Charge-compensated -carborane derivatives in the synthesis of iron(II) bis(dicarbollide) complexes.

A series of stable iron(II) bis(dicarbollide) derivatives [8,8'-(RNHC(Et)HN)-3,3'-Fe(1,2-CBH)] (R = Pr, R = Ph, (CH)OH, (CH)OH, (CH)NMe) was prepared starting from FeCl or [FeCl(dppe)] and the corresponding -carboranyl amidines [10-RNHC(Et)HN-7,8-CBH]. In a similar way, the reactions of the oxonium derivatives of -carborane with FeCl in tetrahydrofuran in the presence of -BuOK lead to the corresponding stable oxonium derivatives iron(II) bis(dicarbollide) [8,8'-(RR'O)-3,3'-Fe(1,2-CBH)] (RR' = (CH), (CH)O(CH), (CH); R = R' = Et), which can be alternatively prepared by the reaction of the parent iron(II) bis(dicarbollide) with tetrahydrofuran or 1,4-dioxane in the presence of MeSO. The cyclic voltammetry studies of the synthesized iron(II) bis(dicarbollide) derivatives revealed that the introduction of amidinium and oxonium substituents leads to a significant increase in the Fe/Fe redox potential relative to the parent iron(II) bis(dicarbollide).

Nickel(II) and Palladium(II) Complexes with η:κ()-Coordinated Dicarbollide Ligands Containing Pendant Pyridine Group.

A series of - and -substituted -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 η:κ()-coordination of the metal center. The single crystal structures of 1-(NCH-2'-S)-1,2-CBH, 1-(NCH-2'-CHS)-1,2-CBH, Cs [7-(NCH-2'-CHS)-7,8-CBH] - and -carboranes and 3-PhP-3-(4(7)-NCH-2'-S)--3,1,2-NiCBH and 3-PhP-3-(4(7)-NCH-2'-CHS)--3,1,2-NiCBH metallacarboranes were determined using single crystal X-ray diffraction.

Nucleophilic addition reactions to nitrilium derivatives [BHNCCH] and [BHNCCHCH]. Synthesis and structures of -dodecaborate-based iminols, amides and amidines.

The synthesis of the acetonitrilium and propionitrilium derivatives of -dodecaborate [BH] was discussed. The nucleophilic addition reactions of water, alcohols and secondary amines to the activated triple bond of the nitrilium derivatives yielded the corresponding iminols, imidates and amidines. The obtained results were supported by X-ray diffraction studies and DFT calculations.

Synthesis of Boronated Amidines by Addition of Amines to Nitrilium Derivative of Cobalt Bis(Dicarbollide).

A series of novel cobalt bis(dicarbollide) based amidines were synthesized by the nucleophilic addition of primary and secondary amines to highly activated B-N≡C-R triple bond of the propionitrilium derivative [8-EtC≡N-3,3'-Co(1,2-CBH)(1',2'-CBH)]. The reactions with primary amines result in the formation of mixtures of and isomers of amidines, whereas the reactions with secondary amines lead selectively to the -isomers. The crystal molecular structures of -[8-EtC(NMe)=HN-3,3'-Co(1,2-CBH)(1',2'-CBH)], -[8-EtC(NEt)=HN-3,3'-Co(1,2- CBH)(1',2'-CBH)] and -[8-EtC(NCH)=HN-3,3'-Co(1,2-CBH)(1',2'-CBH)] were determined by single crystal X-ray diffraction.

Synthesis and crystal structures of nickel(ii) and palladium(ii) complexes with o-carboranyl amidine ligands.

A number of new nido-carboranyl amidines 10-R(CH)NHC(Et)[double bond, length as m-dash]HN-7,8-CBH (n = 2, R = OH, OMe, and NMe; n = 3, R = OH) were synthesized by the nucleophilic addition of amino alcohols and N,N-dimethylethylenediamine to the highly activated -C[triple bond, length as m-dash]N- triple bond of the 10-propionitrilium derivative of nido-carborane. A similar reaction of 10-EtC[triple bond, length as m-dash]N-7,8-CBH with ethylenediamine unexpectedly resulted in the cleavage of the C[triple bond, length as m-dash]N bond to form the ammonium derivative 10-HN-7,8-CBH. The complexation of the synthesized carboranyl amidines 10-MeO(CH)NHC(Et)[double bond, length as m-dash]HN-7,8-CBH and 10-MeN(CH)NHC(Et)[double bond, length as m-dash]HN-7,8-CBH with nickel and palladium phosphine complexes [(PhP)MCl] (M = Ni, Pd) was studied.

The unexpected reactivity of 9-iodo-nido-carborane: from nucleophilic substitution reactions to the synthesis of tricobalt tris(dicarbollide) Na[4,4',4''-(MeOCHCHO)-3,3',3''-Co(μ-O)(μ-S)(1,2-CBH)].

An unusual reactivity of 9-iodo-nido-carborane [9-I-7,8-CBH] towards nucleophiles under strong basic conditions was revealed. The nucleophilic substitution of iodine with O- and N-nucleophiles results in [9-RO-7,8-CBH] (R = H, CHCHOMe) and [9-L-7,8-CBH] (L = Py, NEt, MeNCHCHNMe), respectively. Reaction of [9-I-7,8-CBH] with CoCl in 1,2-dimethoxyethane in the presence of t-BuOK, depending on the order of addition of the reagents, leads either to a diastereomeric mixture of diiodo derivatives cobalt bis(dicarbollide) rac-[4,4'-I-3,3'-Co(1,2-CBH)] and meso-[4,7'-I-3,3'-Co(1,2-CBH)] or to the corresponding mixture of 2-methoxyethoxy derivatives rac-[4,4'-(MeOCHCHO)-3,3'-Co(1,2-CBH)] and meso-[4,7'-(MeOCHCHO)-3,3'-Co(1,2-CBH)].

Synthesis and study of -substituted methylthio derivatives of cobalt bis(dicarbollide).

The -methylthio derivatives of cobalt bis(dicarbollide) were synthesized by reaction of anhydrous CoCl with -carborane [7-MeS-7,8-CBH] and isolated as a mixture of -[1,1'-(MeS)-3,3'-Co(1,2-CBH)] and -[1,2'-(MeS)-3,3'-Co(1,2-CBH)] isomers. The structures of both isomers were studied using DFT quantum chemical calculations. The most preferable geometry of rotamers and the stabilization energy of -methylthio derivatives of cobalt bis(dicarbolide) were calculated.

Carborane Derivative Conjugated with Gold Nanoclusters for Targeted Cancer Cell Imaging.

Polyhedral borane derivatives have been utilized in the treatment of boron neuron capture therapy (BNCT) for brain glioma, and much attention has been paid to search excellent biocompatible boron-rich composites for effective cancer BNCT therapy. In this study, we have exploited the self-assembly of the gold nanoclusters with carborane amino derivatives (GNCs-CB) for the precise bioimaging of cancer cells and targeted delivery of this carborane compound to the tumors. Our observations demonstrate that the GNCs-CB can readily realize accurate tumor imaging and long-term accumulation in tumor sites by EPR effect and nanometer size effect, and thus efficiently implement tumor-targeting delivery of the carborane derivative and facilitate the real-time fluorescent visualization monitoring of the carborane targeted delivery process.

Cyanide free contraction of disclosed 1,4-dioxane ring as a route to cobalt bis(dicarbollide) derivatives with short spacer between the boron cage and terminal functional group.

The 1,4-dioxane derivative of cobalt bis(dicarbollide) reacts with dialkylsulfides and triphenylphosphine to give the corresponding sulfonium and phosphonium derivatives [8-L(CH2CH2O)2-3,3'-Co(1,2-C2B9H10)(1',2'-C2B9H11)] (L = SMe2, S(CH2CH2)2O, PPh3). The treatment of the triphenylphosphonium derivative with sodium hydroxide results in contraction of the side chain with formation of [8-HOCH2CH2O-3,3'-Co(1,2-C2B9H10)(1',2'-C2B9H11)](-). The same product was obtained by treatment of the dimethylsulfonium derivative with the poorly nucleophilic base t-BuOK, whereas the stronger nucleophiles induce the sulfur demethylation to give [8-MeS(CH2CH2O)2-3,3'-Co(1,2-C2B9H10)(1',2'-C2B9H11)](-).

Synthesis of monosubstituted functional derivatives of carboranes from 1-mercapto-ortho-carborane: 1-HOOC(CH(2))(n)S-1,2-C(2)B(10)H(11) and [7-HOOC(CH(2))(n)S-7,8-C(2)B(9)H(11)](-) (n = 1-4).

A general approach to synthesis of monosubstituted functional derivatives of 1,2-dicarba-closo-dodecaborane (ortho-carborane) is proposed. Reactions of the triethylammonium salt of 1-mercapto-ortho-carborane (Et(3)NH)[1-S-1,2-C(2)B(10)H(11)] with ethyl omega-bromoalkyl carboxylates and omega-bromoalkylnitriles in ethanol result in the corresponding carboranyl esters and nitriles that in turn can be converted to carborane-based carboxylic acids 1-HOOC(CH(2))(n)S-closo-1,2-C(2)B(10)H(11) (n = 1-4). Mild deboronation of the closo-carborane cage with CsF in ethanol gives caesium salts of the corresponding nido-carboranes Cs[7-HOOC(CH(2))(n)S-nido-7,8-C(2)B(9)H(11)].