High-Temperature, High-Pressure Hydrothermal Synthesis of Ba₃[B₆O₁₀(OH)₂](CO₃) and Ba₆[B₁₂O₂₁(OH)₂](CO₃)₂, Two Barium Borate Carbonates with 2D Layer and 3D Framework Structures

Two new barium borate carbonates, Ba3[B6O10(OH)2]­(CO3) (1) and Ba6[B12O21(OH)2]­(CO3)2 (2), have been synthesized by high-temperature, high-pressure hydrothermal methods at 460 °C and 600 bar and structurally characterized by single-crystal X-ray diffraction, TGA, IR, and MAS 11B NMR spectroscopy. The descriptors of the fundamental building blocks (FBB) of both structures are 2Δ4□:⟨Δ2□⟩=⟨4□⟩=⟨Δ2□⟩. The FBB of 1 has a chair conformation, and the FBBs of 2 have both chair and boat conformations. Compound 1 adopts a noncentrosymmetric 2D layer structure with the Ba2+ cations and CO32– anions between the layers, whereas compound 2 has a centrosymmetric 3D framework structure containing 9- and 10-ring channels with the Ba2+ cations and CO32– anions at the center or on the edges of the channels. The two structures are two of the few examples where the carbonate groups are isolated and occupy their own independent sites

Neighboring Metal-Induced Oxidative Addition in Conjunction with a Hydride Trap: Formation of [(η⁵-MeC₅H₄)Fe(CO)(μ-η¹:η¹-PPh₂CH₂PPh₂)(μ-H)M(CO)₄] (M = W, Mo)

The reaction of (η4-MeC5H5)Fe(CO)2(η1-dppm), 1, with M(CO)3L3 produced (η5-MeC5H4)Fe(CO)(μ-η1:η1-dppm)(μ-H)M(CO)4, 3 (L3 = (C2H5CN)3, (THF)3, C7H8; M = W, Mo). The novel hydrido-bridged Fe(II)−M(0) compound was likely formed via the following steps:  coordination of the monodentate dppm to M and then CO migration from Fe to M with a sequential or concerted oxidative addition of the endo-C−H bond of the η4-MeC5H5 ligand to give the (η5-MeC5H4)FeH complex, followed by a trapping of the Fe−H bond by M, forming a six-membered heterocyclic ring in 3

Insertion Reactions of CO into the Rhenium−Nitrogen Bond. η²-Carbamoyl Complexes and Their Reactions

Deprotonation of [(CO)2RReNH(CH3)CH2CH2(η5-C5H4)]+X- (R = CO2Me, CO2Et; X = Br) followed by heating under a CO atmosphere yields the corresponding CO insertion compound (CO)2RReC(O)N(CH3)CH2CH2(η5-C5H4). An anologous insertion reaction proceeds more rapidly for the complexes [(CO)2XReNH(CH3)CH2CH2(η5-C5H4)]+Y- (X = Br, I, PhS, and PhSe) in which X is a strong electron-withdrawing group. Without the presence of external ligands, the oxygen of the resultant carbamoyl group binds to the rhenium to fulfill the 18-electron rule. The η2-carbamoyl selenolate complex [(CO)PhSeRe(η2-CO)N(CH3)CH2CH2(η5-C5H4)] (9b) has been characterized by X-ray crystallography. Upon addition of two-electron-donor ligands, such as CO, isocyanides, and trialkyl phosphites, the η2-carbamoyl complexes convert cleanly to the corresponding η1-carbamoyl complexes

Synthesis, Photophysical, and Anion-Sensing Properties of Quinoxalinebis(sulfonamide) Functionalized Receptors and Their Metal Complexes

We report the synthesis, characterization, and photophysical properties of a series of organic receptors and their corresponding ReI and RuII metal complexes as anion probes featuring bis(sulfonamide) interacting sites incorporating highly chromophoric π-conjugated quinoxaline moieties. The interactions with various anions were extensively investigated. These probe molecules are capable of recognizing F-, OAc-, CN-, and H2PO4- with different sensitivities. The probe−anion interactions can be easily visualized via naked-eye colorimetric or luminescent responses. Probe 1 has the weakest acidic sulfonamide N−H protons and therefore simply forms hydrogen-bonding complexes with F-, OAc-, CN-, and H2PO4-. Probe 2 undergoes a stepwise process with the addition of F- and OAc-:  formation of a hydrogen-bound complex followed by sulfonamide N−H deprotonation. Direct sulfonamide N−H deprotonation occurs upon the addition of CN-, while only a hydrogen-bound complex forms with the H2PO4- ion for probe 2 in a dimethyl sulfoxide (DMSO) solution. Similar probe−anion interactions occur in probe 3 with the addition of F-, CN-, or H2PO4-. However, only a genuine hydrogen-bound complex forms in the presence of the OAc- ion in a DMSO solution of probe 3 because of the subtle difference in the pKa values of sulfonamide N−H protons when probes 2 and 3 are compared. Coordination of probe 1 to a ReI center or probe 2 to a RuII center increases the intrinsic acidity of sulfonamide N−H protons and results in an enhanced sensitivity to anions

Synthesis, Photophysical, and Anion-Sensing Properties of Quinoxalinebis(sulfonamide) Functionalized Receptors and Their Metal Complexes

We report the synthesis, characterization, and photophysical properties of a series of organic receptors and their corresponding ReI and RuII metal complexes as anion probes featuring bis(sulfonamide) interacting sites incorporating highly chromophoric π-conjugated quinoxaline moieties. The interactions with various anions were extensively investigated. These probe molecules are capable of recognizing F-, OAc-, CN-, and H2PO4- with different sensitivities. The probe−anion interactions can be easily visualized via naked-eye colorimetric or luminescent responses. Probe 1 has the weakest acidic sulfonamide N−H protons and therefore simply forms hydrogen-bonding complexes with F-, OAc-, CN-, and H2PO4-. Probe 2 undergoes a stepwise process with the addition of F- and OAc-:  formation of a hydrogen-bound complex followed by sulfonamide N−H deprotonation. Direct sulfonamide N−H deprotonation occurs upon the addition of CN-, while only a hydrogen-bound complex forms with the H2PO4- ion for probe 2 in a dimethyl sulfoxide (DMSO) solution. Similar probe−anion interactions occur in probe 3 with the addition of F-, CN-, or H2PO4-. However, only a genuine hydrogen-bound complex forms in the presence of the OAc- ion in a DMSO solution of probe 3 because of the subtle difference in the pKa values of sulfonamide N−H protons when probes 2 and 3 are compared. Coordination of probe 1 to a ReI center or probe 2 to a RuII center increases the intrinsic acidity of sulfonamide N−H protons and results in an enhanced sensitivity to anions

Synthesis, Photophysical, and Anion-Sensing Properties of Quinoxalinebis(sulfonamide) Functionalized Receptors and Their Metal Complexes

We report the synthesis, characterization, and photophysical properties of a series of organic receptors and their corresponding ReI and RuII metal complexes as anion probes featuring bis(sulfonamide) interacting sites incorporating highly chromophoric π-conjugated quinoxaline moieties. The interactions with various anions were extensively investigated. These probe molecules are capable of recognizing F-, OAc-, CN-, and H2PO4- with different sensitivities. The probe−anion interactions can be easily visualized via naked-eye colorimetric or luminescent responses. Probe 1 has the weakest acidic sulfonamide N−H protons and therefore simply forms hydrogen-bonding complexes with F-, OAc-, CN-, and H2PO4-. Probe 2 undergoes a stepwise process with the addition of F- and OAc-:  formation of a hydrogen-bound complex followed by sulfonamide N−H deprotonation. Direct sulfonamide N−H deprotonation occurs upon the addition of CN-, while only a hydrogen-bound complex forms with the H2PO4- ion for probe 2 in a dimethyl sulfoxide (DMSO) solution. Similar probe−anion interactions occur in probe 3 with the addition of F-, CN-, or H2PO4-. However, only a genuine hydrogen-bound complex forms in the presence of the OAc- ion in a DMSO solution of probe 3 because of the subtle difference in the pKa values of sulfonamide N−H protons when probes 2 and 3 are compared. Coordination of probe 1 to a ReI center or probe 2 to a RuII center increases the intrinsic acidity of sulfonamide N−H protons and results in an enhanced sensitivity to anions

Synthesis, Photophysical, and Anion-Sensing Properties of Quinoxalinebis(sulfonamide) Functionalized Receptors and Their Metal Complexes

We report the synthesis, characterization, and photophysical properties of a series of organic receptors and their corresponding ReI and RuII metal complexes as anion probes featuring bis(sulfonamide) interacting sites incorporating highly chromophoric π-conjugated quinoxaline moieties. The interactions with various anions were extensively investigated. These probe molecules are capable of recognizing F-, OAc-, CN-, and H2PO4- with different sensitivities. The probe−anion interactions can be easily visualized via naked-eye colorimetric or luminescent responses. Probe 1 has the weakest acidic sulfonamide N−H protons and therefore simply forms hydrogen-bonding complexes with F-, OAc-, CN-, and H2PO4-. Probe 2 undergoes a stepwise process with the addition of F- and OAc-:  formation of a hydrogen-bound complex followed by sulfonamide N−H deprotonation. Direct sulfonamide N−H deprotonation occurs upon the addition of CN-, while only a hydrogen-bound complex forms with the H2PO4- ion for probe 2 in a dimethyl sulfoxide (DMSO) solution. Similar probe−anion interactions occur in probe 3 with the addition of F-, CN-, or H2PO4-. However, only a genuine hydrogen-bound complex forms in the presence of the OAc- ion in a DMSO solution of probe 3 because of the subtle difference in the pKa values of sulfonamide N−H protons when probes 2 and 3 are compared. Coordination of probe 1 to a ReI center or probe 2 to a RuII center increases the intrinsic acidity of sulfonamide N−H protons and results in an enhanced sensitivity to anions

Reaction of the Half-Sandwich Cationic Aminorhenium Complex with Amines. Preparation of Rhenium Bis(amine) Hydride and Rhenium Isocyanate Complexes

The aminorhenium ester complex {[η5:η1-C5H4CH2CH2NH(CH3)]Re(CO)2(CH2CO2CH3)}+Br- (2a) reacts with n-butylamine in refluxing CH2Cl2 solution, giving the n-butylamine coordinated complex {[η5:η1-C5H4CH2CH2NH(CH3)]Re(CO)(CH2CO2CH3)(n-BuNH2)}+Br- (6a), which was derived via rhenium−carbamoyl bond cleavage of the intermediate. In contrast, the slightly electron-rich methyl complex {[η5:η1-C5H4CH2CH2NH(CH3)]Re(CO)2(CH3)}+CF3SO3- (3) reacts with n-butylamine, giving the n-butylamine hydride complex {[η5:η1-C5H4CH2CH2NH(CH3)]ReH(CO)(n-BuNH2)}+CF3SO3- (7a), which was derived via the coupling of the carbamoyl and the methyl groups followed by an amine coordination. Methyl complex 3 also reacts with tert-butylamine, diethylamine, and ammonia to give the corresponding amine hydride complexes. The presence of an Re−H bond is evidenced by the characteristic hydride resonance in the 1H NMR spectra. The tert-butylamine hydride complex 7b has been characterized by an X-ray analysis. The reaction of both 2 and 3 with hydrazine proceeds via a net loss of 1 mol of ammonia to give isocyanate complexes 12a and 12b, respectively. The structure of 12a is supported by single-crystal X-ray analysis

Ferrocenediyl-Bridged Triiron Complexes^†

The reaction of 2 equiv of CpFe(CO)2I and 1,1‘-dilithioferrocene in the presence of 2 equiv of PPh3 is an intermolecular version of the reaction of CpFe(CO)2I and (η5-C5H4Li)Fe(C5H4PPh2). In the three-component procedure, the PPh3 substitution for iodide on CpFe(CO)2I is much faster than the nucleophilic Fc-addition at the Fe-center or at a CO ligand of CpFe(CO)2I. This one-pot reaction proceeds through [CpFe(CO)2PPh3+] and yields CpFe(CO)(PPh3)[μ,C:η5-C(O)C5H4]Fe[μ,η5:η4-5-exo-(1‘-C5H4)C5H5]Fe(CO)2(PPh3) (4) in 50% yield, with the 1,1‘-dilithioferrocene participating twice in the nucleophilic Fc-additions:  at the Cp-ring and at a CO ligand of [CpFe(CO)2PPh3+]. Complex 4 is a ferrocenediyl-bridged tri-Fe complex with three different Fe-centers:  a metallocene Fe(II), a square-pyramidal pentacoordinate Fe(0), and a half-sandwich acyl-Fe(II). It has been found that, in the second Fc-additions, the pathway from (η5-C5H4Li)Fe[μ,η5:C-C5H4C(O)]FeCp(CO)(PPh3) (9) to 4 proceeds normally, but the pathway from 9 to Fe[(μ,η5:C-C5H4)C(O)FeCp(CO)(PPh3)]2 (5) has been turned off. The preference of Fc-addition for 9 onto the Cp-ring of [CpFe(CO)2PPh3+] could be reasoned by a localization of the Li+ cation in 9

Half-Sandwich Aminorhenium Complexes: Preparation and Regioselective N-<i>versus</i> Re-Alkylations

The aminorhenium complex (CO)2ReNH(CH3)CH2CH2(η5-C5H4) (3), in which the ligating amino group is connected to the cyclopentadienyl ligand, was prepared by irradiation of (η5-C5H4CH2CH2NHCH3)Re(CO)3 (2) in THF. Alkylation of the corresponding anion [(CO)2ReN(CH3)CH2CH2(η5-C5H4)]-Li+ (4) as well as the neutral aminorhenium complex 3 with a variety of electrophiles has been studied. The anion 4 reacted with electrophiles, such as CH3I, CH2CHCH2Br, C6H5CH2Br, and HC⋮CCH2Br, at the nitrogen center to provide (CO)2ReNR(CH3)CH2CH2(η5-C5H4) (5a−d). However, 4 reacted with electrophiles having a carbonyl group or a nitrile group next to the electrophilic carbon, such as BrCH2CO2CH3, BrCH2CO2C2H5, and BrCH2CN, to give rhenium alkylation compounds [(CO)2(R)ReNH(CH3)CH2CH2(η5-C5H4)]+Br- (7e−g) after protonation. The neutral aminorhenium complex 3 reacted with the electrophiles mentioned above to provide exclusive Re-alkylation compounds 7a−g. The structure of the tetraphenylborate salt of 7c, [(CO)2(C6H5CH2)ReNH(CH3)CH2CH2(η5-C5H4)]+BPh4- (8), has been determined by X-ray diffraction