In terms of bonding, isocyanates are closely related to carbon dioxide (CO) and carbodiimides (C(NR)).  The C−N=C=O unit that defines isocyanates is planar, and the N=C=O linkage is nearly linear.  In phenyl isocyanate, the C=N and C=O distances are respectively 1.195 and 1.173 Å.  The C−N=C angle is 134.9° and the N=C=O angle is 173.1°.