I am trying to draw the following reaction schemes using the chemfig package
To draw the triangular scheme I used the commands
\setchemfig{scheme debug=false}
\schemestart
\chemfig{A \+ B}
\arrow(bb--cc){<=>[$\k_{1}$][$\k_{-1}$]}
\chemfig{C}
\arrow(@cc--P)[-135]P %
\arrow(@bb--@P)[-45] %[$\k_{0}$]
\schemestop
It sort of does the job but I can not write the rate constant $k_{0}$ and set P at the vertex of the triangle.
For the second scheme I used the code
\setchemfig{scheme debug=false}
\schemestart
\chemfig{A_1}
\arrow(aa--bb){[$k_{1}$][$k_{-1}$]}
\chemfig{A_2}
\arrow{->[*{0}$k_{22}$][]}[-90]\chemfig{P_2}
\arrow(@aa--pp)[-90]\chemfig{P_1}
\schemestop
As in the first scheme, I am unable to draw the rate constant $k_{21}$ besides the righthandside downarrow.