Metal-assisted in situ formation of a tridentate acetylacetone ligand for complexation of fac-Re(CO)3+ for radiopharmaceutical applications.
Reaction of [NEt4]2[ReBr3(CO)3] with 2,4-pentanedione (acac) yields a complex of the type fac-Re(acac)(OH2)(CO)3 (1) under aqueous conditions. 1 was further reacted with a monodentate ligand (pyridine) to yield a fac-Re(acac)(pyridine)(CO)3 complex (2). Complex 1 was found to react with primary amines to generate a Schiff base (imine) in aqueous solutions. When a mixed-nitrogen donor bidentate ligand, 2-(2-aminoethyl)pyridine, that has different coordination affinities for fac-Re(acac)(OH2)(CO)3 was utilized, a unique tridentate ligand was formed in situ utilizing a metal-assisted Schiff base formation to yield a complex fac-Re(CO)3(3[(2-phenylethyl)imino]-2-pentanone) (3). Tridentate ligand formation was found to occur only with the Re-coordinated acac ligand. Reactions of acac with fac-Re(CO)3Br(2-(2-aminoethyl)pyridine) (4) or a mixture of [NEt4]2[ReBr3(CO)3], acac, and 2-(2-aminoethyl)pyridine did not yield the formation of complex 3 in water.
Benny
Paul D
PD
Department of Chemistry, Washington State University, PO Box 644630, Pullman, Washington 99164, USA. bennyp@wsu.edu
Fugate
Glenn A
GA
Barden
Adam O
AO
Morley
Jennifer E
JE
Silva-Lopez
Elsa
E
Twamley
Brendan
B
D002248:Carbon Monoxide / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D018360:Crystallography, X-Ray; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D010422:Pentanones / Q000737:chemistry*; D019275:Radiopharmaceuticals / Q000737:chemistry*; D012211:Rhenium / Q000737:chemistry*
D008024:Ligands; D010422:Pentanones; D019275:Radiopharmaceuticals; C008790:acetylacetone; D012211:Rhenium; D002248:Carbon Monoxide