Chemistry of 2H-azaphosphirene complexes, 20 - Study on the ring formationof 2H-azaphosphirene complexes using sterically demanding C-2,4,6-trialkylphenyl-substituted aminocarbene tungsten complexes - Detection of a key intermediate

The synthesis of C-2,4,6-trialkylphenyl-substituted ethoxy- and aminocarben e tungsten complexes 1a-c (R = Me, iPr and tBu) and 2a,b (R = Me, iPr) and the reaction of 2a,b with [bis(trimethylsilyl)methylene]chlorophosphane (3) in the presence of triethylamine is reported. The reaction course, which f inally leads to the 2H-azaphosphirene complexes 7a,b, depends strictly on t he steric demands of the aryl group bonded to the carbene atom; only in the case of complex 2a was a dinuclear tungsten carbene complex formed, which was isolated and characterized by single crystal X-ray diffraction. Relativ e to phenyl-substituted derivatives, the 2H-azaphosphirene complexes 7a,b s howed enhanced reactivity towards triethylammonium chloride, furnishing the [bis(trimethylsilyl)methyl]chlorophosphane complex 8. Condensation of 8 wi th complex 2a afforded the novel dinuclear tungsten complex 9a containing a n acyclic C,N,P structural unit with a kappa-C and a kappa-P coordination m ode; an H-bonded adduct of complex Sa and mesitylnitrile, complex 10, was i nvestigated by single crystal X-ray diffraction.