Chromium(III) complexes of multidentate phosphines, arsines, and thioethers. Crystal and molecular structure of the complex mer-[Cr{P(CH2CH2PPh2)3}Cl3

Abstract

Octahedral chromium(III) complexes mer-[CrLX3]{X = Cl or Br; L = PPh(CH2CH2PPh2)2, P(CH2CH2PPh2)3, [–CH2P(Ph)CH2CH2PPh2]2, or S(CH2CH2CH2SMe)2} and fac-[CrLX3][L = CMe(CH2PPh2)3, CMe(CH2AsMe2)3, CMe(CH2SMe)3, AsMe(CH2CH2CH2AsMe2)2, or As(CH2CH2CH2AsMe2)3] have been prepared from [Cr(thf)3X3](thf = tetrahydrofuran) and L in CH2Cl2 under anhydrous conditions. Chromium(III) fluoride complexes [CrLF3][L = PPh(CH2CH2PPh2)2, P(CH2CH2PPh2)3, or CMe(CH2AsMe2)3] are obtained by reaction of [Cr(thf)3Cl3] with AgF in thf, followed by addition of the ligand. The reactions with [Cr(thf)3I3] differ in that both [CrLI3][L =e.g. PPh(CH2CH2PPh2)2 or CMe(CH2AsMe2)3] and CrL2l3 can be isolated depending upon the Cr : L ratio. The [CrLX3] complexes, which have been characterised by i.r. and electronic spectroscopy, conductance and molecular weight measurements, have P3X3, As3X3, or S3X3(X = F, Cl, Br, or l) donor sets. The electronic spectra were analysed to produce Dq, B′, and β35. Treatment of [CrLCl3]{L = P(CH2CH2PPh2)3, As(CH2CH2CH2AsMe2)3, or [–CH2P(Ph)CH2CH2PPh2]2} with AgBF4 in CH2Cl2 produced cis-[CrLCl2]BF4(P4Cl2 or As4Cl2 donor sets). The title complex is monoclinic, a= 14.787(6), b= 21.617(4), c= 14.474(4)A, β= 113.43(3)°, and Z= 4; space group p21/a(no. 14). 2101 Reflections were refined to R= 0.075 (R′= 0.079). The molecular complex has a mer octahedral structure (P3Cl3 co-ordination) with Cr–P(Ph2) 2.466(5) and 2.489(6); Cr–P(CH2)3 2.399(4); Cr–Cl 2.306(4), 2.292(6), and 2.320(5)A. The long Cr–P bonds are due both to the steric crowding, and the relatively weak binding of the phosphorus donors to the hard metal, and both these points are also evident in the electronic spectral parameters.