\documentclass{article}
\usepackage{xymtex}
\usepackage{chemist}
\pagestyle{empty}
\begin{document}

\tetrahedral{0==C;1==\utrigonal{0==C;1==(yl);3D==O;2==O$^-$};2==$^+$H$_3$N;3==\tetrahedral{0==C;1==(yl);2==H;4==H;
3==\dtrigonal{0==C;1==(yl);2==O$^-$;3D==O}};4==H}

\end{document}
