PtCO4

PtCO4, or platinum tetracarbonyl (Pt(CO)4), is a neutral organometallic complex of platinum in the zero oxidation state coordinated by four carbon monoxide ligands. As an 18-electron complex, Pt(0) contributes 10 valence electrons while each CO ligand donates two electrons, giving a stable electron count for a four-coordinate metal carbonyl.

The geometry around platinum in Pt(CO)4 is typically described as tetrahedral, consistent with four terminal carbonyl ligands and a d10 metal center. The Pt–CO bonds arise from a combination of sigma donation from the CO ligands and back-donation from platinum d orbitals into CO π* orbitals, a hallmark of metal carbonyl bonding. In spectroscopic studies, terminal CO ligands in such complexes exhibit strong C–O stretching bands in the high-frequency region, with infrared signatures characteristic of a tetrahedral Pt(CO)4 core. The complex is best understood as a transient species observed under controlled, low-temperature or gas-phase conditions rather than as a stable, isolable solid.

Preparation and occurrence: Pt(CO)4 is not commonly isolated under ambient conditions. It has been detected primarily in gas-phase experiments and cryogenic matrix studies, where it can be generated transiently by photolysis or fragmentation of related carbonyl precursors and observed by infrared spectroscopy. Under ordinary conditions, Pt(CO)4 tends to lose CO ligands or aggregate to other platinum carbonyl species.

Reactivity and context: Pt(CO)4 serves as a reference point for understanding the bonding in low-coordinate platinum carbonyls and the 18-electron rule among group 10 metal carbonyls. It is not widely used as a synthetic intermediate or catalyst, due to its limited stability and tendency to decompose at room temperature. Related compounds, such as Ni(CO)4, illustrate parallel bonding themes in metal carbonyl chemistry.

See also: Ni(CO)4, Fe(CO)5, Pt(CO)2 or other platinum carbonyls.