Preparation and 31P DNMR studies of homodinuclear and cis-mononuclear complexes of Ph 2PNSNPPh 2: crystal structure of cis-Cr(CO) 4(Ph 2PNSNPPh 2)·0.5C 6H 6

Abstract

The reaction of K 2SN 2 with ML n (Ph 2PCl) (ML n = Cr(CO) 5, Mo(CO) 5, MnCp′(CO) 2 (Cp′ = methylcyclopentadienyl)) yields complexes of the type L n MP(Ph) 2NSN(Ph) 2PML n in which the bridging ligand adopts a cis,trans conformation and is coordinated through the phosphorus atoms to the two metal centres. In solution these complexes undergo a cis,trans → trans,cis interconversion, and a 31P DNMR study has provided the activation energies for this process ( E a = 10.1 (M = Cr), 9.8 (M = Mo) and 13.4 (M = Mn) ± 0.2 kcal mol −1). The 31P chemical shifts, infrared frequencies (ν as and ν s (NSN)) and visible absorption maxima for this series of complexes are discussed in terms of the observed activation energies. The reaction of K 2SN 2 with cis-ML n (Ph 2PCl) 2 (ML n = Cr(CO) 4 or Mo(CO) 4) gives complexes of the type cis-ML n (P(Ph) 2NSN(Ph) 2P) in which the chelating cis,cis ligand is coordinated to the metal via both phosphorus atoms. The structure of cis-Cr(CO) 4(P(Ph) 2NSN(Ph) 2P)·0.5C 6H 6 has been determined by X-ray crystallography. Crystal data: triclinic, space group P 1 , a 9.878(1), b 12.240(1), c 12.610(2) Å, α 87.795(9), β 77.018(10), γ 81.027(9)°, V 1467.6(6) Å 3, Z = 2. The structure was solved by direct methods and refined by least-squares techniques to give a final R = 0.034 and R w = 0.036. The geometry around the chromium atom is approximately octahedral, but the planar, chelating PNSNP ligand is tilted at an angle of 126.7° with respect to the plane containing the C 2CrP 2 unit. The PN bond distances are both 1.727(2) Å; the SN distances are 1.525(2) and 1.523(2) Å; the angles at the nitrogen atoms are 129.4(1) and 128.8(1)° and the angle at sulphur is 123.0(1)°.