Access to metastable [GeH₂]_n materials via a molecular “bottom-up” approach

Abstract

The molecular precursor Ge(OtBu)2 was combined with soluble hydride sources to either yield metastable [GeH2]n materials (orange solids) or the deposition of nanoscale films of Ge from solution.

Molecular Sn(ii) precursors for room temperature deposition of crystalline elemental tin

“…of t BuOH (see Scheme 1). 10,11 Our improved route to [Sn(O t Bu) 2 ] 2 ( 1 ) presented here mirrors the synthesis of [Ge(O t Bu) 2 ] 2 reported by us, 6 where two sequential salt-elimination reactions are required. First, the addition of three equiv.…”

“…Interestingly, the free energy of the reaction (Δ r G ) involving Si was determined to be only 14.2 kJ mol −1 less favorable than that of the analogous Sn-based system. Given our recent interest in developing improved routes toward the deposition of Group 14 thin films, 6,8 future work in our lab will investigate the plausibility of preparing bulk samples of Si through similar processes.…”

“…Indeed, the crystallinity of the Sn metal obtained from a room temperature reaction is promising for future applications in device manufacturing. [6][7][8] This reaction method is also desirable as the resulting by-products (i.e., t BuOBpin, (Me 3 Si) 2 NBpin and H 2 ) are highly soluble and/or volatile substances that can easily be removed through washing or by vacuum. Detailed NMR studies were performed to identify the soluble products of each deposition reaction.…”

“…5 In recent work, our team combined [Ge(O t Bu) 2 ] 2 with hydridic boranes, such as pinacolborane (HBpin), to yield a metastable [GeH 2 ] x species, or films of elemental Ge upon treatment of [Ge(O t Bu) 2 ] 2 with excess H 3 B·SMe 2 at 70 °C. 6–8 Based on the hypothesis that the more polar Sn–O linkages in tin( ii ) alkoxides vs. the Ge–O bonds in their Ge counterparts will encourage enhanced reactivity, we now report the reactivity of the Sn( ii ) bis-alkoxide [Sn(O t Bu) 2 ] 2 and an adduct with N -heterocyclic carbene, ImMe 2 ·Sn(O t Bu) 2 (ImMe 2 = [(HCNMe) 2 C:]) with HBpin, leading to the room temperature deposition of crystalline tin from solution; likewise, amide/hydride metathesis involving reactant combinations of Sn[N(SiMe 3 ) 2 ] 2 and excess HBpin gave bulk Sn metal. Our solution-based routes to Sn metal provides alternatives to known gas/vapor phase methods, such as the use of SnH 4 in the formation of tin-containing materials by chemical vapor deposition.…”