Characterization of (methylcyclopentadienyl)trimethylplatinum and low-temperature organometallic chemical vapor deposition of platinum metal

({eta}{sup 5}-Methylcyclopentadienyl)trimethylplatinum, ({eta}{sup 5}-MeCp)PtMe{sub 3}, 1 (MeCp = CH{sub 3}C{sub 5}H{sub 4}), is synthesized from trimethylplatinum iodide and sodium methylcyclopentadienide by the method of Fritz and Schwarzhans. By using care in the purification of bis(methylcyclopentadiene) from dicyclopentadiene, a sample of 1 is obtained showing a melting point of 29.5-30.0{degree}C and a vapor pressure of 0.053 Torr at 23{degree}C, {sup 1}H and {sup 13}C NMR spectra have been obtained. Coupling constants to the cyclopentadienyl ring carbons are found to differ, Hz: {sup 195}Pt-{sup 13}C{sub Me} = 13.62, while {sup 195}Pt-{sup 13}C{sub H} = 2.82 or 5.34. Five separate resonances are observed for the ring carbon atoms of the MeCp group in the solid ({sup 1}H){sup 13}C NMR. However, only one signal is observed at {minus}73{degree}C or higher for the 3 methyl groups on Pt, indicating a low barrier for rotation of these groups in the solid state. The principal finding, of significance to the solid-state NMR, is the intermolecular contacts of 3.98, 4.55, and 4.94 {angstrom} between closest ring-carbon atoms on independent molecules in adjacent unit cells. These contacts are too close to permit rotation of the MeCp rings. The ring is pentahapto-bonded with almost identical Pt to ring-carbon distances within the limited accuracy of this determination, {angstrom}, C{sub (Me)}-Pt = 2.266, C{sub (H)}-Pt = 2.260, 2.314, 2.354, and 2.324. For deposition of metallic platinum, a stream of Ar gas at ambient pressure is first saturated with the vapor of 1 at 23{degree}C. This is then conducted into a chamber containing H{sub 2} gas such that the ratio of saturated Ar:H{sub 2} = 4:1. A substrate such as a glass slide or a Si(100) wafer, placed near the outlet of the saturated Ar gas stream and heated to 120{degree}, becomes coated with a film of highly reflective Pt metal.