I have no idea what your symbolic system is. See if the matlabFunction function will work to convert your ordinary differential equations to a form ode45 can use.
For helpful examples, use Search Answers and search using matlabFunction as the search string. There are probably hundreds of threads that begin with symbolic differential equations, then use odeToVectorField and matlabFunction to convert them to anonymous functions (or function files) that the ODE solvers can use.
