Search PubMed⌕ Search

Biomedical subjects

Carsten D Brandt

Publications and source records attributed to Carsten D Brandt.

12 recordsLinked to original sources
PubMed2007

Pillars, layers, pores and networks from nickeltripyrrins: a porphyrin fragment as a versatile building block for the construction of supramolecular assemblies.

Sterically hindered nickel- tripyrrins [Ni(trpy)X] with different di-, tri- and tetradentate anions X have been prepared with the aim of finding coordination polymers formed by self-association. The syntheses were performed by simple ligand-exchange reactions and proceeded successfully with the pseudohalides CN(-), OCN(-), SCN(-), SeCN(-), N(CN)(2) (-) (dicyanoamido, dca) and C(CN)(3) (-) (tricyanomethanido, tcm), the cyanidometallates [Ag(CN)(2)](-) and [Ni(CN)(4)](2-) and the salicylate anion (sal(-)). X-ray crystallographic analyses revealed that the complexes with cyanido and isocyanato ligands, as well as the compound with a salicylato ligand, are prototypes for structurally distinct monomeric species in the solid state, whereas one-dimensional coordination polymers or supramolecular three-dimensional networks are formed from all other combinations. The polymeric compounds display a variety of individual pillar and network architectures with functionalised pores and clefts and with the Ni(trpy) fragments in different relative orientations. Hydrogen bonding and pi stacking were found to be additional structure-directing effects, which increased the structural complexity of the system. The Ni(trpy) subunit has thus been proven to be a versatile building block for the construction of supramolecular assemblies and metal organic frameworks (MOFs) from pentacoordinate Ni(II) ions.

Journal Article↗
PubMed2006

Monomeric and polymeric copper and zinc tripyrrins.

Neutral transition metal complexes of different alpha,omega-dimethyltripyrrins TrpyMX with M = Cu(II) and Zn(II) have been prepared with a variety of anionic halogeno and pseudohalogeno ligands X, and have been studied with respect to coordination modes and structural distortion. Only four- and five-coordinate species have been observed throughout the series. All four-coordinate species display unstrained, but distorted tetrahedral or strained and distorted square-planar coordination environments for zinc(II) and copper(II) species, respectively, thus following the expectations from simple ligand field arguments. Five-coordinate species do not form easily and were observed either in donor solvents or in the solid as 1D coordination polymers with distorted trigonal-bipyramidal coordination and different topologies.

Journal Article↗
PubMed2004

Extending the coordination capabilities of tertiary phosphines and arsines: preparation, molecular structure, and reactivity of dinuclear rhodium complexes with PR3 and AsR3 in a doubly bridging coordination mode.

The reactions of [Rh2(kappa2-acac)2(mu-CPh2)2(mu-PR3)] (PR3= PMe34, PMe2Ph 7, PEt38) with an equimolar amount of Me3SiX (X = Cl, Br, I) afforded the unsymmetrical complexes [Rh2X(kappa2-acac)(mu-CPh2)2(mu-PR3)]5, 9-12, which contain the phosphine in a semi-bridging coordination mode. From 4 and excess Me3SiCl, the tetranuclear complex [[Rh2Cl(mu-Cl)(mu-CPh2)2(mu-PMe3)]2]6 was obtained. In contrast, the reaction of 4 with an excess of Me3SiX (X = Br, I) yielded the dinuclear complexes [Rh2X2(mu-CPh2)2(mu-PMe3)]13, 14 in which, as shown by the X-ray crystal structure analysis of 14, the bridging phosphine is coordinated in a truly symmetrical bonding mode. While related compounds with PEt3 and PMe2Ph as bridging ligands were prepared on a similar route, the complex [Rh2Cl2(mu-CPh2)2(mu-PiPr3)]19 was obtained from the mixed-valence species [(PiPr3)Rh(mu-CPh2)2Rh(kappa2-acac)2]17 and HCl. The reaction of [Rh2(kappa2-acac)2(mu-CPh2)2(mu-SbiPr3)]3 with AsMe3 gave the related Rh(mu-AsMe3)Rh compound 21. With Me3SiCl, the acac ligands of 21 can be replaced stepwise by chloride to give [Rh2Cl(kappa2-acac)(mu-CPh2)2(mu-AsMe3)]23 and [[Rh2Cl(mu-Cl)(mu-CPh2)2(mu-AsMe3)]2]24, the latter being isomorphous to the phosphine-bridged dimer 6.

Journal Article↗
PubMed2004

A new family of dinuclear rhodium complexes containing tertiary phosphanes in a semibridging or doubly bridging bonding mode.

The reactions of [Rh(2)Cl(kappa(2)-acac)(mu-CPh(2))(2)(mu-SbiPr(3))] (3) and [Rh(2)(kappa(2)-acac)(2)(mu-CPh(2))(2)(mu-SbiPr(3))] (4) with PMe(3) lead to exchange of the bridging ligand and afford the novel PMe(3)-bridged counterparts 5 and 6, in which the phosphane occupies a semibridging (5) or a doubly bridging (6) position. In both cases, the bonding mode was confirmed crystallographically. Treatment of 6 with CO causes a shift of PMe(3) from a bridging to a terminal position and gives the unsymmetrical complex [(kappa(2)-acac)Rh(mu-CPh(2))(2)(mu-CO)Rh(PMe(3))(kappa(2)-acac)] (7). Similarly to 5 and 6, the related compounds 10 and 11 with one or two acac-f(3) ligands were prepared. While both PEt(3) and PnBu(3) react with 3 by exchange of the bridging stibane for phosphane to give compounds 12 and 13, the reactions of 4 with PMePh(2) and PnBu(3) afford the mixed-valent Rh(0)Rh(II) complexes [(PR(3))Rh(mu-CPh(2))(2)Rh(kappa(2)-acac)(2)] (17, 18) in high yields. In contrast, treatment of 4 with PEt(3) and PMe(2)Ph generates the phosphane-bridged compounds [Rh(2)(kappa(2)-acac)(2)(mu-CPh(2))(2)(mu-PR(3))] (14, 15) exclusively. Stirring a solution of 14 (R=Et) in benzene for 15 h at room temperature leads to complete conversion to the mixed-valent isomer 16. The reaction of 6 with an equimolar amount of CR(3)CO(2)H (R=F, H) or phenol in the molar ratio of 1:10 results in substitution of one acac by one trifluoracetate, acetate, or phenolate ligand without disturbing the [Rh(2)(mu-CPh(2))(2)(mu-PR(3))] core. From 6 and an excess of CR(3)CO(2)H, the symmetrical bis(trifluoracetato) and bis(acetate) derivatives [Rh(2)(kappa(2)-O(2)CCR(3))(2)(mu-CPh(2))(2)(mu-PMe(3))] (21, 22) were obtained.

Journal Article↗
PubMed2004

Vinyl and carbene ruthenium(II) complexes from hydridoruthenium(II) precursors.

The reactions of the hydrido compounds [RuHCl(CO)(L)2][L = PiPr3 (1), PCy3 (2)] with HC(triple bond)CR (R = H, Ph, tBu) afforded by insertion of the alkyne into the Ru-H bond the corresponding vinyl complexes [RuCl(CHCHR)(CO)(L)2], 3-8, which upon protonation with HBF4 gave the cationic five-coordinated ruthenium carbenes [RuCl(CHCH2R)(CO)(L)2]BF4, 9-14. Subsequent reactions of the carbene complexes with PR3(R = Me, iPr) and CH3CN led either to deprotonation and re-generation of the vinyl compounds or to cleavage of the ruthenium-carbene bond and the formation of the six-coordinated complexes [RuCl(CO)(CH3CN)2(PiPr3)2]BF4, 17, and [RuH(CO)(CH3CN)2(PiPr3)2]X, 18a,b. The acetato derivative [RuH(2-O2CCH3)(CO)(PCy3)2], 19, also reacted with acetylene and phenylacetylene by insertion to yield the related vinyl complexes [Ru(CHCHR)(kappa2-O2CCH3)(CO)(PCy3)2], 20, 21, of which that with R = H was protonated with HBF4 to yield the corresponding cationic ruthenium carbene 22. With [RuHCl(H2)(PCy3)2], 25, as the starting material, the five-coordinated chloro(hydrido)ruthenium(II) compounds [RuHCl(PCy3)(dppf)], 26(dppf = [Fe(eta5-C5H4PPh2)2]), [RuHCl[Sb(CH2Ph)3](PCy3)2], 27, and [RuHCl(CH3CN)(PCy3)2], 30, were prepared. The reactions of 27 with HCCR (R = H, Ph) gave the hydrido(vinylidene) complexes [RuHCl(CCHR)(PCy3)2], 28 and 29, whereas treatment of 30 with HC(triple bond)CPh afforded the vinyl compound [RuCl(CHCHPh)(CH3CN)(PCy3)2], 31. The molecular structures of 11(R = tBu, L = PiPr3) and 26 were determined crystallographically.

Crystallography, X-Ray↗
PubMed2003

Rhodium(I) and rhodium(III) complexes formed by coordination and C-H activation of bulky functionalized phosphanes.

The reaction of [[RhCl(C(8)H(14))(2)](2)] (2) with iPr(2)PCH(2)CH(2)C(6)H(5) (L(1)) led, via the isolated dimer [[RhCl(C(8)H(14))(L(1))](2)] (3), to a mixture of three products 4 a-c, of which the dinuclear complex [[RhCl(L(1))(2)](2)] (4 a) was characterized by Xray crystallography. The mixture of 4a-c reacts with CO, ethene, and phenylacetylene to give the square-planar compounds trans-[RhCl(L)(L(1))(2)] (L=CO (5), C(2)H(4) (6), C=CHPh (9)). The corresponding allenylidene(chloro) complex trans-[RhCl(=C=C=CPh(2))(L(1))(2)] (11), obtained from 4 a-c and HC triple bond CC(OH)Ph(2) via trans-[RhCl[=C=CHC(OH)Ph(2)](L(1))(2)] (10), could be converted stepwise to the related hydroxo, cationic aqua, and cationic acetone derivatives 12-14, respectively. Treatment of 2 and [[RhCl(C(2)H(4))(2)](2)] (7) with two equivalents of tBu(2)PCH(2)CH(2)C(6)H(5) (L(2)) gave the dimers [[RhCl(C(8)H(14))(L(2))](2)] (15) and [[RhCl(C(2)H(4))(L(2))](2)] (16), which both react with L(2) in the molar ratio of 1:2 to afford the five-coordinate aryl(hydrido)rhodium(III) complex [RhHCl(C(6)H(4)CH(2)CH(2)PtBu(2)-kappa(2)C,P)(L(2))] (17) by C-H activation. The course of the reactions of 17 with CO, H(2), PhC triple bond CH, HCl, and AgPF(6), leading to the compounds 19-21, 24, and 25 a, respectively, indicate that the coordinatively unsaturated isomer of 17 with the supposed composition [RhCl(L(2))(2)] is the reactive species. Labeling experiments using D(2), DCl, and PhC triple bond CD support this proposal. With either [Rh(C(8)H(14))(eta(6)-L(2)-kappaP]PF(6) or [Rh(C(2)H(4))(eta(6)-L(n)-kappaP]PF(6) (n=1 and 2) as the starting materials, the corresponding halfsandwich-type complexes 27, 28, and 32 were obtained. The nonchelating counterpart of the dihydrido compound 32 with the composition [RhH(2)(PiPr(3))(eta(6)-C(6)H(6))]PF(6) (35) was prepared stepwise from [Rh(C(2)H(4))(PiPr(3))(eta(6)-C(6)H(6))]PF(6) and H(2) in acetone via the tris(solvato) species [RhH(2)(PiPr(3))(acetone)(3)]PF(6) (34) as intermediate. The synthesis of the bis(chelate) complex [Rh(eta(4)-C(8)H(12))(C(6)H(5)OCH(2)CH(2)PtBu(2)-kappa(2)O,P)]BF(4) (39) is also described. Besides 4 a, the compounds 17, 25 a, and 39 have been characterized by Xray crystal structure analysis.

Journal Article↗
PubMed2002

An unprecedented dinuclear alkylrhodium(III) complex built up by two 14-electron [RhCl2(alkyl)(PR3)] units.

Reaction of HCl with [RhCl(C2H4)(PR3)]2 affords the dinuclear alkylrhodium(III) complex [RhCl2(C2H5)(PR3)]2, the structure of which has been determined crystallographically. PR3 is the formerly unknown trialkyl phosphine tBu2PCH2CH2C6H3-2,6-Me2, prepared in three steps from tBuPCl2. Treatment of the title compound with CO gives the mononuclear rhodium dicarbonyl cis-[RhCl(CO)2(PR3)], being the first fully characterized complex of this type.

Journal Article↗