Nickel(II) and Palladium(II) Complexes with η5:κ1(N)-Coordinated Dicarbollide Ligands Containing Pendant Pyridine Group.

A series of C- and B-substituted nido-carborane derivatives with a pendant pyridyl group was prepared. The synthesized compounds were used as ligands in the complexation reactions with bis(triphenylphosphine)nickel(II) and palladium(II) chlorides to give six new metallacomplexes with unusual η5:κ1(N)-coordination of the metal center. The single crystal structures of 1-(NC5H4-2'-S)-1,2-C2B10H11, 1-(NC5H4-2'-CH2S)-1,2-C2B10H11, Cs [7-(NC5H4-2'-CH2S)-7,8-C2B9H11] closo- and nido-carboranes and 3-Ph3P-3-(4(7)-NC5H4-2'-S)-closo-3,1,2-NiC2B9H10 and 3-Ph3P-3-(4(7)-NC5H4-2'-CH2S)-closo-3,1,2-NiC2B9H10 metallacarboranes were determined using single crystal X-ray diffraction.

Synthesis of Zwitter-Ionic Conjugate of Nido-Carborane with Cholesterol.

9-HC≡CCH2Me2N-nido-7,8-C2B9H11, a previously described carboranyl terminal alkyne, was used for the copper(I)-catalyzed azide-alkyne cycloaddition with azido-3ß-cholesterol to form a novel zwitter-ionic conjugate of nido-carborane with cholesterol, bearing a 1,2,3-triazol fragment. The conjugate of nido-carborane with cholesterol, containing a charge-compensated group in the linker, can be used as a precursor for the preparation of liposomes for BNCT (Boron Neutron Capture Therapy). The solid-state molecular structure of a nido-carborane derivative with the 9-Me2N(CH2)2Me2N-nido-7,8-C2B9H11 terminal dimethylamino group was determined by single-crystal X-ray diffraction.

Synthesis and Structure of Nido-Carboranyl Azide and Its "Click" Reactions.

Novel zwitter-ionic nido-carboranyl azide 9-N3(CH2)3Me2N-nido-7,8-C2B9H11 was prepared by the reaction of 9-Cl(CH2)3Me2N-nido-7,8-C2B9H11 with NaN3. The solid-state molecular structure of nido-carboranyl azide was determined by single-crystal X-ray diffraction. 9-N3(CH2)3Me2N-nido-7,8-C2B9H11 was used for the copper(I)-catalyzed azide-alkyne cycloaddition with phenylacetylene, alkynyl-3ß-cholesterol and cobalt/iron bis(dicarbollide) terminal alkynes to form the target 1,2,3-triazoles. The nido-carborane-cholesterol conjugate 9-3ß-Chol-O(CH2)C-CH-N3(CH2)3Me2N-nido-7,8-C2B9H11 with charge-compensated group in a linker can be used as a precursor for preparation of liposomes for Boron Neutron Capture Therapy (BNCT). A series of novel zwitter-ionic boron-enriched cluster compounds bearing a 1,2,3-triazol-metallacarborane-carborane conjugated system was synthesized. Prepared conjugates contain a large amount of boron atom in the biomolecule and potentially can be used for BNCT.

Bis(dicarbollide) Complexes of Transition Metals as a Platform for Molecular Switches. Study of Complexation of 8,8'-Bis(methylsulfanyl) Derivatives of Cobalt and Iron Bis(dicarbollides).

Complexation of the 8,8'-bis(methylsulfanyl) derivatives of cobalt and iron bis(dicarbollides) [8,8'-(MeS)2-3,3'-M(1,2-C2B9H10)2]- (M = Co, Fe) with copper, silver, palladium and rhodium leads to the formation of the corresponding chelate complexes, which is accompanied by a transition from the transoid to the cisoid conformation of the bis(dicarbollide) complex. This transition is reversible and can be used in design of coordination-driven molecular switches based on transition metal bis(dicarbollide) complexes. The solid-state structures of {(Ph3P)ClPd[8,8'- (MeS)2-3,3'-Co(1,2-C2B9H10)2-κ2-S,S']} and {(COD)Rh[8,8'-(MeS)2-3,3'-Co(1,2-C2B9H10)2-κ2-S,S']} were determined by single crystal X-ray diffraction.

Tungsten carbonyl σ-complexes with charge-compensated nido-carboranyl thioether ligands.

Charge-compensated nido-carboranyl thioether ligands [7-MeS-10-Me2S-7,8-C2B9H10] and [7,8-(MeS)2-10-Me2S-7,8-C2B9H9] were prepared and fully characterized. They readily react with labile tungsten carbonyls to give σ-complexes - mono-substituted (CO)5W[7-MeS-10-Me2S-7,8-C2B9H10-κ(1)-S(1)] and (CO)5W[7,8-(MeS)2-10-Me2S-7,8-C2B9H9-κ(1)-S(1)] and chelate (CO)4W[7,8-(MeS)2-10-Me2S-7,8-C2B9H9-κ(2)-S(1),S(2)]. The synthesized metallocomplexes were characterized by multinuclear NMR spectroscopy and single crystal X-ray diffraction. The donor ability of the 7-methylsulfide-nido-carborane ligand is not sensitive to introduction of the charge-compensating dimethylsulfonium group.

A new approach to the synthesis of functional derivatives of nido-carborane: alkylation of [9-MeS-nido-7,8-C2B9H11]⁻.

A series of asymmetrically substituted sulfonium derivatives of nido-carborane [9-R(Me)S-nido-7,8-C2B9H11] (R = Et, Pr, Bu, Bn, CH=CH2, CH2CH=CH2, CH2C≡CH, CH=C=CH2) were prepared by alkylation of the 9-methylthio-nido-7,8-carborane. The synthesized compounds are the first examples of diastereomers combining nido-carborane and sulfonium chiral centers.