Roser Reina

Anionic and neutral spiked triangle clusters of mercury : a comparative study of the metal ligand redistribution process

Abstract The action of the NEt + 4 salts of the anions [Fe 2 (CO) 8 ] 2− and [Fe 2 (CO) 6 (μ-CO)(μ-PPh 2 )] − on ClHg-m complexes (m = Mo(CO) 3 Cp, W(CO) 3 Cp, Mn(CO) 5 , Co(CO) 4 , and Fe(CO) 2 Cp) has been investigated. In the first case, anionic spiked triangle clusters of formula [Fe 2 (CO) 6 (μ-CO) 2 (μ-Hg-m)] − were obtained in high yields, and no metal ligand redistribution reactions were detected. However, the action of [Fe 2 (CO) 6 (μ-CO)(μ-PPh 2 )] − on the same bimetallic transition metal-mercury compounds gave the neutral species [Fe 2 (CO) 6 (μ-CO)(μ-PPh 2 )(μ-Hg-m)], which spontaneously redistributed to [Hg{Fe 2 (CO) 7 (μ-PPh 2 )} 2 ] and m 2 Hg. Only the molybdenum derivative could be isolated in pure form. The different behaviour of the two series of complexes in the redistribution process is discussed.

Anionic trimetallic compounds containing FeEM skeletons (E = Zn, Cd, Hg; M = Fe, Mo, W). Crystal structure of [N(PPh3)2]2[(OC)4FeHgFe(CO)4]

Dichlorides of group 12 elements react with (NEt4)[HFe(CO)4] in tetrahydrofuran to give the di-hydrides [(OC)4HFeEFeH(CO)4] (E = Zn, Cd, Hg) in good yields. These compounds undergo proton abstraction by nBuLi to give di-anions [(OC)4FeEFe(CO)4]2-, stabilized as their bis(triphenylphosphine)nitrogen(+) (PPN+) salts. (PPN)2[(OC)4FeHgFe(CO)4] crystallizes in the triclinic system, space group P1 with a 20.382(3), b 15.328(2), and c 13.420(2) A; α 115.96(3), β 108.89(2), and γ 87.09(2)o, and Z = 2. The anion consists of an almost linear spine (FeHgFe angle 178.7(1)o), with an average FeHg bond distance of 2.546(2) A. The Fe atoms display a trigonal bipyramidal geometry, and the equatorial CO groups linked to the iron atoms are in an eclipsed conformation, resulting in an idealized D3h symmetry. The existence of two conformers for this anion and the presence of Hg · · · CO backbonding are discussed on the basis of qualitative molecular orbital theory. The [(OC)4FeHgFe(CO)4]2- anion undergoes redistribution reactions with [M(CO)3(η-C5H5)]2 Hg (M = Mo, W) to give the new unsymmetrical anions [(OC)4FeHgM(CO)3(η-C5H5)]-.

Anionic iron clusters as building blocks for the synthesis of higher nuclearity compounds containing 11- and 12-group elements

Abstract Anionic iron clusters have been widely used as building blocks for the formation of mixed metal clusters with 11- and 12- group elements. This review summarizes the results reported in this area, paying special attention to the structural features of the metal core of the species reported.

Electrospray mass spectrometric studies of some heterometal anionic carbonyl clusters

Electrospray mass spectra (ESMS) are reported for a series of anionic transition-metal clusters of the type (PPh4)[Fe3(CO)10(μ-CO){μ-Hg(m)}] (m = Mo(CO)3Cp; Co(CO)4; Fe(CO)2Cp; W(CO)3Cp; Mn(CO)5) and also for the species of higher nuclearity (NEt4)[Fe6C(CO)16AuPPh3] in methanol solution. The results were compared with those obtained by FAB-MS, and they indicate that ESMS is the most appropriate technique by which to obtain control fragmentation. Information about the strength of the different metal-metal bonds present in the cluster can be deduced from the species generated.

Iron carbonyl complexes of heterocyclic α-diimines: systematic synthesis, crystal structures of [Fe(CO)3(L)] and [Fe2(CO)7(L)] (L=2,2′-bipyridine and 1,10-phenantroline), and their AIM analysis ☆

Heterocyclic α-diimines {2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (4,4′-Me 2 bpy), 1,10-phenantroline (phen), 4,7-dimethyl-1,10-phenantroline (4,7-Me 2 phen) and 2,9-dimethyl-1,10-phenantroline (2,9-Me 2 phen)} react, in a wide range of conditions, with iron clusters of nuclearity one, two or three. Two kinds of compounds, [Fe(CO) 3 (α-diimine)] (type 1 ) and [Fe 2 (CO) 7 (α-diimine)] (type 2 ), are afforded in all cases. We propose a reaction mechanism to explain this behaviour. The crystal structures of compounds [Fe(CO) 3 (bpy)] ( 1a ), [Fe(CO) 3 (phen)] ( 1b ), [Fe 2 (CO) 7 (bpy)] ( 2a ) and [Fe 2 (CO) 7 (phen)] ( 2b ) at 173 K were determined by single-crystal X-ray diffraction methods. In contrast, reaction of the pentanuclear iron cluster [Fe 5 C(CO) 15 ] with bpy led to the tetranuclear salt [Fe(bpy) 3 ][(μ-H)Fe 4 C(CO) 12 ] 2 ( 3 ). The electronic structures of the mono- and di-iron derivatives with bpy and phen were analysed using the atoms in molecules (AIM) theory. Their comparative study seems to rule out the existence of FeFe bond in the dinuclear complexes.

Anions [Fe2(CO)8]2– and [Fe2(CO)6(µ-CO)(µ-PPh2)]– as building blocks for the synthesis of mixed-metal clusters. Crystal structure of [Fe2(CO)6(µ-CO)(µ-PPh2){µ-Cu(PPh3)}]

Treatment of the salt [NEt4]2[Fe2(CO)8] with a tetrahydrofuran solution of the complex [Cul(PPh3)] gives an anionic orange-red cluster [NEt4][Fe2(CO)6(µ-CO)2{µ-Cu(PPh3)}]1 which is air- and thermally unstable. When [NEt4][Fe2(CO)6(µ-CO)(µ-PPh2] and [MX(PPh3)](M = Cu, Ag or Au) are allowed to react in the presence of TIBF4, the new neutral clusters [Fe2(CO)6(µ-CO)(µ-PPh2)-{µ-M(PPh3)}](M = Cu, 2; Ag, 3; or Au, 4) are obtained in ca. 80% yield. These relatively air-stable clusters have been characterized by IR and 31P NMR spectroscopy and the structure of 2 has been established by single-crystal X-ray diffraction studies: triclinic, space group P, with a= 11.081(3), b= 12.190(3), c= 15.808(4)A, α= 76.41(2), β= 87.03(2), γ= 80.48(2)°, Z= 2 and R= 0.05. The basic skeleton consists of the first example of a Fe2Cu triangle. In this, the iŕon–iron bond is bridged by a phosphido and a carbonyl group.

Cobalt/Mercury Carbide Clusters Based on Trigonal-Prismatic or Octahedral Co6C Skeletons − X-ray Crystal Structure of (NEt4)2[Co6C(CO)12{HgW(CO)3Cp}2]

The anionic transition metal clusters (NEt4)[Co6C(CO)x{HgM}] [M = W(CO)3Cp, Mo(CO)3Cp, Fe(CO)2Cp, Co(CO)4, Mn(CO)5] (x = 13 or 15) have been obtained by reaction of the corresponding octahedral (x = 13) or trigonal-prismatic (x = 15) cobalt carbido carbonyl clusters with the mercury derivatives ClHgM. Metal skeleton rearrangements and some redox processes have been found to be induced by varying both the temperature and the solvent, resulting in new compounds containing tetra- or hexacoordinated mercury atoms.

Use of the anions [W2(CO)10]2− and [MO2(CO)8(μ-H)(μ-L)]− (L = bidentate phosphines) in the synthesis of mercury-transition metal clusters

Abstract The reaction of the PPN + (bis(triphenylphosphine)nitrogen(+)) salt of [W 2 (CO) 10 ] 2− with ClHg-m complexes (m = Mo(CO) 3 Cp, W(CO) 3 Cp, Fe(CO) 2 Cp, Mn(CO) 5 , and Co(CO) 4 gives high yields of the new trimetallic clusters (PPN)[(OC) 5 WHgm] along with (PPN)]W(CO) 5 Cl], the crystal structure of which has been determined. The W atom in the anion is octahedrally surrounded by five carbonyl groups and one chloride ligand, giving an approximately C 4 v symmetry. Attempts to use the anion [MO 2 (CO) 8 (μ-H)(μ-L)]− (L = dppm, dppe, dppp) to give spiked triangular clusters of the type [MO 2 (CO) 8 (μ-H)(μ-L)(μ-Hgm)] was unsuccessful; although tetrametallic chain-type complexes of formula [(OC) 4 HMo(μ-L)Mo(CO) 4 {HgMo(CO) 3 (Cp}] are thought to be formed in THF solutions, processes involving ligand metal redistribution and mercury extrusion precluded their isolation.

Synthesis, characterization and electrochemical studies of the heterometallic diclusters [{Fe2(μ-CO)(CO)6(μ-PPh2)Au}2(diphosphine)] (diphosphine=dppm, dppip, dppe, dppp)

Abstract Treatment of [(ClAu)2(diphosphine)] {diphosphine=bis(diphenylphosphino)methane (dppm), bis(diphenylphosphino)isopropane (dppip), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp)} with two equivalents of the anion [Fe2(μ-CO)(CO)6(μ-PPh2)]− in the presence of TlBF4 gives the new heterometallic diclusters [{Fe2(μ-CO)(CO)6(μ-PPh2)Au}2(diphosphine)] that have been isolated and characterized. Their 31P-NMR spectra show different patterns as a function of the diphosphine ligand. The electrochemical behavior of these compounds has been investigated and compared with that of the mono- [Fe2(μ-CO)(CO)6(μ-PPh2)(μ-AuPPh3)] and tricluster [{Fe2(μ-CO)(CO)6(μ-PPh2)Au}3(triphos)] derivatives.

Mixed cobalt/gold clusters based on octahedral or prismatic Co6C skeletons

The reaction of AuCl(PPh3) in THF with [Co6C(CO)15]2−1 afforded [Co6C(CO)15{AuPPh3}]−3, with a metal skeleton consisting of a Co6C trigonal prism capped by a AuPPh3 group. 3 incorporated a new AuPPh3+ fragment giving [Co6C(CO)13{AuPPh3}2] 4. The crystal structure of 4 reveals that the metal skeleton consists of a cobalt octahedron with a face capped by an Au2(PPh3)2 unit. The reaction of AuCl(PPh3) with the anion [Co6C(CO)13]2−, 2 produced the octahedral cluster [Co6C(CO)13{AuPPh3}]− in which a face appears to be capped by a AuPPh3+ group according to the crystal structure determination. This compound reacts with an excess of AuPPh3+ to give 4, and produces 3 by reversible reaction with a mild stream of CO. The electrochemical behaviour of these species has been investigated by cyclic voltammetry and coulometry.