An Approach to Novel Complexes with a Tungsten−Phosphorus Triple Bond

Abstract

The metathesis reaction of [W2(OtBu)6] with tBuCP leads to the phosphido complex [(tBuO)3WP] (1), which can be stabilized when the reaction is carried out in the presence of Lewis acidic carbonyl complexes of the type [M(CO)5thf] (M = Cr, W). However, further reaction of the metathesis products [(tBuO)3WCtBu] and [(tBuO)3WP→M(CO)5] [M = W (4a), Cr (4b)] with tBuCP leads after subsequent 1,3-OtBu shift to the metallaphosphacyclobutadiene derivatives [(tBuO)2W2P(OtBu)] (2a) and [(tBuO)2WC(tBu)PP(OtBu)] [M = W (5a), M = Cr (5b)]. To prevent the latter, the bulky phosphaalkyne Ar‘CP (Ar‘ = 2,4,6-tBu3C6H2) was employed in the three-component reaction instead of tBuCP. Surprisingly here, a “head-to-tail” dimerization of Ar‘CP occurs to give the novel phosphinidene complexes [M(CO)4P(R‘)C(Ar‘)P] [M = Cr (6a), M = W (6b); R‘ = 2,4-tBu2-7-Me2-indanyl]. In the case of [W(CO)5thf], additionally, the complex [W(CO)22] (7) is formed. The function of [W2(OtBu)6] in this reaction is uncertain, but stoichiometric amounts of [W2(OtBu)6] are essential to obtain complex 6. Reduction of the size of the alkoxide ligands by the use of [W2(ONp)6] (Np = CH2tBu) in the three-component reaction with Ar‘CP leads to the trinuclear cluster compounds [W3(μ3-P)(μ-ONp)3(ONp)6] (8) and [W3(μ3-P)(μ-ONp)3(ONp)6] (9). The crucial step of the side-product free synthesis of the phosphido complexes 4 is the introduction of MesCP (Mes = 2,4,6-Me3C6H2) into the three-component system of [W2(OtBu)6], RCP, and [W(CO)5thf]. Comprehensive structural and spectroscopic data are given for the products. Furthermore, a 31P NMR experiment was conducted following the reaction of [W2(OtBu)6] with MesCP from −70 °C to ambient temperature. In the range of −60 to −40 °C, a singlet at 845 ppm with one pair of tungsten satellites (1JW,P = 176 Hz) was observed for the complex [(tBuO)3WP] (1).