The HEM.cif in  $Phenix/chem_data/mon_lib

has ideal angles of 1.337 for single bonds on the vinyl groups.

HEM   CAC     CBC   coval         1.337 0.02

HEM   CAB     CBB   coval         1.337 0.02

As far as I know these are single bonds and the ideal bond angles should be around 1.5.

-Yarrow