Synthesis and Chemistry of Dihydridoborate Group 7 Metal Complexes with Varied N,E-Chelated Ligands (E = O, NH, or S).

Several dihydridoborate group 7 metal complexes have been synthesized and their structural aspects have been described from various N,S-, N,N-, and N,O-chelated borate species, such as Na[(H3B)mp] (mp = 2-mercaptopyridyl), Na[(H3B)amt] (amt = 2-amino-5-mercapto-1,3,4-thiadiazolyl), Na[(H3B)hp] (hp = 2-hydroxypyridyl), Na[(H2B)bap] (bap = bis(2-aminopyridyl)), and Na[(H2B)bdap] (bdap = bis(2,6-diaminopyridyl)). Room temperature photolysis of [M2(CO)10] (M = Mn or Re) with these borate species afforded dihydridoborate complexes [(CO)3M(µ-H)2BHL] 1-6 (1, M = Mn, L = mp; 2, M = Re, L = mp; 3, M = Mn, L = amt; 4, M = Mn, L = hp; 5, M = Mn, L = ap; 6, M = Mn, L = dap, ap = 2-aminopyridyl, dap = 2,6-diaminopyridyl). In complexes 1-3, the corresponding (H2BHL) units are coordinated to the metal centers through the (κ3-H,H,S) mode. However, in complexes 4 and 5 (or 6), the connection is via (κ3-H,H,O) and (κ3-H,H,N) modes of coordination, respectively. Complexes 1 and 5 underwent hydroboration reactions with terminal alkynes that yielded trans-hydroborated species [Mn(CO)3(µ-H)2(NC5H4E)B(PhC═CH2)] (7, E = S; 8, E = NH). Density functional theory (DFT) calculations have been carried out to investigate the electronic structures of these dihydridoborate species as well as the nature of bonding in them.

MT1-MMP and ADAM10/17 exhibit a remarkable overlap of shedding properties.

Membrane-type-I matrix metalloproteinase (MT1-MMP) is one of six human membrane-bound MMPs and is responsible for extracellular matrix remodelling by degrading several substrates like fibrillar collagens, including types I-III, or fibronectin. Moreover, MT1-MMP was described as a key player in cancer progression and it is involved in various inflammatory processes, as well as in the pathogenesis of Alzheimer's disease (AD). The membrane-tethered metalloprotease meprin ß as well as a disintegrin and metalloproteinase 10 (ADAM10) and ADAM17 are also associated with these diseases. Interestingly, meprin ß, ADAM10/17 and MT1-MMP also have a shared substrate pool including the interleukin-6 receptor and the amyloid precursor protein. We investigated the interaction of these proteases, focusing on a possible connection between MT1-MMP and meprin ß, to elucidate the potential mutual regulations of both enzymes. Herein, we show that besides ADAM10/17, MT1-MMP is also able to shed meprin ß from the plasma membrane, leading to the release of soluble meprin ß. Mass spectrometry-based cleavage site analysis revealed that the cleavage of meprin ß by all three proteases occurs between Pro602 and Ser603 , N-terminal of the EGF-like domain. Furthermore, only inactive human pro-meprin ß is shed by MT1-MMP, which is again in accordance with the shedding capability observed for ADAM10/17. Vice versa, meprin ß also appears to shed MT1-MMP, indicating a complex regulatory network. Further studies will elucidate this well-orchestrated proteolytic web under distinct conditions in health and disease and will possibly show whether the loss of one of the above-mentioned sheddases can be compensated by the other enzymes.

Nontuberculous Mycobacteria Lung Disease (NTM-LD): Current Recommendations on Diagnosis, Treatment, and Patient Management.

Nontuberculous mycobacteria (NTM) are a group of ubiquitous environmental bacteria that can be found in soil, dust, and water. Mycobacterium avium complex (MAC) is the most common pathogen and the one most associated with chronic pulmonary disease. In recent years, the prevalence of Mycobacterium avium complex-related pulmonary disease (MAC-PD) has increased and is an emerging public health concern. This is due to a combination of environmental and geographic factors, dynamic changes in organism virulence and antimicrobial susceptibility, and evolving host susceptibility. Given the dynamic nature of the disease, management of NTM pulmonary disease (NTM-PD) often includes a multimodal approach including antimicrobial therapy, airway clearance techniques, limiting environmental exposures, and reducing susceptibility to NTM through prevention of reflux and maintenance of body weight. This review will explore the most recent concepts in the diagnosis, treatment, and management of individuals with NTM pulmonary infection.

Coordination and Hydroboration of Ru(II)-Borate Complexes: Dihydridoborate vs. Bis(dihydridoborate).

Treatment of [Cp*RuCl2 ]2 , 1, [(COD)IrCl]2 , 2 or [(p-cymene)RuCl2 ]2, 3 (Cp*=η5 -C5 Me5, COD= 1,5-cyclooctadiene and p-cymene=η6 -i PrC6 H4 Me) with heterocyclic borate ligands [Na[(H3 B)L], L1 and L2 (L1 : L=amt, L2 : L=mp; amt=2-amino-5-mercapto-1,3,4-thiadiazole, mp=2-mercaptopyridine) led to the formation of borate complexes having uncommon coordination. For example, complexes 1 and 2 on reaction with L1 and L2 afforded dihydridoborate species [LA M(µ-H)2 BHL] 4-6 (4: LA =Cp*, M=Ru, L=amt; 5: LA =Cp*, M=Ru, L=mp; 6: LA =COD, M=Ir, L=mp). On the other hand, treatment of 3 with L2 yielded cis- and trans-bis(dihydridoborate) species, [Ru{(µ-H)2 BH(mp)}2 ], cis-7 and trans-7. The isolation and structural characterization of fac- and mer-[Ru{(µ-H)2 BH(mp)}{(µ-H)BH(mp)2 }], 8 from the same reaction offered an insight into the behaviour of these dihydridoborate species in solution. Fascinatingly, despite having reduced natural charges on Ru centres both at cis-and trans-7, they underwent hydroboration reaction with alkynes that yielded both Markovnikov and anti-Markovnikov addition products, 10 a-d.

High-power solid-state amplifier for superconducting radio frequency cavity test facility.

A horizontal test facility is set up at the Raja Ramanna Centre for Advanced Technology to test the superconducting radio frequency dressed cavities. Along with the cryomodule, control instrumentation, and the power coupler, this facility incorporates a high-power solid-state amplifier for establishing the desired cavity voltage gradient during the testing. This article describes the design, construction, rigorous testing, and measured results of this high-power solid-state radio frequency amplifier and its constituent components. Its maximum output power is 36 kW (average) at the operating frequency of 650 MHz. Its main features are its modular and scalable design with in-house developed constituent components. These components include 500 W, 20 dB gain modules, novel two-tier radial dividers, combiners, power sensors, and aperture-coupled directional couplers. Their excellent reprise performance for the multiple quantities confirms the design methodology presented here. The measured wall plug efficiency of this 36 kW amplifier is 43.6%, and its power gain is 86 dB. The designed radial combiner is highly efficient (power-combining efficiency of 98.4%), and the directional coupler exhibits a very low loss (insertion loss of 0.05 dB).

Homocubane Chemistry: Synthesis and Structures of Mono- and Dicobaltaheteroborane Analogues of Tris- and Tetrahomocubanes.

Room-temperature reactions between [Cp*CoCl]2 (Cp* = η5-C5Me5) and large excess of [BH2E3]Li (E = S or Se) led to the formation of homocubane derivatives, 1-7. These species are bimetallic tetrahomocubane, [(Cp*Co)2(µ-S)4(µ3-S)4B2H2], 1; bimetallic trishomocubane isomers, [(Cp*Co)2(µ-S)3(µ3-S)4B2H2], 2 and 3; monometallic trishomocubanes, [M(µ-E)3(µ3-E)4B3H3] [4: M = Cp*Co, E = S; 5: M = Cp*Co, E = Se and 6: M = {(Cp*Co)2(µ-H)(µ3-Se)2}Co, E = Se], and bimetallic homocubane, [(Cp*Co)2(µ-Se)(µ3-Se)4B2H2], 7. As per our knowledge, 1 is the first isolated and structurally characterized parent prototype of the 1,2,2',4 isomer of tetrahomocubane, while 3, 4, and 5 are the analogues of parent D 3-trishomocubane. Compounds 2 and 3 are the structural isomers in which the positions of the µ-S ligands in the trishomocubane framework are altered. Compound 6 is an example of a unique vertex-fused trishomocubane derivative, in which the D 3-trishomocubane [Co(µ-Se)3(µ3-Se)4B3H3] moiety is fused with an exopolyhedral trigonal bipyramid (tbp) moiety [(Cp*Co)2(µ-H)(µ3-Se)2}Co]. Multinuclear NMR and infrared spectroscopy, mass spectrometry, and single crystal X-ray diffraction analyses were employed to characterize all the compounds in solution. Bonding in these homocubane analogues has been elucidated computationally by density functional theory methods.

Five-Membered Ruthenacycles: Ligand-Assisted Alkyne Insertion into 1,3-N,S-Chelated Ruthenium Borate Species.

Building upon previous work, the chemistry of [(η6 -p-cymene)Ru{P(OMe)2 OR}Cl2 ], (R=H or Me) has been extended with [H2 B(mbz)2 ]- (mbz=2-mercaptobenzothiazolyl) using different Ru precursors and borate ligands. As a result, a series of 1,3-N,S-chelated ruthenium borate complexes, for example, [(κ2 -N,S-L)PR3 Ru{κ3 -H,S,S'-H2 B(L)2 }], (2 a-d and 2 a'-d'; R=Ph, Cy, OMe or OPh and L=C5 H4 NS or C7 H4 NS2 ) and [Ru{κ3 -H,S,S'-H2 B(L)2 }2 ], (3: L=C5 H4 NS, 3': L=C7 H4 NS2 ) were isolated upon treatment of [(η6 -p-cymene)RuCl2 PR3 ], 1 a-d (R=Ph, Cy, OMe or OPh) with [H2 B(mp)2 ]- or [H2 B(mbz)2 ]- ligands (mp=2-mercaptopyridyl). All the Ru borate complexes, 2 a-d and 2 a'-d' are stabilized by phosphine/phosphite and hemilabile N,S-chelating ligands. Treatment of these Ru borate species, 2 a'-c' with various terminal alkynes yielded two different types of five-membered ruthenacycle species, namely [PR3 {C7 H4 S2 -(E)-N-C=CH(R')}Ru{κ3 -H,S,S'-H2 B(L)2 }], (4-4'; R=Ph and R'=CO2 Me or C6 H4 NO2 ; L=C7 H4 NS2 ) and [PR3 {C7 H4 NS-(E)-S-C=CH(R')}Ru{κ3 -H,S,S'-H2 B(L)2 }], (5-5', 6 and 7; R=Ph, Cy or OMe and R'=CO2 Me or C6 H4 NO2 ; L=C7 H4 NS2 ). All these five-membered ruthenacycle species contain an exocyclic C=C moiety, presumably formed by the insertion of a terminal alkyne into the Ru-N and Ru-S bonds. The new species have been characterized spectroscopically and the structures were further confirmed by single-crystal X-ray diffraction analysis. Theoretical studies and chemical-bonding analyses established that charge transfer occurs from phosphorus to ruthenium center following the trend PCy3

Hydroboration of Alkynes: η4-Alkene-Borane versus η4-E-Boratabutadiene.

A series of hydroborated η4-σ,π-alkene-borane complexes have been synthesized from the reaction of ruthenium-bis(σ)borate complex [Cp*Ru(µ-H)2BH(S-CH═S)] (1) and terminal as well as internal alkynes. Likewise, the reactions of manganese-bis(σ)borate complexes [Mn(CO)3(µ-H)2BHNCSC6H4(NL)] (L = NCSC6H4 or H) were explored with terminal alkynes that yielded boratabutadiene complexes [Mn(CO)3{(NCSC6H4)2N}{(R1MeC)═B(HC═CHR1)}] [R1 = phenyl (4a) or p-tolyl (4b)] via triple hydroboration of alkynes. These complexes feature a boratabutadiene ligand that is coordinated to a metal through the η4-CBCC mode. To the best of our knowledge, these are the first examples of η4-E-boratabutadiene-coordinated manganese complexes generated by the trans-hydroboration of alkynes. The steric and electronic effects of the borate ligands have been demonstrated using a less sterically hindered manganese-bis(σ)borate complex, [Mn(CO)3(µ-H)2BH(HN2CSC6H4)], that generated monohydroborated complexes [(CO)3Mn(µ-H)2(HN2CSC6H4)B(R1C═CHR2)] (for 6, R1 = Ph and R2 = H; for 7, R1 = p-Tol and R2 = H; for 8, R1 = R2 = Ph). Theoretical studies using density functional theory methods and chemical bonding analyses established the bonding and stability of these species.

Correction: Mercapto-benzothiazolyl based ruthenium(ii) borate complexes: synthesis and reactivity towards various phosphines.

Correction for 'Mercapto-benzothiazolyl based ruthenium(ii) borate complexes: synthesis and reactivity towards various phosphines' by Mohammad Zafar, et al., Dalton Trans., 2019, DOI: 10.1039/c9dt00498j.

Mercapto-benzothiazolyl based ruthenium(ii) borate complexes: synthesis and reactivity towards various phosphines.

The synthesis and reactivity of ruthenium complexes containing an anionic boron based ligand, supported by mercapto-benzothiazolyl heterocycles are presented. Specifically, the reaction of [(η6-p-cymene)Ru{P(OMe)2OR}Cl2], (1a: R = Me; 1b: R = H) with [H2B(mbz)2]- (mbz = 2-mercaptobenzothiazolyl) at room temperature afforded a series of borate complexes, namely [(L)Ru{κ3-H,S,S'-H2B(L)2}P(O)(OMe)(HL)], 2, [Ru{κ3-H,S,S'-H2B(L)2}2], 3 and [(κ2-N,S-L)P(OMe)3Ru{κ3-H,S,S'-H2B(L)2}], 4a; (L = C7H4NS2). The pivotal feature of 2 is the coordination of the Ru centre with a phosphorus atom of secondary phosphine oxide and mercapto-benzothiazolyl ligands. On the other hand, 3 features dual RuH-B interactions between Ru and B-H bonds of [H2B(mbz)2]-. Interestingly, along with 3, compound [(κ2-N,S-L)P(OPh)3Ru{κ3-H,S,S'-H2B(L)2}], 4b (L = C7H4NS2), was isolated upon treatment of the same borate with [(η6-p-cymene)RuCl2P(OPh)3], 1c, which is stabilized by δ-B-H interactions and one phosphite ligand. Furthermore, compound 3 promptly reacts with P(OR)3 to generate [(OR)3PRu-{κ2-S,S'-H2B(L)2}{κ3-H,S,S'-H2B(L)2}], (5a: R = Me, 5b: R = Ph; L = C7H4NS2) by breaking one of the RuH-B interactions. Upon heating, compound 5a converts into [(OMe)2OPRu{κ2-S,S'-HB(L)2}{κ3-H,S,S'-H2B(L)2}], 6a (L = C7H4NS2) by release of methane gas. Compound 6a is a unique example wherein the boron atom of the borate ligand is bound to an oxygen atom of the phosphite unit. In contrast, the thermolysis of 3 with PR2R' yielded [Ru{κ3-H,S,S'-H2B(L2)}(PR2R')2(L)], (7a: R = Me, R' = Ph; 7b: R = Ph; R' = Me; L = C7H4NS2), respectively, revealing the incorporation of two triphosphine ligands in the coordination sphere of ruthenium. Density functional theory (DFT) calculations were undertaken to provide an insight into the electronic structures of the complexes.

An Efficient Method for the Synthesis of Boratrane Complexes of Late Transition Metals.

In a quest for efficient precursors for the synthesis of boratrane complexes of late transition metals, we have developed a useful synthetic method using [L'M(µ-Cl)Clx ]2 as precursors (L'=η6 -p-cymene, M=Ru, x=1; L'=COD, M=Rh, x=0 and L'=Cp*, M=Ir or Rh, x=1; COD=1,5-cyclooctadiene, Cp*=η5 -C5 Me5 ). For example, treatment of Na[(H3 B)bbza] or Na[(H2 B)mp2 ] (bbza=bis(benzothiazol-2-yl)amine; mp=2-mercaptopyridyl) with [L'M(µ-Cl)Clx ]2 yielded [(η6 -p-cymene)RuBH{(NCSC6 H4 )(NR)}2 ] (2; R=NCSC6 H4 ), [{N(NCSC6 H4 )2 }RhBH{(NCSC6 H4 )(NR)}2 ] (3; R=NCS-C6 H4 ), [(η6 -p-cymene)RuBH(L)2 ] (5; L=C5 H4 NS), and [Cp*MBH(L)2 ] (6 and 7; L=C5 H4 NS, M=Ir or Rh). In order to delineate the significance of the ligands, we studied the reactivity of [(COD)Rh(µ-Cl)]2 with Na[(H3 B)bbza], which led to the formation of the isomeric agostic complexes [(η4 -COD)Rh(µ-H)BHRh(C14 H8 N3 S2 )3 ], 4 a and 4 b, in parallel to the formation of 16-electron square-pyramidal rhodaboratrane complex 3. Compounds 4 a and 4 b show two different geometries, in which the Rh-B bonds are shorter than in the reported Rh agostic complexes. The new compounds have been characterized in solution by various spectroscopic analyses, and their structural arrangements have been unequivocally established by crystallographic analyses. DFT calculations provide useful insights regarding the stability of these metallaboratrane complexes as well as their M→B bonding interactions.

Design, Synthesis, and Chemistry of Bis(σ)borate and Agostic Complexes of Group†7 Metals.

A series of new bis(σ)borate and agostic complexes of group 7 metals have been synthesized and structurally characterized from various borate ligands, such as trihydrobis(benzothiazol-2-yl)amideborate (Na[(H3 B)bbza]), trihydro(2-aminobenzothiazolyl)borate (Na[(H3 B)abz]), and dihydrobis(2-mercaptopyridyl)borate (Na[(H2 B)mp2 ]) (bbza=bis(benzothiazol-2-yl)amine, abz=2-aminobenzothiazolyl, and mp=2-mercaptopyridyl). Photolysis of [Mn2 (CO)10 ] with Na[(H3 B)bbza] formed bis(σ)borate complex [Mn(CO)3 (µ-H)2 BHNCSC6 H4 (NR)] (1; R=NCSC6 H4 ). Octahedral complex [Re(CO)2 (N3 C2 S2 C12 H8 )2 ] (2) was generated under similar reaction conditions with [Re2 (CO)10 ]. Similarly, when [Mn2 (CO)10 ] was treated with Na[(H3 B)abz], bis(σ)borate complex [Mn(CO)3 (µ-H)2 BH(HN2 CSC6 H4 )] (3) and the agostic complex [Mn(CO)3 (µ-H)BH(HN2 CSC6 H4 )2 ] (4) were formed. To probe the potential formation of agostic complexes of the heavier group 7 metals, we carried out the photolysis of [M2 (CO)10 ] with Na[(H2 B)mp2 ] and found that [M(CO)3 (µ-H)BH(C5 H4 NS)2 ] (5: M=Re; 6: M=Mn) was formed in moderate yield. Complexes 1 and 3 feature a (κ3 -H,H,N) coordination mode, whereas 4, 5, and 6 display both (κ3 -H,N,N) and (κ3 -H,S,S) modes of the corresponding ligands. To investigate the lability of the CO ligands of 1 and 3, we treated the complexes with phosphine ligands that generated novel bis(σ)borate complexes [Mn(µ-H)2 (BHNCSC6 H4 )(NR)(CO)2 PL2 L'] (R=NCSC6 H4 ; 7 a: L=L'=Ph; 7 b: L=Ph, L'=Me) and [Mn(µ-H)2 BHN(NCSC6 H4 )R(CO)2 PL2 L'] (R=NCSC6 H4 ; 8 a: L=L'=Ph; 8 b: L=Ph, L'=Me). Complexes 7 and 8 are structural isomers with different coordination modes of the bbza ligand. In addition, DFT calculations were performed to shed some light on the bonding and electronic structures of these complexes.