<p:commandButton update="panel1"  actionListener="#{bean.button1}" value="button1" disabled="#{bean.disable}"> 

     <f:setPropertyActionListener value="#{false}" target="#{bean.disable}"/>   

 </p:commandButton> 

​

​

 <p:commandButton update="panel2"  actionListener="#{bean.button2}" value="button1" disabled="#{!(bean.disable)}"> 

     <f:setPropertyActionListener value="#{true}" target="#{bean.disable}"/>    

 </p:commandButton>