Ab initio MP2/aug'-cc-pVTZ calculations have been carried out on the pnicogen-bonded complexes HnF(5-n)P:N-base, for n = 0-5 and nitrogen bases NC(-), NCLi, NP, NCH, and NCF. The structures of these complexes have either C-4v or C-2v symmetry with one exception. P-N distances and interaction energies vary dramatically in these complexes, while F-ax-P-F-eq angles in complexes with PF5 vary from 91 degrees at short P-N distances to 100 degrees at long distances. The value of this angle approaches the F-ax-P-F-eq angle of 102 degrees computed for the Berry pseudorotation transition structure which interconverts axial and equatorial F atoms of PF5. The computed distances and Fax-P-Feq angles in complexes F5P:N-base are consistent with experimental CSD data. For a fixed acid, interaction energies decrease in the order NC(-) > NCLi > NP > NCH > NCF. In contrast, for a fixed base, there is no single pattern for the variations in distances and interaction energies as a function of the acid. This suggests that there are multiple factors that influence these properties. The dominant factor appears to be the number of F atoms in equatorial positions, and then a linear F-ax-P...N rather than H-ax-P...N alignment. The acids may be grouped into pairs (PF5, PHF4) with four equatorial F atoms, then (PH4F, PH2F3) with F-ax-P...N linear, and then (PH3F2 and PH5) with Hax-P...N linear. The electron-donating ability of the base is also a factor in determining the structures and interaction energies of these complexes. Charge transfer from the N lone pair to the sigma* P-Aax orbital stabilizes HnF(5)-nP:N-base complexes, with Aax either Fax or Hax. The total charge-transfer energies correlate with the interaction energies of these complexes. Spin-spin coupling constants (1p)J(P-N) for (PF5, PHF4) complexes with nitrogen bases are negative with the strongest bases NC- and NCLi but positive for the remaining bases. Complexes of (PH4F, PH2F3) with these same two strong bases and H4FP:NP have positive (1p)J(P-N) values but negative values for the remaining bases. (PH5, PH3F2) have negative values of (1p)J(P-N) only for complexes with NC(-). Values of (1J)(P-Fax) and (1J)(P-Hax) correlate with the P-Fax and P-Hax distances, respectively.