Fiorenzo Refosco

Structural survey of technetium complexes

Abstract The review, with 294 references and 41 figures, reports on the main structural features of 240 Tc complexes whose X-ray crystal structure has been determined during the period 1986–1992. It comprises seven major sections: oxo-; nitrido-; diazenido-, hydrazido- and imido-; Schiff base-; chalcogenide-; pnictide-; nitrosyl- and thionitrosyl-technetium complexes. The survey concludes with two comprehensive tables summarizing some properties of Tc complexes vs . oxidation state.

Structural overview of technetium compounds (1993–1999)

Abstract This paper investigates the structural aspects of technetium-containing complexes. The focus is on the description of the various coordination environments around the technetium center. The complexes are divided according to the coordination sphere and the most significant structural parameters are reviewed and discussed. The review covers the crystallographic determinations published in the years between 1993 and 1999.

Synthesis and structural characterization of copper(I) complexes bearing N-methyl-1,3,5-triaza-7-phosphaadamantane (mPTA) Cytotoxic activity evaluation of a series of water soluble Cu(I) derivatives containing PTA, PTAH and mPTA ligands

New copper(I) complexes containing the water soluble N-methyl-1,3,5-triaza-7-phosphaadamantane (mPTA) phosphine have been synthesized by ligand-exchange reactions starting from [Cu(CH(3)CN)(4)][BF(4)] or [Cu(CH(3)CN)(4)][PF(6)] precursors and (mPTA)X (X=CF(3)SO(3), I). Depending on the ligand counter ion, the hydrophilic [Cu(mPTA)(4)][(CF(3)SO(3))(4)(BF(4))] 3a and [Cu(mPTA)(4)][(CF(3)SO(3))(4)(PF(6))] 3c complexes or the iodine-coordinated [Cu(mPTA)(3)I]I(3)4 species were obtained respectively and fully characterized by spectroscopic methods. Single crystal structural characterization was undertaken for [Cu(mPTA)(3)I]I(3).H(2)O, 4.H(2)O, and [Cu(mPTA)(4)][(CF(3)SO(3))(2)(BF(4))(3)] .0.25H(2)O, 3b.0.25H(2)O, the latter obtained by crystallization of [Cu(mPTA)(4)][(CF(3)SO(3))(4)(BF(4))] 3a. The cytotoxicity of analogous tetrahedral homoleptic Cu(I) derivatives [Cu(PTA)(4)](BF(4)) 1, [Cu(PTAH)(4)][Cl(4)(BF(4))] 2, [Cu(mPTA)(4)][(CF(3)SO(3))(4)(BF(4))] 3a and [Cu(mPTA)(4)][(CF(3)SO(3))(4)(PF(6))] 3c was evaluated against a panel of several human tumor cell lines. All the complexes showed in vitro antitumor activity comparable to that of the reference metallodrug cisplatin. Tests performed on cisplatin sensitive and resistant cell lines showed that against human ovarian 2008/C13(*) cell line pair, the resistance factor of copper derivatives was roughly 7-fold lower than that of cisplatin, whereas against human cervix cancer A431/A431-Pt cell line pair it was about 2.5-fold lower. These results, confirming the circumvention of cisplatin resistance, support the hypothesis that phosphine copper(I) complexes follow different cytotoxic mechanisms than do platinum drugs.

Synthesis, characterization and electrochemical studies on technetium(V) and rhenium(V) oxo-complexes with N,N'-2-hydroxypropane-1,3-bis(salicylideneimine)

Ligand-exchange reactions of potential quinquedentate Schiff base ligands derived from salicylaldehyde and 1,3-diamino-2-hydroxypropane (H 3 L) with [MOCl 4 ] − (M = Tc and Re) have been investigated. The complexes [MOCl 2 (ROH)(H 2 L·HCl)] ( I ) (R = Me, Et), [ReOCl(HL)] ( II ) and μ-O[MO(HL)] 2 ( III ) were synthesized and characterized by the usual physicochemical measurements. Cyclic voltammetries for both III complexes reveal two separate and single-electron redox processes. The crystal structure of μ-O[TcO(HL)] 2 was determined by single-crystal X-ray diffraction methods. Crystals are monoclinic, space group P 2 1 / c , with a = 9.423(6), b = 19.666(9), c = 22.785(11) A, β = 99.41(4)° and Z = 4. X-ray diffraction provides 2842 observed reflections (up to θ = 40°) and the structure has been refined by full-matrix least-squares methods to R = 0.10. The ‘dimeric’ structure of μ-O[TcO(HL)] 2 consists of two distorted octahedral TcO(HL) moieties bridged by an oxygen atom which occupies the sixth coordination site of each moiety with the TcOTc angle nearly linear (173°).

Rhenium(V) oxo complexes with schiff base ligands containing four or five coordination sites. X-ray molecular structure of [N,N′-3-azapentane-1,5-diylbis(salicylideneiminato)(3-)-O,O′,N,N′,N″]oxorhenium(V)

Abstract The reactions of [ReOCl4]− with Schiff base ligands derived from salicylaldehyde and 1,5-diamino- pentane (H2L1a), -hexane (H2L1b), -heptane (H2L1c) or diethylentriamine (H3L2) have been investigated. The complexes ReOCl2(EtOH)HL1n (I) (n=a, b or c), Re2O2(MeOH)2Cl4HL2 (II), ReOClL1n (III) and ReOL2 (IV), have been synthesized and characterized with the usual physicochemical measurements. The crystal structure of ReOL2 was determined by single crystal X-ray methods. Crystals are monoclinic, space group P21/c, with a=9.470(7), b=9.358(8), c=21.859(12) A, β=99.23(8)16° and Z=4. X-ray diffraction provides 5601 observed reflections (up to 2⊖=60°) and the structure has been refined by full-matrix least-squares methods to R=0.061. The monomeric structure consists of distorted octahedral ReOL2 units. One oxygen atom of the N3O2 pentadentate ligand is located trans to the rheniumoxo oxygen bond, while the remaining four coordinating atoms lie on the equatorial plane of the octahedron assuming that the oxo-oxygen occupies an apex. The arrangement of the two iminophenolate groups is explained as a function of the length of the aliphatic chain joining the two imine groups.

Monooxorhenium(V) complexes with the tridentate Schiff baseN-(2-hydroxyphenyl)salicylideneimine

SummaryThe reactions of the tridentate Schiff base ligandN-(2-hydroxyphenyl) salicylideneimine (HOPhsalH) with oxotetrachlororhenate (IV) have been investigated. The complexes (Bu4N)[ReOCl3(HOPhsal)], (Bu4N)[ReOCl2(OPhsal)],cis- [ReOCl(MeOH)(OPhsal)],trans-[ReOCl(MeOH)(OPhsal)] (1), trans-[ReOCl(OH2)(OPhsal)] · Et2O (2), trans-[ReOCl(OH2)(OPhsal)] · Me2CO,cis-[ReOCl(PPh3)(OPhsal)],cis-[ReOCl(PMe2Ph)(OPhsal)](3) have been synthesized and characterized. The crystal structures of(1), (2) and(3) have been solved from three-dimensional x-ray data by Patterson and Fourier methods and refined by least-squares methods to R 0.10 for(1), 0.042 for(2) and 0.059 for(3). In all the three complexes, the ligands surrounding the rhenium atom are at the apices of a distorted octahedron, with the equatorial ONO donor atoms of the tridentate Schiff base bent away from the Ooxo and toward the loosely bound MeOH in(1), H2O in(2) and Cl in(t3). The fourth equatorial substituent is Cl (1 and2) and PMe2Ph(3) and the rhenium atoms lie 0.30–0.37 Å above the best plane through the four equatorial atoms, in the direction of the Ooxo. All interatomic distances and angles are normal.

Synthesis and characterization of technetium(V) oxo-complexes with quadridentate Schiff-base ligands: X-ray structures of µ-oxo-bis-{oxo[N,N′-propane-1,3-diylbis(salicylideneiminato)]technetium(V)} and chloro-oxo[N,N′-propane-1,3-diylbis(salicylideneiminato)]-technetium(V)

The reactions of quadridentate Schiff-base ligands derived from salicylaldehyde and diamines with [TcOCl4]– have been investigated. The complexes [NBu4][TcOCl3(Hsalpd)], [NBu4][TcOCl3(Hsalbd)], [{TcO(salpd)}2O], [TcOCl(salpd)], and [TcOCl(salbd)][salpd =N,N′-propane-1,3-diylbis-(salicylideneiminate), salbd =N,N′-butane-1,4-diylbis(salicylideneiminate)] were isolated from the reaction mixture in ethanol. The complexes have been characterized by elemental analysis and by i.r. spectroscopy. The crystal structures of [{TcO(salpd)}2]O (1) and [TcOCl(salpd)](2) have been determined from three-dimensional X-ray data: (1), monoclinic, space group P21/c, a= 15.041 (2), b= 12.630(3), c= 16.522(4)A, β= 95.35(3)° and Z= 4; (2), orthorhombic, space group Pn21a, a= 12.010(4), b= 11.702(4), c= 11.625(6)A, and Z= 4. The structures have been solved by Patterson and Fourier methods and refined by least-squares methods to R 0.059 for (1) and 0.076 for (2). The ‘dimeric’ structure of (1) consists of two crystallographically independent and chemically well separated TcO(salpd) moieties bridged by an oxygen atom with the bridging Tc–O–Tc angle symmetrically imposed at 180°. A novel feature is the presence of the almost linear OTc–O–TcO group. The technetium atoms have octahedral co-ordination, with the equatorial plane formed by the N2O2 donor set, and the chelate ligand, as a whole, is very nearly planar. The structure of (2) consists of discrete molecules of [TcOCl(salpd)] with a pseudo-octahedral co-ordination around technetium. The salpd ligand occupies the four equatorial positions, whereas the Cl and the oxygen are trans to each other in axial positions. The two salicylaldimine groups are bent in an ‘umbrella shape’. Bond distances (A) in the ‘inner core’: (1), TcO 1.68, Tc–O(bridging) 1.90, Tc–O 2.01, and Tc–N 2.12 A; (2), TcO 1.66, Tc–O 1.98, Tc–N 2.12, Tc–Cl 2.44 A, estimated standard deviations being 0.01 A for (1) and 0.02 A for (2).

Novel TcP3X3 (XS, O) cores in Tc(III) chemistry

Reaction of pertechnetate with the two bidentate functionalized phosphines (2-diphenylphosphino)-thiopheenol and -phenol; X-ray structure.

Synthesis and characterization of technetium(V) and rhenium(V) oxo-complexes with Schiff-base ligands containing the ONN donor-atom set. Molecular structure of trans-dichloro-oxo[1-(8′-quinolyliminomethyl)-2-naphtholato-NN′O]technetium(V)

Six-co-ordinate complexes of technetium(V) and rhenium(V) containing the MO3+(M = Tc or Re) core were synthesized from [MOCl4]–via ligand-exchange reactions using tridentate Schiff-base ligands containing the ONN donor-atom set. The complexes of general formula [MOCl2Ln][n= 1 – 4; L1= 1-(8′-quinolyliminomethyl)-2-naphtholate, L2=N-(8′-quinolyl)salicylideneiminate, L3= 3-methoxy-N-(8′-quinolyl)salicylideneiminate, L4=N-(2′-dimethylaminoethyl)salicylideneiminate] were characterized by means of physico-chemical measurements and [TcOCl2L1] also by X-ray diffraction analysis. The technetium co-ordination environment in the last complex is a distorted octahedron with the N2O ligand-atom set and the oxo-oxygen occupying the equatorial plane and the two chlorine atoms, respectively trans, in axial positions. The complex crystallizes in monoclinic space group P21/a with a= 23.262(8), b= 7.301(4), c= 11.444(5)A, β= 98.98(5)°, and Z= 4. The structure has been refined to R= 0.048 for 2 693 observed reflections.

Mixed tri- and bi-dentate Schiff-base complexes of technetium(V) and rhenium(V). The crystal structure of N-(2-oxidophenyl)salicylideneiminato-NOO′)oxo(8-quinolinolato-NO)technetium(V)

Six-co-ordinate complexes of technetium(V) and rhenium(V) containing the MO3+ core with triand bi-dentate Schiff-base ligands were synthesized and characterized. The complexes with general formula [MO(L1)L][M = Tc or Re; L1=N-(2-oxidophenyl)salicylideneiminate; L = salicylideneiminate, N-methyl- and N-phenyl-salicylideneiminate, or 8-quinolinolato (quin)] were characterized by elemental analysis, i.r.,1H n.m.r., and mass spectroscopy. The structure of [TcO(L1)(quin)] was also determined by X-ray analysis. The co-ordination around the metal is approximately octahedral. The phenolic oxygen of the quip ligand is trans to the TcO group. The tridentate Schiff-base ligand lies on the equatorial plane with respect to TcO. The complex crystallizes in monoclinic space group P21/n with a= 15.496(8), b= 10.355(4), c= 12.122(5)A, β= 109.03(6)°, and Z= 4. The structure has been refined to R= 0.054 for 2 025 observed reflections.