Alkyne coupling at a rhenium–monocarborane substrate: synthesis of Re,B-η2:σ-butadienyl complexes

Abstract

Treatment of 7-NH(2)Bu(t)-nido-7-CB(10)H(12) in tetrahydrofuran (THF) with LiBu(n)(3 equiv) and then [ReBr(CO)(3)(THF)(2)] gives the rhenacarborane dianion [1-NHBu(t)-2,2,2-(CO)(3)-closo-2,1-ReCB(10)H(10)](2-), isolated as the bis-[N(PPh(3))(2)](+) salt (4). Iodine oxidation of this Re(I) intermediate gives the Re(III) complex [1,2-mu-NHBu(t)-2,2,2-(CO)(3)-closo-2,1-ReCB(10)H(10)] 6 in which the carborane functions formally as an 8-electron (6pi+ 2sigma) donor. Reaction of with ligands L in the presence of Me(3)NO gives substituted products [1,2-mu-NHBu(t)-2,2-(CO)(2)-2-L-closo-2,1-ReCB(10)H(10)][L = PPh(3)(7a), CNXyl (7b; Xyl = C(6)H(3)Me(2)-2,6), or Bu(t)C triple bond CH (7c)]. Formation of complex 7c is unexpectedly accompanied by [1,2-mu-NHBu(t)-2,2-(CO)(2)-3,2-sigma:eta(2)-{C(=CHBu(t))-CH=CHBu(t)}-closo-2,1-ReCB(10)H(9)] 8a, in which an alkyne-derived dienyl group is bound to both the rhenium centre and to an adjacent boron vertex. Complex 8a is also obtained from 7c with Bu(t)C triple bond CH and Me(3)NO. The same reaction of 7c, using PhC triple bond CH or CNXyl instead of Bu(t)C triple bond CH, gives, respectively, [1,2-micro-NHBu(t)-2,2-(CO)(2)-3,2-sigma:eta(2)-{C(=CHBu(t))-CH=CHPh}-closo-2,1-ReCB(10)H(9)] 8b and [1,2-micro-NHBu(t)-2-Bu(t)C triple bond CH-2-CO-2-CNXyl-closo-2,1-ReCB(10)H(10)] 9. Addition of donors L to results in displacement from rhenium of the pendant dienyl moiety, yielding [1,2-mu-NHBu(t)-2,2-(CO)(2)-2-L-3-{C(=CHBu(t))-CH=CHBu(t)}-closo-2,1-ReCB(10)H(9)][L = PMe(3)(10a), CNBu(t)(10b)]. Single-crystal X-ray diffraction analyses have confirmed the novel structural features of compounds 6, 7c, 8b and 9.

Metal complexes of monocarbon carboranes bearing C-amine or -amino substituents

“…An X-ray diffraction study confirmed that in this iodo derivative there are two intramolecular amino bridges between cage vertices and the molybdenum [38]. Interestingly, on reaction with PEt 3 in refluxing thf a CO molecule in 39 is substituted by the phosphine, rather than an amino bridge being lifted, with formation of an {MoI(CO) 2 (PEt 3 )} group.…”

“…Elimination of H 2 from G again produces a piperidinyl group bridging between a cage a-boron and the molybdenum center, as seen in H, which is the anion of 35. In contrast the reaction between [7-NHBu t -nido-7-CB 10 [38]. An X-ray diffraction analysis of 36 confirmed its molecular structure.…”

“…The difference in reactivity towards [Mo(CO) 3 -(NCMe [NH(CH 2 ) 5 = piperidine] [38]. In this way several new complexes were discovered containing one or two intramolecular amino groups bridging between cage vertices and the molybdenum center.…”

Aerobically stable and substitutionally labile α-diimine rhenium dicarbonyl complexes

“…10 The reagent has been used successfully for the decarbonylation of different Re tricarbonyl complexes. [10][11][12][13][14][15][16][17] Kurtz et al, e.g., prepared a series of compounds of the type cis-[Re(diimine)(CO) 2 (L)Cl] (where L ¼ P(OEt) 3 , PMe 3 ) by exploiting the trans-labilizing effect of phosphorus ligands to facilitate carbonyl replacement. 12,17 Similarly the group of Wilson synthesized and structurally characterized analogous complexes as the active photoactivated species in a study that reported the in vitro anticancer activity of rhenium(I) tricarbonyl complexes bearing water-soluble phosphines.…”

Aerobically Stable and Substitutionally Labile α-Diimine Rhenium Dicarbonyl Complexes

“…10 The reagent has been used successfully for the decarbonylation of different Re tricarbonyl complexes. [10][11][12][13][14][15][16][17] Kurtz et al, e.g., prepared a series of compounds of the type cis-[Re(diimine)(CO) 2 (L)Cl] (where L = P(OEt) 3 , PMe 3 ) by exploiting the trans-labilizing effect of phosphorus ligands to facilitate carbonyl replacement. 12,17 Similarly the group of Wilson synthesized and structurally characterized analogous complexes as the active photoactivated species in a study that reported the in vitro anticancer activity of rhenium(I) tricarbonyl complexes bearing water-soluble phosphines.…”