Raquel Garcia

Rhenium(I) organometallic complexes with novel bis(mercaptoimidazolyl)borates and with hydrotris(mercaptoimidazolyl)borate: chemical and structural studies

Lithium salts of novel poly(mercaptoimidazolyl)borate anions [H(R)B(tim Me ) 2 ] − have been synthesised under mild conditions by reaction of the corresponding lithium organoborohydrides with 2-mercapto-1-methylimidazole. Treatment of the Re(I) starting materials [Re(CO) 5 Br] or (NEt 4 ) 2 [Re(CO) 3 Br 3 ] with the stoichiometric amount of Li[H(R)B(tim Me ) 2 ] (R=Me ( 1 ), Ph ( 2 )) or Na[HB(tim Me ) 3 ] gave the tricarbonyl complexes [Re{κ 3 -R(μ-H)B(tim Me ) 2 }(CO) 3 ] (R=Me ( 3 ), Ph ( 4 )) and [Re{κ 3 -HB(tim Me ) 3 }(CO) 3 ] ( 5 ). These complexes were also prepared under aqueous and aerobic conditions, in almost quantitative yield, using (NEt 4 ) 2 [ReBr 3 (CO) 3 ] as starting material. Compounds 1 – 5 have been characterised by the usual analytical techniques and by X-ray crystallographic analysis in the case of 3 – 5 . The X-ray diffraction analysis of 3 – 5 showed that the rhenium atom adopts a slightly distorted octahedral coordination with a facial arrangement of the carbonyl ligands. In complex 5 the three remaining coordination positions are occupied by the three thione sulphur atoms from the tripodal hydrotris(2-mercapto-1-methylimidazolyl)borate, and in 3 and 4 these positions are occupied by the two thione sulphur atoms and by one hydrogen atom, which is involved in a strong agostic BH⋯Re interaction.

Tris(pyrazolyl)methane 99mTc tricarbonyl complexes for myocardial imaging

Novel ether-containing tris(pyrazolyl)methane chelators stabilize thefac-[99mTc(CO)3]+ moiety providing complexes with significant, fast and stable heart uptake, together with a extremely fast liver clearance.

Rhenium oxocomplexes with the heteroscorpionate phenyltris(pyrazolyl)borate: synthesis and structural studies

Abstract The rhenium(VII) complex [{κ 3 -PhB(pz) 3 }ReO 3 ] ( 1 ) has been prepared and its reactivity towards triphenylphosphine has been evaluated. Reduction of 1 with PPh 3 in the presence of ClSiMe 3 yields [{κ 3 -PhB(pz) 3 }ReOCl 2 ] ( 2 ), while its reduction in the presence of pyridine leads to trans -[{κ 2 -PhB(pz) 3 }ReO 2 (py) 2 ] ( 3 ). Complexes 1 – 3 were fully characterized, including by X-ray diffraction analysis. The structural analysis confirmed the κ 3 - ( 1 and 2 ) or κ 2 - ( 3 ) coordination mode of the heteroscorpionate ligand.

Disruption of Unprecedented B‐H…M Agostic Interactions: An Alternative Approach for Labeling Bioactive Molecules

The agostic B‐H…Re bond in complexes [Re{κ3‐R(μ‐H)B(timMe)2}(CO)3] (R=H (1), Ph (2), timMe = 2‐mercapto‐1‐methylimidazolyl) is readily cleaved by t‐butylisonitrile or cyclohexylisonitrile leading to the mixed‐ligand complexes [Re{κ2‐Ph(μ‐H)B(timMe)2}(C≡NtBu)(CO)3] (3) and [Re{κ2‐H(μ‐H)B(timMe)2}(C≡N‐cyclohexyl)(CO)3] (4), respectively. Bearing in mind the so‐called [2 + 1] mixed ligand approach for the development of target‐pecific radiopharmaceuticals, reactions of 1 with isonitriles carrying the (2‐methoxyphenyl)piperazine pharmacophore (part of WAY 100635) were also studied and the complexes [Re{κ2‐H(μ‐H)B(timMe)2}(C≡N‐R′‐WAY)(CO)3] (R′ = butylene (5), pentylene (6) or hexylene (7)) isolated. The novel mixed Re(I) tricarbonyl complexes (3–7) have been characterized by the usual analytical techniques, which included X‐ray diffraction analysis in the cases of 3, 4 and 5. The affinity of the complexes 5–7 toward the 5‐HT1A receptors was tested in competitive receptor binding assays and the IC50 values found were in the 21.9–66.5 nM range. Complex 7, with the longest spacer length between the isonitrile function and the pharmacophore, has shown an improved selectivity towards the 5‐HT1A subtype of receptors when compared with 5 and 6. This work has been partially supported by the FCT (POCTI/QUI/42939/2001) and by COST B12. Raquel Garcia would like to thank Fundação para a Ciência e Tecnologia for a PhD research grant.

Rhenium(I) tris(carbonyl) complexes with soft scorpionates

The novel tris(mercaptoimidazolyl)borate ligands Li[RB(timMe)3] (R = Me (1), Ph (2)) have been synthesized by reaction, in refluxing toluene, of 2-mercapto-1-methylimidazole with lithium methylborohydride or phenylborohydride, respectively. By reacting 1 and 2 with the Re(I) starting material (NEt4)2[Re(CO)3Br3], the tris(carbonyl) complexes [Re{RB(timMe)3-κ3S,S,S}(CO)3] (R = Me (3), Ph (4)) have been obtained in moderate yields. Compounds 1–4 have been characterized by IR, 1H, and 11B NMR spectroscopies, and also by X-ray crystallographic analysis in the case of 3. The X-ray diffraction analysis of 3 showed that the rhenium atom adopts a slightly distorted octahedral coordination with a facial arrangement of the carbonyl ligands. The three remaining coordination positions are occupied by the thione sulfur atoms from the tripodal methyltris(2-mercapto-1-methylimidazolyl)borate, which adopts a typical propeller-like configuration.