Synthesis of Ortho- and Meta-Re(I)-Metallocarboranes in Water

Abstract

A series of metallocarboranes of the types rac-[M(CO)3(eta(5)-7-R-7,8-C2B9H11)]-, rac-[M(CO)3(eta(5)-7-R-8-R'-7,8-C2B9H11)]-, and rac-[M(CO)3(eta(5)-7-R-7,9-C2B9H11)]- (M=Re) were prepared by reacting [NEt4]2[Re(CO)3Br3] or [Re(CO)3(OH2)3]Br with the corresponding carboranes in the presence of aqueous solutions of either alkali metal or tetraalkylammonium fluoride salts. Carborane derivatives that were investigated included those containing pyridine, amino, carboxylic acid, carbohydrate, and aryl substituents. During the course of the research, it was discovered that Re metallocarboranes can be prepared directly from the respective closo-clusters under similar reaction conditions used with nido-carboranes. Reaction yields ranged from modest to excellent depending on the carborane isomer and the nature of the cage substituent(s). A crystal structure of an amine-substituted Re metallocarborane was obtained where the complex crystallized in the orthorhombic space group P2(1)2(1)2(1) with a=8.982(2) A, b=11.563(3) A, c=16.811(4) A, alpha=beta=gamma=90 degrees, V=1746.1(7) A3, Z=4, and R1=0.0684.

Synthesis and screening of bifunctional radiolabelled carborane-carbohydrate derivatives

“…We recently described the preparation and labelling of simple carboranyl glycoside derivatives of glucose with both Tc and iodine [44,45]. Building on the success of the model system, a nido-carboranyl glycoside 1 that contains a benzoic acid group for conjugation to targeting vectors such as peptides, proteins, or antibodies was developed (Fig.…”

Nucleoside-metallacarborane conjugates - synthesis of a uridine - bearing 3,3,3-(CO)3-closo-3,1,2-ReC2B9H10 complex

“…This direct synthesis of Re-carborane complexes allows the number of steps necessary to prepare the desired compound to be reduced. 11,12,19,28 Briefly, 3′,5′-diacetyl-2′-O-(o-carboran-1-yl)uridine (1) was synthesised from uridine in a five-step procedure, as described by Soloway's group. 29 Compound 1 was combined with a slight excess of [NEt 4 ] 2 [ReBr 3 (CO) 3 ] in a solution of 500 mM TEAF containing a small quantity of absolute ethanol, which was needed to solubilise compound 1.…”

“…[8][9][10][11][12][13][14] Rhenacarboranes were prepared several years ago. 11,12,[14][15][16][17][18][19][20] 131 I-rhenacarborane is enzymatically stable and is able to cross the blood-brain barrier (BBB) by transmembrane diffusion, allowing this compound to accumulate in the brain in substantial amounts. 21 The biomedical applications of icosahedral carboranes make use of their extraordinary hydrophobicities when employed as substituents in biomolecules, their apparent invisibility to know enzyme systems and their boron content, which is suitable for Boron Neutron Capture Therapy (BNCT There is an entire area of radiopharmaceuticals devoted to the application of radiolabeled nucleic acids, and the use of the components of nucleic acids, nucleosides and nucleotides, may be advantageous.…”

Glycoconjugates of polyhedral boron clusters

“…Since Re and Tc exists in the same group of the periodic table, a variety of Re and 99 Tc carborane complexes have been prepared using mild tetraethyl ammonium fluoride (TEAF) as the reagent instead of using strong bases like KF or NaH [35]. hours.…”