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Papers by Robert Hilts
Introduction: Amines are polar, water-soluble organics found in all meteorites that contain amino... more Introduction: Amines are polar, water-soluble organics found in all meteorites that contain amino acids.It has been proposed that meteoritic amines are produced by the thermal decarboxylation of amino acids[1].The analysis of amines using GC-MS techniques has proven to be problematical owing to the high water solubility and high volatility of these compounds. In addition, the strong interactions of polar amine molecules with the stationary phase of a typical polysiloxane column lead to extensive tailing, poor resolution of peaks and low detector response [2]. To circumvent these disadvantages the highly polar amines have been converted to less polar derivatives that are more amenable to GC analysis by substitution of amine N-H hydrogens with weakly polar moieties such as acyl, silyl, dinitrophenyl and methyl groups [2]. The derivatives of amines generally have much weaker interactions with stationary phases and thus are more volatile in terms of their chromatographic behavior, which...
Meteoritics & Planetary Science, 2019
The Tagish Lake carbonaceous chondrite exhibits a unique compositional heterogeneity that may be ... more The Tagish Lake carbonaceous chondrite exhibits a unique compositional heterogeneity that may be attributed to varying degrees of aqueous alteration within the parent body asteroid. Previous analyses of soluble organic compounds from four Tagish Lake meteorite specimens (TL5b, TL11h, TL11i, TL11v) identified distinct distributions and isotopic compositions that appeared to be linked to their degree of parent body processing (Herd et al. 2011; Glavin et al. 2012; Hilts et al. 2014). In the present study, we build upon these initial observations and evaluate the molecular distribution of amino acids, aldehydes and ketones, monocarboxylic acids, and aliphatic and aromatic hydrocarbons, including compound-specific d 13 C compositions, for three additional Tagish Lake specimens: TL1, TL4, and TL10a. TL1 contains relatively high abundances of soluble organics and appears to be a moderately altered specimen, similar to the previously analyzed TL5b and TL11h lithologies. In contrast, specimens TL4 and TL10a both contain relatively low abundances of all of the soluble organic compound classes measured, similar to TL11i and TL11v. The organic-depleted composition of TL4 appears to have resulted from a relatively low degree of parent body aqueous alteration. In the case of TL10a, some unusual properties (e.g., the lack of detection of intrinsic monocarboxylic acids and aliphatic and aromatic hydrocarbons) suggest that it has experienced extensive alteration and/or a distinct organicdepleted alteration history. Collectively, these varying compositions provide valuable new insights into the relationships between asteroidal aqueous alteration and the synthesis and preservation of soluble organic compounds.
Lunar and Planetary Science Conference, Mar 1, 2008
The C2 ungrouped Tagish Lake meteorite preserves a range of lithologies, reflecting variable degr... more The C2 ungrouped Tagish Lake meteorite preserves a range of lithologies, reflecting variable degrees of parent-body aqueous alteration. Here, we report on soluble organic compounds, including aliphatic and aromatic hydrocarbons, monocarboxylic acids, and amino acids, found within specimens representative of the range of aqueous alteration. We find that differences in soluble organic compounds among the lithologies may be explained by oxidative, fluid-assisted alteration, primarily involving the derivation of soluble organic compounds from macromolecular material. In contrast, amino acids probably evolved from precursor molecules, albeit in parallel with other soluble organic compounds. Our results demonstrate the role of parent-body alteration in the modification of organic matter and generation of prebiotic compounds in the early solar system, and have implications for interpretation of the complement of soluble organic compounds in carbonaceous chondrites.
Lunar and Planetary Science Conference, Mar 1, 2021
79th Annual Meeting of the Meteoritical Society, Aug 1, 2016
Introduction: Amines are polar, water-soluble organics found in all meteorites that contain amino... more Introduction: Amines are polar, water-soluble organics found in all meteorites that contain amino acids.It has been proposed that meteoritic amines are produced by the thermal decarboxylation of amino acids[1].The analysis of amines using GC-MS techniques has proven to be problematical owing to the high water solubility and high volatility of these compounds. In addition, the strong interactions of polar amine molecules with the stationary phase of a typical polysiloxane column lead to extensive tailing, poor resolution of peaks and low detector response [2]. To circumvent these disadvantages the highly polar amines have been converted to less polar derivatives that are more amenable to GC analysis by substitution of amine N-H hydrogens with weakly polar moieties such as acyl, silyl, dinitrophenyl and methyl groups [2]. The derivatives of amines generally have much weaker interactions with stationary phases and thus are more volatile in terms of their chromatographic behavior, which leads to better separation on the column. In the last decade base-deactivated columns that give good separations of underivatized aliphatic and aromatic amines have been successfully developed [3]. Consequently, volatile amines in aqueous media can now be routinely and reproducibly analyzed by the combination of SPME(solid-phase microextraction) techniques with base-deactivated GC columns that have been specifically engineered to directly separate amines(see for example [4]). The great advantage of this analytical method is that it sidesteps derivatization,which invariably entails the loss of amines, especially those that are more volatile, through side reactions and incomplete transfer during isolation and workup. Results and Discussion: An aqueous test solution containing an in-house collection of amines standards, viz. N-ethylaniline (100 ppm), dipropylamine (100 ppm), methylamine (100 ppm) and piperidine (100 ppm) was prepared in 80 mL of Millipore water. The majority of this solution (70 mL) was set aside for SPME-GC(CP Volamine)MS analysis while the remaining 10 mL was adjusted to ca. pH = 2 using concentrated HCl to convert all of the amines into their corresponding, non-volatile ammonium salts. The water from this acidified mixture was removed on a rotary evaporator , affording a colourless residue. The solid was dissolved in ca. 3 mL of Millipore water and the pH was brought up to 8 by adding ca. 1 mL of 8 M NaOH(aq). The SPME-GC(CP-Volamine) trace of the reconstituted amine mixture was found to contain the same four amine standards as were seen in solution prior to the protonation step. Thus, this result proves that our amine to ammonium to amine methodologycan be used for the direct determination of volatile alkyl amines and aromatic amines. Application of our new SPME-GC(CP-Volamine)MS method to an aqueous extract of a 2-gram sample of the Tagish Lake stone10a afforded a GC trace that contained three different polar aromatic compounds, namely acetophenone , 4-phenylpyridine and 2-phenyl-1,2-propane diol. In the absence of any isotope ratio data, we cannot conclude whether these three aromatic species are indigenous or terrestrial contaminants. It should be pointed out, however, that acetophenone, has been liberated from the Tagish Lake meteorite by the application of heat [5], and thus it does not seem unreasonable to conclude that the acetophenone seen in the trace for 10a likely has an extraterrestrial origin.
Meteoritics and Planetary Science Supplement, Sep 1, 2010
Meteoritics & Planetary Science, Oct 14, 2018
Compound-specific carbon isotope analysis (δ 13 C) of meteoritic organic compounds can be used to... more Compound-specific carbon isotope analysis (δ 13 C) of meteoritic organic compounds can be used to elucidate the abiotic chemical reactions involved in their synthesis. The soluble organic content of the Murchison carbonaceous chondrite has been extensively investigated over the years, with a focus on the origins of amino acids and the potential role of Strecker-cyanohydrin synthesis in the early solar system. Previous δ 13 C investigations have targeted α-amino acid and α-hydroxy acid Strecker products and reactant HCN; however, δ 13 C values for meteoritic aldehydes and ketones (Strecker precursors) have not yet been reported. As such, the distribution of aldehydes and ketones in the cosmos and their role in prebiotic reactions have not been fully investigated. Here, we have applied an optimized O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) derivatization procedure to the extraction, identification and δ 13 C analysis of carbonyl compounds in the Murchison meteorite. A suite of aldehydes and ketones, dominated by acetaldehyde, propionaldehyde and acetone, were detected in the sample. δ 13 C values, ranging from −10.0‰ to +66.4‰, were more 13 C-depleted than would be expected for aldehydes and ketones derived from the interstellar medium, based on interstellar 12 C/ 13 C ratios. These relatively 13 C-depleted values suggest that chemical processes taking place in asteroid parent bodies (e.g. oxidation of the IOM) may provide a secondary source of aldehydes and ketones in the solar system. Comparisons between δ 13 C compositions of meteoritic aldehydes and ketones and other organic compound classes were used to evaluate potential structural relationships and associated reactions, including Strecker synthesis and alteration-driven chemical pathways.
Meteoritics & Planetary Science, Jul 31, 2012
The distribution and isotopic and enantiomeric compositions of amino acids found in three distinc... more The distribution and isotopic and enantiomeric compositions of amino acids found in three distinct fragments of the Tagish Lake C2-type carbonaceous chondrite were investigated via liquid chromatography with fluorescence detection and time-of-flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. Large l-enantiomeric excesses (l ee 43-59%) of the a-hydrogen aspartic and glutamic amino acids were measured in Tagish Lake, whereas alanine, another a-hydrogen protein amino acid, was found to be nearly racemic (d l) using both techniques. Carbon isotope measurements of d-and l-aspartic acid and d-and l-alanine in Tagish Lake fall well outside of the terrestrial range and indicate that the measured aspartic acid enantioenrichment is indigenous to the meteorite. Alternate explanations for the l-excesses of aspartic acid such as interference from other compounds present in the sample, analytical biases, or terrestrial amino acid contamination were investigated and rejected. These results can be explained by differences in the solid-solution phase behavior of aspartic acid, which can form conglomerate enantiopure solids during crystallization, and alanine, which can only form racemic crystals. Amplification of a small initial l-enantiomer excess during aqueous alteration on the meteorite parent body could have led to the large l-enrichments observed for aspartic acid and other conglomerate amino acids in Tagish Lake. The detection of nonterrestrial l-proteinogenic amino acid excesses in the Tagish Lake meteorite provides support for the hypothesis that significant enantiomeric enrichments for some amino acids could form by abiotic processes prior to the emergence of life.
Meteoritics and Planetary Science Supplement, Sep 1, 2012
ABSTRACT We describe the cryogenic curation facility at the University of Alberta, and provide an... more ABSTRACT We describe the cryogenic curation facility at the University of Alberta, and provide an update on results of baseline contamination studies, as well as the challenges of working in the cold.
M&PSA, Sep 1, 2013
ABSTRACT We describe the cryogenic curation facility at the University of Alberta, and provide an... more ABSTRACT We describe the cryogenic curation facility at the University of Alberta, and provide an update on results of baseline contamination studies, as well as the challenges of working in the cold.
Lunar and Planetary Science Conference, Mar 1, 2009
ChemInform, Aug 17, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of the Chemical Society, 1992
Journal of Organometallic Chemistry, Jun 1, 1991
Reactions of [MCl(cod)]2, M = Rh or Ir, cod = cyclooctadiene, with CH{P(S)Ph2}3 give the complex ... more Reactions of [MCl(cod)]2, M = Rh or Ir, cod = cyclooctadiene, with CH{P(S)Ph2}3 give the complex cations, [M(cod){CH(P(S)Ph2)3}]+, which are isolated in high yield as BF4− or ClO4− salts. These are the first reported examples of CH{P(S)Ph2}3 complexes in which the methine proton is retained after coordination. The high acidity of this proton is demonstrated by easy deprotonation to corresponding [M(cod){C(P(S)Ph2)3}] complexes. The 31P NMR spectrum of [Rh(cod){CH(P(S)Ph2)3}]BF4 remains a single line to −100°C whereas that of [Rh(cod){C(P(S)Ph2)3}] is resolved into two resonances at −60°C, suggesting that the former complex is 5-coordinate with an η3 (S,S,S) ligand and the latter 4-coordinate, η2 (S,S). The 4-coordinate structure is confirmed by X-ray diffraction studies of [Rh(cod){C(P(S)Ph2)3}] and [Ir(CO)2{C(P(S)Ph2)3}] which both show approximately square planar metal centers, η2 ligands with the third sulfur non-coordinated (“dangling”), and trigonal planar geometry at the central carbon of the tris(phosphinesulfide) ligand. [Rh(cod){C(P(S)Ph2)3}] and [Ir(CO)2{C(P(S)Ph2)3}] crystallize in the Pbca space group (Z = 8) with respective unit cells: a = 20.427(4) A, b = 16.931(2) A, c = 23.138(3) A; and a = 22.140(6) A, b = 22.317(5) A, c = 14.792(3) A. Line shape analysis for a variable temperature 31P NMR study of [Rh(cod){C(P(S)Ph2)3}] gives ΔGo‡ 46 ± 2 kJ mol−1 for the dynamic exchange of coordinated and non-coordinated sulfur.
Coordination Chemistry Reviews, Dec 1, 1994
This review is primarily concerned with the synthesis, structure and fluxional behaviour of cycli... more This review is primarily concerned with the synthesis, structure and fluxional behaviour of cyclic and acyclic chalcogen-nitrogen systems containing phosphorus(V) or phosphorus(Ill). The cyclic Ph4P2N4S2R-and PhaP2N4S 2-anions (and their selenium analogues) are versatile ligands for both early and late transition metals. Mono-, di-, tri-and tetradentate bonding modes have been established for the eight-membered P2N4S2 ring in these inorganic heterocycles. Ligation occurs through sulphur (or selenium) and/or nitrogen, while the coordinatively saturated phosphorus(V) centres serve as an informative probe of ttuxional processes. By contrast, coordination occurs exclusively through phosphorus in both the cyclic and acyclic phosphorus(Ill) systems. In order to provide a background for the discussion of the coordination chemistry of hybrid P-N/S-N systems, the review begins with a short account of N-bonded complexes of cyclophosphazenes
Meteoritics & Planetary Science, Jan 13, 2023
Introduction: Amines are polar, water-soluble organics found in all meteorites that contain amino... more Introduction: Amines are polar, water-soluble organics found in all meteorites that contain amino acids.It has been proposed that meteoritic amines are produced by the thermal decarboxylation of amino acids[1].The analysis of amines using GC-MS techniques has proven to be problematical owing to the high water solubility and high volatility of these compounds. In addition, the strong interactions of polar amine molecules with the stationary phase of a typical polysiloxane column lead to extensive tailing, poor resolution of peaks and low detector response [2]. To circumvent these disadvantages the highly polar amines have been converted to less polar derivatives that are more amenable to GC analysis by substitution of amine N-H hydrogens with weakly polar moieties such as acyl, silyl, dinitrophenyl and methyl groups [2]. The derivatives of amines generally have much weaker interactions with stationary phases and thus are more volatile in terms of their chromatographic behavior, which...
Meteoritics & Planetary Science, 2019
The Tagish Lake carbonaceous chondrite exhibits a unique compositional heterogeneity that may be ... more The Tagish Lake carbonaceous chondrite exhibits a unique compositional heterogeneity that may be attributed to varying degrees of aqueous alteration within the parent body asteroid. Previous analyses of soluble organic compounds from four Tagish Lake meteorite specimens (TL5b, TL11h, TL11i, TL11v) identified distinct distributions and isotopic compositions that appeared to be linked to their degree of parent body processing (Herd et al. 2011; Glavin et al. 2012; Hilts et al. 2014). In the present study, we build upon these initial observations and evaluate the molecular distribution of amino acids, aldehydes and ketones, monocarboxylic acids, and aliphatic and aromatic hydrocarbons, including compound-specific d 13 C compositions, for three additional Tagish Lake specimens: TL1, TL4, and TL10a. TL1 contains relatively high abundances of soluble organics and appears to be a moderately altered specimen, similar to the previously analyzed TL5b and TL11h lithologies. In contrast, specimens TL4 and TL10a both contain relatively low abundances of all of the soluble organic compound classes measured, similar to TL11i and TL11v. The organic-depleted composition of TL4 appears to have resulted from a relatively low degree of parent body aqueous alteration. In the case of TL10a, some unusual properties (e.g., the lack of detection of intrinsic monocarboxylic acids and aliphatic and aromatic hydrocarbons) suggest that it has experienced extensive alteration and/or a distinct organicdepleted alteration history. Collectively, these varying compositions provide valuable new insights into the relationships between asteroidal aqueous alteration and the synthesis and preservation of soluble organic compounds.
Lunar and Planetary Science Conference, Mar 1, 2008
The C2 ungrouped Tagish Lake meteorite preserves a range of lithologies, reflecting variable degr... more The C2 ungrouped Tagish Lake meteorite preserves a range of lithologies, reflecting variable degrees of parent-body aqueous alteration. Here, we report on soluble organic compounds, including aliphatic and aromatic hydrocarbons, monocarboxylic acids, and amino acids, found within specimens representative of the range of aqueous alteration. We find that differences in soluble organic compounds among the lithologies may be explained by oxidative, fluid-assisted alteration, primarily involving the derivation of soluble organic compounds from macromolecular material. In contrast, amino acids probably evolved from precursor molecules, albeit in parallel with other soluble organic compounds. Our results demonstrate the role of parent-body alteration in the modification of organic matter and generation of prebiotic compounds in the early solar system, and have implications for interpretation of the complement of soluble organic compounds in carbonaceous chondrites.
Lunar and Planetary Science Conference, Mar 1, 2021
79th Annual Meeting of the Meteoritical Society, Aug 1, 2016
Introduction: Amines are polar, water-soluble organics found in all meteorites that contain amino... more Introduction: Amines are polar, water-soluble organics found in all meteorites that contain amino acids.It has been proposed that meteoritic amines are produced by the thermal decarboxylation of amino acids[1].The analysis of amines using GC-MS techniques has proven to be problematical owing to the high water solubility and high volatility of these compounds. In addition, the strong interactions of polar amine molecules with the stationary phase of a typical polysiloxane column lead to extensive tailing, poor resolution of peaks and low detector response [2]. To circumvent these disadvantages the highly polar amines have been converted to less polar derivatives that are more amenable to GC analysis by substitution of amine N-H hydrogens with weakly polar moieties such as acyl, silyl, dinitrophenyl and methyl groups [2]. The derivatives of amines generally have much weaker interactions with stationary phases and thus are more volatile in terms of their chromatographic behavior, which leads to better separation on the column. In the last decade base-deactivated columns that give good separations of underivatized aliphatic and aromatic amines have been successfully developed [3]. Consequently, volatile amines in aqueous media can now be routinely and reproducibly analyzed by the combination of SPME(solid-phase microextraction) techniques with base-deactivated GC columns that have been specifically engineered to directly separate amines(see for example [4]). The great advantage of this analytical method is that it sidesteps derivatization,which invariably entails the loss of amines, especially those that are more volatile, through side reactions and incomplete transfer during isolation and workup. Results and Discussion: An aqueous test solution containing an in-house collection of amines standards, viz. N-ethylaniline (100 ppm), dipropylamine (100 ppm), methylamine (100 ppm) and piperidine (100 ppm) was prepared in 80 mL of Millipore water. The majority of this solution (70 mL) was set aside for SPME-GC(CP Volamine)MS analysis while the remaining 10 mL was adjusted to ca. pH = 2 using concentrated HCl to convert all of the amines into their corresponding, non-volatile ammonium salts. The water from this acidified mixture was removed on a rotary evaporator , affording a colourless residue. The solid was dissolved in ca. 3 mL of Millipore water and the pH was brought up to 8 by adding ca. 1 mL of 8 M NaOH(aq). The SPME-GC(CP-Volamine) trace of the reconstituted amine mixture was found to contain the same four amine standards as were seen in solution prior to the protonation step. Thus, this result proves that our amine to ammonium to amine methodologycan be used for the direct determination of volatile alkyl amines and aromatic amines. Application of our new SPME-GC(CP-Volamine)MS method to an aqueous extract of a 2-gram sample of the Tagish Lake stone10a afforded a GC trace that contained three different polar aromatic compounds, namely acetophenone , 4-phenylpyridine and 2-phenyl-1,2-propane diol. In the absence of any isotope ratio data, we cannot conclude whether these three aromatic species are indigenous or terrestrial contaminants. It should be pointed out, however, that acetophenone, has been liberated from the Tagish Lake meteorite by the application of heat [5], and thus it does not seem unreasonable to conclude that the acetophenone seen in the trace for 10a likely has an extraterrestrial origin.
Meteoritics and Planetary Science Supplement, Sep 1, 2010
Meteoritics & Planetary Science, Oct 14, 2018
Compound-specific carbon isotope analysis (δ 13 C) of meteoritic organic compounds can be used to... more Compound-specific carbon isotope analysis (δ 13 C) of meteoritic organic compounds can be used to elucidate the abiotic chemical reactions involved in their synthesis. The soluble organic content of the Murchison carbonaceous chondrite has been extensively investigated over the years, with a focus on the origins of amino acids and the potential role of Strecker-cyanohydrin synthesis in the early solar system. Previous δ 13 C investigations have targeted α-amino acid and α-hydroxy acid Strecker products and reactant HCN; however, δ 13 C values for meteoritic aldehydes and ketones (Strecker precursors) have not yet been reported. As such, the distribution of aldehydes and ketones in the cosmos and their role in prebiotic reactions have not been fully investigated. Here, we have applied an optimized O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) derivatization procedure to the extraction, identification and δ 13 C analysis of carbonyl compounds in the Murchison meteorite. A suite of aldehydes and ketones, dominated by acetaldehyde, propionaldehyde and acetone, were detected in the sample. δ 13 C values, ranging from −10.0‰ to +66.4‰, were more 13 C-depleted than would be expected for aldehydes and ketones derived from the interstellar medium, based on interstellar 12 C/ 13 C ratios. These relatively 13 C-depleted values suggest that chemical processes taking place in asteroid parent bodies (e.g. oxidation of the IOM) may provide a secondary source of aldehydes and ketones in the solar system. Comparisons between δ 13 C compositions of meteoritic aldehydes and ketones and other organic compound classes were used to evaluate potential structural relationships and associated reactions, including Strecker synthesis and alteration-driven chemical pathways.
Meteoritics & Planetary Science, Jul 31, 2012
The distribution and isotopic and enantiomeric compositions of amino acids found in three distinc... more The distribution and isotopic and enantiomeric compositions of amino acids found in three distinct fragments of the Tagish Lake C2-type carbonaceous chondrite were investigated via liquid chromatography with fluorescence detection and time-of-flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. Large l-enantiomeric excesses (l ee 43-59%) of the a-hydrogen aspartic and glutamic amino acids were measured in Tagish Lake, whereas alanine, another a-hydrogen protein amino acid, was found to be nearly racemic (d l) using both techniques. Carbon isotope measurements of d-and l-aspartic acid and d-and l-alanine in Tagish Lake fall well outside of the terrestrial range and indicate that the measured aspartic acid enantioenrichment is indigenous to the meteorite. Alternate explanations for the l-excesses of aspartic acid such as interference from other compounds present in the sample, analytical biases, or terrestrial amino acid contamination were investigated and rejected. These results can be explained by differences in the solid-solution phase behavior of aspartic acid, which can form conglomerate enantiopure solids during crystallization, and alanine, which can only form racemic crystals. Amplification of a small initial l-enantiomer excess during aqueous alteration on the meteorite parent body could have led to the large l-enrichments observed for aspartic acid and other conglomerate amino acids in Tagish Lake. The detection of nonterrestrial l-proteinogenic amino acid excesses in the Tagish Lake meteorite provides support for the hypothesis that significant enantiomeric enrichments for some amino acids could form by abiotic processes prior to the emergence of life.
Meteoritics and Planetary Science Supplement, Sep 1, 2012
ABSTRACT We describe the cryogenic curation facility at the University of Alberta, and provide an... more ABSTRACT We describe the cryogenic curation facility at the University of Alberta, and provide an update on results of baseline contamination studies, as well as the challenges of working in the cold.
M&PSA, Sep 1, 2013
ABSTRACT We describe the cryogenic curation facility at the University of Alberta, and provide an... more ABSTRACT We describe the cryogenic curation facility at the University of Alberta, and provide an update on results of baseline contamination studies, as well as the challenges of working in the cold.
Lunar and Planetary Science Conference, Mar 1, 2009
ChemInform, Aug 17, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of the Chemical Society, 1992
Journal of Organometallic Chemistry, Jun 1, 1991
Reactions of [MCl(cod)]2, M = Rh or Ir, cod = cyclooctadiene, with CH{P(S)Ph2}3 give the complex ... more Reactions of [MCl(cod)]2, M = Rh or Ir, cod = cyclooctadiene, with CH{P(S)Ph2}3 give the complex cations, [M(cod){CH(P(S)Ph2)3}]+, which are isolated in high yield as BF4− or ClO4− salts. These are the first reported examples of CH{P(S)Ph2}3 complexes in which the methine proton is retained after coordination. The high acidity of this proton is demonstrated by easy deprotonation to corresponding [M(cod){C(P(S)Ph2)3}] complexes. The 31P NMR spectrum of [Rh(cod){CH(P(S)Ph2)3}]BF4 remains a single line to −100°C whereas that of [Rh(cod){C(P(S)Ph2)3}] is resolved into two resonances at −60°C, suggesting that the former complex is 5-coordinate with an η3 (S,S,S) ligand and the latter 4-coordinate, η2 (S,S). The 4-coordinate structure is confirmed by X-ray diffraction studies of [Rh(cod){C(P(S)Ph2)3}] and [Ir(CO)2{C(P(S)Ph2)3}] which both show approximately square planar metal centers, η2 ligands with the third sulfur non-coordinated (“dangling”), and trigonal planar geometry at the central carbon of the tris(phosphinesulfide) ligand. [Rh(cod){C(P(S)Ph2)3}] and [Ir(CO)2{C(P(S)Ph2)3}] crystallize in the Pbca space group (Z = 8) with respective unit cells: a = 20.427(4) A, b = 16.931(2) A, c = 23.138(3) A; and a = 22.140(6) A, b = 22.317(5) A, c = 14.792(3) A. Line shape analysis for a variable temperature 31P NMR study of [Rh(cod){C(P(S)Ph2)3}] gives ΔGo‡ 46 ± 2 kJ mol−1 for the dynamic exchange of coordinated and non-coordinated sulfur.
Coordination Chemistry Reviews, Dec 1, 1994
This review is primarily concerned with the synthesis, structure and fluxional behaviour of cycli... more This review is primarily concerned with the synthesis, structure and fluxional behaviour of cyclic and acyclic chalcogen-nitrogen systems containing phosphorus(V) or phosphorus(Ill). The cyclic Ph4P2N4S2R-and PhaP2N4S 2-anions (and their selenium analogues) are versatile ligands for both early and late transition metals. Mono-, di-, tri-and tetradentate bonding modes have been established for the eight-membered P2N4S2 ring in these inorganic heterocycles. Ligation occurs through sulphur (or selenium) and/or nitrogen, while the coordinatively saturated phosphorus(V) centres serve as an informative probe of ttuxional processes. By contrast, coordination occurs exclusively through phosphorus in both the cyclic and acyclic phosphorus(Ill) systems. In order to provide a background for the discussion of the coordination chemistry of hybrid P-N/S-N systems, the review begins with a short account of N-bonded complexes of cyclophosphazenes
Meteoritics & Planetary Science, Jan 13, 2023