Palladium(II) and platinum(II) complexes of a chiral pentacyclic phosphine, (1S, 4R, 4aS, 5aR, 6R, 9S, 9aS, 10aR)-4,6,11,11,12,12-hexamethyl-10-phenyl-dodecahydro-1,4:6,9-dimethano-phenoxaphosphinine (phenop), show diverse structures dependent upon the chosen metal-containing starting material and reaction conditions. With palladium acetate, a P,C-cyclometallated dimeric complex [Pd(μ-κ²-OAc)(μ-κ¹-OAc)(κP,κC¹⁴-phenop)]₂, 4, is obtained through metallation at the C(14) methyl to form a six-membered chelate. The acetato bridged dimer is readily converted to the halo-bridged species [Pd(μ-X)(κP,κC¹⁴-phenop)]₂, where X is chloride (5) or bromide (6). Reaction of one equivalent of phenop with Pd(COD)Cl₂ or Na₂PdCl₄ gives a different phosphapalladacycle dimer [Pd(μ-Cl)(κP,κC⁸-phenop)]₂, 7, with a five-membered chelate and metallation at the C(8) methylene carbon. The analogous platinum derivative [Pt(μ-Cl)(κP,κC⁸-phenop)]₂, 8, is obtained from the 1 ∶ 1 reaction of phenop and K₂PtCl₄. An unusual ligand–ligand coupled product, 9, has been isolated in low yield from the reaction of phenop and Pd(COD)Cl₂. The zerovalent Pd(κP-phenop)₂, 10, and a monodentate silver(I) derivative, [Ag(κP-phenop)(CF₃SO₃)], 11, have also been prepared. These new complexes have been fully characterised by spectroscopic and other techniques including single crystal X-ray structure determinations of phenop, 7–9 and 11.