Bite angle βn for a chelated complex of dppf (A) [7]; [1]FCP and its dihedral angle α (B) [16]; [2]FCP and its dihedral angle α (C) [23,24]; phospha [1]FCP, where R = Ph, CH(Me)(NMe2) and R’ = NiPr2, Ph, tBu, Cl, etc. (D) [15]; arsa [1]FCP (E) [15]; azabora [2]FCP (F) [25]; aza [2]FCP, where ER’2 = SiMe2, SntBu2, SitBu2, and R = SiMe3 (G) [23]; azaphospha [2]FCP (H) [24]; azacarbaphospha [3]FCP (I) [24]; diazacarba [3]FCP with paramagnetic substituents (J) [26,28,29,30]; arylamino-1,3-diaza [3]ferrocenophanes (K) [26]; intermediate for photoinduced ROP of D (L) [15,27]; 1,1′-diisocyanatoferrocene (M) [31,32,33]; and 1,1′-dipthalimidoferrocene (N) [34,35].