#K^+[Pb(OH)_3]^-# is the SALT of potassium ion, #K^+#, and the complex ion, #[Pb(OH)_3]^-#. I do not know whether this ion has been actually isolated and characterized; #[Pb(OH)_4]^(2-)# is better known. In either case, we could potentially exchange the potassium cation for other cations such as #Na^+# or #Li^+#, but probably not for #NH_4^+#, why not?