Base‐catalysed condensation of Ph2P–C5H5 (1) with an excess of acetone leads to a fulvene‐like diphenyl(4,4,6‐trimethyl‐4,5‐dihydropentalen‐2‐yl)phosphane Ph2P‐C11H13 (3) as a product of double condensation. Carbometallation of 3 with MeLi, followed by aqueous work‐up, results in formation of a new cyclopentadienylphosphane bearing a highly sterically demanding, anellated 1,1,3,3‐tetramethylcyclopentane moiety (4, Ph2P‐CpTMH). It reacts with chalcogene oxidants (H2O2, S8, Se) to form the corresponding phosphane chalcogenides Ph2P(=X)CpTMH, X = O (5), S (6), Se (7) in high yields. Quaternization of 4 with MeI gives the phosphonium salt 8 as a single isomer in high yield. Dehydrohalogenation of 8 by reaction with nBuLi gives CpTM‐phosphonium ylide Ph2P(CpTM)Me (9). An alternative protocol towards 9 that includes deprotonation of 8 with benzylpotassium followed by P‐alkylation is superior and gives 9 in more than 95 % yield. Staudinger reaction of 4 with tBuN3 gives onlyP‐amino‐cyclopentadienylidenephosphorane Ph2P(CpTM)NHtBu (10), whereas with Me3SiN3 only the tautomeric P‐imino‐cyclopentadienylphosphane Ph2P(NSiMe3)CpTMH (11) was isolated. Hydrolysis of 11 with wet MeCN leads to the new parent P‐amino‐cyclopentadienylidenephosphorane Ph2P‐(CpTM)NH2 (12). Treatment of 4 with benzylpotassium followed by transmetallation with FeCl2 leads to the sterically most crowded ferrocenyl‐bisphosphane [{Ph2P‐CpTM}2Fe] (13, dppfTM) in high yield. Its X‐ray diffraction analysis reveals an anti‐orientation of phosphane functionalities at both cyclopentadienyl rings. However, upon reaction of dppfTM with [PdCl2(MeCN)2], a constrained syn‐orientation is achieved in the product [{dppfTM}PdCl2] (14). Halogen exchange by reaction of 14 with NaI leads to the corresponding [{dppfTM}PdI2] (15). Molecular structures of 4, 9, 13 and 15 have been confirmed by XRD studies.