Hypercoordination by Multiple Dangling Benzylmethoxy Ligands in Highly Crowded Triaryltin Bromide [(2-MeOCH2 C6 H4 )]3 SnBr and Diaryltin Mixed Halides [(2-MeOCH2 C6 H4 )]2 SnBrCl, and a related Distannane and Distannoxane.

The reaction between the Grignard reagent formed from Mg and 2-bromobenzylmethyl ether and SnCl4 produced four products: [2-(MeOCH2 )C6 H4 ]3 SnBr (1), [2-(MeOCH2 )C6 H4 ]2 SnX2 (2, X2 =Br2 (a) and BrCl (b)), [{2-(MeOCH2 )C6 H4 }3 Sn]2 (3), and [{2-(MeOCH2 )C6 H4 }2 SnBr]2 O (4). In the case of 1, two of the three dangling arm O atoms coordinate to the central tin atom with O-Sn internuclear distances of 2.53 (O1) and 2.91 (O2) Å, the shorter interaction being trans to the Br atom, the other trans to a phenyl carbon atom. In the case of 2a the resulting hexacoordinate structure exhibits two very short O-Sn interactions of 2.42 and 2.50 Å, well below the sum of the VdW radii of O and Sn, 3.69 Å. The sterically crowded ditin compound 3 was obtained in trace amounts and the structure demonstrates no dangling O-Sn interactions. General changes in structure compared to other distannane systems are reflective of the great steric crowding. Distannoxane 4, has a Sn-O-Sn bond angle of 148.1(2)° which is larger compared to other distannoxane structures. The intermolecular interactions between Sn-O 2.470(3) and 2.521(3)Å and 2.665(3) and 2.629(3)Å for Sn1 and Sn2 respectively are responsible for a distorted octahedral geometry around the two tin atoms. The various 119 Sn, 13 C and 1 H NMR spectra are in accord with their structural analysis for 1 and 2, and in the solid state 13 C NMR spectrum of 1 the dangling methylene group is observable whereas is solution there is a rapid dynamic equilibrium resulting in a single resonance for all methylene groups.

Resonance and electrostatics making the difference in boron- and aluminum-halide structures and exchange reactivity.

The mechanism of the gas-phase halogen-exchange reaction between boron- and aluminum-halides (i.e., BX3 + BX3 and AlX3 + AlX3, X = F, Cl, or Br) was discovered using density functional theory. The reaction takes place via a two-step mechanism with the intermediacy of a diamond-core structure analogous to diborane. Good agreement was found between the simulated reaction features and experimental observations, which demonstrate slow kinetics and an equilibrium process for boron species and dimer formation in the case of aluminum-halides. This computational and theoretical study also reveals and quantifies the effect of resonance on the thermodynamic stability of the central intermediate and conceptualizes the extreme stability difference (∼50 kcal mol-1) between boron and aluminum diamond-core bridge structures. Through an interaction energy decomposition analysis in combination with electronic structure analyses, we revealed that, beyond the resonance stabilization in free boron-halides, superior electrostatics in aluminum-halides results in the different reactivities, i.e., dimer formation for the latter species whereas substituent exchange for the former ones.

Hypercoordinated eka-tin materials with dangling aryl-methoxy and -methylthio ligands exhibiting intramolecular secondary bonding and aryl bond stabilization in reactions with organotin chlorides.

The syntheses of [2-(CH3ECH2)C6H4]PbPh3-nCln, (n = 0, E = O (4), E = S (5); n = 1, E = O (6), E = S (7); n = 2, E = O (8), are described. NMR and single crystal data illustrate significant Pb⋯E interactions increasing as n progresses from 0 to 2. The Pb⋯E interactions stabilize the Pb-aryl bonding to the extent that the reactions of 4 and 5 with Me2SnCl2 result in interchange of a Ph group and Cl to produce 6 and 7, respectively, together with Me2PhSnCl.

Aminomethyl Transfer (Mannich) Reactions Between an O-Triethylsilylated Hemiaminal and Anilines, Rn C6 H5-n NH2 Leading to New Diamines, Triamines, Imines, or 1,3,5-Triazines Dependent upon Substituent R.

The reactions of the Mannich reagent Et3 SiOCH2 NMe2 (1) with a variety of anilines (mono-substituted RC6 H4 NH2 , R=H, 4-CN, 4-NO2 , 4-Ph, 4-Me, 4-MeO, 4-Me2 N; di-substituted R2 C6 H3 NH2 , R2 =3,5-(CH3 )2 , 3,5-(CF3 )2 ; tri-substituted R3 C6 H2 NH2 , R3 =3,5-Me2 -4-Br and a "super bulky" aniline (Ar*NH2 ) [Ar*=2,6-bis(diphenylmethyl)-4-tert-butylphenyl]) led to the formation of a range of products dependent upon the substituent. With electron-withdrawing substituents, previously unknown diamines, RC6 H4 NH(CH2 NMe2 ) [R=CN (2 a), NO2 (2 b)] and R2 C6 H3 NH(CH2 NMe2 ) [R2 =3,5-(CF3 )2 (2 c)] were formed. Further reaction of 2 a, b, c with 1 yielded the corresponding triamines RC6 H4 N(CH2 NMe2 )2 (R=CN (3 a), NO2 (3 b) and R2 C6 H3 N(CH2 NMe2 )2 , R2 =3,5-(CF3 )2 (3 c). The new polyamines were characterized by NMR spectroscopy, and for 2 a, 2 c, and 3 c, by single crystal XRD. In the case of electron-donating groups, R=4-OMe, 4-NMe2 , 4-Me, 3,5-Me2 , 3,5-Me2 -4-Br, and for R=4-Ph, the reactions with 1 immediately led to the formation of the related 1,3,5-triazines, R=4-MeO (5 a), 4-Me2 N (5 b), 4-Me (5 c), 3,5-Me2 (5 d), 3,5-Me2 -4-Br (5 e), 4-Ph (5 f), 4-Cl (5 g). The "super bulky" aniline rapidly produced a single product, namely the corresponding imine Ar*N=CH2 (4) which was also characterized by single crystal XRD. Imine 4 is both thermally and oxidatively stable. All reactions are very fast, thus based upon the presence of Si we are tempted to denote the reactions of 1 as examples of "Silick" chemistry.

A utility for organoleads: selective alkyl and aryl group transfer to tin.

Me4Pb and Ph4Pb readily transfer methyl or phenyl groups to an equivalent molar ratio of tin(iv) chlorides in the order SnCl4 > MeSnCl3 > Me2SnCl2 > Me3SnCl, often in a selective manner. Me3PbCl and Ph3PbCl specifically transfer a single methyl/phenyl group under the same reaction conditions to produce recovered yields in >75%. Specific transfer of 2 methyl groups from PbMe4 can be achieved at elevated temperatures and/or a 2 : 1 molar ratio Pb : Sn.

Siloxymethylamines as Aminomethylation Reagents for Amines Leading to Labile Diaminomethanes That can be Trapped as Their [Mo(CO)4 ] Complexes.

Compound Et3 SiOCH2 NMe2 transfers Me2 NCH2 to R2 NH (R2 =Et2 , PhMe, [Cr(η(6) -C6 H5 )(CO)3 ]Me, PhH) to form previously unknown diaminomethanes, Me2 NCH2 NR2 and, in the case of R2 =PhH, the triamine Me2 NCH2 N(Ph)CH2 NMe2 . The diaminomethanes exhibit an unreported disproportionation to a mixture of (R2 N)2 CH2 , (Me2 N)2 CH2 , and Me2 NCH2 NR2 , which can be trapped as their [Mo(CO)4 (diamine)] complexes. Whereas PhMeNCH2 NMe2 is a labile material, the metal-substituted ([(η(6) -C6 H5 )Cr(CO)3 ]MeNCH2 NMe2 is a stable material. The triamine Me2 NCH2 N(Ph)CH2 NMe2 is unstable with respect to transformation to 1,3,5-triphenyltriazine, but is readily trapped as the bidentate-triamineMo(CO)4 . All metal complexes were characterized by single-crystal X-ray diffraction.

Unprecedented one-pot sequential thiolate substitutions under mild conditions leading to a red emissive BODIPY dye 3,5,8-tris(PhS)-BODIPY.

The simple reaction of phenylthiol with 8-MeS-BODIPY (1) in dichloromethane was readily accomplished to form 8-PhS-BODIPY (2). If the reaction is performed in THF 3,8-bis(phenylthio)-BODIPY (3) and 3,5,8-tris(phenylthio)-BODIPY (4) are sequentially formed in an unprecedented reaction. This provides a simple new methodology for the introduction of the phenylthio-moiety in the 3- and 5-positions. Alkyl thiols do not form multi-thiolated products under identical conditions, as exemplified using EtSH, where only 8-EtS-BODIPY (5) is formed.

Platinum-Catalyzed Reduction of DMF by 1,1,3,3-Tetramethyldisiloxane, HMeSi2OSiMe2H: New Intermediates HSiMe2OSiMe2OCH2NMe2 and HSiMe2(OSiMe2)3OCH2NMe2 and Their Further Chemical Reactivity.

The use of Karstedt's catalyst to study the reduction of Me2NCHO (DMF) by the popular "dual SiH"-containing tetramethyldisiloxane, HMe2SiOSiMe2H (1), has revealed that the first step in the process involves an initial single hydrosilylation to form HSiMe2OSiMe2OCH2NMe2 (3). This intermediate is readily isolated and purified via distillation. In the continued presence of the catalyst, 3 transforms to the transient tetrasiloxane HMe2SiOSiMe2OSiMe2OSiMe2OCH2NMe2 (4), along with the formation of Me3N. The tetrasiloxane 4 itself transforms to Me3N and (Me2SiO) n (n = 4-6). Despite the demonstrated reactivity of 3, it can also be used to perform the expected metal-catalyzed hydrosilylation chemistry of the SiH group as well as reactions of the SiOCH2NMe2 functionality involving siloxane chain extension and is thus an important new reagent for siloxane chemistry.

8-Alkoxy- and 8-aryloxy-BODIPYs: straightforward fluorescent tagging of alcohols and phenols.

We demonstrate herein that both alcohols and phenols can be tagged with a BODIPY (borondipyrromethene) moiety to yield highly fluorescent products. Thus, 8-(methylthio)-BODIPY (1) undergoes an S(N)Ar-type reaction with a host of alcohols and phenols in the presence of a base and a Cu(I) additive. The BODIPY dyes bearing alkoxy or nonfunctionalized phenoxy moieties are characterized by a highly efficient fluorescence emission, regardless of the media, in the blue-green part of the visible region. Complementary to this, the presence of electron-donor groups at the aryl ring leads to an intramolecular charge-transfer process, which quenches the fluorescence mainly in polar media. In addition to simple alcohols and phenols, four natural products (eugenol, menthol, cholesterol, and estrone) were labeled in a simple fashion. X-ray structures of the cholesterol and estrone derivatives are discussed. In fact, the BODIPY bearing cholesterol stands out as a bright fluorescence biological marker.

8-Amino-BODIPYs: structural variation, solvent-dependent emission, and VT NMR spectroscopic properties of 8-R2N-BODIPY.

New 8-NR2-BODIPYs, R2 = H(i)Pr (3a), H(i)Bu (3b), and Et2 (4), are reported. Restricted rotation about the C8-N bond in such molecules has been observed for the first time (3a and 3b) and evaluated using VT NMR. The fluorophores 3a and 3b are blue emitters, and the efficiency of the emission is closely related to the polarity of the solvent, e.g., hexane > toluene > DCM > THF > MeOH > H2O, an effect also noted by emission variation in alcohol solvents H(CH2)nOH, n = 1-6. In mixed-solvent systems, addition of 10-15% of the more polar solvent results in transformation of the emission properties to those of the bulk polar solvent. Compound 4 has zero emission in all solvents. The crystal structures of 3a, 3b, and 4 are reported, along with that of the parent 8-NH2-BODIPY (2). Compounds 2, 3a, and 3b exhibit trigonal planar N atoms which are coplanar with the BODIPY core; 4 exhibits a very significant distortion that breaks the planarity of the extended BODIPY π system due to the steric impact of the two ethyl groups, an observation that explains the lack of emission for 4.

Metal-catalyzed reduction of HCONR'2, R' = Me (DMF), Et (DEF), by silanes to produce R'2NMe and disiloxanes: a mechanism unraveled.

We demonstrate that using Mo(CO)(6), Mo(CO)(5)NMe(3), and (η(5)-C(5)H(5))Mn(CO)(3) as catalysts for the silane, R(3)SiH, reduction of N,N-dimethylformamide (DMF), and N,N-diethylformamide (DEF), we can observe, intercept, and isolate, the important siloxymethylamine intermediates, R(3)SiOCH(2)NR'(2), R' = Me, Et, for the first time. In the presence of excess DMF such intermediates thermally react with a variety of silanes to form the corresponding disiloxanes in the absence of a metal catalyst. We also show that the germanium hydrides, Et(3)GeH and Bu(3)GeH, also reduce DMF to form trimethylamine and the corresponding digermoxane but observe no intermediates R(3)GeOCH(2)NMe(2). Bu(3)SnH reduces DMF, but along with the low yields of Bu(3)SnOSnBu(3) (but no Bu(3)SnOCH(2)NMe(2)) significant side products are obtained including (Bu(3)Sn)(2) and Bu(4)Sn. In the absence of DMF the siloxymethylamines can undergo metal-catalyzed reactions with silanes, germanes and stannanes to form disiloxanes, and R(3)SiOER(3) E = Ge, Sn, respectively. To date, the most efficient catalyst for this latter process is (η(5)-C(5)H(5))Mo(CO)(3)CH(3) via a photochemical reaction.

Cytotoxic effects of two organotin compounds and their mode of inflicting cell death on four mammalian cancer cells.

In this report, we have tested the cytotoxicity of two organotin (OT) compounds by flow cytometry on a panel of immortalized cancer cell lines of human and murine origin. Although the OT compounds exhibited varying levels of cytotoxicity, diphenylmethyltin chloride was more toxic than 1,4-bis (diphenylchlorostannyl)p-xylene on all cell lines tested. The OT compounds were found to be highly cytotoxic to lymphoma cell lines with lower toxicity toward the HeLa cervical cancer cell line. In order to discern the mechanism by which cell death was induced, additional experiments were conducted to monitor characteristic changes consistent with apoptosis and/or necrosis. Cell lines treated with the experimental compounds indicated that there was no consistent mode of cell death induction. However, both compounds induced apoptosis in the pro-B lymphocyte cell line, NFS-70. The work presented here also demonstrates that the two OT compounds possess selective cytotoxicity against distinct transformed cell lines.

Arenechromiumtricarbonyl complexes of silyl(germyl)(stannyl)- and silyl(germyl)(plumbyl)methanes including unexpected formation of arenechromiumtricarbonyldimethylsilanol, (eta-C(6)H(5))Cr(CO)(3)SiMe(2)OH.

Treatment of PhMe(2)SiCH(2)GeMe(3) (1) with t-BuLi followed by addition of Me(3)ECl, E = Sn, Pb, results in the formation of phenylsilyl(germyl)stannyl- and phenylsilyl(germyl)plumbyl-methanes, PhMe(2)Si(Me(3)Ge)(EMe(3))CH, E = Sn (2), Pb (3). The thermal reaction of 1, 2 and 3 with Cr(CO)(6) yields the corresponding aryl-Cr(CO)(3) analogs, {(eta(6)-C(6)H(5))Cr(CO)(3)}Me(2)Si(Me(3)Ge)CH(2) (4) and {(eta(6)-C(6)H(5))Cr(CO)(3)}Me(2)Si(Me(3)Ge)(EMe(3))CH, E = Sn (5), Pb (6). The thermal treatment of 2 with Cr(CO)(6) in wet THF/di-n-butyl ether mixture results in the formation of the arenechromiumtricarbonyl silanol {(eta(6)-C(6)H(5))Cr(CO)(3)}Me(2)SiOH (7) which exhibits amphiphilic character, forming H-bonded chains in the solid state in a head-to-head arrangement of the areneCr(CO)(3) units.

Phosphine induced migratory CO insertion into the Fe-CH2 bond of the organometallic polymer -[(eta(5)-C5H4)Fe(CO)2CH2SiMe2]n- and characterization of model iron complexes.

Thermal and photochemical treatment of 1-sila-3-ferracyclobutane, (eta(5)C(5)H(4))Fe(CO)(2)CH(2)SiMe(2) (1) results in ring-opening polymerization (ROP). Phosphine-induced migratory CO insertion into the Fe-CH(2) bond of the preformed polymer, -[(eta(5)-C(5)H(4))Fe(CO)(2)CH(2)SiMe(2)](n)- (2) results in either linear polymers, -[(eta(5)-C(5)H(4))Fe(CO)(PR(3))C(O)CH(2)SiMe(2)](n)- [R(3) = Me(2)Ph (3), Ph(3) (4)] or diphosphine bridged polymers, -{[(eta(5)-C(5)H(4))Fe(CO)C(O)CH(2)SiMe(2)](2)(P-P)}(n)- [P-P = dppe (5), dppp (6), dppb (7), trans-dppen (8), dmpe (9); dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,2-bis(diphenylphosphino)propane, dppb = 1,2-bis(diphenylphosphino)butane, cis-dppen = cis-1,2-bis(diphenylphosphino)ethylene, dmpe = 1,2-bis(dimethylphosphino)ethane]. The analogous model complexes, {[(eta(5)-C(5)H(5))Fe(CO)C(O)CH(3)](2)P-P} [P-P = dppp (10), dppb (11), trans-dppen (12), dmpe (13)] were synthesized and characterized as models of the acylated polymers. The X-ray crystal structure of 11 and 13 were determined to establish the bridging nature of the diphosphines in the model complexes and to get insight of the crystal packing.

Methyl transfer from Fe (and Mo) to Sn: formation of (eta(5)-C(5)H(5))M(CO)(n)Sn(t)Bu(2)Me (M = Fe, n = 2; M = Mo, n = 3) complexes from photochemical irradiation of (eta(5)-C(5)H(5))M(CO)(n)Me and (t)Bu(2)SnH(2).

Formation of an Sn-CH(3) bond, concomitantly with an Sn-M (M = Fe, Mo), is readily achieved from the photochemical reactions of (t)Bu(2)SnH(2) with (eta(5)-C(5)H(5))M(CO)(n)Me (M = Fe, n = 2; M = Mo, n = 3) via the intermediacy of (eta(5)-C(5)H(5))M(CO)(n)Sn(t)Bu(2)H.

Formation of silicon-carbon bonds by photochemical irradiation of (eta-C(5)H(5))Fe(CO)(2)SiR(3) and (eta-C(5)H(5))Fe(CO)(2)Me to obtain R(3)SiMe.

Photochemical irradiation of an equimolar mixture of (eta(5)-C(5)H(5))Fe(CO)(2)SiR(3), FpSiR(3), and FpMe leads to the efficient formation of the silicon-carbon coupled product R(3)SiMe, R(3) = Me(3), Me(2)Ph, MePh(2), Ph(3), ClMe(2), Cl(2)Me, Cl(3), Me(2)Ar (Ar = C(6)H(4)X, X = F, OMe, CF(3), NMe(2). Similar chemistry occurs with related germyl and stannyl complexes at slower rates, Si > Ge> >>Sn. Substitution of an aryl hydrogen in FpSiMe(2)C(6)H(4)R' has little effect upon the rate of the reaction whereas progressive substitution of methyl groups on silicon by Cl slows the process. Also changing FpMe to FpCH(2)SiMe(3) dramatically slows the reaction as does the use of (eta(5)-C(5)Me(5))Fe(CO)(2) derivatives. A mechanism involving the initial formation of the 16e(-) intermediate (eta(5)-C(5)H(5))Fe(CO)Me followed by oxidative addition of the Fe-Si bond, accounts for the experimental results obtained.

Intramolecular chalcogen-tin interactions in [(o-MeEC6H4)CH2]2SnPh(2-n)Cl(n) (E = S, O, CH2; n = 0, 1, 2) and intermolecular chlorine-tin interactions in the meta- and para-methoxy isomers.

Organotin(IV) compounds of the type [(o-MeEC(6)H(4))CH(2)](2)SnPh(2-n)Cl(n) were synthesized, E = O, n = 0 (1), n = 1 (2), and n = 2 (3); E = S, n = 0 (4), n = 1 (5), and n = 2 (6); and E = CH(2), n = 0 (7), n = 1 (8), and n = 2 (9). The dichloro compounds 3 and 6 have been investigated by single-crystal X-ray diffraction and exhibit bicapped tetrahedral geometry at the tin atom as a consequence of significant intramolecular Sn...O (3) and Sn...S (6) secondary bonding, in monomolecular units. Compound 3, when crystallized from a hexane/THF solvent mixture, shows two different conformers, 3' and 3'', in the crystal structure; 3' has two equivalent Sn...O interactions, while 3'' has two nonequivalent Sn...O interactions. Upon the recrystallization of 3 from hexane, only a single structural form is observed, 3'. The Sn...E distances in 3', 3'', and 6 are 71.3, 73.5 and 72.9, and 76.3% of the SigmavdW radii, respectively. The meta- and para-substituted isomers of 3 (10, 11) exhibit a distortion at the tin atom due to self-association via intermolecular Sn...Cl interactions, resulting in polymeric structures. (119)Sn NMR spectroscopy suggests that the intramolecular Sn...E interactions persist in solution for the dichloride compounds 3 and 6.

Effects of a series of triorganotins on ATP levels in human natural killer cells.

Natural killer (NK) cells are our initial immune defense against viral infections and cancer development. Thus, agents that are able to interfere with their function increase the risk of cancer and/or infection. A series of triorganotins, (trimethyltin (TMT), dimethylphenyltin (DMPT), methyldiphenyltin (MDPT), and triphenyltin (TPT)) have been shown to decrease the lytic function of human NK cells. TPT and MDPT were much more effective than DMPT or TMT at reducing lytic function. This study investigates the role that decreased ATP levels may play in decreases in the lytic function of NK cells induced by these OTs. A 24 h exposure to as high as 10 muM TMT caused no decrease in ATP levels even though this level of TMT caused a greater than 75% loss of lytic function. TPT at 200 nM caused a decrease in ATP levels of about 20% while decreasing lytic function by greater than 85%. There was no association between ATP levels and lytic function for any of the compounds when NK cells were exposed for 1h or 24 h. However, after a 48 h exposure to both DMPT and TPT decreased lytic function was associated with decreased ATP levels. There was an association between decreased lytic function and decreased ATP levels after a 6 day exposure to each of the four compounds. These studies indicate that the loss of lytic function seen after 1 h and 24 h exposures to this series of organotins cannot be accounted for by decreases in ATP. However, after longer exposures loss of lytic function may be in part be attributable to inadequate ATP levels.