The co-ordination chemistry of molybdenum and tungsten. Part 9. Oxomolybdenum-(IV) and -(V) complexes of methyl-substituted bidentate Group 5B ligands

Abstract

The preparation of oxomolybdenum(v) complexes [MoOCI,( L-L)] with the bidentate ligands (L-L) 1,3-bis(di-methy1phosphino)propane. 1.3-bis(dimethylarsino)propane. (3-dimethylphosphinopropyl)dimethylarsine, ophenylenebis(dimethy1arsine). and (2-dimethy1arsinophenyl)dimethylstibine are described. On the basis of their e.s.r. spectra the first three complexes have fac structures. Oxomolybdenum(1v) cations [MoO(CI) (L-L),] + have been prepared from [MoOCI,(PMe,Ph),] and L-L, and are shown by lH n.rn.r. to have trans-pseudo-octahedral structures. WE recently reported4 the synthesis of a range of oxomolybdenum(v) complexes of phenyl-substituted Oxomob!ybdenum(v) CompZexes.-The reaction of [Mo-' phosphorus and arsenic bidentate ligands, [MoOCl,-OCl,( thf),] (thf = tetrahydrofuran) with o-phenylene-(L-L)] , and their reduction under appropriate conditions bis(dimethy1arsine) (pdma) ,t (2-dimethylarsinopheny1)to oxomolybdenum(1v) cations, [MoO(Cl) (L-L),] +. The dimethylstibine (dmads), 1,3-bis(dimethylphosphino)properties of the complexes and the conditions under propane (dmpp) , 1 ,3-bis(dimethy1arsino) propane (dmap) , RESULTS AND DISCUSSION

Synthesis, properties and structural features of molybdenum(v) oxide trichloride complexes with neutral chalcogenoether ligands

“…The five complexes described have room temperature magnetic moments of ∼1.7 B.M., similar to other MoOCl 3 complexes, 1,2,8,9 and close to the spin-only value expected for a…”

“…19 In order to allow comparisons with the WOCl 4 , WOCl 3 , WSCl 4 and WSCl 3 chemistry, we have examined the chemistry of MoOCl 3 with neutral chalcogenoethers and report here complexes of mono-and bi-dentate thio-, seleno-and telluroethers. Data on diphosphine analogues, which clarifies some of the (inconsistent) earlier studies, [7][8][9] is also presented.…”

“…The IR spectra are significantly different to those of [MoOCl 3 (L-L)] (L-L = dithioether or diphosphine), 8,9 but are similar to those of [{MoOCl 2 (EMe 2 )} 2 (µ-Cl) 2 ]. In particular, the ν(MovO) vibrations are at higher frequency (985-1000 cm −1 ), and in addition to several terminal ν(Mo-Cl) modes ∼320-300 cm −1 , also show a peak ∼250 cm −1 , probably due to a chloride bridge.…”

“…This complex appears to be the first structurally characterised molybdenum-ditelluroether complex in a positive formal oxidation state of the metal; all previously reported complexes are substituted carbonyls. 33,34 Analogous complexes with some diphosphine and diarsine ligands have been reported, 8,9 and the structure of (the previously unknown) […”

“…[4][5][6] Interest in high oxidation molybdenum complexes bearing sulfur donor ligands stems in part from the presence of Mo-S coordination in the molybdenum-containing enzymes, nitrate reductase, sulfite oxidase and Fe-Mo nitrogenases which involve (anionic) cysteine or sulfide ligands. [4][5][6] The chemistry with neutral P-and As-donor ligands with Mo(V) has also been investigated, [7][8][9][10][11] but sulfur-based ligands were mostly represented by charged thiolate and dithiocarbamate ligands. [2][3][4] More recent work has reported a series of extremely moisture sensitive Mo(VI) complexes [MoO 2 X 2 (dithioether)] (X = Cl or Br; dithioether = RS(CH 2 ) 2 SR, R = Me, Et, i Pr), which have distorted octahedral structures with the sulfur donor atoms trans to MovO; 12,13 there are also some thia-macrocyclic analogues.…”