title: ESIMS targeted synthesis of novel {Pt2S2} derivatives

authors: Fortney-Zirker, Ryland

subjects: Inorganic Chemistry

abstract: Electrospray ionisation mass spectrometry (ESIMS) was used to investigate ring-
opening reactions of several epoxides with the nucleophilic dinuclear PtII
complexes
[Pt2(μ-E)2(PPh3)4] (E = S, 1a; Se, 1b) and several activated cyclopropanes, N -
tosylaziridine, and thiirane with 1a. Epoxides cyclohexene oxide, styrene oxide,
epibromohydrin, and 2,2-dimethyloxirane were found to undergo ring-opening when
reacted with 1a and derivatives [Pt2(μ-S)(μ-S C6H10OH)(PPh3)4]BPh4 (5[BPh4],
[Pt2(μ-S)(μ-S C8H8OH)(PPh3)4]BETI (6[BETI]), [Pt2(μ-S CH2CH(OH)CH2 μ-S)-
(PPh3)4][PF6]2 (3[PF6]2), and [Pt2(μ-S)(μ-S CH2C(Me)2OH)(PPh3)4]BPh4 (7 [BPh4])
were respectively isolated and structurally characterised with 31P{1H} and 195Pt nu-
clear magnetic resonance (NMR) spectroscopy, and for 5, 3 and 7 single crystal X-
ray diffraction (XRD) studies. 6 was found to be a mixture of isomers, and crystals
suitable for a single crystal XRD experiment were not obtained. Both styrene oxide
and epibromohydrin underwent ring-opening when reacted with 1b and the respec-
tive derivatives [Pt2(μ-Se)(μ-Se C8H8OH)(PPh3)4]+ and [Pt2(μ-Se CH2CH(OH)-
CH2 μ-Se)(PPh3)4]2+ were characterised by ESIMS. The fully substituted epoxide
2,3-dimethyl-2,3-epoxybutane did not undergo ring-opening when treated with 1a
in refluxing methanol for several hours. 5,6-Epoxy-5,6-dihydro-[1,10]-phenanthro-
line resulted in ring-opening when reacted with 1a however the resulting deriva-
tive [Pt2(μ-S)(μ-S C12H8N2O)(PPh3)4]+ (8) was found to decompose readily in
solution. Cyclopropanes cyclopropyl methyl ketone and trans-1,2-dibenzoylcyclo-
propane did not undergo ring-opening when reacted with 1a. The more activated
2,2,3,3-tetracyanocyclopropane and diethylcyclopropane-1,2-dicarboxylate both re-
i
sulted in ring-opening when reacted with 1a resulting in the isolation of deriva-
tives [Pt2(μ-S)(μ-S C(CN)2)(PPh3)4] (12) and [Pt2(μ-S)(μ-S C2H4CH(CO2Et)2)-
(PPh3)4]BETI (11[BETI]) respectively which were structurally characterised by het-
eronuclear NMR spectroscopy (12 31P{1H}, 195Pt{1H}; 11 1H, 31P{1H}) and single
crystal XRD studies. 12 was found to have a carbanionic center and is proposed
to result from an intramolecular rearrangement of the initially formed [Pt2(μ-S)(μ-
S C(CN)2C(CN)2CH3)(PPh3)4]+ (31). Bromomethylcyclopropane did not result
in ring-opening when reacted with 1a, however alkylation resulted in [Pt2(μ-S)(μ-
S CH2C3H5)(PPh3)4]+ (10) which was isolated as 10[BPh4] and structurally char-
acterised by 31P{1H}-NMR spectroscopy and single crystal XRD. 10[BPh4] did not
undergo ring-opening when refluxed in methanol. N -tosylaziridine resulted in the
ring-opened derivative [Pt2(μ-S)(μ-S C2H4NHtosyl)(PPh3)4]+ (13) when reacted
with 1a and was isolated as 13[PF6] and structurally characterised by 31P{1H}-NMR
spectroscopy and single crystal XRD. Thiirane appeared to rapidly undergo ring-
opening when reacted with 1a however only polymeric decomposition species were
detected by ESIMS. The previously reported reaction of 1a and 2-chloro-N -methyl-
pyridinium iodide (14[I]) was reexamined. Salts of 14 sans iodide were synthesized
using alkylating agents trimethyloxonium tetrafluoroborate or dimethyl sulfate giv-
ing 14[BF4] or 14[CH3SO4] respectively. The reaction of 1a and 14 was found to
result in the dicationic complex [Pt2(μ-S)(μ-S C6H7N)(PPh3)4]2+ (2) which was
isolated as the bis-hexafluorophosphate salt 2[PF6]2 and structurally characterised
with 31P{1H}-NMR spectroscopy, 195Pt{1H}-NMR spectroscopy, and single crystal
XRD. The 2-mercapto-N -methylpyridinium ligand in 2 was proposed to be an ex-
cellent leaving group and the reaction of 2 with excess bromide resulted in the isola-
tion of the mixed-bridged complex [Pt2(μ-S)(μ-Br)(PPh3)4]BPh4 (16[BPh4]) which
was structurally characterised with 31P{1H}-NMR spectroscopy and single crystal
XRD. The thiols N -acetylcysteamine, 2-mercapto-1-methylimidazole, and 2-amino-
thiophenol were reacted with 2 to give [Pt2(μ-S)(μ-S C2H4NHC( O)CH3)(PPh3)4]+
(38), [Pt2(μ-S)(μNS-S C3H2N2CH3)(PPh3)4]+ (17), and [Pt2(μ-S)(μ-S C6H4NH2)-
ii
(PPh3)4]+ (39) respectively which were isolated as 38[BF4], 17[BETI], and 39[BF4].
17[BETI] was structurally characterised (31P{1H}-NMR spectroscopy, 195Pt{1H}-
NMR spectroscopy, single crystal XRD) and found to contain a novel 6-membered
Pt-S-Pt-S-C-N heterocycle. 38 was characterised using NMR spectroscopy (1H, 13C,
31P{1H}, and 195Pt{1H}). 39 was characterised using 31P{1H}-NMR spectroscopy.
2 was reacted with selenourea resulting in the detection by ESIMS of the mixed-
bridged [Pt2(μ-S)(μ-Se)(PPh3)4]+ (23) which decomposed over the course of several
days to 1a and 1b. When the diaryldichalcogenides Ph2Se2, Ph2Te2, di-4-ethoxy-
phenyl-ditelluride were reduced with hydrazine to the corresponding chalcogeno-
late anion and reacted with 2, substitution of the 2-mercapto-N -methylpyridinium
zwitterion resulted and mixed-bridged derivatives [Pt2(μ-S)(μ-E R)(PPh3)4]+ (E-
R = Se-Ph, 18; Te-Ph, 47; Te-C6H4-OEt, 19) detected by ESIMS. 18[BF4] and
19[BF4] were isolated and structurally characterised with heteronuclear NMR spec-
troscopy (31P{1H}-NMR, 195Pt{1H}-NMR) and single crystal XRD. A bridging hy-
drazine species was observed when reacting 2 with hydrazine reduced diaryldichalco-
genides, and the reaction between 2 and hydrazine was found to result in [Pt2-
(μ-S)(μ-NH NH2)(PPh3)4]+ (21) which was isolated as 21[BPh4] and structurally
characterised with 31P{1H} and 195Pt{1H}-NMR spectroscopy

text: ESIMS targeted synthesis of novel {Pt2S2} derivatives Electrospray ionisation mass spectrometry (ESIMS) was used to investigate ring-
opening reactions of several epoxides with the nucleophilic dinuclear PtII
complexes
[Pt2(μ-E)2(PPh3)4] (E = S, 1a; Se, 1b) and several activated cyclopropanes, N -
tosylaziridine, and thiirane with 1a. Epoxides cyclohexene oxide, styrene oxide,
epibromohydrin, and 2,2-dimethyloxirane were found to undergo ring-opening when
reacted with 1a and derivatives [Pt2(μ-S)(μ-S C6H10OH)(PPh3)4]BPh4 (5[BPh4],
[Pt2(μ-S)(μ-S C8H8OH)(PPh3)4]BETI (6[BETI]), [Pt2(μ-S CH2CH(OH)CH2 μ-S)-
(PPh3)4][PF6]2 (3[PF6]2), and [Pt2(μ-S)(μ-S CH2C(Me)2OH)(PPh3)4]BPh4 (7 [BPh4])
were respectively isolated and structurally characterised with 31P{1H} and 195Pt nu-
clear magnetic resonance (NMR) spectroscopy, and for 5, 3 and 7 single crystal X-
ray diffraction (XRD) studies. 6 was found to be a mixture of isomers, and crystals
suitable for a single crystal XRD experiment were not obtained. Both styrene oxide
and epibromohydrin underwent ring-opening when reacted with 1b and the respec-
tive derivatives [Pt2(μ-Se)(μ-Se C8H8OH)(PPh3)4]+ and [Pt2(μ-Se CH2CH(OH)-
CH2 μ-Se)(PPh3)4]2+ were characterised by ESIMS. The fully substituted epoxide
2,3-dimethyl-2,3-epoxybutane did not undergo ring-opening when treated with 1a
in refluxing methanol for several hours. 5,6-Epoxy-5,6-dihydro-[1,10]-phenanthro-
line resulted in ring-opening when reacted with 1a however the resulting deriva-
tive [Pt2(μ-S)(μ-S C12H8N2O)(PPh3)4]+ (8) was found to decompose readily in
solution. Cyclopropanes cyclopropyl methyl ketone and trans-1,2-dibenzoylcyclo-
propane did not undergo ring-opening when reacted with 1a. The more activated
2,2,3,3-tetracyanocyclopropane and diethylcyclopropane-1,2-dicarboxylate both re-
i
sulted in ring-opening when reacted with 1a resulting in the isolation of deriva-
tives [Pt2(μ-S)(μ-S C(CN)2)(PPh3)4] (12) and [Pt2(μ-S)(μ-S C2H4CH(CO2Et)2)-
(PPh3)4]BETI (11[BETI]) respectively which were structurally characterised by het-
eronuclear NMR spectroscopy (12 31P{1H}, 195Pt{1H}; 11 1H, 31P{1H}) and single
crystal XRD studies. 12 was found to have a carbanionic center and is proposed
to result from an intramolecular rearrangement of the initially formed [Pt2(μ-S)(μ-
S C(CN)2C(CN)2CH3)(PPh3)4]+ (31). Bromomethylcyclopropane did not result
in ring-opening when reacted with 1a, however alkylation resulted in [Pt2(μ-S)(μ-
S CH2C3H5)(PPh3)4]+ (10) which was isolated as 10[BPh4] and structurally char-
acterised by 31P{1H}-NMR spectroscopy and single crystal XRD. 10[BPh4] did not
undergo ring-opening when refluxed in methanol. N -tosylaziridine resulted in the
ring-opened derivative [Pt2(μ-S)(μ-S C2H4NHtosyl)(PPh3)4]+ (13) when reacted
with 1a and was isolated as 13[PF6] and structurally characterised by 31P{1H}-NMR
spectroscopy and single crystal XRD. Thiirane appeared to rapidly undergo ring-
opening when reacted with 1a however only polymeric decomposition species were
detected by ESIMS. The previously reported reaction of 1a and 2-chloro-N -methyl-
pyridinium iodide (14[I]) was reexamined. Salts of 14 sans iodide were synthesized
using alkylating agents trimethyloxonium tetrafluoroborate or dimethyl sulfate giv-
ing 14[BF4] or 14[CH3SO4] respectively. The reaction of 1a and 14 was found to
result in the dicationic complex [Pt2(μ-S)(μ-S C6H7N)(PPh3)4]2+ (2) which was
isolated as the bis-hexafluorophosphate salt 2[PF6]2 and structurally characterised
with 31P{1H}-NMR spectroscopy, 195Pt{1H}-NMR spectroscopy, and single crystal
XRD. The 2-mercapto-N -methylpyridinium ligand in 2 was proposed to be an ex-
cellent leaving group and the reaction of 2 with excess bromide resulted in the isola-
tion of the mixed-bridged complex [Pt2(μ-S)(μ-Br)(PPh3)4]BPh4 (16[BPh4]) which
was structurally characterised with 31P{1H}-NMR spectroscopy and single crystal
XRD. The thiols N -acetylcysteamine, 2-mercapto-1-methylimidazole, and 2-amino-
thiophenol were reacted with 2 to give [Pt2(μ-S)(μ-S C2H4NHC( O)CH3)(PPh3)4]+
(38), [Pt2(μ-S)(μNS-S C3H2N2CH3)(PPh3)4]+ (17), and [Pt2(μ-S)(μ-S C6H4NH2)-
ii
(PPh3)4]+ (39) respectively which were isolated as 38[BF4], 17[BETI], and 39[BF4].
17[BETI] was structurally characterised (31P{1H}-NMR spectroscopy, 195Pt{1H}-
NMR spectroscopy, single crystal XRD) and found to contain a novel 6-membered
Pt-S-Pt-S-C-N heterocycle. 38 was characterised using NMR spectroscopy (1H, 13C,
31P{1H}, and 195Pt{1H}). 39 was characterised using 31P{1H}-NMR spectroscopy.
2 was reacted with selenourea resulting in the detection by ESIMS of the mixed-
bridged [Pt2(μ-S)(μ-Se)(PPh3)4]+ (23) which decomposed over the course of several
days to 1a and 1b. When the diaryldichalcogenides Ph2Se2, Ph2Te2, di-4-ethoxy-
phenyl-ditelluride were reduced with hydrazine to the corresponding chalcogeno-
late anion and reacted with 2, substitution of the 2-mercapto-N -methylpyridinium
zwitterion resulted and mixed-bridged derivatives [Pt2(μ-S)(μ-E R)(PPh3)4]+ (E-
R = Se-Ph, 18; Te-Ph, 47; Te-C6H4-OEt, 19) detected by ESIMS. 18[BF4] and
19[BF4] were isolated and structurally characterised with heteronuclear NMR spec-
troscopy (31P{1H}-NMR, 195Pt{1H}-NMR) and single crystal XRD. A bridging hy-
drazine species was observed when reacting 2 with hydrazine reduced diaryldichalco-
genides, and the reaction between 2 and hydrazine was found to result in [Pt2-
(μ-S)(μ-NH NH2)(PPh3)4]+ (21) which was isolated as 21[BPh4] and structurally
characterised with 31P{1H} and 195Pt{1H}-NMR spectroscopy

year: 2024-10-18

title: Personal and relationship dimensions of higher education science and engineering learning communities

authors: Eames, Chris W.

subjects: higher education

abstract: The research reported here follows previous articles in this special issue which detail a national study involving a team of researchers across four higher education institutions in New Zealand. A key theme that emerged from a collection of questionnaire, interview and observational data was the central importance of teacher–student and student–student relationships, as part of the learning communities. Both teachers and students highlighted the value of developing a personal dimension to their relationships that engendered a greater sense of access and loyalty to that community. Contextual factors such as approachability of teachers, class size and teaching environment appeared to be important to relationship building and enculturation in higher education science and engineering learning communities.

text: Personal and relationship dimensions of higher education science and engineering learning communities The research reported here follows previous articles in this special issue which detail a national study involving a team of researchers across four higher education institutions in New Zealand. A key theme that emerged from a collection of questionnaire, interview and observational data was the central importance of teacher–student and student–student relationships, as part of the learning communities. Both teachers and students highlighted the value of developing a personal dimension to their relationships that engendered a greater sense of access and loyalty to that community. Contextual factors such as approachability of teachers, class size and teaching environment appeared to be important to relationship building and enculturation in higher education science and engineering learning communities.

year: 2008

title: Te Whariki revisited: How approaches to assessment can make valued learning visible

authors: McLachlan, Claire

abstract: In 2016, Te Whariki: He Whariki Matauranga mō ngā Mokopuna o Aotearoa: Early Childhood Curriculum (Te Whariki) (Ministry of Education [MoE], 2017), New Zealand’s early childhood curriculum was updated for the first time in 20 years. Although the gazetted principles, strands and goals of the curriculum were not part of the update, the remainder of the curriculum was revised to meet the changing social and linguistic context, the revised national curriculum and associated documents, reviews of early childhood practice and relevant theory and research. The updated curriculum has reduced learning outcomes (from 118 to 20) and stronger guidance on the need for both informal and formal approaches to assessment to ensure children’s learning in each strand are assessed. This article reflects on the changes between the 1996 and 2017 version of the curriculum in relation to assessment and the rationale for the changes. Approaches to both ‘in the moment’ and planned assessment are explored and the usefulness of approaches which enable teachers to reflect on ‘discrepant data’ and support children’s learning in each strand are examined.

text: Te Whariki revisited: How approaches to assessment can make valued learning visible In 2016, Te Whariki: He Whariki Matauranga mō ngā Mokopuna o Aotearoa: Early Childhood Curriculum (Te Whariki) (Ministry of Education [MoE], 2017), New Zealand’s early childhood curriculum was updated for the first time in 20 years. Although the gazetted principles, strands and goals of the curriculum were not part of the update, the remainder of the curriculum was revised to meet the changing social and linguistic context, the revised national curriculum and associated documents, reviews of early childhood practice and relevant theory and research. The updated curriculum has reduced learning outcomes (from 118 to 20) and stronger guidance on the need for both informal and formal approaches to assessment to ensure children’s learning in each strand are assessed. This article reflects on the changes between the 1996 and 2017 version of the curriculum in relation to assessment and the rationale for the changes. Approaches to both ‘in the moment’ and planned assessment are explored and the usefulness of approaches which enable teachers to reflect on ‘discrepant data’ and support children’s learning in each strand are examined.

year: 2018