I think there would be plenty of complex organic molecules. I mean you basically have a planet wide Urey-Miller experiment running for millennia with no life to eat any of the molecules generated, so they'd just... build up. I can't remember where I read it (so you'll just need to take my word for it), but some scientist posited that the pre-biotic Earth's oceans may have had a foot or so of oily sludge floating on them.

But it's important to consider that, even though they aren't eaten, these generated compounds aren't just idly siting around on this pre-biotic Earth. Waves are whipping the ocean sludge into an emulsion on every shore line of the world, tide pools are filling, getting baked by the sun and then washed into the ocean again. Lightning strikes are electrolizing the sludge and lava from primordial volcanos is scorching it. Most importantly with no ozone layer the sun's UV is blasting the Earth, breaking apart molecules or crosslinking them together into new more complex molecules.