In Search of Fulminate Analogues: L_n M≡CP=NR

The "CPNR" ligand may be viewed as being isolobal with fulminate, CNO; however, attempts to prepare a complex of such a ligand resulted instead in a range of novel imino and aminophosphinocarbyne complexes. Sequential treatment of [Mo(≡CBr)(CO)₂ (Tp*)] (Tp*=hydrotris(dimethylpyrazolyl)borate) with nBuLi and ClP=NMes* (Mes*=C₆ H₂ tBu₃ -2,4,6) afforded mixtures of the complexes [Mo(≡CPnBuNHMes*)(CO)₂ (Tp*)] and traces of the bimetallic products [Mo₂ {μ₂ -C₂ P₂ O(NHMes)₂ }(CO)₄ (Tp*)₂ ] and [Mo₂ (μ₂ -C₂ PNHMes)(CO)₄ (Tp*)₂ ]. The reaction of [W(≡CBr)(CO)₂ (Tp*)] with nBuLi and ClP=NMes* afforded predominantly the mononuclear carbyne [W{≡CP(=NMes*)nBu₂ })(CO)₂ (Tp*)] and traces of the binuclear complex [W₂ (μ-C₂ PNHMes)(CO)₄ (Tp*)₂ ] which is also obtained when tBuLi is used. Although not isolable, the intended complexes [M(≡CPNMes*)(CO)₂ (Tp*)] could be generated in situ and spectroscopically characterized via the reactions of the stannyl carbynes [M(≡CSnnBu₃ )(CO)₂ (Tp*)] and ClP=NMes*. The preceding observations are mechanistically interpreted with reference to a computational interrogation of the model complex [Mo(≡CP=NCH₃ )(CO)₂ (Tp*)], the LUMO of which has considerable phosphorus character.