NEW BIDENTATE LIGANDS PPH2CH2C(BU(T))=NNR2 (R = H OR ME) AND PPH2CH2C(BU(T))=NN=CHPH AND THEIR COMPLEXES WITH GROUP-6 METAL-CARBONYLS

Treatment of tert-butylmethyl ketone dimethylhydrazone with LiBu, followed by PPh2Cl, gave the crystalline phosphino dimethylhydrazone PPh2CH2C(But)=NNMe2 2a having the C=NNMe2 group in the Z configuration. This phosphine with [Mo(CO)4(nbd)] (nbd = norbornadiene) gave [Mo(CO)4{PPh2CH2C(But)=NNMe2}] 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 [Mo(CO)4{PPh2CH2C(But)=N-NMe2}] 4, with a five-membered chelate ring and an E arrangement around C=NNMe2. When 3a was heated in diglyme [MeO(CH2)2O(CH2)2OMe] to ca. 150-degrees-C the phosphino imine complex [Mo(CO)4{PPh2CH2C(But)=NH}] 5 was formed. Compound 2a with hydrazine gave the corresponding phosphino hydrazone 2c, containing a C=NNH2 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 [M(CO)4{PPh2CH2C(But)=NNH2}] (M = Mo 3d, W 3e or Cr 3f). When 3d was heated in diglyme to ca. 150-degrees-C it also gave complex 5. The oxidation of molybdenum(0) complex 3d with bromine gave the seven-co-ordinate molybdenum(II) complex [MoBr2(CO)3{PPh2CH2C(But)=NNH2}] 6. Compound 2c was condensed with benzaldehyde to give the phosphino mixed-azine PPh2CH2C(But)=NN=CHPh 7a, which with H2O2 formed the phosphine oxide 7b. The phosphine 7a reacted with [M(CO)4(nbd)] to give [M(CO)4{PPh2CH2C(But)=NN=CHPh}] (M = Mo 8a, W 8b or Cr 8c). Complex 8a with bromine gave the seven-co-ordinate molybdenum(II) complex [MoBr2(CO)3{PPh2CH2C(But)=NN= CHPh}] 9. Crystals of complex 3a are monoclinic, space group P2(1)/n with a = 892.3(1), b = 1920.1(3), c = 1493.6(3) pm, beta = 105.67(1)-degrees and Z = 4, R = 0.0250 for 3530 observed reflections. The structure shows that the C=NNMe2 group has the Z configuration and that the NMe2 group is co-ordinated to molybdenum, giving a six-membered ring.