Disilicon(1+) Physical and Chemical Properties
Disilicon(1+)
A cationic two‑atom silicon species (Si2+) encountered in fundamental cluster chemistry and gas‑phase studies, relevant for analytical and materials R&D.
| CAS Number | Not specified for this entry |
| Family | Cationic silicon cluster |
| Typical Form | Gas-phase ionic species |
| Common Grades | EP |
Disilicon(1+) is a homonuclear silicon dimer existing as a singly charged cationic cluster; its empirical formula is \(\mathrm{Si}_2^{+}\). Structurally this species comprises two silicon atoms bonded to one another with a net positive charge distributed over the dimer framework. Electronic structure is dominated by silicon valence orbitals (primarily 3s and 3p), and bonding in the cationic dimer reflects partial electron deficiency compared with neutral silicon–silicon bonding motifs; the charge leads to enhanced electrostatic potential and strong propensity to interact with nucleophiles or coordinating ligands.
As a small cationic cluster, disilicon(1+) behaves as a strong Lewis acid in the gas phase and in coordination chemistry contexts. It is nonpolar only in the trivial sense of being homonuclear, but the positive charge confers high polarizability and strong long-range Coulombic interactions. Classical acid–base pKa concepts are not directly applicable to an isolated gas-phase dimer cation, but reactivity trends follow general cluster chemistry: facile coordination to electron donors, susceptibility to oxidation by O2 or other oxidants, and rapid reaction with protic solvents leading to hydrolysis or ligand exchange. These properties make the species important primarily in fundamental studies of cluster electronic structure, ion–molecule reaction mechanisms, and in contexts where silicon-containing ions occur (plasmas, gas-phase deposition and analytical mass spectrometry).
Common commercial grades reported for this substance include: EP.
Basic Physical Properties (Density, Melting Point, Boiling Point)
Atomic Weight
The computed molecular weight (dimer mass) is \(56.17\,\mathrm{g}\,\mathrm{mol}^{-1}\) (listed as 56.17).
This value corresponds to the sum of two silicon atomic masses for the charged dimer; it is a computed molecular mass rather than a macroscopic atomic-weight specification for a bulk solid.
Appearance and Physical State
No experimentally established value for this property is available in the current data context.
Density
No experimentally established value for this property is available in the current data context.
Melting Point
No experimentally established value for this property is available in the current data context.
Boiling Point
No experimentally established value for this property is available in the current data context.
Chemical Properties (Reactivity and Oxidation States)
Oxidation States
The species carries a net formal charge of \(+1\) (formal charge value reported as 1). For a homonuclear dimer such as \(\mathrm{Si}_2^{+}\), assigning integer oxidation states to individual atoms is intrinsically ambiguous because the positive charge is delocalized across the bonding framework; the chemically relevant description is that the dimer is an electron-deficient cationic unit rather than two silicon atoms in well-defined, separate oxidation states.
Reactivity with Air and Water
As a cationic silicon cluster, \(\mathrm{Si}_2^{+}\) is expected to be highly reactive toward oxidants and nucleophiles. In the presence of molecular oxygen or other oxidizing gases it will undergo oxidation pathways that produce silicon oxides or oxidized cluster fragments in gas-phase or surface-mediated reactions. Contact with protic media (water, alcohols) generally leads to rapid reaction—hydrolysis, proton transfer, or ligand exchange—producing more stable silicon-oxygen or silicon-hydrogen containing products. These behaviors reflect the strong electrophilic character of the charged cluster.
Reactivity with Acids and Bases
\(\mathrm{Si}_2^{+}\) functions as a Lewis acid and will coordinate to Lewis bases (e.g., donor ligands, solvent molecules) and undergo complexation. In strongly basic media, nucleophilic attack on silicon centers can occur; in strongly acidic media, protonation of coordinated ligands or counter-ion-driven processes may dominate. Specific reaction pathways depend critically on phase (gas vs condensed), counterions, and ligand environment.
Isotopic Composition
Stable Isotopes
Elemental silicon commonly occurs with stable isotopes \(\mathrm{^{28}Si}\), \(\mathrm{^{29}Si}\), and \(\mathrm{^{30}Si}\). The isotopic composition of any macroscopic sample of \(\mathrm{Si}_2^{+}\) will reflect the isotopic distribution of the source silicon unless isotopic enrichment or separation procedures have been performed.
Radioisotopes
No experimentally established value for this property is available in the current data context.
Thermodynamic Parameters
Heat Capacity and Related Data
No experimentally established value for this property is available in the current data context.
Enthalpy and Gibbs Energy
No experimentally established value for this property is available in the current data context.
Identifiers and Synonyms
Registry Numbers and Codes
- Molecular formula: \(\mathrm{Si}_2^{+}\) (listed as Si2+)
- Molecular weight: \(56.17\,\mathrm{g}\,\mathrm{mol}^{-1}\) (listed as 56.17)
- Exact mass / Monoisotopic mass: 55.95385307
- Formal charge: 1
- SMILES: [Si][Si+]
- InChI: InChI=1S/Si2/c1-2/q+1
- InChIKey: MEMLCQNRJARANC-UHFFFAOYSA-N
- ChEBI identifier: CHEBI:30591
- Wikidata identifier: Q27113885
- Internal compound identifier (CID): 16019982
SMILES and InChI strings are presented as plain text identifiers for cheminformatics use.
Synonyms and Common Names
Depositor-supplied synonyms include: - disilicon(1+) - CHEBI:30591 - RefChem:1083826 - lambda1-silanylsilicon(1+) - Si2(+) - Si2 - Q27113885
Industrial and Commercial Applications
Major Use Sectors
No concise application summary is available in the current data context; in practice this substance is selected based on its general properties described above.
However, at the class level, cationic silicon clusters are relevant in sectors concerned with fundamental cluster science, semiconductor processing plasmas, gas-phase ion chemistry, and analytical mass spectrometry where silicon-containing ions and cluster formation are encountered.
Typical Application Examples
- Fundamental studies of silicon cluster electronic structure and bonding using gas-phase spectroscopy and mass spectrometry.
- Model systems in ion–molecule reaction kinetics and mechanistic investigations relevant to plasma-assisted thin-film deposition and chemical vapor deposition processes.
- Analytical contexts where silicon cations are observed as transient species during ionization or sputtering.
Safety and Handling Overview
Storage and Handling Considerations
As a reactive, electron-deficient silicon cation, \(\mathrm{Si}_2^{+}\) is typically encountered and generated under controlled, instrumented conditions (e.g., gas-phase ion sources, plasma reactors). General handling principles for reactive silicon species apply: exclude exposure to air and moisture where possible (use inert atmosphere techniques), minimize generation of free ionic species outside closed systems, and use equipment designed for low-pressure or controlled-atmosphere operation. Do not store or handle this species in uncontrolled bulk form; appropriate containment and process controls are required when generating or manipulating charged silicon clusters.
For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
Occupational Exposure and Protective Measures
Occupational controls should follow standard industrial hygiene practices for reactive gases/ion sources and particulate/sputtered species: local exhaust ventilation or containment of ionization sources, engineering controls to prevent exposure, and use of personal protective equipment (appropriate gloves, eye protection, and laboratory coats). Avoid inhalation and skin contact with reactive silicon-containing aerosols or condensates. Training in handling pressurized gas systems, vacuum/plasma equipment, and ion sources is recommended for operators.
