Francis P. McCullough

The coordination chemistry of molybdenum and tungsten. Part XIV. Dioxomolybdenum(VI) complexes of bidentate, tridentate, and tetradentate Schiff bases containing oxygen, nitrogen and sulphur donors

A large number of bidentate, tridentate, tetradentate Schiff base ligands containing oxygen, nitrogen, and sulphur donor atoms have been complexed to the cis-MoO2 moiety. The structures of the resulting complexes are postulated on the basis of infrared and proton n.m.r. arguments previously developed by Yamada. In the case of the complexes of the tetradentate ligands, the nature of the backbone between the imine groups determines which cis isomer is found.

Synthesis and properties of Group 5B ligand analogues of o-phenylenebis(dimethylarsine), o-C6H4(EMe2)(E′Me2) where E, E′= P, N, As, or Sb

Lithium dimethylphosphide prepared from lithium and PMe2Ph in tetrahydrofuran reacts with o-dichlorobenzene to produce o-phenylenebis(dimethylphosphine). Similar reactions using the appropriate o-bromophenyl derivatives o-C6H4Br(Y)(Y = NMe2, AsMe2, or SbMe2) yield o-C6H4(PMe2)Y. o-Phenylenebis(dimethylstibine) is best prepared from (o-bromophenyl)dimethylstibine and Na[SbMe2]. Preparations for the other members of the series, o-C6H4(AsMe2)(SbMe2), o-C6H4(AsMe2)(NMe2), and o-C6H4(SbMe2)(NMe2), and for (o-methoxyphenyl)- and (o-methylthiophenyl)-dimethylphosphine o-C6H4(PMe2)Z (Z = OMe or SMe) are reported. The 1H and 31P n.m.r. and mass spectra of the ligands, intermediates, and quaternary derivatives are reported and discussed.

Working haem analogues; reversible oxygenation of the manganese–tertiary phosphine complexes MnLX2

The reversible oxygenation of the complexes MnLX2(L = tertiary phosphine, but not PPh3, X = action) has been investigated; these complexes resemble haemoglobin and myoglobin to a remarkable degree as reversible dioxygen carriers.

The chemistry of molybdenum and tungsten. Part XIV. Oxomlybdenum(V) complexes of quinolines

Abstract Oxomolybdenum(V) complexes of substituted hydroxyquinolines have been obtained by the reaction of MoOCl 3 (THF) 2 (THF = tetrahydrofuran) with 8-hydroxyquinolidine, isoquinoline, 3-methylsoquinoline, 6-methylquinoline, 7-methylquinoline, 5,6-benzoquinoline, 8-mercaptoquinoline and 2,2′-biquinolyl. Various types of complexes have been isolated ranging from the simple substitution of two THF ligands to produce [MoOCl 3 (ligand) 2 ] to dimeric and possibly trimeric oxo-bridged species such as [Mo 2 O 3 Cl 4 (ligand) 2 ], [Mo 2 O 3 Cl 4 (ligand) 3 ] and [Mo 3 O 5 Cl 5 (ligand) 3 ]. An attempt is made to relate the steric bulk of the donors to the formation of polynuclear species. For complexes containing nitrogen donors e.p.r. g values are ∼1.94, and for sulphur involvement g = 1.967.

The coordination chemistry of molybdenum and tungsten. Part V. Open-chain tetrathioether complexes of molybdenum(IV) and (V) and tungsten(IV) and (V)

Abstract The tetrathioethers α, ω-bis(methylthioalkylthio)alkanes, CH 3 S(CH 2 ) n S(CH 2 ) m S(CH 2 ) n SCH 2 (n = m = 2; n = 2, m = 3; n = 3, m = 2, n = m = 3, ligand), yield seven-co-ordinate [MCl 4 (ligand) (M = Mo, W), seven-coordinate [WoCl 3 (ligand)] in which the thioethers act as tridentate ligands, and six-coordinate [MoOCl 3 ) 2 (ligand)] in which the ligand acts in a tetraligate bimetallic manner. 2-5-Dithiahexane (dth) similarly yielded [MCl 4 (dth)(RCN)] and [MoOCl 3 (dth)]. The electronic, infrared and electron paramagnetic resonance spectral properties of these complexes are reported and discussed.

Platinum metal complexes of the methoxyphenylstibines Ph3-nSb(o-MeOC6H4)n (n = 1, 2, 3,)o-Me2SbC6H4OMe and of Me2Sb(CH2)2O(CH2)2O(CH2)2SbMe2

Abstract The stibine-ether Me2Sb(o-C6H4OMe) (L) forms cis-[PdL2Cl2], cis-[PtL2Cl2], fac-[RhL3Cl3] and mer-[IrL3Cl3] which contain the ligand bonded only through antimony, and [RhL2Cl3] which contains one monodentate (Sb-coord) and one cheating (Sb- O) ligand. The latter complex reacts with CO to give [RhL2(CO)Cl3]. The Ph3-nSb(o-C6H4OMe)n (n = 1, 2, 3) form only mer-[RhL3Cl3] and mer-[IrL3Cl3]. For Pd(II) and Pt(II) the [ML2Cl2] complexes are trans when L = Sb(o-C6H4OMe)3, but cis with L = Ph2Sb(o-C6H4OMe). The potentially tetradentate Me2Sb(CH2)2O(CH2)2O(CH2)2SbMe (L′), behaves as a trans chelating bidentate in [PdL′Cl2], and coordinates only via the antimony. The preparations of RhL′Cl3, IrL′Cl3, RuL′(CO)Cl2 and (OsCl4)2L′·H2O are described. Infrared, electronic and 1H NMR spectra are reported for all the complexes.

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

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.

Diphosphine and diarsine complexes of chromium(III). Crystal and molecular structure of [NPrn4][Cr(cis-Ph2PCHCHPPh2)Cl4]

cis-[Cr(L–L)X4]– ions (X = Cl, Br, or I; L–L = diphosphine or diarsine) have been isolated as tetra-alkylammonium salts by reaction of [NR4]X, [Cr(thf)3X3](thf = tetrahydrofuran), and L–L. The reaction of [Cr(thf)3X3] with L–L′ in CH2Cl2 gave Cr(L–L′)1,5X3[L–L′=o-C6H4(AsMe2)2, o-C6H4(AsMe2)(PMe2), o-C6H4(NMe2)(PMe2), or o-C6H4(PMe2)(SbMe2)], which are formulated as trans-[Cr(L–L′)2X2]cis-[Cr(L–L′)X4]. In the case of o-C6H4(PMe2)2 only, it is possible to isolate both Cr[o-C6H4(PMe2)2]1,5X3 and [Cr{o-C6H4(PMe2)2}2X2]X depending upon the Cr : L–L ratio. The ligand Me2As(CH2)3AsMe2 gave Cr(L–L)1,5X3(X = Cl or Br) complexes for which a ligand-bridged structure is proposed [X3(L–L)Cr(L–L)Cr(L–L)X3]. Weaker donors (Ph2PCH2CH2PPh2, cis-Ph2PCHCHPPh2, or Ph2AsCH2CH2AsPh2) react with [Cr(thf)3X3] to give [Cr(L–L)2X3] which contain one uni- and one bi-dentate diphosphine or diarsine, and in the presence of moisture [Cr(L–L)(H2O)X3] can be isolated. The complexes [Cr(L–L)2X2]Y [X = Cl or Br; Y = ClO4– or PF6–; L–L =o-C6H4(AsMe2)2 or o-C6H4(PMe2)2] have also been obtained The complexes have been characterised by analysis, conductance, i.r. and electronic spectroscopy, and the electronic spectra analysed (d3) to produce Dq, B′, and β35. The title complex is triclinic, a= 17.534(3), b= 11.930(2), c= 11.108(3)A, α= 116.30(2), β= 75.12(2), γ= 110.61(1)°, and Z= 2; space group P(no. 2). 1 757 Reflections were refined to R= 0.0656 (R′= 0.0658). The structure consists of tetrahedral NPrn4+ cations, and pseudo-octahedral [Cr(Ph2PCHCHPPh2)Cl4]– anions. In the anion Cr–P = 2.485(4) and 2.511(4)A; Cr–Cl = 2.331 (4), 2.31 9(4), 2.31 8(4), and 2.31 6(4)A; P–Cr–P = 81.2°. The diphosphine does not exert any trans influence, consistent with weak binding to the hard CrIII ion.

The chemistry of molybdenum and tungsten. Part 7. Oxomolybdenum(V) and oxotungsten(V) complexes of neutral aromatic Schiff-base ligands

A series of oxomolybdenum(V) and oxotungsten(V) complexes of potentially quadridentate (N2O2 donor set) and quinquedentate (N3O2 donor set) Schiff-base ligands, [MOCl3(H2L)](M = Mo or W), has been prepared in which the ligands bind only via the imine nitrogens, acting as neutral N2 donors in contrast to the usual binding of these ligands as dianionic N2O2 or N3O2 species. With small chelate backbones between the imine groups the resulting [MOCl3(H2L)] complexes appear to be monomeric, and whilst i.r. spectra do not enable a choice to be made between mer and fac structures we have employed e.s.r. results, notably using a series of specially synthesised model complexes, to deduce that these complexes have a mer configuration. With long chelate backbones (six carbon atoms) between the imine groups it is suggested that the [MOCl3(H2L)] complexes are dimeric and contain at least two isomeric forms. The molybdenum(V) complexes exhibit giso values in fhe range 1.934–1.945 and the tungsten(V) complexes in the range 1.72–1.80.