Oxorhenium(V) complexes containing tridentate Schiff-base and monothiol coligands

Schiff base chemistry of the rhenium(V)-oxo core with '3+2' ligand donor sets

Reactions of [ReOCl(3)(PPh(3))(2)] with the bidentate ligands 2-(2-hydroxyphenyl) benzoxazole and (2'-hydroxyphenyl)-2-thiazoline resulted in the isolation of the complexes [ReOCl(2)(OC(6)H(4)-2-C=NC(6)H(4)-2-O)(PPh(3))] (1) and [ReOCl(2)(OC(6)H(4)-2-C=NCH(2)CH(2)S)(PPh(3))] (2). Reactions of 1 with the tridentate Schiff base ligands salicylaldehyde 2-hydroxyanil (H(2)L(1b)), salicylaldehyde 2-mercaptoanil (H(2)L(2b)) afnd S-benzyl-2-[(2-hydroxyphenyl)methylene] dithiocarbazate (H(2)L(3b)) yielded the '3+2' rhenium(V) oxo species [ReO(OC(6)H(4)-2-C=NC(6)H(4)O) (OC(6)H(4)CH=NC(6)H(4)O)] (3), [ReO(OC(6)H(4)-2-C=NC(6)H(4)O)-(OC(6)H(4)CH=NC(6)H(4)S)] (4) and [ReO(OC(6)H(4)-2-C=NC(6)H(4)O){OC(6)H(4)CH=N-N=C(SCH(2)C(6)H(5))S}] (5). Similarly, the reactions of [ReOCl(2)(OC(6)H(4)-2-C=NC(6)H(4)S)(PPh(3))] (2) with H(2)L(2b), H(2)L(3b) and 2-[(2-hydroxyphenyl) methylene]-N-phenyl-hydrazinecarbothioamide (H(2)L(4b)) were exploited to prepare [ReO(OC(6)H(4)-2-C=NC(6)H(4)S)(OC(6)H(4)CH=NC(6)H(4)O)] (6), [ReO(OC(6)H(4)C=NC(6)H(4)S){OC(6)H(4)CH=N-N=C (SCH(2)C(6)H(5))S}] (7) and [ReO(OC(6)H(4)-2-C=NC(6)H(4)S){OC(6)H(4)CH=N-N=C(NHC(6)H(5))}] (8), respectively.

Synthesis and structural characterization of rhenium(I) tricarbonyl complexes with the bidentate ligands o-(diphenylphosphino)benzaldehyde (P∩O) and o-[(diphenylphosphino)benzylidene]analine (P∩N)

A series of rhenium(I) tricarbonyl complexes with bidentate P,O donor ligand o-(diphenylphosphino)benzaldehyde (P∩O) and its Schiff base P,N donor ligand o-[diphenylphosphino)benzylidene]analine (P∩N) have been synthesized and structurally characterized. All the complexes of the type [ReX(CO)(3)(LL)] (where LL = P∩O, P∩N) reveal a distorted octahedral structure with the three carbonyl ligands arranged in the facial fashion. Crystal data for 1, C(22)H(15)ClO(4)PRe·1/2C(6)H(14): triclinic, P1, a=8.7430(4), b=9.5767(4), c=13.9449(6) Å, α=93.651(1), β=101.265(1), γ=93.048(1); V=1140.20(9) Å(3), Z=2.2, C(22)H(15)BrO(4)Pre: monoclinic, C2/c, a=31.6800(16), b=8.8880(4), c=18.4517(9) Å, β=124.990(1); V=4256.4(4) Å(3), Z=8. 3, C(28)H(20)ClNO(3)Pre: monoclinic, C2/c, a=22.675(4), b=8.803(2), c=28.218(5) Å, β=100.192(3); V=5543.5(16) Å(3), Z=8.4, C(28)H(20)BrNO(3)Pre: monoclinic, C2/c, a=23.035(1), b=8.7561(4), c=28.269(1) Å, β=100.811(1); V=5600.4(5) Å(3), Z=8.

Syntheses and structural characterization of rhenium-bis-hydrazinopyrimidine core complexes with thiolate and Schiff base coligands

The reaction of perrhenate with 2-hydrazinopyrimidine in MeOH-HCl yields [ReCl(3)(eta(1)-NNC(4)H(3)N(2)H)(eta(2)-HNNC(4)H(3)N(2))] (1). The analogous reaction with Na(2)MoO(4) yields [MoCl(3)(eta(1)-NNC(4)H(3)N(2)H)(eta(2)-HNNHC(4)H(3)N(2))] (1a). The reaction of 1 with pyrimidine-2-thiol and triethylamine produces [Re(eta(1)-C(4)H(3)N(2)S)(eta(2)-C(4)H(3)N(2)S)(eta(1)-NNC(4)H(3)N(2))(eta(2)-HNNC(4)H(3)N(2))] (2), while reaction of 1 with the Schiff base HSC(6)H(4)N=C(H)C(6)H(4)OH provides [Re(eta(3)-SC(6)H(4)N=C(H)C(6)H(4)O)(eta(1)-NNC(4)H(3)N(2))(eta(2)-C(6)H(4)O)(eta(1)-NNC(5)H(4)N)(eta(2)-HNNC(5)H(4)N)] (4), was also synthesized by reacting [ReCl(3)(eta(1)-NNC(5)H(4)NH)(eta(2)-HNNC(5)H(4)N)] with HSC(6)H(4)N=C(H)C(6)H(4)OH. The crystal structures of 1-4 have been determined.

An unexpected '4+2' [N(3)S]:[NS] rhenium(IV) complex formed upon cleavage of a Re(V) imido bond

The reaction of [Re(NMe)Cl(3)(PPh(3))(2)] with the pentadentate [N(3)S(2)] ligand pyN(2)H(2)S(2)-H(2) [2,6-bis(2-mercaptophenylamino)dimethylpyridine] (1) in the presence of triethylamine did not yield the anticipated six-coordinate complex [Re(NMe)(eta(5)-pyN(2)HS(2))] (2), but rather resulted in cleavage of the Re(V)=NMe bond. A novel six-coordinate Re(IV) [N(3)S]/[NS] complex [Re(eta(4)-SC(6)H(4)-2-NCH(2)-C(5)H(3)N-C=NC(6)H(4)-2-S)(eta(2)-NHC(6)H(4)-2-S)] (4) was thus obtained with the simultaneous coordination of 2-aminothiophenol, a dianionic bidentate [NS] donor resulting from the decomposition of the parent ligand and ligand 3, a dianionic tetradentate [N(3)S] donor formed by partial self-condensation and subsequent oxidation of the parent ligand 1. Crystal data for 4: C(25)H(18)N(4)S(3)Re.CH(2)Cl(2), monoclinic, space group P2(1)/n, a = 9.255(2) A, b = 11.181(2) A, c = 25.316(4) A, beta = 97.434(3) degrees , V = 2587.8(7) A(3) and Z = 4.

The syntheses and structures of '3+2' and '2+2+1' oxorhenium mixed-ligand complexes employing 8-hydroxy-5-nitroquinoline as the bidentate N,O donor ligand

The syntheses and structural characterizations of a series of novel '3+2' and '2+2+1' mixed-ligand complexes carrying 8-hydroxy-5-nitroquinoline (HL) as the bidentate N,O donor atom system are reported. Thus one-pot reactions of [ReOCl(3)(PPh(3))(2)] with dianionic tridentate ligands H(2)L(n) (where H(2)L(1)=HOC(6)H(4)-2-CH=NC(6)H(4)-2-OH; H(2)L(2)=HOC(6)H(4)-2-CH=N-C(6)H(4)-2-SH; H(2)L(3)=HOC(6)H(4)-2-CH=NN=C(NHC(6)H(5))-SH; H(2)L(4)=2-CH(2)OH-C(5)H(3)N-6-CH(2)SH; and H(2)L(5)=2-CO(2)H-C(5)H(3)N-6-CO(2)H) and HL afforded a series of '3+2' oxorhenium complexes of the type [ReO(H(2)L(n))(L)] 2-6, which exhibit distorted octahedral geometries. Crystals of 1 are monoclinic space group C2/c, a=16.702(1), b=14.275(1), c=22.363(2) A, beta=108.083(1) degrees V=5068.2(7) A(beta) and Z=8; those of 2 are monoclinic space group P2(1)/n, a=8.5093(4) b=38.518(2), c=11.6092(5) A, beta=97.708(1) degrees , V=3770.7(3) A(3) and Z=8; those of 5 are triclinic, space group P1-, a=7.5899(8), b=10.322(1), c=11.905(1) A, alpha=78.636(2) degrees , beta=74.229(2) degrees , gamma=71.391(2) degrees , V=844.3(2) A(3), and Z=2. Upon reaction of 2,6-pyridinedimethanol (H(2)L(6)) with the intermediate complex [ReOCl(2)(L)(PPh(3))] (1), only one of the two methylene hydroxy group was deprotonated and a new '2+2+1' complex [ReO(OCH(3))(HL(6))(L)].CH(3)OH (7) was obtained. Crystal data for 7: monoclinic P2(1)/n, a=12.0579(6), b=11.0993(6), c=14.9262(8) A, beta=107.872(1) degrees , V=1901.2(2) A(3), and Z=8. In the preparation of complex 3, cleavage of the C=N bond of the Schiff base H(2)L(2) was observed and the '2+2+1' complex 8 [ReO(PPh(3))(eta(2)-NHC(6)H(4)-2-S)(L)].CH(2)Cl(2) having 2-aminothiophenol as a dianionic bidentate ligand was isolated. Crystals of 8 are monoclinic space group C2/c, a=25.627(2), b=8.1305(6) c=31.404(2) A beta=96.147(1) degrees , V=6505.7(8) A(3), and Z=8. Reduction of HL to 8-hydroxy-5-aminoquinoline was realized during the formation of complex 6, and a new complex 9 was thus isolated involving the coordination of two sets of N,O donor atoms from L and 8-hydroxy-5-aminoquinoline while a methoxy oxygen atom completes the octahedral coordination geometry. Crystals of 9 are monoclinic space group P2(1)/n, a=7.5330(6), b=15.095(1), c=16.394(1) A, beta=99.690(2) degrees , V=1837.7(3) A(3), and Z=4.

Schiff base chemistry of the {ReO} core: structural characterization of the unusual '3 + 2' complex [ReO(eta-OC(6)H(4)-CH=NC(6)H(4)-2-S)(eta-OC(6)H(4))]

The reaction of [ReOCl(3)(PPh(3))(2)] with salicylaldehyde-2-mercaptoanil (1) in methanol yields [ReO(OCH(3))(PPh(3))(eta(3)-OC(6)H(4)CH=NC(6)H(4)S)] (3). Reaction of 3 with 2-(2-hydroxyphenyl)benzothiazole (2) produces [ReO(eta(3)-OC(6)H(4)CH=NC(6)H(4)S)( eta(2)-OC(6)H(4))] (4) in good yield. Compound 4 may also be prepared directly from the reaction of [ReOCl(3)(PPh(3))(2)] with excess 1, after prolonged reaction times in the presence of atmospheric oxygen. The structure of 3 exhibits a distorted octahedral Re(V) center coordinated to a terminal oxo-group, a methoxy ligand, a triphenylphosphine ligand, and the N, O and S donors of the tridentate Schiff base ligand. The octahedral geometry of 4 is defined by the terminal oxo-group, the N, O and S donors of the tridentate Schiff base ligand, and the N and O donors of the bidentate 2-(2-hydroxophenyl)benzothiazole ligand. Oxidation and cyclization of the Schiff base salicylaldehyde-2-mercaptoanil to produce 2-(2-hydroxyphenyl)benzothiazole is precedented and in this instance may be driven by the formation of the robust '3+2' complex 4.

Investigations of the {ReO} core: A '2+2' complex from bidentate and potentially trident ligands: [ReO(η-HOC(6)H(4)-2-CH(2)NC(6)H(4)S)(η-SC(5)H(4)N)(PPh(3))]

The reaction of [ReOCl(3)(PPh(3))(2)] with N-(2-hydroxybenzyl)-2-mercaptoaniline (H(3)hbma) (2) and 2-mercaptopyridine in hot CHCl yields [ReO(η(2)-HOC(6)H(4)-2-CH(2)NC(6)H(4)S)(η(2)-SC(5)H(4)N)(PPh(3))] (3). The structure of 3 consists of distorted octahedral Re(V) monomers. The coordination geometry at the rhenium is defined by a terminal oxo-group, the nitrogen and sulfur donors of the chelating mercaptopyridine, the nitrogen and sulfur donors of a bidentate (Hhbma)(2-) ligand, and the phosphorus of the PPh(3) group. The -C(6)H(4)OH arm of (Hhbma)(2-) is pendant, and the coordinated nitrogen of this ligand is present as a deprotonated amido nitrogen.

Structural characterizations of an Re(IV) complex [ReCl(4)(OPPh(3))(2)] and of an imino species [ReOCl(2)(PPh(3))(eta-OC(6)H(4)-2-CH=NH)] prepared from the reaction of [ReOCl(3)(PPh(3))(2)] with salicylaldoxime

The reaction of [ReOCl(3)(PPh(3))(2)] with salicylaldoxime unexpectedly yields [ReCl(4)(OPPh(3))(2)] (1) and [ReOCl(2)(PPh(3))(eta(2)-OC(6)H(4)-2-CH=NH)] (2). The crystal structure of the Re(IV) complex 1 consists of discrete mononuclear units. The Re site is bound to four chlorides and two trans oxygens of the OPPh(3) groups. The crystal structure of 2 is also mononuclear with the geometry of the Re(V) center defined by a terminal oxo-group, two cis chlorides, the phosphorus of the PPh(3), and the nitrogen and oxygen donors of the phenoxyimino ligand [OC(6)H(4)-2-CH=NH](-).

Synthesis and characterization of complexes of the {ReO} core with SNS and S donor ligands

The reaction of [ReOCl(3)(PPh(3))(2)] with N,N-bis(2-mercaptoethyl)benzylamine and 4-bromobenzenethiol allowed for the isolation of [ReO{eta(3)-(SCH(2)CH(2))(2)N(CH(2)C(6)H(5))}-(eta(1)-C(6)H(4)Br-4-S)] (1). The reaction of [ReOCl(3)(PPh(3))(2)] with [(HSCH(2)CH(2))(2)N(CH(2)C(5)H(4)N)] and the appropriate thiol in chloroform treated with triethylamine has led to the isolation of a series of neutral rhenium complexes of the type [ReO{eta(3)-(SCH(2)CH(2))(2)N(CH(2)C(5)H(4)N)}(eta(1)-C(6)H(4)X-4-S)] (X = Br (2), Cl (3), F (4), and OCH(3) (5)) and [ReO{eta(3)-(SCH(2)CH(2))(2)N(CH(2)C(5)H(4)N)}(eta(1)-C(6)H(4)OCH(3)-4-CH(2)S)] (6). Likewise, under similar reaction conditions, the use of the related tridentate ligand, [(HSCH(2)CH(2))(2)N(CH(2)CH(2)C(5)H(4)N)], has led to the isolation of a series of rhenium complexes of the type [ReO{eta(3)-(SCH(2)CH(2))(2)N(CH(2)CH(2)C(5)H(4)N)}(eta(1)-C(6)H(4)X-4-S)] (X=Br (7), Cl (8), OCH(3) (9)), as well as [ReO{eta(3)-(SCH(2)CH(2))(2)N(CH(2)CH(2)C(5)H(4)N)}(eta(1)-C(6)H(4)Cl-4-CH(2)S)].0.5CH(3)(CH(2))(4)CH(3) (10). These compounds are extensions of the '3+1' approach to the synthesis of materials with the {MO}(3+) core (M=Tc and Re), which have applications in nuclear medicine. The ligands chosen allow systematic exploration of the consequences of para-substitution on the monodentate thiolate ligand [S] and of derivatization of the substituent R on the tridentate aminodithiol ligand [SNS] of the type (HSCH(2)CH(2))(2)NR. Such modifications can influence lipophilicity, charge, size and molecular weight of the complex and consequently the biodistribution.

Oxorhenium(V) complexes containing tridentate Schiff-base and monothiol coligands

The reaction of [n-(C(4)H(9))(4)N][ReOBr(4)(OPPh(3))] with the tridentate Schiff-base [HOC(6)H(4)C(H)NC(6)H(4)SH] allows for the isolation of [ReOBr{eta(3)-(OC(6)H(4)C(H)NC(6)H(4)S)}] (1). The reaction of [n-(C(4)H(9))(4)N][ReOBr(4)(OPPh(3))] with [HOC(6)H(4)C(H)NC(6)H(4)SH] and the appropriate benzenethiol (C(6)H(4)X-4-SH) where X=H, Br, Cl, F, and OCH(3) in methanol-acetonitrile treated with triethylamine has led to the isolation of a series of rhenium complexes of the type [ReO{eta(3)-(OC(6)H(4)C(H)NC(6)H(4)S)} (eta(1)-C(6)H(4)X-4-S)] (X=H (2), Br (3), Cl (4), F (5), and OCH(3) (6)). Likewise, under similar reaction conditions, the use of benzylmercaptan ligands of the type (C(6)H(4)X-4-CH(2)SH) where X=H, Cl, F, and OCH(3) has led to the isolation of a series of rhenium complexes of the type [ReO{eta(3)-(OC(6)H(4)C(H)NC(6)H(4)S)} (eta(1)-C(6)H(4)X-4-CH(2)S)] (X=H (7), Cl (8), F (9), and OCH(3) (10)). The incorporation of the appropriate amine functionality into the substituent R of the monodentate ligand allows for the isolation of a cationic oxorhenium(V) species, namely, [ReO{eta(3)-(OC(6)H(4)C(H)NC(6)H(4)S)} (eta(1)-C(5)H(4)NH-2-S)][Br] (11).