How do I solve for one variable in terms of other variables in Mathematica?

I'm fairly new to Mathematica, and I'm trying to solve a complicated equation with multiple variables. I've tried the following...

Reduce[-2 (m^2/36 + n^2/4)^(1/4) Sin[1/2 ArcTan[n/2, -(m/6)]] == y, {n}]


Where I would like to have n on one side of the equation, defined by m and y. Is this the correct notation and I just need to wait longer for the equation to solve? Or am I making a mistake somewhere?

-
I'd only be able to use an analytical solution for the next part of my problem. So if an equation is too complicated for Mathematica will it say so? Or just never output an answer? –  Tait Jul 29 at 7:20

Solve[FullSimplify[TrigToExp[-2 (m^2/36 + n^2/4)^(1/4) Sin[1/2 ArcTan[n/2,-(m/6)]]==y]],n]

{{n -> (m^2 - 9 y^4)/(18 y^2)}}