The reaction of [(C3Ph3)Ni (PPh3),]C104 with P (CH2CH2PPh2)3 (pp3) and NaBPh4 yields the [(C3Ph3)Ni (pp3)]BPh4-complex. After long exposure of the solution of this compound in acetone/butanol to the air a new derivative [(C3Ph3)-Ni (pp2po)]BPh4 .0.5 C4H90H, where pp2po is (Ph,PCH2CH2),P (CH2CH2POPh2), is obtained. Complete X-ray analysis has been carried out for the latter complex: a= 18.303 (5); b= 29.445 (6), c= 13.305 (5) A, p= 112.70 (9)"; space group monoclinic, P21/a, Z = 4 . Disorder problems were encountered in the refinement of the structure. The best R is 0.093. One of the arms of the parent pp3-molecule, not coordinated to the metal, undergoes oxidation. The Ni-atom, coordinated by the three remaining P-atoms of the ligand, is also linked in a roughly v3-mode to the cyclopropenium ligand. The geometry of the molecule is examined in detail. Extended HMO-calculations were performed to interpret how the variation of P-Ni-P angles affects the bonding between the Nip3-and C3H3-fragments. The conclusion is that the overall energy of the complex may be lowered in spite of a weakening of the Ni-cyclopropenium linkage. Extensions are made to other systems containing a linkage between a metal and a X3-ring (X= P, As).