New bidentate ligands PPh2CH2C(But)NNR2(R = H or Me) and PPh2CH2C(But)NNCHPh and their complexes with Group 6 metal carbonyls

Abstract

Treatment of tert-butylmethyl ketone dimethylhydrazone with LiBu, followed by PPh₂Cl, gave the crystalline phosphino dimethylhydrazone PPh₂CH₂C(Bu^t)NNMe₂2a having the CNNMe₂ group in the Z configuration. This phosphine with [Mo(CO)₄(nbd)](nbd = norbornadiene) gave [[graphic omitted]Me₂}]3a, with a six-membered chelate ring; the corresponding tungsten 3b and chromium 3c complexes were made similarly. When phosphine 2a was heated with [Mo(CO)₆] some 3a was formed together with the isomeric complex [[graphic omitted]NMe₂}]4, with a five-membered chelate ring and an E arrangement around CNNMe₂. When 3a was heated in diglyme [MeO(CH₂)₂O(CH₂)₂OMe] to ca. 150 °C the phosphino imine complex [[graphic omitted]H}]5 was formed. Compound 2a with hydrazine gave the corresponding phosphino hydrazone 2c, containing a CNNH₂ moiety, in over 90% yield. The phosphines 2a or 2c, with sulfur, gave the corresponding phosphine sulfides. The phosphine 2c with [M(CO)₄(nbd)] gave [[graphic omitted]H₂}](M = Mo 3d, W 3e or Cr 3f). When 3d was heated in diglyme to ca. 150 °C it also gave complex 5. The oxidation of molybdenum(0) complex 3d with bromine gave the seven-co-ordinate molybdenum(II) complex [[graphic omitted]H₂}]6. Compound 2c was condensed with benzaldehyde to give the phosphino mixed-azine PPh₂CH₂C(Bu^t)NNCHPh 7a, which with H₂O₂ formed the phosphine oxide 7b. The phosphine 7a reacted with [M(CO)₄(nbd)] to give [[graphic omitted]CHPh}](M = Mo 8a, W 8b or Cr 8c). Complex 8a with bromine gave the seven-co-ordinate molybdenum(II) complex [[graphic omitted]CHPh}]9. Crystals of complex 3a are monoclinic, space group P2₁/n with a= 892.3(1), b= 1920.1(3), c= 1493.6(3) pm, β= 105.67(1)° and Z= 4, R= 0.0250 for 3530 observed reflections. The structure shows that the CNNMe₂ group has the Z configuration and that the NMe₂ group is co-ordinated to molybdenum, giving a six-membered ring.