using a complex dilation on a figure I know that a dilation increases or decreases a figure, and a negative amount inverts it through a point, but what about an imaginary dilation? is it possible?

Good question. Yes, with the correct interpretation it is indeed possible. That interpretation happens in the complex number plane.

There multiplication by a positive real number is a dilation. Multiplication by $-1$ is an inversion.

Multiplication by an arbitrary complex number is a rotation and a dilation. You can see the amounts by writing the number in polar form.

The two examples you started with are special cases, the first when the angle is $0$, the second when the stretch is $1$ and the angle is $\pi$ (half a circle). Multiplication by $i$ is a turn through a quarter of a circle.

PS This question is similar to your other one, at rotational symmetry on a circle .