Mario,

you've answered your own question

Datasheet says 1101000+0 = address+write bit = D0 Hex

which is 68hex with another bit added on = D0 hex

i2c deals in bytes:

therefore to access a device you code must:

send start sequence
send address with r/w bit
.....
send stop sequence

therefore to read the device the address and r/w bit = D1 hex and to write the device the value is D0 hex (I could be back to front here!!)

no magic here my friend. You could've tried both values - at least one would've worked and there would be your answer.