Preparation and reactions of nitrosyl complexes of molybdenum and tungsten; X-ray structure of trans-[Mo(OH)(NO)(Ph2PCH2CH2PPh2)2]·2C4H8O

Abstract

The nitrosyl complexes trans-[MX(NO)(dppe)₂](1; X = NCO, H, or OH; dppe = Ph₂PCH₂CH₂PPh₂; M = Mo or W) have been prepared by treating trans-[M(N₂)₂(dppe)₂] with MeN(NO)C(O)NH₂ in tetrahydrofuran (thf)(X = NCO), Et₂NNO in thf or thf–MeOH (X = H), or Et₂NNO in thf–K₂[CO₃](X = OH). The crystal structure of trans-[Mo(OH)(NO)(dppe)₂]·2thf shows the trans geometry and a linear MO–N–O system apparently with a rather long MO–N distance [1.985(7)Å] and rather short Mo–OH distance [1.922(8)Å]. A series of analogues (1; X = N₃, Cl, Br, I, or NCS) has been prepared by metathesis. Chemical oxidation of these compounds gives the complexes [MI(NO)(dppe)₂][I₃](from I₂), [MX(NO)(dppe)₂]Y (Y = FeCl₄, CuCl₂, or BF₄), [Mo(NO)(NCR)(dppe)₂][BF₄], and [Mo(NO)(NCR)(dppe)₂][BF₄]₂(Ag[BF₄] in RCN, R = Me or Ph). Halogen (Cl₂ or Br₂) oxidation of (1; X = Cl or Br) gives the compounds [MCl₂(dppe)₂] and [MBr₂(dppe)₂]Br. These reactions and other physical properties of the complexes are discussed in terms of their structural and electrochemical data and possible mechanisms for the formation of (1; X = OH or H) are considered.