Find the number of molecules which are not having $3\mathrm{c}-2\mathrm{e}$ bond from the following.

${\mathrm{Al}}_2{\left({\mathrm{CH}}_3\right)}_6,{\mathrm{Si}}_2{\mathrm{H}}_6,{\mathrm{B}}_2{\mathrm{H}}_6,{\mathrm{C}}_2{\mathrm{H}}_6,{\mathrm{Si}}_2{\mathrm{Cl}}_6,{\mathrm{Al}}_2{\mathrm{Cl}}_6$

A three-center two-electron (3c–2e) bond is an electron-deficient chemical bond where three atoms share two electrons. So the number of molecules which are not having 3c-2e bond are ${\mathrm{Si}}_2{\mathrm{H}}_6,{\mathrm{C}}_2{\mathrm{H}}_6,{\mathrm{Si}}_2{\mathrm{Cl}}_6,{\mathrm{Al}}_2{\mathrm{Cl}}_6$.