Complexes of an azine diphosphine with Group 6 metal carbonyls: crystal structures of Z,Z-PPh2CH2C(But)N–NC(But)CH2PPh2 and [Mo(CO)3(E,Z-PPh2CH2C(But)N–N(But)CCH2PPh2)]

Abstract

Treatment of the azine MeC(Bu^t)NNC(Bu^t)Me with 2 equivalents of LiBuⁿ, followed by 2 equivalents of PPh₂Cl, gives the azine diphosphine Z,Z-PPh₂CH₂C(Bu^t)N–N(Bu^t)CCH₂PPh₂1. This new diphosphine was treated with H₂O₂ to give the corresponding diphosphine dioxide 2a and with monoclinic sulfur to give the diphosphine disulfide 2b. Treatment of [M(CO)₃(η⁶-cht)](cht = cyclohepta-2,4,6-triene) with 1 gave the metal tricarbonyl fac-[[graphic omitted]Ph₂}](M = Mo, 3a; W, 3b; or Cr, 3c) in which the azine diphosphine is bonded in the E,Z configuration. Complexes 3a and 3b were also made by treating the corresponding metal hexacarbonyls with the azine diphosphine 1. Treatment of [M(CO)₄(nbd)](M = Mo, W, or Cr; nbd = norbornadiene) with 1 gave the tetracarbonyl complexes [[graphic omitted]Ph₂}]4 with the E,Z-azine diphosphine acting as a bidentate ligand. On heating, these tetracarbonyl complexes 4 were converted into the tricarbonyl complexes 3. Treatment of either 3a or 4a with 1 mol equivalent of bromine gave the neutral molybdenum(II) complex [[graphic omitted]Ph₂}]5, whereas the tungsten complexes 3b and 4b with bromine gave the cation [[graphic omitted]Ph₂}]⁺ isolated as its BPh₄^– salt 6. Proton, ¹³C-{¹H} and ³¹P-{¹H} NMR and infrared data are given. Crystals of 1 are monoclinic, space group P2₁/n, with a= 1667.2(2), b= 572.85(6), c= 1811.0(2) pm, β= 111.595(8)° and Z= 2; final R factor 0.0519 for 2049 observed reflections. Crystals of 3a are monoclinic, space group P2₁/n, with a= 985.7(1), b= 1870.2(2), c= 2220.8(2) pm, β= 93.71(1)° and Z= 4, final R factor 0.0354 for 5219 observed reflections.