The 3-dimensional abelian complex is C3\mathbb C^{3} with its usual vector-space operations and identically zero bracket:

[x,y]=0for all x,y.[x,y]=0\qquad\text{for all }x,y.
Morphisms

Every complex-linear map to another abelian complex preserves the bracket. Hence endomorphisms form M3(C)M_{3}(\mathbb C) and automorphisms are the invertible matrices. A homomorphism from an arbitrary Lie algebra to this object must kill every commutator.