DSpace at VNU: Rhenium and technetium complexes with tridentate S,N,O ligands derived from benzoylhydrazine

Polyhedron 28 (2009) 3945–3952 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly Rhenium and technetium complexes with tridentate S,N,O ligands derived from benzoylhydrazine Hung Huy Nguyen a,1, Ulrich Abram b,* a b Department of Chemistry, Hanoi University of Sciences, 19 Le Thanh Tong, Hanoi, Viet Nam Institute of Chemistry and Biochemistry, Freie Universität Berlin, Fabeckstr 34-36, D-14195 Berlin, Germany a r t i c l e i n f o Article history: Received 25 August 2009 Accepted 14 September 2009 Available online 29 September 2009 Keywords: Rhenium Technetium Mixed-ligand complexes Benzoylthioureas X-ray structure a b s t r a c t A potentially tridentate ligand with an S,N,O donor set, H2L, is formed by the reaction of N-[(diethylaminothiocarbonyl)benzimidoyl chloride with benzoylhydrazine Reactions of H2L with (NBu4)[MOCl4] complexes (M = Re, Tc) give five-coordinate, neutral oxo complexes of the composition [MOCl(L)] Mixed-ligand complexes of rhenium(V) containing the tridentate L2À ligand and bidentate N,N-dialkylN0 -benzoylthioureato ligands (R2btuÀ) are formed in high yields when (NBu4)[ReOCl4] is treated with mixtures of H2L and HR2btu Another approach to the mixed-ligand products is the reaction of [ReOCl(L)] with an equivalent amount of HR2btu Ó 2009 Elsevier Ltd All rights reserved Introduction The widespread use of the radionuclide 99mTc in diagnostic nuclear medicine and the potential of the b-emitting radioisotopes 186 Re and 188Re in radiotherapy cause a continuing interest in the coordination chemistry of technetium and rhenium [1,2] In this context, there is a permanent need for efficient chelating systems Ligands, which are suitable for the stabilization of the {MV@O}3+ cores (M = Re, Tc) are of particular interest, since reduction of [MO4]À ions from the commercial generator systems with common reducing agents frequently form oxometallates(V) Ligand systems, which stabilize this core under physiological conditions are tetradentate N,S,O chelators [3,4] However, the tuning of the biological properties of the resulting complexes by variations in the periphery of the ligands is difficult and sometime results in the formation of different stereoisomers [4] Mixed-ligand approaches give access to a smooth tuning of the ligand properties and, thus, of their biological behavior Following the so-called mixed-ligand concept, many ‘3+1’ systems, which are neutral complexes with a [MO]3+ core and a mixed-ligand set of a dianionic tridentate ligand containing one or more sulfur donor atoms, such as [SSS], [SOS], [SNS], [SNN], or [ONS], and a monodentate thiolate were studied [5] Finally, it * Corresponding author Tel.: +49 30 838 54002; fax: +49 30 838 52676 E-mail address: abram@chemie.fu-berlin.de (U Abram) Present address: Institute of Chemistry and Biochemistry, Freie Universität Berlin, Fabeckstr 34-36, D-14195 Berlin, Germany 0277-5387/$ - see front matter Ó 2009 Elsevier Ltd All rights reserved doi:10.1016/j.poly.2009.09.012 was found that many of these ‘3+1’ complexes were relatively unstable in vitro and in vivo due to a ready substitution of the labile monothiolate RSÀ by physiological thiols such as cysteine or glutathione [6] Generally, this may be explained by the 16 valence electron nature of the five-coordinate ‘3+1’ complexes Replacement of the labile monothiolate by bidentate ligands results in so-called ‘3+2’ systems with a closed-shell electron configuration and, thus, a higher stability is expected [7] Several ‘3+2’ mixed-ligand complexes with ligands carrying different donor sets such as [SNS]/ [PO] [7], [NOS]/[NO] [8], [NOS]/[NN] [9], [NON]/[OO] [10], [NOS]/ [SN] [11] or [ONO]/[PO] were studied [12] Some of them show interesting properties, which encourage further studies and the introduction of hitherto not regarded ligand systems in such considerations In previous papers, we described synthesis and characterization of a new class of tridentate N-(dialkylaminothiocarbonyl)benzamidine ligands (H2R2tcba) which form stable, five-coordinate complexes of the composition [ReOCl(R2tcba)] (1) [13], and elucidated the coordination chemistry of N,N-dialkyl-N0 -benzoylthioureas, HR2btu, with rhenium and technetium (Scheme 1) [14] The advantage of these two ligand classes is the convenience of modifications in the periphery of their chelating system This allows the variation of fundamental properties of the products such as solubility, polarity and lipophilicity and also gives access to bioconjugation via the periphery of the tridentate ligands With complexes of the types and 2, appropriate starting materials are available with the bidentate and tridentate ligands already in coordination positions, which are expected for the intended mixedligand compounds, and we could show that stable mixed-ligand 3946 H.H Nguyen, U Abram / Polyhedron 28 (2009) 3945–3952 R1 N N NH R2 S O OH Et R3 H N N N R4 S HR2btu Cl N N O O Cl Re O R2 R3 S Cl N N S Re R4 Cl O R1 N N R2 S M R3 S O NH N Et S H2L Scheme Synthesis of H2L R1 O HN R3, R4 = alkyl or aryl Ph3P N - Et3N.HCl N O R1R2 = Et2 or Morph O Et S Et2tcbCl H2R2tcba N N Et PhCONHNH2 Et3N, Me2CO N N R4 M = Re, Tc Scheme Related ligands and hitherto known rhenium complexes complexes of the composition [MO(R2tcba)(R2btu)] (M = Re, Tc) (3) can readily be prepared [15] In extension of this work, we synthesized a novel tridentate ligand, H2L, by the reaction of N-(diethylaminothiocarbonyl)benzimidoyl chloride (R2tcbCl) with benzoylhydrazine and studied its reaction patterns with common rhenium and technetium complexes can readily be checked by thin-layer chromatography and is conveniently indicated by the formation of a colorless precipitate of NEt3ÁHCl, which is almost insoluble in acetone The IR spectrum of H2L is characterized by absorptions of the NH stretches at 3225 and 3163 cmÀ1 and a very strong absorption at 1655 cmÀ1, which can be assigned to the C@O vibration The 1H NMR spectrum reflects the hindered rotation around the C–NEt2 bond, which is typically indicated by broad singlet signals corresponding to the ethyl residues This has also been found for other thiocarbamoylbenzamidines [13,15–18] Fig illustrates the structure of H2L together with the intramolecular hydrogen bond between the nitrogen atom of the benzoylhydrazone unit and the sulfur atom An additional intermolecular hydrogen bond is established between N3 and O57 Selected bond lengths and angles are summarized in Table The positions of the hydrogen atoms at the atoms N3 and N59 are indicated by peaks of electron density in the final Fourier maps of the structure refinement and the fact that they are involved in hydrogen bonds This finding is also consistent with the bond lengths of the C–N bonds in the ligand framework, in which the C4–N5 bond of 1.266(4) Å is within the expected range of a C@N double bond and the C4–N3 distance of 1.431(4) Å is a typical C–N single bond This is in perfect agreement with structure C of Scheme and a description as a benzoylhydrazone Such a bonding situation is hitherto without precedence for the thiocarbamoylbenzamidines under study In corresponding structures, such as derivatives with aromatic amines [13] or thiosemicarbazones [17], a hydrogen atom Results and discussion 2.1 Synthesis and structure of H2L Reactions of N-(N0 ,N0 -dialkylaminothiocarbonyl)benzimidoyl chlorides with primary amines have been shown to be a convenient approach for the synthesis of bidentate S,N ligands [16] or tridentate S,N,O, S,N,N or S,N,S chelators [13,17] The coordination behavior of the obtained ligands strongly depends on the amines used, since they significantly influence the basicity of the N donor position and the denticity of the resulting ligand system While the coordination chemistry of the bidentate ligands has been studied with a variety of metal ions [18], the tridentate systems have hitherto only be used for the formation of rhenium and technetium complexes [13,17] The novel benzoylhydrazine derivative H2L is formed by the reaction of N-(N0 ,N0 -diethylaminothiocarbonyl)benzimidoyl chloride and benzoylhydrazine In the presence of the supporting base NEt3, the reaction proceeds quickly and under mild conditions The product can be isolated as colorless, microcrystalline, analytically pure solid in high yields (Scheme 2) The progress of the reaction Fig Molecular structure of H2L Thermal ellipsoids represent 50% probability [23] Table Selected bond lengths (Å) in H2L S1–C2 C2–N3 C2–N6 N3–C4 1.694(4) 1.373(4) 1.335(4) 1.431(4) C4–N5 N5–N59 N59–C58 C58–O57 1.266(4) 1.383(4) 1.376(4) 1.222(4) 3947 H.H Nguyen, U Abram / Polyhedron 28 (2009) 3945–3952 R2 R1 N H N N S Ph O N H Ph R2 R1 N S A R R N S N Ph Ph N H R2 R N N Ph Ph O N SH N Ph N H Ph R2 E OH H N S D C R2 OH B O H N R1 N H N N R1 N N Ph N Ph OH N SH N N Ph Ph F Fig Molecular structure of [TcOCl(L)] (4) Thermal ellipsoids represent 50% probability [23] H atoms are omitted for clarity Scheme Conformers of H2L locates on the nitrogen atom N5 and a double bond is established between C4 and N3 It can also not be excluded that in solution and/or in metal complexes of the compound the other conformers of Scheme play a considerable role 2.2 [MOCl(L)] complexes (M = Tc, Re) The reaction of H2L with the common technetium(V) precursor (NBu4)[TcOCl4] in methanol at room temperature gives rapidly a red solid of the composition [TcOCl(L)] (4) (Scheme 4) The infrared spectrum of complex exhibits a strong bathochromic shift of the mC@O band of about 150 cmÀ1, together with the disappearance of absorptions in the region above 3150 cmÀ1, which correspond to mNH stretches in the uncoordinated H2L Both results indicate chelate formation with a large degree of p-electron delocalization within the chelate rings and the expected double deprotonation of the ligand An intense band appearing at 976 cmÀ1 can be assigned to the Tc@O vibration [19] The 1H NMR spectrum provides additional evidence for the proposed composition and molecular structure of the complex The rotation around the C–NEt2 bond in is more restricted than that in the uncoordinated H2L This is reflected by two sets of well resolved signals corresponding to the methyl groups The corresponding signals of the methylene protons are sparingly resolved and appear as a broad signal Fig depicts the molecular structure of compound as a prototype compound for these types of complexes Selected bond lengths and angles are listed in Table The technetium atom possesses a distorted square–pyramidal coordination environment with an oxo ligand in the apical position and the square plane formed by the donor atoms of the tridentate ligand and the chloro ligand This square plane is slightly distorted, with a main deviation of 0.097(1) Å from a mean least-square plane for atom O57 The Tc atom is situated by 0.691(1) Å above the basal plane towards the oxo ligand All O10–Tc–X angles (X = equatorial donor Table Selected bond lengths (Å) and angles (°) in [TcOCl(L)] (4) and [ReOCl(L)](5) M–O10 M–Cl M–S1 M–N5 M–O57 S1–C2 C2–N3 O10–M–Cl O10–M–S1 O10–M–N5 O10–M–O57 S1–M–N5 1.644(2) 2.3356(6) 2.2878(6) 1.994 (2) 1.970(1) 1.756(2) 1.335(3) 108.03(6) 108.62(6) 107.08(7) 111.92(7) 89.99(5) 1.647(9) 2.349(3) 2.276(3) 1.972(9) 1.967(7) 1.74(1) 1.36(1) 110.0(4) 108.1(3) 107.9(5) 112.5(4) 91.4(2) C2–N6 N3–C4 C4–N5 N5–N59 N59–C58 C58–O57 1.333(3) 1.317(3) 1.351(3) 1.409(2) 1.281(3) 1.340(2) 1.34(1) 1.30(1) 1.37(1) 1.43(1) 1.28(1) 1.33(1) S1–M–O57 S1–M–Cl N5–M–O57 N5–M–Cl O57–M–Cl 139.45(4) 82.92(2) 77.57(6) 144.63(5) 85.55(4) 139.4(2) 84.5(1) 76.3(3) 141.2(3) 82.0(2) atom) fall in the range between 107° and 112° This is in good agreement with the typical bonding situation of square–pyramidal TcVO complexes [19] The Tc@O distance of 1.644(2) Å is within the expected range of a technetium–oxygen double bond [19] Despite the fact that the six-membered ring formed by Tc, S1, C2, N3, C4 and N5 is not planar with a maximum distortion from the mean least-square plane of 0.263(1) Å for the Tc atom, a reasonable delocalization of p-electrons is observed Consequently, the C–S and C–N bonds inside the chelate ring possess partially double bond character The bonding situation in the five-membered chelate ring is similar to those in typical benzoylhydrazone complexes with shortened C58–N59 and lengthened C58–O57 bonds, being both in the range between carbon–nitrogen and carbon–oxygen single and double bonds The reaction of H2L with (NBu4)[ReOCl4] is much slower than that with the analogous technetium starting material The ligand exchange product of the composition [ReOCl(L)] (5) can be isolated after a period of several hours as red, microcrystalline solid directly from the reaction mixture in good yield Addition of a supporting Et O Cl Cl M Cl N - Cl M = Re, Tc + HN NH N S Et Et N + NEt3, MeOH - (HNEt3)Cl N O O S M O (4) M = Tc Scheme Synthesis of [MOCl(L)] complexes N N Cl (5) M = Re Et 3948 H.H Nguyen, U Abram / Polyhedron 28 (2009) 3945–3952 base like NEt3 accelerates the rate of the reaction, but results in the formation of side-products, which are mainly formed by solvolysis of the complex The IR spectrum of reveals a m(Re@O) frequency at 991 cmÀ1 [19] and a strong bathochromic shift of the C@N band as a consequence of the complex formation The 1H NMR spectrum of is very similar to that of 4, except that the resolution of the methylene proton signals is much better than in the spectrum of the technetium compound and four overlapping multiplet signals with ABX3 coupling patterns of CH2 protons can be identified in the region between 3.9 and 4.1 ppm In the 13C NMR spectrum of 5, the separated signals of two ethyl groups are also observed due to the hindered rotation The resonances assigned for C@N, C@S and C@O, respectively, appear at 166.69, 172.70 and 173.73 ppm The molecular structure of is virtually identical with that of its technetium analogue Therefore, no extra figure is given for this compound Selected bond lengths and angles are compared with the corresponding values of in Table The atomic numbering scheme of Fig has also been applied for the rhenium compound As discussed for technetium compound 4, the metal atom in has a distorted square–pyramidal coordination sphere and is located 0.691(1) Å above the equatorial plane formed by S1, N5, O57 and Cl The Re–O distance of 1.647(9) Å is within the typical range of a rhenium–oxygen double bond [19] All other structural features discussed above for the technetium complex holds also true for the rhenium analogue 2.3 Mixed-ligand complexes of the composition [ReO(L)(R1R2btu)] Mixed-ligand complexes of the composition [ReO(L)(R1R2btu)] (6) can be synthesized by two different routes (Scheme 5) The first approach concerns a two-step synthesis, in which is used as the starting compound This labile square–pyramidal complex is treated with equimolar amounts of benzoylthioureas in warm CH2Cl2/ MeOH and the mixed-ligand complexes are obtained in high yields The complexes can alternatively be prepared in one-pot reactions from (NBu4)[ReOCl4] and stoichiometric amounts of the tridentate benzamidine and bidentate benzoylthioureas The yields of such reactions are not significantly lower than those obtained from the two-step procedure When the ligands are added subsequently, the supporting base should be added a few minutes after Et N N N O N (TBA)[ReOCl4] (5) Re O Et S Cl HR1R2btu,H2L, Et3N HR R btu, Et3N Et N N N O N Et S Re R1 S O O N N (6) R2 a: R1 = R2 = Ph b: NR1R2 = morpholinyl Scheme Synthesis of the mixed-ligand complexes the addition of the second ligand in order to avoid undesired sidereactions The products are readily soluble in CH2Cl2, but sparingly soluble in MeOH Single crystals of good quality are obtained by slow evaporation of CH2Cl2/MeOH mixtures of the complexes Infrared spectra of complexes not show any absorption in the regions above 3100 cmÀ1, which indicates the expected double deprotonation of benzamidines and the single deprotonation of the benzoylthiourea ligands during complex formation Additionally, the sharp intense absorptions in the range between 1620 and 1690 cmÀ1, which are assigned to the mC@N and mC@O stretches in the spectra of the non-coordinated benzamidines and benzoylthioureas shift to the range between 1500 and 1540 cmÀ1 and appear as broad bands Intense bands each at 972 cmÀ1 are assigned to the Re@O stretches [19] They appear about 20 cmÀ1 bathochromically shifted with respect to the corresponding absorption in Because of the hindered rotation around the C–NR2 bonds and the rigidity of the tertiary amine nitrogen atoms in both the benzamidine and benzoylthiourea ligands, the 1H NMR spectra of are complicate Especially for complex 6b, the rigidity of the morpholinyl moiety in the coordinated morphbtuÀ ligand makes all eight protons of the morpholine ring magnetically inequivalent This is indicated by four well resolved multiplet signals with ABXY splitting patterns at 4.29, 4.34, 4.46 and 4.58 ppm of four different CH2–O protons and four CH2–N protons appear in two multiplet signals at 3.74 and 3.89 ppm The 13C NMR spectra of the complexes are more simple, since they are only influenced by hindered rotation around the C–NR2 bonds As the consequence, two separated signals for each CH2 and CH3 carbon atoms in NEt2 groups and/or CH2–N and CH2–O atoms of the morpholinyl moiety are observed The chemical shifts of the aromatic carbon atoms, which can not be unambiguously assigned, are in the range between 127 ppm and 136 ppm Resonances of the carbon atoms of the C@X groups (X = N, O, S) appear in the range from 163 ppm to 187 ppm The very similar structures between benzoylthioureas and thiocarbamoylbenzamidines produce difficulties in the assignment of the C@X signals in the 13C NMR spectra of the complexes Nevertheless, with respect to their analogous coordination sphere, the chemical shifts of the C@N, C@S and C@O signals of (L)2À in the two complexes should be essentially the same and appear at 163 ppm, 174 ppm and 176 ppm FAB+ mass spectra of the mixed-ligand complexes show intense peaks of the molecular ions with the expected isotopic patterns Interestingly, fragments which result from the loss of R1R2NC„N residues of the R1R2btuligand appear in all spectra as intense signals The molecular structures of 6a and 6b are depicted in Fig Selected bond lengths and angles are given in Table In these structures, the rhenium atoms exhibit distorted octahedral coordination environments Axial positions are occupied by terminal oxo ligands and the oxygen atoms of the bidentate R1R2btuÀ ligands The tridentate thiocarbamoylbenzamidine ligands coordinate meridional and the remaining position of the equatorial coordination sphere is occupied by the sulfur atom of the R1R2btuÀ ligand The metal atoms are located slightly above the mean least-square planes formed by the atoms S1, N5, O57 and S12 toward the oxo ligand with a distance of 0.410(2) Å for 6a and 0.381(3) Å for 6b The Re@O distances of 1.644(8) and 1.659(7) Å are in the expected range of rhenium–oxygen double bonds A remarkable structural feature in complexes is the coordination of the benzoylic oxygen atoms trans to the oxo ligands The Re–O15 bonds of 2.219(7) and 2.249(6) Å are at the upper limit of trans-O@Re–O single bond lengths in Re(V) oxo complexes Similar values have previously been reported only for some complexes with small monodentate neutral ligands such as H2O, MeOH or Me2CO [19] However, the C14–O15 bonds are not significantly shorter than corresponding distances in R1R2btuÀ ligands in other 3949 H.H Nguyen, U Abram / Polyhedron 28 (2009) 3945–3952 rhenium complexes [14] All Re–S11 and C12–S11 bond lengths are in the typical range of Re–S single bonds and CAS bonds with partially double bond character as has been previously reported for oxorhenium(V) complexes with a variety of benzoylthiourea ligands [19] In the benzamidine moiety, the Re–S1 and Re–N5 bond distances are lengthened by about 0.03–0.06 Å compared to the values in Additionally, the Re–S1 bonds are by about 0.06 Å shorter than the Re–S11 bonds which are in their cis positions While the two chelate rings of the benzamidine ligands are almost planar, the six-membered rings of the benzoylthioureas are dramatically distorted This is mainly due to the large deviations of the Re atoms of 1.448(6) Å (compound 6a) and 1.483(8) Å (compound 6b) from the least-square planes formed by the other atoms of the chelate rings Nevertheless, a considerable delocalization of p-electron density inside the chelate rings is observed for both the benzoylthiourea and the benzamidine ligands This is mainly indicated by the observation of almost identical bond lengths for all C–N bonds, which fall within the range between C–N single and double bonds The bond length equalization is also extended to the C2–N6 and C12–N16 bonds (1.33–1.36 Å), which are clearly shorter than expected for C–N single bonds The partial transfer of electron density into these bonds well agrees with the 1H NMR spectra of the compounds, which indicate a rigid arrangement of –NR1R2 moieties Conclusions We could demonstrate that the tridentate ligand H2L readily forms five-coordinate technetium and rhenium complexes of the composition [MOCl(L)] The remaining chloro ligand is labile and can readily be replaced by bidentate chelators such as N,N-dialkyl-N0 -benzoylthioureas The resulting mixed-ligand complexes can also be prepared in one-pot reactions starting from (NBu4) [ReOCl4] and mixtures of H2L and benzoylthioureas The presented study on prototype compounds is the experimental basis of ongoing studies in our laboratory which deal with ligands of the same type, which contain anchor groups for the conjugation to peptides or proteins Experimental 4.1 Materials Fig Molecular structures of (a) [ReO(L)(Ph2btu)] (6a) and (b) [ReO(L)(morphbtu)} (6b) Thermal ellipsoids represent 50% probability [23] H atoms are omitted for clarity All reagents used in this study were reagent grade and used without further purification Solvents were dried and freshly distilled prior use unless otherwise stated (NBu4)[ReOCl4], Table Selected bond lengths (Å) and angles (°) in [ReO(L)(Ph2btu)] (6a) and [ReO(L)(morphbtu)] (6b) Re–O10 Re–S1 Re–N5 Re–O57 Re–O15 Re–S11 O10–Re–Sl O10–Re–S11 O10–Re–N5 O10–Re–O57 O10–Re–O15 O57–Re–N5 O57–Re–S1 O57–Re–S11 6a 6b 1.659(7) 2.313(2) 2.041(7) 2.043(5) 2.249(6) 2.391(2) 103.3(3) 101.6(3) 102.1(3) 95.7(3) 172.1(3) 78.1(3) 160.8(2) 92.2(2) 1.644(8) 2.327(3) 2.020(9) 2.052(7) 2.214(7) 2.403(3) 102.8(3) 98.5(3) 102.8(4) 96.0(3) 169.9(3) 77.8(3) 160.5(2) 96.3(2) 6a 6b S1–C2/S11–C12 C2–N3/C12–N13 N3–C4/N13–C14 C4–N5/C14–O15 C2–N6/C12–N16 1.75(1)/1.770(9) 1.36(1)/1.34(1) 1.31(1)/1.32(1) 1.32(1)/1.263(9) 1.36(1) /1.35(1) 1.77(1)/1.75(1) 1.33(2)/1.34(1) 1.34(1)/1.32(1) 1.32(1)/1.27(1) 1.32(1)/1.33(1) O57–Re–O15 N5–Re–S1 N5–Re–S11 N5–Re–O15 S1 –Re–S11 S1 –Re–O15 S11 –Re–O15 76.6(2) 94.5(2) 155.1(2) 77.8(2) 87.26(9) 84.5(1) 77.7(2) 75.3(3) 92.7(3) 158.4(3) 80.7(3) 86.3(1) 86.4(2) 77.7(2) 3950 H.H Nguyen, U Abram / Polyhedron 28 (2009) 3945–3952 (NBu4)[TcOCl4] [20] were prepared by published methods HR1R2btu ligands [21] and N-(diethylaminothiocarbonyl)benzimidoyl chloride [16] were synthesized by the standard procedures of Beyer et al 4.2 Radiation precautions 99 Tc is a weak bÀ-emitter All manipulations with this isotope were performed in a laboratory approved for the handling of radioactive materials Normal glassware provides adequate protection against the low-energy beta emission of the technetium compounds Secondary X-rays (bremsstrahlung) play an important role only when larger amounts of 99Tc are used 4.3 Physical measurements Infrared spectra were measured as KBr pellets on a Shimadzu FTIR-spectrometer between 400 and 4000 cmÀ1 ESI mass spectra were measured with an Agilent 6210 ESI-TOF (Agilent Technologies) All MS results are given in the form: m/z, assignment Elemental analysis of carbon, hydrogen, nitrogen, and sulfur were determined using a Heraeus vario EL elemental analyzer The 99 Tc values were determined by standard liquid scintillation counting NMR-spectra were taken with a JEOL 400 MHz multinuclear spectrometer 4.4 Synthesis of the ligand H2L chloride N-(N0 ,N0 -Diethylaminothiocarbonyl)benzimidoyl (1.227 g, mmol) was dissolved in 10 mL dry acetone and slowly added to a stirred mixture of benzoylhydrazine (680 mg, mmol) and NEt3 (1.51 g, 15 mmol) in 10 mL of dry acetone The mixture was stirred for h at room temperature The formed precipitate of NEt3ÁHCl was filtered off and the filtrate was evaporated under reduced pressure The residue was re-dissolved in 10 mL CH2Cl2 and extracted two times with brine solution (2 Â 10 mL) The organic phase was dried over MgSO4 and evaporated under reduced pressure to dryness The resulting residue was treated with diethylether (15 mL) and stored at À20 °C for 24 h The crude product was filtered off, dried under vacuum and recrystallized from CH2Cl2/n-hexane Yield: 56% (0.991 g) Anal Calc for C19H22N4OS: C, 64.38; H, 6.26; N, 15.81; S, 9.05 Found: C, 64.51; H, 6.42; N, 15.62; S, 9.00% IR (m in cmÀ1): 3225(m), 3163(m), 3043(m), 2931(m), 1655(vs), 1542(vs), 1504(vs), 1481(vs), 1261(s), 1142(m), 1072(m), 1026(m), 779(m), 713(s), 694(s).1H NMR (CDCl3; d, ppm): 0.92 (s, br, 3H, CH3), 1.00 (s, br, 3H, CH3), 3.40 (s, br, 2H, CH2), 3.76 (s, br, 2H, CH3), 7.36–7.48 (m, 6H, Ph), 7.77 (d, J = 7.2 Hz, 2H, Ph), 7.84 (d, J = 7.4 Hz, 2H, Ph) 7.50 (t, J = 7.3 Hz, H, Ph), 7.84 (d, J = 7.9 Hz, H, Ph), 8.01 (d, J = 8.1 Hz, H, Ph) 4.5.2 [ReO(L)Cl] (5) The red microcrystalline was prepared from (NBu4)[ReOCl4] and H2L by a similar procedure as described for 4, except that the reaction time was increased and the precipitation of the product was finished only after h Yield: 61% (36 mg) Anal Calc for C19H20ClN4O2SRe: C, 38.67; H, 3.42; N, 9.49; S, 5.43 Found: C, 38.47; H, 3.50; N, 9.41; S, 5.22% IR (m in cmÀ1): 3055(w), 2989(w), 2932(w), 1508(vs), 1438(m), 1389(m), 1326(m), 1292(m), 1145(w), 1072(w), 1026(w), 991(s), 775(m), 709(m), 691(s) 1H NMR (CDCl3, d, ppm): 1.33 (t, J = 7.1 Hz, 3H, CH3), 1.39 (t, J = 7.1 Hz, 3H, CH3), 3.90 (m, 2H, CH2), 4.12 (m, 2H, CH2), 7.32 (t, J = 7.2 Hz, 2H, Ph), 7.38 (t, J = 7.0 Hz, 1H, Ph), 7.43 (t, J = 7.5 Hz, 2H, Ph), 7.51 (t, J = 7.4 Hz, 1H, Ph), 7.85 (d, J = 7.9 Hz, 2H, Ph), 8.05 (d, J = 8.3 Hz, 2H, Ph).13C NMR (CDCl3, d, ppm): 12.91, 13.20 (CH3), 47.41, 47.83 (N–CH2), 127.70, 127.78, 128.45, 128.65, 130.94, 131.76, 132.10 and 134.98(Ph), 166.69 (C@N), 172.70(C@S), 173.73 (C@O) 4.5.3 [ReO(L)(R1R2btu)] (6) Method [ReO(L)Cl] (59 mg, 0.1 mmol) was dissolved in CH2Cl2 (10 mL) HR1R2btu (0.1 mmol) and three drops of NEt3 were added under stirring The red colored solution was heated under reflux for h and the solvent was removed under vacuum to dryness The resulting residue was either washed with cold MeOH or recrystallized from CH2Cl2/MeOH to give red crystalline products Method A mixture of H2L (35 mg, 0.1 mmol) and HR1R2btu (0.1 mmol) in mL acetone was added to a solution of (NBu4) [ReOCl4] (58 mg, 0.1 mmol) in mL CH2Cl2 After stirring at room temperature for 10 min, three drops of NEt3 were added and the mixture was heated under reflux for h This resulted in the formation of a dark red solution The solvent was removed in vacuo and the residue was treated as described in method 4.5 Syntheses of complexes 4.5.4 Data for [ReO(L)(Ph2btu)] (6a) Yield: 63% (56 mg) for method 1, 71% (63 mg) for method Anal Calc for C39H35N6O3S2Re: C, 52.86; H, 3.98; N, 9.48; S, 7.24 Found: C, 52.00; H, 3.25; N, 9.37; S, 6.93% IR (m in cmÀ1): 3055(w), 2978(w), 2924(w), 1512(vs),1450(s), 1427(vs), 1404(vs), 1334(m), 1257(m), 972(s), 694(s) 1H NMR (CDCl3; d, ppm): 1.23 (t, 3H, CH3), 1.25 (t, 3H, CH3), 3.74 (m, 2H, CH2), 3.91 (m, 1H, CH2), 4.00 (m, 1H, CH2), 6.99(t, J = 7.9 Hz, 2H, Ph), 7.2–7.4(m, 19H, Ph), 7.79(d, J = 8.4 Hz, 2H, Ph), 7.99(d, J = 8.4 Hz, 2H, Ph) 13C NMR (CDCl3; d, ppm): 13.35 (CH3), 13.38 (CH3), 46.58 (CH2), 47.49 (CH2), 127–136 (Ph), 163.20 (C@N, L2À), 173.10 (C@S, Ph2btuÀ), 174.05 (C@S, L2À), 176.18 (C@O, L2À), 186.95 (C@O, Ph2btuÀ) FAB+ MS (m/z): 909, 11%, [M+Na]+; 887, 40%, [M+H]+; 814, 6%, [MÀNEt2]+; 692, 65%, [MÀPh2NC„N]+ 4.5.1 [TcO(L)Cl] (4) H2L (42 mg, 0.12 mmol) dissolved in mL MeOH was added dropwise to a stirred solution of (NBu4)[TcOCl4] (58 mg, 0.1 mmol) in mL MeOH The color of the solution immediately turned deep red and a red precipitate deposited within a few minutes The red powder was filtered off, washed with cold methanol and dried under vacuum X-ray quality single crystals of were obtained by slow evaporation of a dichloromethane/methanol solution Yield: 50% (26 mg) Anal Calc for C19H20ClN4O2STc: Tc, 20.8 Found: Tc, 20.7% IR (m in cmÀ1): 3055(w), 2985(w), 2932(w), 2870(w), 1504(vs), 1434(m), 1389(s), 1354(m), 1327(m), 1292(m), 1174(w), 1095(w), 1064(w), 1026(w), 976(s), 775(m), 698(s) 1H NMR (CDCl3; d, ppm): 1.30 (t, J = 7.1 Hz, H, CH3), 1.37 (t, J = 7.1 Hz, H, CH3), 3.90–4.00 (m, H, CH2), 7.32 (t, J = 7.4 Hz, H, Ph), 7.36 (t, J = 6.9 Hz, H, Ph), 7.42 (t, J = 7.7 Hz, H, Ph), 4.5.5 Data for [ReO(L)(morphbtu)] (6b) Yield: 40% (32 mg) for method 1, 59% (47 mg) for method Anal Calc for C31H33N6O4S2Re: C, 46.31; H, 4.14; N, 10.55; S, 7.98 Found: C, 46.22; H, 4.04; N, 10.40; S, 8.12% IR (m in cmÀ1): 3062(w), 2978(w), 2926(w), 1520(vs),1488(vs), 1420(vs), 1350(s), 1311(s), 1234(m), 1110(m), 1065(m), 1026(m), 972(s), 771(m), 694(s) 1H NMR (CDCl3; d, ppm): 1.23 (t, 3H, CH3), 1.25 (t, 3H, CH3), 3.74 (m, 2H, morphNCH2), 3.89 (m, 2H, morphNCH2), 3.95– 4.05 (m, 4H, NCH2), 4.29 (m, 1H, morphOCH2), 4.34 (m, 1H, morphOCH2), 4.46 (m, 1H, morphOCH2), 4.58 (m, 1H, morphOCH2), 7.09 (t, J = 7.7 Hz, 2H, Ph), 7.21–7.27(m, 4H, Ph), 7.34–7.41 (m, 3H, Ph), 7.68(d, J = 7.1 Hz, 2H, Ph), 7.81(d, J = 8.3 Hz, 2H, Ph), 7.90 (d, J = 8.3 Hz, 2H, Ph) 13C NMR (CDCl3; d, ppm): 13.37 (CH3), 13,40 (CH3), 46.59 (NCH2), 47.57 (NCH2), 48.32 (NCH2), 49.81 (NCH2), 67.12 (OCH2), 67.34 (OCH2), 127.37, 127.72, 127.96, 3951 H.H Nguyen, U Abram / Polyhedron 28 (2009) 3945–3952 Table X-ray structure data collection and refinement parameters Formula Mw Crystal system a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Space group Z Dcalc (g cmÀ3) l (mmÀ1) No of reflections No of independent No of parameters R1/wR2 Goodness-of-fit (GOF) CSD deposit number H2L [TcOCl(L)] (4) [ReOCl(L)] (5) [ReO(L)(Ph2btu)] (6a) [ReO(L)(morphbtu)] (6b) C19H22N4OS 354.48 orthorhombic 15.496(3) 14.953(2) 15.847(2) 90 90 90 3671.9(10) Pbca 1.282 0.191 9423 4744 249 0.0505/0.0886 0.741 CCDC-728398 C19H20ClN4O2STc 501.90 monoclinic 12.148(1) 12.886(1) 13.126(1) 90 98.02(1) 90 2034.6(3) P21/n 1.639 0.964 16 151 5473 254 0.0288/0.0618 0.948 CCDC-728400 C19H20ClN4O2ReS 590.10 monoclinic 9.718 (1) 13.510(1) 15.564(1) 90 95.28(1) 90 2034.7(3) P21/n 1.926 6.229 15 294 5483 254 0.0749/0.1676 0.916 CCDC-728399 C39H35N6O3ReS2 886.05 monoclinic 15.940(5) 13.429(5) 18.565(5) 90 111.56(1) 90 3696(2) Cc 1.592 3.447 13 016 7280 461 0.0534/0.1268 1.086 CCDC-728401 C31H33N6O4ReS2 803.95 triclinic 9.547(5) 10.245(5) 16.751(5) 105.03(1) 90.08(1) 97.66(1) 1567(1)  P1 128.48, 129.56, 129.80, 130.42, 130.67, 131.44, 132.01, 135.42 and 136.47 (Ph), 163.25 (C@N, L2À), 171.99 (C@S, morphbtuÀ), 173.93 (C@S, L2À), 176,19 (C@O, L2À), 184.85 (C@O, morphbtuÀ) FAB+ MS (m/z): 827, 9%, [M+Na]+; 805, 38%, [M+H]+; 692, 37%, [MÀmorphC„N]+; 572, 35%, [ReO2(L2À)]+ 4.6 X-ray crystallography The intensities for the X-ray determinations were collected on a STOE IPDS 2T instrument with Mo Ka radiation (k = 0.71073 Å) Standard procedures were applied for data reduction and absorption correction Structure solution and refinement were performed with SHELXS97 and SHELXL97 [22] Hydrogen atom positions were calculated for idealized positions and treated with the ‘riding model’ option of SHELXL More 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1997 [23] L.J Farrugia, J Appl Crystallogr 30 (1997) 565  ... bidentate ligands has been studied with a variety of metal ions [18], the tridentate systems have hitherto only be used for the formation of rhenium and technetium complexes [13,17] The novel benzoylhydrazine. .. the rhenium atoms exhibit distorted octahedral coordination environments Axial positions are occupied by terminal oxo ligands and the oxygen atoms of the bidentate R1R2btuÀ ligands The tridentate. .. novel tridentate ligand, H2L, by the reaction of N-(diethylaminothiocarbonyl)benzimidoyl chloride (R2tcbCl) with benzoylhydrazine and studied its reaction patterns with common rhenium and technetium