[Rutherford]

Whole problem uploaded. I am interested in the 2nd and 3rd question. Why do the NMR and IR spectra change for each compound? How is it explained?

[kriggy]

The spectra change because the safrole gets coordinated - ie. the the molecule and bonds change.
My guess would be that it gets coordinated by the π-bond electrons in bond between C9-C10 thats why you see the 100cm^-1 shift in IR spectra. Then safrole gets deprotonated at H5 and forms complex with 2 Pt atoms each coordinated by 1 molecule of safrole and 2 bridging Cl atoms. Then you get the complex with 1 Pt atom, I guess the shift in last NMR are due to different ligand in C complared to the B but Im not realy sure on this last one.
Hope it helps.

[Rutherford]

Great help. Everything fits.
What is the driving force for these reactions? I would say the trans effect. And it is not obeyed in the 3rd reaction because a bidentate ligand would lose one linkage, right?

[Radu]

    I think the driving force is the formation of entropically favorable chelated cycles, which show a great stability relatively to the starting ethene compound.
    Moreover, I think that the trans effect is not obeyed because , even if the trans series for ligands places aryls before pi-coordinated alkenes in order of increasing the trans effect, the platinum drowns the electrons from C5 aryl anion very closely to inner methal sphere( because aryl anion is a soft, highly polarizable anion). We can spot this from the NMR, where we can see that H6, even if the closest one to C5 anion, is the most deshielded).  So the aryl group directs the substitution, and aparently the trans effect isn't obeyed.