Mechanistic Insight into the Reaction of Phenyl Isocyanate with Ditungsten Hexa-tert-butoxide: Isolation and Characterization of Early Intermediates

Article abstract of DOI:10.1021/ja00302a011

By working at low temperature (-80 to -45 deg C) the purple crystalline compound W2(OCMe3)6*(μ-PhNCO) (1), which is known to be a precursor in the preparation of W2(OCMe3)4*<μ-PhNC(OCMe3)O>2 (2) from W2(OCMe3)6 and PhNCO, has been isolated and its structure determined.The molecule consists of a (RO)3W=W(OR)3 (R = tert-butyl) moiety (W-W = 2.488(1) Angstroem) bridged by the PhNCO molecule and the structure is quite similar to that of W2(OR)6*(μ-tolylNCNtolyl) recently reported by us.Compound 1 will react with additional PhNCO at temperatures above -15 deg C to give 2.It has also been found that 1 reacts with PMe3 to give W2(OR)5(PMe3)<μ-PhNC(OR)O> (3), which has also been structurally characterized.The molecule contains a (RO)3W<*>W(OR)2PMe3 moiety bridged by the bidentate PhNC(OR)O(-) ligand.Crystallographic data for the two compounds are as follows. 1: P2₁/c; a=11.054(6) Angstroem, b=17.821(7) Angstroem, c=19.401(8) Angstroem, β=100.52(2) deg; V=3758(2) Angstroem³, Z=4. 3: P1; a=10.2916(6) Angstroem; b=21.1376(7) Angstroem, c=22.0929 Angstroem, α=117.04(1) deg, β=90.33(4) deg, γ=93.73(4) deg; V=4268.2(3) Angtroem³; Z=4.Mechanistic pathways for the formation of 2 are discussed critically in the light of the new structural information.