[Kolokotronis]

"Many Orthodox deny the validity of Catholic sacraments: baptisms, eucharists, ordinations, etc."

Other than some non-canonical ecclesial assemblies which self describe as Orthodox, I am unaware of any Orthodox Church which holds this position. About whom are you speaking?

[SaltyJoe]

"Many Orthodox deny the validity of Catholic sacraments...

I'm not aware of this either. I've only seen the Orthodox and Catholic differences as a different flavors of salt (yep, salt tastes differently around the world depending on where it comes from).