Halogen free synthesis of aminosilanes by catalytic dehydrogenative coupling
Compounds and method of preparation of Si—X and Ge—X compounds (X═N, P, As and Sb) via dehydrogenative coupling between the corresponding unsubstituted silanes and amines (including ammonia) or phosphines catalyzed by metallic catalysts is described. This new approach is based on the catalytic dehydrogenative coupling of a Si—H and a X—H moiety to form a Si—X containing compound and hydrogen gas (X═N, P, As and Sb). The process can be catalyzed by transition metal heterogenous catalysts such as Ru(0) on carbon, Pd(0) on MgO) as well as transition metal organometallic complexes that act as homogeneous catalysts. The —Si—X products produced by dehydrogenative coupling are inherently halogen free. Said compounds can be useful for the deposition of thin films by chemical vapor deposition or atomic layer deposition of Si-containing films.
1. A halogen free precursor compound having the formula:
where E=Si; n 1 =1; n 2 =1; k=1; R 1 and R 2 =silyl; R 3 and R 4 are independently selected from H, linear or branched C 1 to C 6 alkyl, linear or branched C 1 to C 8 alkenyl, linear or branched C 1 to C 8 alkynyl, C 6 to C 10 aryl, linear or branched C 1 to C 6 alkyl ether; and the detectable amount of halogen is less than 5 ppm.
2. The halogen free precursor compound of claim 1 , wherein R 3 and R 4 ═C 1 to C 6 alkyl.
3. The halogen free precursor compound of claim 2 , wherein R 3 and R 4 =Et.
4. The halogen free precursor compound of claim 2 , wherein R 3 and R 4 =iPr.
5. A method of preparing a precursor compound having the formula:
where E=Si, n 1 =1; n 2 =1; k=1; R 1 and R 2 =silyl; R 3 and R 4 are independently selected from H, linear or branched C 1 to C 6 alkyl, linear or branched C 1 to C 8 alkenyl, linear or branched C 1 to C 8 alkynyl, C 6 to C 10 aryl, linear or branched C 1 to C 6 alkyl ether; the amino groups may be bound to any E atom, comprising:
a) contacting the reactants R 1 R 2 NH and R 3 R 4 NH and E k H 2(k+1) in the presence of a transition metal catalyst forming a reaction mixture;
b) optionally adding a solvent to the reaction mixture;
c) maintaining the reaction mixture at a temperature between about 0° C. to about 300° C.;
d) allowing the reaction to proceed to form the (R 1 R 2 N) n1 (R 3 R 4 N) n2 E k H (2(k+1)−n1−n2) precursor compound;
e) separating the (R 1 R 2 N) n1 (R 3 R 4 N) n2 E k H (2(k+1)−n1−n2) precursor compound from the reaction mixture;
wherein the reaction mixture temperature may vary during the synthesis and is maintained such that the temperature of the reaction mixture is not allowed to drop below about 0° C. and not exceed about 300° C.
6. The method of claim 5 , wherein the catalyst is selected from the group consisting of Ru, Pd, Rh, Ir, Fe, Ni, Pt, Cr, Cu and Au.
7. The method of claim 5 , wherein R 3 and R 4 ═C 1 to C 6 alkyl.
8. The method of claim 7 , wherein R 3 and R 4 =Et.
9. The method of claim 7 , wherein R 3 and R 4 =iPr.