily prepared by reacting indium(I) chloride with cyclopentadienyllithium:^[2]

InCl + CpLi → CpIn + LiCl

InCp reacts with BF₃, BCl₃, BBr₃, BI₃ and trimethylborane B(CH₃)₃ to form adducts,^[3] e.g.:

CpIn + BF₃ → CpIn·BF₃

In these adducts the bonding of the Cp ligand to the indium atom changes from η⁵ (π complexing) to η¹ (σ bonding).

Salts containing the InX₂⁻ anion containing indium in the +1 oxidation state have been prepared from cyclopentadieneindium; for example:^[4]

CpIn + HCl + N(Et₄)Cl → N(Et₄)InCl₂+ C₅H₆

Structure and bonding

Solid CpIn is polymeric consisting of zigzag chains of alternating indium atoms and C₅H₅ units. Two indium atoms interact with the opposite faces of each C₅H₅⁻ ring, nearly perpendicularly to the ring plane, and two rings interact with each indium atom, forming an angle of about 128°.^[5] In the CpIn monomer present in the vapour phase the indium atom sits on the central axis of the aromatic cyclopentadienyl anion, C₅H₅⁻.

Bonding studies have shown that the aromatic ring electrons of the cyclopentadienyl anion interact with the indium 5s and 5p atomic orbitals, and that the lone pair on the indium atom is a dominant feature.^[6]

Ball-and-stick and space-filling models of CpIn chains in the crystal structure of cyclopentadienylindium(I)