Not sure if this is the correct forum but here goes. I am trying to prove [Ta,Tb] = ifabcTc Where (Ta)bc = -ifabc and fabcare the structure constants for SU(3). I picked f123 and generated the three 8 x 8 matrices .. T1, T2 and T3. The matrices components are all 0 except for, (T1)23 = -i (T(1)47 = -i/2 (T1)56 = i/2 (T2)46 = -i/2 (T2)57 = -i/2 (T3)45 = -i/2 (T3)67= i/2 When I compute [T1,T2] I get 0. What am I missing?