Older versions of MATLAB did have a slightly different syntax for the multcompare function which was:
This has been changed in later releases to:
but the latter is backwards compatible ... that is the former statement works in any version of MATLAB.
That being said you are passing in a vector containing 2 values, 1 and 2. Now alpha represents the significance level used in the hypothesis test. We can only perform the test at a single significance level, so you cannot pass in a vector as you do. Furthermore, it makes no sense to perform a hypothesis test at a significance level of 0 or 1, so the allowed range of value is (0,1).
Maybe try a reasonable significance level:
saida_multcompare, tabela_multcompare, stats_multcompare] = multcompare(stats_ANOVA, 0.05,'display','off');
If this was not what you intended, you will have to explain what you were trying to do with that function call above? What does [1,2] represent?