RESUMEN
Aerobic oxidation of metallaborane compounds is an unexplored field apart from the few reports on accidental oxidation leading to oxametallaboranes. An effective method for the synthesis of group 5 oxametallaboranes has been developed by the oxidation of [(Cp*M)2(B2H6)2] (M = Ta/Nb) (Cp* = η5-C5Me5). The reaction of [(Cp*M)2(B2H6)2] (M = Ta/Nb) with O2 gas at room temperature yielded oxametallaboranes [(Cp*M)2(B4H10O)] (for 1, M = Nb; for 2, M = Ta). Density functional theory calculations signify an increase in the HOMO-LUMO energy gap for 1 and 2 as compared to that for the parent metallaboranes, [(Cp*M)2(B2H6)2] (M = Ta/Nb). Reaction of 1 and 2 with [Ru3(CO)12] led to the isolation of fused metallaborane clusters [(Cp*Nb)2(B2H4O){Ru(CO)2}2(B2H4){Ru(CO)3}2{µ-H}4] (3) and [(Cp*Ta)2(B3H4O){Ru(CO)2}3{µ7-B}{µ-CO}2{µ-H}4] (4). The structure of 3 may be considered as a fusion of five subunits [two tetrahedra (Td), two square pyramids (sqp), and one trigonal bipyramid (tbp)]. One of the key features of cluster 4 is the presence of a µ7-boride atom that shares three cluster units (one monocapped trigonal prism and two Td). All the compounds have been characterized by mass spectrometry, infrared spectroscopy, and 1H, 13C, and 11B nuclear magnetic resonance spectroscopy, and the structural types were unequivocally established by crystallographic analysis of compounds 1, 3, and 4.
RESUMEN
A high-yielding synthetic route for the preparation of groupâ 9 metallaboratrane complexes [Cp*MBH(L)2], 1 and 2 (1, M=Rh, 2, M=Ir; L=C7H4NS2) has been developed using [{Cp*MCl2}2] as precursor. This method also permitted the synthesis of an Rh-N,S-heterocyclic carbene complex, [(Cp*Rh)(L2)(1-benzothiazol-2-ylidene)] (3; L=C7H4NS2) in good yield. The reaction of compound 3 with neutral borane reagents led to the isolation of a novel borataallyl complex [Cp*Rh(L)2B{CH2C(CO2Me)}] (4; L=C7H4NS2). Compound 4 features a rare η(3)-interaction between rhodium and the B-C-C unit of a vinylborane moiety. Furthermore, with the objective of generating metallaboratranes of other early and late transition metals through a transmetallation approach, reactions of rhoda- and irida-boratrane complexes with metal carbonyl compounds were carried out. Although the objective of isolating such complexes was not achieved, several interesting mixed-metal complexes [{Cp*Rh}{Re(CO)3}(C7H4NS2)3] (5), [Cp*Rh{Fe2(CO)6}(µ-CO)S] (6), and [Cp*RhBH(L)2W(CO)5] (7; L=C7H4NS2) have been isolated. All of the new compounds have been characterized in solution by mass spectrometry, IR spectroscopy, and (1)H, (11)B, and (13)Câ NMR spectroscopies, and the structural types of 4-7 have been unequivocally established by crystallographic analysis.
RESUMEN
Among the series of stable closo-borate dianions, [B n H n ]2-, the X-ray crystallographic structure of [B7H7]2- was determined only in 2011. To explore its chemistry and stability, we have isolated and structurally characterized two new transition metal complexes of the heptaborane, [(Cp2M)2B9H11] (Cp = η5-C5H5; M = Zr or Hf). The structures of [(Cp2M)2B9H11] contain a pentagonal bipyramidal B7 core, coordinated by two {Cp2M} and two {BH2} units equatorially. Structural and spectroscopic characterizations and DFT calculations show that [(Cp2M)2B9H11] complexes are substantially more stable than the parent dianion, in either [B7H7]2- or ( n Bu4N)2[B7H7]. Our theoretical study and chemical bonding analyses reveal that the surprising stability of the two new heptaborane metal complexes is due to multi-center covalent bonds related to the two exo-{Cp2M} units, as well as electrostatic interactions between the {Cp2M} units and the B7 core. The facile syntheses of the heptaborane metal-complexes will allow further exploration of their chemistry.
RESUMEN
A new TPE based low molecular weight gelator (LMWG) which displays both AIE and MCIE phenomena in gel state has been synthesized. LMWG self-assembles to form 1D nanofibers which undergo morphology transformation to coordination polymer gel (CPG) nanotubes upon metal ion coordination. CPG shows enhanced mechanical stability along with tunable emission properties.