Metal-halogen Bonds Research Articles

Insertion of lsocyanides into niobium– and tantalum–halogen bonds

Isocyanides RNC (R = Me or But) insert into the metal–halogen bond of niobium and tantalum pentahalides or tantalum tribromide oxide to give the complexes [MX4{CX(NR)}(CNR)](A : M = Nb or Ta; X = Cl or Br; R = Me or But), [TaBr2{CBr(NMe)}3(CNMe)], and [TaBr2O{CBr(NMe)}(CNMe)]. The complex [NbCl4{CCl(NMe)}(CNMe)] gives the further insertion products [NbCl3{CCl(NMe)}2L1] on treatment with L1= MeNC or PPh3, but treatment of [MX4{CX(NBut)}(CNBut)] with L2= PPh3, PMe2Ph, or PMePh2, or L3= Ph2PCH2CH2PPh2 or cis-Ph2PCH = CHPPh2 displaces ButNC to give [MX4{CX(NBut)}L2](M = Ta, X = Cl or Br) and [MX3{CX(NBut)}L3]X (M = Ta, X = Br; M = Nb, X = Cl). The complex [TaBr3{CBr(NMe)}(dppe)]Br (dppe = Ph2PCH2CH2PPh2) has also been prepared from [TaBr5(dppe)]. Reaction of [NbCl3{CCl(NMe)}2(CNMe)] with Li[AlH4] gives dimethylamine but no higher amines. Hydrogen or deuterium chloride reacts with [NbCl4{CCl(NMe)}(CNMe)] to give a product with N–H or N–D bonds which could not be purified. The physical properties of these complexes are reported and their structures and possible mechanism of formation are discussed.

ChemInform Abstract: SEMI‐EMPIRICAL UHF‐MO STUDIES OF THE SPIN DISTRIBUTION AND THE BONDING CHARACTER OF IRON‐GROUP FLUORIDES AND SOME OTHER SIMILAR TRANSITION METAL HALIDES

CNDO- and INDO-type UHF-MO calculations are carried out on MF6n− (M=V(II), Cr(III), Mn(II), Fe(III), Ni(II)), NiCl64−, MnCl64−, MnCl42−, MnBr64−, and CuCl42−. The calculated spin fractions on the ligand orbitals agree well with the experimental values, with a few exceptions. Spin transfers to ligands are mainly attributed to the spin delocalization (SD) mechanism, except those to the 2s and 2pσ, orbitals of the F ligand in CrF63− and VF64−, in which spin transfer to those orbitals results from the spin polarization (SP) mechanism. Unpaired electrons are also transferred into the 4s and 4p orbitals of the central metal ion by the SP mechanism. The spin transfers to the ligand due to both the SD and SP mechanisms increase in the order of F<Cl<Br in MnX64− and NiX64−. The following characterisities of metal-halogen bonds are established; (1) the covalent interaction between the metal d-orbital and the fluorine atom increases in the order Ni(II)<Mn(II)∼ Fe(III)<Cr(III)∼V(II) in MF6n−, and (2) in metal-halogen...

Semi-empirical UHF-MO Studies of the Spin Distribution and the Bonding Character of Iron-group Fluorides and Some Other Similar Transition Metal Halides

Abstract CNDO- and INDO-type UHF-MO calculations are carried out on MF6n− (M=V(II), Cr(III), Mn(II), Fe(III), Ni(II)), NiCl64−, MnCl64−, MnCl42−, MnBr64−, and CuCl42−. The calculated spin fractions on the ligand orbitals agree well with the experimental values, with a few exceptions. Spin transfers to ligands are mainly attributed to the spin delocalization (SD) mechanism, except those to the 2s and 2pσ, orbitals of the F ligand in CrF63− and VF64−, in which spin transfer to those orbitals results from the spin polarization (SP) mechanism. Unpaired electrons are also transferred into the 4s and 4p orbitals of the central metal ion by the SP mechanism. The spin transfers to the ligand due to both the SD and SP mechanisms increase in the order of F&amp;lt;Cl&amp;lt;Br in MnX64− and NiX64−. The following characterisities of metal-halogen bonds are established; (1) the covalent interaction between the metal d-orbital and the fluorine atom increases in the order Ni(II)&amp;lt;Mn(II)∼ Fe(III)&amp;lt;Cr(III)∼V(II) in MF6n−, and (2) in metal-halogen covalent interactions, the s-character of halogen decreases in the order F&amp;gt;Cl&amp;gt;Br, while the p-character increases in the same order.

Reactions d'insertion de fluorogermylenes sur diverses liaisons σ. Nouvelles syntheses de derives polymetalles du groupe IVB

Difluorogermylene which exhibits a strong carbene activity gives many insertion reactions in σ bonds. In the same type of reactions, the lower reactivity of phenylfluorogermylene is generally similar to reactivity of the phenylchlorogermylene. The polymetallated derivatives of Group IVB metals formed by insertion reactions of these germylenes in σ bonds, like metalhalogen, metalhydrogen, metaloxygen, metalsulfur, metalnitrogen and metalmetal bonds, have low stability and thermally decompose via α-elimination processes to form germylenes and fluoro-organometallics. The polymetallated derivatives have been characterised by spectroscopy and chemical investigations: alkylation or arylation of their M(IVB)X bonds (X = halogen, oxygen etc.). The insertation reactions of difluoro-, phenylfluoro- and phenylchloro-germylenes into the intracyclic germaniumoxygen bond of diastereoisomeric oxaermacycloalkanes are generally stereospecific and can be interpreted by a concerted mecanism.

Insertion reactions of diazocyclopentadienes with halo—transition metal complexes

The reactivity of diazocyclopentadiene and diazotetraphenylcyclopentadiene, known precursors of interesting carbenes, towards some rhodium, iridium and manganese complexes has been investigated. It was found that reactions of halo-bridged-dirhodium species and manganese pentacarbonyl halides with diazocyclopentadienes at room temperature yielded halo-substituted cyclopentadienyl complexes. This reaction can be considered an insertion of the diazo species into the metal halogen bond accompanied by loss of dinitrogen. The intermediacy of free carbenes is considered unlikely.

Molecular force and compliance constants for some metal-halogen bonds in complexes

The force and compliance constants of some metal-halogen coordinated bonds of MX 2, MX 3 − and MX 4 2− (M = Zn, Cd, Hg; X = Cl, Br, I) for their free state and for solutions in anhydrous tri- n-butyl phosphate (TBP) are evaluated and the effect of complexing with TBP on the compliance of the bonds is studied.

ChemInform Abstract: ELECTRONIC SPECTRA OF SOME PENTACARBONYLHALOGENOMETAL COMPLEXES AND RELATED SPECIES

AbstractDie UV‐ und sichtbaren Absorptionsspektren der Komplexe (I) werden mitgeteilt.

Intensity studies on the Raman-active fundamentals of hexahalogeno-anions of second- and third-row transition and non-transition metals. The calculation of parallel and perpendicular bond polarisability derivatives

The Raman spectra of solutions (generally aqueous acid) of the ions MF62–(M = Pt or Sn), MCl62–(M = Re, Os, Ir, Pd, Pt, Sn, or Pb), MCl63–(M = Rh or Ir), MBr62–(M = Os, Ir, Pt, or Sn) and MI62–(M = Pt or Sn) have been recorded, and accurate values for the frequencies of the ν1(a1g), ν2(eg), and ν5(t2g) fundamentals are reported, some for the first time. The intensities of these three fundamentals of each ion were measured using the rotating sample technique at four different exciting lines and they are reported by reference to the 935 cm–1 band of the perchlorate ion as internal standard. The results are discussed in terms of the pre-resonance Raman effect. The intensities of ν1(a1g) fundamentals have been used to determine values for the metal–halogen bond polarisability derivatives (MX′) at zero exciting frequency. These MX′ values, coupled with the relative molar intensities of the ν1(a1g) and ν2(eg) fundamentals in each case, lead to values for the parallel and perpendicular MX bond polarisability derivatives. Factors affecting the magnitudes of these quantities are discussed.

Electronic spectra of some pentacarbonylhalogenometal complexes and related species

U.v. and visible absorption spectra of the complexes [M(CO)5X](M = Mn, Re, Cr, MO, or W; X = Cl, Br, or I) are reported. These and spectra of [Mn(CO)5X](X = H, Me, CF3, and SiH3) and other metal carbonyl halide complexes are assigned using a molecular-orbital bonding picture based on recent approximate calculations and photoelectron spectra of these species. The highest-filled orbital of the halogeno-complexes is considered to have part metal dπ and part halogen pπ character. The unique lowest-energy band, which gives rise to the colour of these complexes and is not present in the other metal pentacarbonyl species discussed, is assigned to a 1A1→1E transition with electron transfer from this highest-filled orbital to a mainly σ* orbital of the metal–halogen bond. This is in contrast to earlier assignments which considered the acceptor orbital to have mainly π*(CO) character.

NQR spectra of some group IVB organometallic halides

Summary NQR 35Cl 79Br and 81Br frequencies have been measured for some organometallic halides of tin and germanium. A comparison of the data with earlier results for silicon and carbon indicates that π-bond character exists only in the Si-Cl and, to a lesser degree, the Ge-Cl bond. The ionic character in the metal-halogen bond bond decreases in all series with additional halogen substitution. The tin-halogen compounds show a very low lying NQR frequency which can be explained in terms of halogen-bridging in the crystals.

Palladium(II) complexes with dithiooxamide, N,N′-dimethyl- and N,N′-dicyclohexyl-dithiooxamide

Palladium(II) gives diamagnetic square-planar complexes: Pd L 2, Pd L 2(ClO 4) 2 and Pd L 3 (ClO 4) 2 with dithiooxamide; Pd LX 2 ( X = Cl, Br, I) and PdL 2 X 2 ( X = Cl, Br, ClO 4) with N, N′-dimethyl- and N,N′-dicyclohexyl-dithiooxamide. I.R. v(CN) and v(CS) bands show that these dithiooxamides act as S,N bidentate ligands. v(PdN) and v(PdS) bands are assignable in the regions 480–485 and 410-320 cm −1, respectively. v(Pd X) bands, inPd LX 2 complexes, are characteristic of terminal metal-halogen bonds. Electronic spectra show only one band assignable to d-d transitions.

Metal–metal and metal–halogen bond cleavage by lanthanide and related metals

Finely-divided lanthanide and other metals react with substrates such as Mn(CO)5Br, h3–C3H5Fe(CO)3I,[h5–C5H5Mo(CO)3]2, and h5–C5H5Cr(CO)3HgCI in THF to yield reactive solutions which can be utilized as reagents for the synthesis of various organometallic compounds.

The far-infrared spectra of dihalogenotetra(pyridine)metal(II) complexes and related six-co-ordinate compounds containing terminal metal-halogen bonds

Far-infrared (450-80 cm −1, in some cases to 20 cm −1) and some Raman spectra have been studied for MX 2(pyridine) 4 [ M = Mn; X = I. M = Co; X = Cl or Br. M = Ni; X = Cl, Br, or I], MX 2(pyridine- d 5) 4 [ M = Co or Ni; X = Cl], MX 2(pyrazole) 4 [ M = Ni; X = Cl, Br, or I. M = Mn; X = Cl or Br], and MX 2(hydrazine) 2 [ M = Mn or Co; X = Cl or Br]. Assignments are reported for ν( MX), ν( MN), and some of the deformation modes. The ν( MX) bands are similar in position to those found in octahedral halogen-bridged complexes of these metals, but are of lower intensity relative to ν( MN), and markedly dependent upon M- X bond length. Careful analysis of the spectra is needed to assign ν( MX) and to distinguish terminal from bridged halogen in this type of environment.

Interaction of indium(I) halides with organometallic complexes containing metal-metal and metal-halogen bonds

Interaction of indium(I) halides with organometallic complexes containing metal-metal and metal-halogen bonds

Nuclear quadrupole resonance spectra and π-bonding of some nickel(II) complexes

The nuclear quadrupole resonance spectra of some tetrahedral and square-planar nickel(II) complexes are reported: it is shown that the π-bonding character of the metal–halogen bond is ca. 10%.

Investigation of para-, meta-, and ortho- chlorophenyldiazonium double salts by nuclear quadrupole resonance and infrared spectroscopy

1. Both the NQR frequencies and the infrared frequencies vCN2 depend slightly on the nature of the metal anion in chloride complexes of diazonium double salts. 2. A relationship has been established between the NQR and vCN2 infrared frequencies and the nature of the halide in the complex anion. 3. The metal-halogen bond in the complex anion is substantially covalent.

Analyse vibrationnelle de complexes hexahalogénés à l'état cristallisé

Resume The vibrational spectra of 31 crystalline hexachloro and hexabromo-metallates have been recorded. The calculation of force constants has been carried out from a modified Urey-Bradley force field, including the effect of cations on the internal vibrations of the anion. The relation between the degree of covalency of the metal-halogen bond and the stretching force constant is discussed.

Electron-impact studies of organometallic molecules. Part III. Some carbonylmetal halides and cyclopentadienyls

The mass spectra of several carbonyl halides of manganese, rhenium, iron, and ruthenium; of [π-C 5H 5Ru(CO) 2] 2; of the cyclopentadienyl carbonyl halides of iron and ruthenium; and of CoRe(CO) 9, π-C 5H 5RuRe(CO) 7, and π-C 5H 5RuCo(CO) 6 are described and discussed in terms of relative strengths of the metalcarbonyl, metalhalogen, and metalmetal bonds present in the compounds.

The Raman spectra of complex anions of formula MX4 n? where M is Au III , Pt II , or Pd II , and X is a halogen atom

The Raman spectra of solid samples of the salts K2PtCl4, K2PtBr4, K2Ptl4, Na2Ptl4, K2PdCl4, K2PdBr4, KAuBr4, and KAul4 are reported. Agreement between the spectra recorded and those of aqueous solutions of the PtCl42– and AuBr4– anions is satisfactory in most respects suggesting that the phase does not seriously effect the vibration frequencies. The Raman and far-infrared spectra are assigned to fundamental modes of vibration. Force constants for the metal–halogen bonds are computed, compared, and discussed in relation to the stabilities and reactivities of these complex ions.

Raman Spectra of a Series of Square Planar Anions

OVER the past 10 years a number of reports have appeared in the literature on the infra-red spectra of square planar co-ordination compounds. Interest has been demonstrated in the exact whereabouts, in terms of frequency, of absorption bands associated primarily with stretching vibrations of metal–halogen bonds. A number of attempts have been made to estimate force constants for the metal ligand bonds in simple cases. A careful consideration of species with formula [MX4]n− and trans [MX2Y2], where M is a metal such as platinum(II), palladium(II) or gold (III), X is a halogen and Y is a donor system such as ammonia, a thio-ether or a phosphine, can provide a large amount of information particularly if the symmetric stretching modes of vibration are identified. Unfortunately, these modes are inactive in infra-red spectroscopy, and although they can be analysed by Raman spectroscopy, it is extremely difficult to obtain scattering data on deeply coloured materials such as these. The only reliable Raman spectra of compounds of this type is that due to Stammreich and Forneris1, who report three lines for each of the three anions, PtCl4− −, AuCl4− and AuBr4− using aqueous solutions and exciting the spectra with yellow, red or near-infra-red sources, as appropriate. An attempt which I made to obtain a spectrum from a solution of potassium tetrabromoplatinite by exciting the spectrum with an electrodeless rubidium arc was unsatisfactory; two indistinct features were observed near Δv = 190 and 120 cm−1.