Fausto Calderazzo

Organometallic derivatives of palladium, platinum, and gold

Abstract Information obtained in my and other research groups on halo carbonyls of palladium, platinum, and gold are surveyed. While for platinum(II), allthe three halo (Cl, Br, I) complexes are well established both in solution and in the solid state for the PtX2(CO)2, Pt2X4(CO)2 and [PtX3(CO)]− series, the bromo derivatives of palladium(II) and gold(I) are stable only in solution,under carbon monoxide. No evidence for the existence of iodo carbonyl derivatives of palladium(II) and gold(I) has been observed. the σ-component of the MCO bond appears to predominate.

Synthesis and Structural Characterization of Iron(II) Derivatives of Heterocyclic Tridentate Amines

Abstract Compounds of general formula FeX2(L) {L=2,6-bis(3,5-dimethyl-N-pyrazolyl)pyridine, C15H17N5; bis[3,5-dimethyl-N-pyrazolyl)methyl]-isopropylamine, C15H25N5; bis(benzimidazol-2-yl-methyl)amine, C16H15N5, 1,3-bis(benzimidazolyl)propane, C17H16N4; bis(benzimidazolyl-2-methyl)ether, C16H14N4O; bis(benzimidazolyl-2-methyl)thioether, C16H14N4S} have been synthesized by reacting the amine with Fe4Cl8(THF)6 or FeI2(CO)4 in toluene. The complexes FeCl2(C15H17N5)·MeCN and FeCl2(C16H15N5)(MeOH) have been characterized by single crystal X-ray diffraction together with the parent triamines, C15H17N5 and C16H15N5, for comparison. The reaction of FeI2(CO)4 with bis(benzimidazolyl-2-methyl)thioether, C16H14N4S, led to the product of partial carbonyl substitution FeI2(CO)2(C16H14N4S).

Eight-coordinate chelate complexes of zirconium(IV) and niobium(IV): X-ray diffractometric and EPR investigations

Abstract The N,N -diethylcarbamato derivative of zirconium(IV), Zr(O 2 CNEt 2 ) 4 has been studied by X-ray crystallography. Crystal data: C 20 H 40 Na 4 O 8 Zr, monoclinic, space group C 2/ c , a = 14.057(1), b = 12.168(1), c = 16.746(2) A, β = 108.071(4)°, Z = 4, D c = 1.356, F(000) = 1168, T = 213 K. The compound is isotypic with the corresponding niobium(IV) derivative with a dodecahedral coordination at the zirconium atom. By reaction of NbCl 4 (THF) 2 with Tl(hfacac), the hexafluoroacetylacetonato derivative of niobium (IV), Nb(hfacac) 4 , has been prepared and structurally characterized. The compound crystallizes in the orthorhombic space group Pna 2 1 with the following cell constants: a = 10.399(4), b = 15.852(9), c = 119.073(1) A. It is not isotypic with the corresponding zirconium(IV) derivative, Zr(hfacac) 4 . Crystal data: C 20 H 4 F 24 O 8 Zr, monoclinic, space group P 2 1 / n , a = 11.974(4), b = 20.451(6), c = 13.140(3) A, β = 104.487(11)°, Z = 4, D c = 1.960, F(000) = 1776, T = 223 K. Although in both compounds the central metal atom shows a square antiprismatic coordination, the coordination mode of the ligands is different and slight deviations from the D 4 (llll) and C 2 (llss) ideal geometries have been observed in the case of niobium and zirconium, respectively. An EPR study has been performed on the Nb(IV) derivatives as diluted solid solutions in frozen organic solvents or in the diamagnetic matrix of the corresponding zirconium(IV) compound. The EPR spectra have confirmed the presence of non-interacting paramagnets in the solid solutions and, in the case of Nb(O 2 CNEt 2 ) 4 , the point symmetry of the paramagnetic centre has been found to be in agreement with the results of the X-ray investigation. An EPR spectrum of rhombic symmetry has been observed for the hexafluoroacetylacetonato derivative of Nb(IV) when diluted in frozen THF solution or in Zr(hfacac) 4 .

Carbonyl derivatives of phthalocyaninatoiron(II), especially those containing group VI axial donor atoms. Crystal and molecular structure of carbonyl(N,N-dimethylformamide)phthalocyaninatoiron(II) and mössbauer studies of some of the products

Abstract The carbonyl adduct of phthalocyaninatoiron(II), FePc, with N , N -dimethylformamide (DMF) as axial ligand, FePc(CO)DMF, was prepared by the reaction of iron carbonyls, Fe(CO) 5 or Fe 2 (CO) 9 , with o -phthaalonitrile in DMF as solvent. Several carbonyl adducts of FePc of general formula FePc (CO)L are reported, with L being a ligand with oxygen, sulphur and nitrogen donor atoms (L = tetrahydrofuran, H 2 O, CH 3 OH, dimethylsulphoxide, tetrahydrothiophene, ammonia, n-propylamine, diethylamine, triethylamine). The crystal and molecular structure of FePc(CO)DMF·DMF was investigaed by X-ray diffraction methods. The compound has a monoclinic unit cell and space group P 2 1 / n , a 9.86(1), b 17.35(3), c 19.79(4) », β 87.9(2)°, Z = 4, U 3383 » 3 , D 3 1.458 g cm −3 . The iron atom is hexacoordinated to the four inner nitrogen atoms of the macrocyle, to carbon monoxide (Fe—C distance 1.72(2) ») and to DMF (Fe—O distance 2.07(1) »). The extra DMF occupies lattice sites. All of the compounds reported in this paper are substantially diamagnetic. Mossbauer spectra show typical isomer shift parameters for the bis-adducts and for the carbonyl adduct, substantially independent of the nature of the axial ligand. The quadrupole splitting parameter of the carbonyl adducts is strongly affected by the nature of the axial ligand.

Synthesis and reactivity of η6-arene derivatives of niobium(II), niobium(I), and niobium(O)

Abstract The primary reduction products in the Al/AlX 3 /NbX 5 /arene system, namely Nb(η 6 -arene)(AlX 4 ) 2 , X = Cl, arene = benzene, hexamethylbenzene; X = Br, arene = hexamethylbenzene, have been isolated. Tetrahydrofuran at room temperature reacts with Nb(η 6 -hexamethylbenzene)(AlBr 4 ) 2 , to give the aluminium-free complex Nb 2 (η 6 -hexamethylbenzene) 2 Br 4 , whose crystal structure was determined by X-ray diffraction methods. In the presence of tetrahydrofuran or dimethoxyethane, the η 6 -mesitylene-tetrahaloaluminato complexes are further reduced by aluminium to bis-mesityleneniobium(0), Nb(mes) 2 , which undergoes: a) disproportionation with CO to [Nb(mes) 2 (CO)] + [Nb(CO) 6 ] − , b) oxidation by V(CO) 6 or (4,4′-dimethyl-2,2′-dipyridyl)(BPh 4 ) 2 under carbon monoxide to [Nb(mes) 2 (CO)]X, X = [V(CO) 6 ] − or BPh 4 − . The structure of [Nb(mes) 2 (CO)] BPh 4 has been determined by X-ray diffraction methods. In the presence of CO, Nb(mes) 2 is reduced by CoCp ☆ 2 [Cp ☆ = η 5 -C 5 (CH 3 ) 5 ] to [Nb(CO) 6 ] − , which was isolated as its CoCp ☆ 2 + derivative; it efficiently deoxygenates CO 2 to CO in the presence of carbon monoxide acceptors such as the [Nb(mes) 2 (THF)] + cation.

Carbonyl complexes of noble metals with halide ligands: I. Platinum(II) / halide exchange, dimerization, isomerization, 13C NMR data and crystal and molecular structure of Pt2I4(CO)2

Room temperature and atmospheric pressure carbonylation of PtI2 in toluene gave trans-PtI2(CO)2 as the predominant isomer, together with cis-PtI2(CO)2. Lowering of p(CO) resulted in conversion of PtI2(CO)2 into Pt2I4(CO)2 both in solution and in the solid state. The iodide-bridged centrosymmetric Pt2I4(CO)2 was studied by single crystal X-ray diffractometry. Monoclinic; space group C2/c; a 10.772(2); b 9.077(1); c 13.001(3) A; β 112.26(2)°; U 1176.5(5) A3; Z = 4; Dcalc 5.385 g cm−3; Mo-Kα radiation (λ 0.71069 A); μ(Mo-Kα) 343.6 cm−1; F(000) = 1584. The structure consists of Pt2I2(μ-I)2(CO)2 units with tetracoordinated square planar platinum bonded to two bridging iodides, one terminal iodide and one terminal CO group. The PtPt nonbonding distance is 3.846(2) A. A new preparative procedure for the monomeric halo carbonyls PtX2(CO)2 (X  Br, I) involves treatment of cis-PtCl2(CO)2 with dry HX in toluene. Addition of CO to Pt2Br4(CO)2 occurs readily to give cis-PtBr2(CO)2 through the transient trans-PtBr2(CO)2. The 13C NMR spectra data for the platinum complexes show that: (a) values of J(PtC) decreases in the sequence Pt2X4(CO)2 > [PtX3(CO)]− > cis-PtX2 (CO)2 ⪆ trans-PtX2(CO)2 > [PtX5(CO)]−; (b) within each series of compounds, values of J(PtC) decrease in the sequence Cl > Br > I.

Preparation and crystal and molecular structure of two trialkylamine adducts of HCo(CO)4 showing a preferential NR3H+⋯[(OC)3Co(CO)]– interaction

HCo(CO)4 and trialkylamines in hydrocarbon solution form 1:1 adducts, which may be described as NR3H+⋯[Co(CO)4]– ion pairs; X-ray crystal structure determinations show that in the solid state the inter-acting unit NEt2H+⋯[Co(CO)4]– has an N ⋯ Co contact of 3.72 A with the nitrogen hydrogen on the threefold axis of rotation interacting with the C3Co part of the [Co(CO)4]– anion, in a sort of ‘elongated’ HCo(CO)4 structure, and a substantially similar molecular structure was found for NMe3H+⋯[Co(CO)4]–, the N ⋯ Co contact being reduced to 3.39 A.

AROMATIC-HYDROCARBONS, CARBOCYCLIC LIGANDS SPANNING SEVERAL OXIDATION-STATES IN BOTH MAIN-GROUP AND TRANSITION-ELEMENTS - RECENT ADVANCES WITH EARLY TRANSITION-D ELEMENTS

Abstract In this paper some synthetic procedures to obtain ( η 6 -arene)metal derivatives are reviewed. The metal-atom-arene-vapor co-condensation technique is the most appropriate to generate complexes of polycyclic aromatic hydrocarbons or heterocycles. As far as the aluminium halide-mediated synthesis is concerned, two classes of reaction are observed. When AlX 3 is used with a metal halide in the presence of an aromatic hydrocarbon in the absence of any reducing agent, AlX 3 can function as a dehalogenating agent, to give ionic compounds of general formula [M( η 6 -arene) n ](AlX 4 ) m , or it can add across the MX bond with formation of M( μ -X) n AlX 4− n systems. In both cases the metal displays its typical oxidation state. However, the use of AlX 3 in combination with aluminium (the Fischer-Hafner reducing system) affords ionic or covalent low-oxidation-state metal( η 6 -arene) complexes. Attention is focused on our most recent results concerning the synthesis, properties and reactivity of η 6 -arene derivatives of Group 4 and 5 elements, showing, inter alia, the first example of a tetraarylborate anion behaving as a 12-electron donor to one metal atom and low-valent η 6 -arene compounds as useful reagents in the inorganic and coordination chemistry of the corresponding metal in nonaqueous systems.

Synthesis of N,N-dialkylcarbamato complexes of Group 4 metals (Ti, Zr, Hf) by the metal chloride–NHR2–CO2 system (R = Et or Pri): crystal and molecular structure of [Hf(O2CNPri2)4]

The compounds [M(O2CNR2)4](M = Ti, Zr or Hf; R = Et or Pri) have been prepared by treating the corresponding metal tetrachloride with CO2–NHR2 in toluene. The structure of [Hf(O2CNPri2)4] has been solved by X-ray diffraction methods. Crystal data: monoclinic, space group P21/c, a= 12.756(3), b= 22.131(9), c= 14.548(5)A, β= 113.03(2)° and Z= 4. It consists of monomeric units, the hafnium atom being surrounded by the eight oxygen atoms of the four N,N-diisopropylcarbamato groups in a slightly distorted dodecahedral arrangement. By reaction with anhydrous hydrogen halides HX (X = Cl, Br or I) the hexahalogenometalate(IV) anions, [MX6]2–, as the diethylammonium derivatives, have been obtained in high yields. The redox reaction between [Ti(O2CNEt2)4] and [V(η-C5Me5)2] gives the titanium(III) and vanadium(III) complexes [{Ti(O2CNEt2)3}n] and [V(η-C5Me5)2(O2CNEt2)], respectively.

Studies on organometallic compounds with hetero multiple bridges : V. Crystal and molecular structure of the parent rhenium complex Re2Br2(CO)6(THF)2 and substituted products of tricarbonylrhenium(I) derived from it

Abstract Reactions of the tetrahydrofuran adduct Re 2 Br 2 (CO) 6 (THF) 2 with some phosphorous- and nitrogen-containing donors under mild conditions are reported, which led to the formation of substituted products of tricarbonylrhenium(I). Bromide abstraction from the THF adduct by secondary amines and CS 2 produced the dithiocarbamato derivatives Re(S 2 CNR 2 )(CO) 3 (HNR 2 ) whose behaviour in solution with CO was also investigated. Mass spectral data for some of the substituted products have been measured. The title compound crystallizes in the space group P 2 1 / n with cell constants a = 8.661(2), b = 11.251(3), c = 11.424(3) A and β = 110.36(2)°, U = 1043.67 A 3 and D calc = 2.686 g cm −3 , Z = 2. The molecule consists of a planar Re 2 Br 2 moiety, as demanded by symmetry. The two THF groups are on opposite sides of this plane and the three CO groups around each rhenium atom are arranged in a fac arrangement. The unique ReBr distances are 2.642(5) and 2.644(4)A, while the ReO distance is 2.129(31) A. The ReBrRe and BrReBr angles are 97.3(2) and 82.7(1)°, respectively. The Re⋯Re nonbonding distance is 3.967(3) A. The THF ligands consist of a nearly planar C 4 fragment (maximum deviation from planarity 0.06 A), while the oxygen is 0.348 A out of that plane, the angle defined by the C 4 plane and the COC fragment of the THF ligand being 24.99°. Final values of the discrepancy indices are R ( F ) = 0.074 and R w ( F ) = 0.095.