Hmmm... Can you put the following code into it's own R chunk or run it from the console by itself? What is the output?
min(log(Datos$TotalWorkingYears), na.rm=TRUE)
(This alone shouldn't give the from error because you aren't asking to create a sequence here.)
Also, could you post the Datos$TotalWorkingYears vector (depending how long it is)?
To be clear, I suspect the problem is with the data itself, not your code, as the following seems to work fine:
x<- seq(min(log(airquality$Ozone), na.rm=TRUE) , max(log(airquality$Ozone), na.rm=TRUE), length=50)