cron - minimize skype after autostart

"Launch skype in the background" is not an option now so I'm trying to bypass it. I tried to add this line to the autostart file:

&& sleep 5 && xdotool windowminimize $(xdotool search --onlyvisible --class Skype)

but this command opens skype as an empty window and I dunno why.

I tried to make a cron:

@reboot sleep 60 && xdotool windowminimize $(xdotool search --onlyvisible --class Skype)

It doesn't work as well and I dunno why.

Can you tell me why these options doesn't work for me and how to make them behave itself? :D

Tnank you!

I updated to 17.10 and switched from Unity to Gnome. It fixed the problem.