We report a method for converting white phosphorus (P4) directly into tetra- and pentaphosphanes using N-heterocyclic carbene (NHC) copper(I) complexes. The insertion of P4 into the metal-element bonds of the NHC complexes (6Dipp)Cu(Nu) [Nu = OtBu and N(iPr)2] affords [(6Dipp)Cu(κ2-P4OtBu)] (1) and [(6Dipp)Cu{κ2-P4N(iPr)2}] (3), which exhibit rotation of the [P4Nu]− ligand around the copper center in solution. This fluxional process is suppressed at low temperature, as shown by variable-temperature 31P{1H} NMR spectroscopy. Treatment of 1 with W(CO)5(thf) resulted in the formation of the bimetallic complex [(6Dipp)Cu(μ,κ2:κ1-P4OtBu){W(CO)5}] (2) which does not show fluxional behavior. Reactions of 1 and 3 with p-block element halides release metal-free asymmetrically substituted bicyclo[1.1.0]tetraphosphabutane ‘butterfly’ compounds. The polyphosphanes P4(PMes2)(OtBu) (4a), P4[P{N(iPr)2}2](OtBu) (4b), P4[P{N(iPr)2}2]{N(iPr)2} (4c), and P4(BPh2){N(iPr)2} (5) were isolated as stable compounds. Treatment of 4c with the NHC IMes induces further phosphorus–phosphorus bond cleavage and rearrangement to give NHC-phosphinidene adduct [cyclo-P3{N(iPr)2}(P{N(iPr)2}2)(P═IMes)] (6). Compound 4c also reacts with W(CO)5(thf) and CuBr·SMe2 to give coordination complexes [W(CO)5{κ1-P4(P{N(iPr)2}2)(N{iPr}2)}] (7) and [Cu(Br){κ2-P4(P{N(iPr)2}2)(N{iPr}2)}] (8), respectively, demonstrating the ability of 4c to serve as a mono- and bidentate ligand for transition metals. All compounds were characterized crystallographically and spectroscopically.