Cyclotriphosphorus Complexes: Solid-State Structures and Dynamic Behavior of Monoadducts with Carbonyl Fragments

Treatment of the cyclo-P3 complexes [(triphos)MP3] [triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane; M =
Co (1), Rh (2)] with stoichiometric amounts of [M‘(CO)5(thf)]n+ (n = 0, M‘ = Cr, Mo, W; n = 1, M‘ = Re) and
[W(CO)4(PPh3)(thf)] yields the compounds [{(triphos)M}(μ,η3:1-P3){M‘(CO)5}] [M = Co; M‘ = Cr (3a), Mo
(3b), W (3c). M = Rh; M‘ = W (4)], [{(triphos)Co}(μ,η3:1-P3){Re(CO)5}]BF4·C7H8 (5) and [{(triphos)Rh}(μ,η3:1-P3){W(CO)4PPh3}]·2CH2Cl2 (6). The X-ray structures of 5 and 6 have been determined. Crystal data:  5,
monoclinic space group P21/n, a = 14.754(2) Å, b = 24.886(4) Å, c = 15.182(2) Å, β = 103.38(1)°, Z = 4; 6,
monoclinic space group P21/n, a = 14.872(3) Å, b = 27.317(6) Å, c = 16.992(4) Å, β = 111.75(5)°, Z = 4. The
effects of η1 coordination on the MP3 core are discussed by comparing the MP3 skeletons in the above structures
with those of the previously characterized bis and tris end-on adducts of organometallic fragments of 1. Variable
temperature NMR data for the compounds provide evidence for fluxional processes in solution that may be
interpreted as {(triphos)M} rotation about its C3 axis and {M‘(CO)5} or {M‘(CO)4PPh3} scrambling over the P3
cycle. The activation parameters of the fragment scrambling process are determined.