Adducts of cyclotriphosphorus complexes: synthesis, solid state structure and solution behaviour of the bis-adducts [{(triphos)Co}(P3){M(CO)5}2] [triphos=MeC(CH2PPh2)3; M=Cr, Mo, W]

Treatment of [(triphos)CoP3] (1) [triphos=1,1,1-tris(diphenylphosphinomethyl)ethane] which has a pseudotetrahedral core formed by three unsubstituted phosphorus atoms and one cobalt, with an excess of Group 6 pentacarbonyl moieties affords the compounds [{(triphos)Co}(μ3,η3:1:1-P3){M(CO)5}2] [M=Cr (2), Mo (3), W (4)]. The notable features of the solid state structure of 4 are compared with those of the bischromium adduct 2. The variable temperature NMR data of the compounds are suggestive of three fluxional processes in solution which may be interpreted as {(triphos)Co} rotation about its C3 axis, {M(CO)5} scrambling over the P3 cycle and a concerted motion of the two {M(CO)5} fragments.