How is the π portion of the M=C bond in transition metals formed?

[plexus0208]

Homework Statement

Transition metal species are known that contain multiple metal-carbon bonds, for example, M=CH2. Describe how the π portion of the M=C bond would be formed using a pure d orbital on M and in what plane the protons on the CH2 group would lie. (A d orbital is employed because it is lower energy and because it extends out toward the carbon atom, which gives rise to better overlap with the orbital on C.) What hybrid orbitals could be employed to form the s portion of the M=C bond?

Homework Equations

The Attempt at a Solution

For the first part of the problem, I think you can use a dxz orbital on M when the carbon has a pz orbital. But what do they mean by what plane the protons on the CH2 group would lie? Also, advice on the last part of the question would be appreciated...

 

[chemisttree]

Pi bond is formed when the lobes of a p orbital overlap with 2 of the lobes of the d orbital. This would occur above and below the plane described by the three sigma bonds of the -CH2 group. There are 2 d orbitals on the metal that can interact in that way.

 

[plexus0208]

d_x^2-y^2 and d_z^2?