It appears that you generated just one row of the desired 18 x 18 matrix. Why not generate a row of 18*18=324 complex numbers and then partition the result into a matrix? Something like this slight modification to your code should work.
datos = Partition[
Riffle[RandomVariate[NormalDistribution[], 18^2],
RandomVariate[NormalDistribution[], 18^2]], 2];
Partition[Apply[Plus, {#[[1]], #[[2]]*I} & /@ datos, 1],
18] // MatrixForm