W2CL4(NR2)(2)(PR3')(2) MOLECULES .9. NEW MIXED-VALENT W-III W-IV FACE-SHARING BIOCTAHEDRAL COMPLEXES WITH CHELATING BIS(DIPHENYLPHOSPHINO)PROPANE AND DIALKYLAMIDO LIGANDS/

The triply-bonded ditungsten(III) species trans,trans-W2Cl4(NBu2n)(2)( dppp) (1) and a new mixed-valent W-III/W-IV complex (dppp) ClW(mu-Cl)( 3)WCl2(NBu2n) (3) have been isolated from the reaction of W2Cl4 (NBu2n )(2)(NHBu2n)(2) with 1,3-bis(diphenylphosphino)propane (dppp). A compl ex similar to 3, (dppp)ClW(mu-Cl)(3)WCl2(NEt2) (2), has also been prep ared. Both 2 and 3 are characterized by a W-2(7+) core and they adopt face-sharing bioctahedral geometry with a chelating dppp ligand. The W -W distances in 2 and 3 are both 2.660(1) Angstrom and each of them sh ows an EPR signal at g = 1.88. The structure of 1 contains a W-2(6+) c ore with a W-W distance of 2.3055(8) Angstrom. It has a bridging dppp ligand and a trans,trans stereochemistry. (C) 1997 Elsevier Science Lt d.