Infrared Spectra of Group 14 Hydrides in Solid Hydrogen:  Experimental Observation of PbH₄, Pb₂H₂, and Pb₂H₄

Laser-ablated Si, Ge, Sn, and Pb atoms have been co-deposited with pure hydrogen at 3.5 K to form the group 14 hydrides. The initial SiH(2) product reacts completely to SiH(4), whereas substantial proportions of GeH(2), SnH(2), and PbH(2) are trapped in solid hydrogen. Further hydrogen atom reactions form the trihydride radicals and tetrahydrides of Ge, Sn, and Pb. The observation of PbH(4) at 1815 cm(-)(1) and PbD(4) at 1302 cm(-)(1) is in agreement with the prediction of quantum chemical calculations for these unstable tetrahydride analogues of methane. In addition, new absorptions are observed for Pb(2)H(2) and Pb(2)H(4), which have dibridged structures based on quantum chemical calculations.