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Rhenium(III) and rhenium(V) complexes stabilized by the potentially tetradentate ligand tris(2-diphenylphosphinoethyl)amine
No full textThe reaction of the rhenium(V) nitrido complex [Re(N)Cl2(PPh3)2] with the tripodal ligand N(CH2CH2PPh2)3 (NP3) in THF gave [Re(N)Cl2(η2-P,P-NP3)] (1) in which NP3 acts as a tridentate ligand using the nitrogen and two phosphorus donors for coordination. Refluxing 1 in a polar solvent such as ethanol produced [(η4-NP3)Re(N)Cl]Cl (2) in which NP3 acts as a tetradentate ligand. Treatment of complex [Re(O)Cl3(AsPh3)2] containing the [Re=O]3+ core with NP3 in THF yielded [ReCl3{η3-N,P,P-(N{CH2CH2Ph 2}2{CH2CH2P(O)Ph2})}] (3). Complexes 1 and 3 have been characterized by single-crystal X-ray analyses. © 2002 Elsevier Science B.V. All rights reserved
Backward synthesis of rhenium(I)γ-hydroxyvinylidene and γ-methoxy-vinylidene complexes and their conversion to the allenylidene [Re=C=C=CPh2(CO)2(MeC(CH2Ph2)3](OSO2CF3).
No full textThe reactivity of the rhenium() allenylidene complex [Re{C C CPh2}(CO)2(triphos)](OTf ) (1) [triphos =
MeC(CH2PPh2)3] towards ionic nucleophiles and electrophiles has been explored. Nucleophiles regioselectively attack
the Cγ carbon atom leading to the formation of σ-alkynyl complexes, while electrophiles attack the Cβ atom yielding
carbyne complexes. The sequential addition of OH and H to 1 at low temperature gave the γ-hydroxyvinylidene
complex [Re{CC(H)C(OH)Ph2}(CO)2(triphos)](OTf ) which regenerated 1 above 40 C via H2O elimination
1,3-Cycloaddition of pyrazole to the allenylidene ligand in [Re{C=C=CPh2}(CO)(2){MeC(CH2PPh2)(3)}](+)
No full textThe reaction of the allenylidene complex [Re{C/C/CPh2}(CO)2(triphos)]OTf (1) (triphos/MeC(CH2PPh2)3;OTf/OSO2CF3) with pyrazole gave the 1,2,3-diheterocyclization product [Re{C/CHCPh2(N2C3H)3}(CO)2(triphos)]Y (Y/OTf, 2OTF;Y/BPh4, 2BPh4). The molecular structure of this complex was determined by a single-crystal X-ray analysis.
Treatment of 2 with sodium methoxide gave the pyrazolyl-functionalized alkynyl derivative [Re{C/CCPh2(N2C3H3)}(CO)2(triphos)] (3) via selective deprotonation of the vinylic hydrogen, followed by back opening of the metal-bound heterocycle.
Protonation of 3 with triflic acid in dichloromethane re-generated 1 and free pyrazole. The overall result of this deprotonation/
protonation sequence allowed us to propose a reliable mechanism for the formation of the 1,2,3-diheterocyclization product 2OTf
Nucleophilic addition of phosphines to rhenium allenylidenes. Unprecedented double P-H bond activation to give an eta(1)-P-phospha-1-butadienyl ligand
No full textTertiary phosphines PMe3xPhx (x = 0–2) react with the rhenium allenylidene [(triphos)(CO)2Re(C=C=CPh2)]OTf (1)
yielding γ-phosphonioalkynyl complexes [(triphos)(CO)2Re{C=CCPh2(PMe3xPhx)}]OTf [x = 0, (2); 1, (4); 2 (7)]
which convert into the α-phosphonioallenyl derivatives [(triphos)(CO)2Re{C(PMe3xPhx)=C=CPh2}]OTf [x = 0, (3);
1, (5); 2 (6)] at higher tempereature. The reactions of 1 with secondary, PHPh2, and primary, PH2CH2Fc
(Fc = ferrocenyl), phosphines proceed with a similar mechanism, followed by single or double P–H bond cleavage.
The γ-phosphonioalkynyl [(triphos)(CO)2Re{C=CCPh2(PHPh2)}]OTf (9) and the α-phosphonioallenyl [(triphos)-
(CO)2Re{C(PHPh2)=C=CPh2}]OTf (10) have been intercepted by in situ NMR spectroscopy. On increasing the
temperature, 10 undergoes a selective 1,3-P,C-H shift to give the α-phosphoniobutadienyl derivative [(triphos)-
(CO)2Re{C(=PPh2)CH=CPh2}]OTf (8). With the primary phosphine PH2CH2Fc, the initially formed
α-phosphoniobutadienyl complex [(triphos)(CO)2Re{C(=PHFc)CH=CPh2}]OTf (11) transforms into the η1-P-phospha-1-butadienyl complex [(triphos)(CO)2Re{P(CH2Fc)=CHCH=CPh2}]OTf (12) upon heating at 50 C
Unprecedented eta(1)-P-basal coordination of P4X3 molecules (X = S, Se). An experimental and theoretical study of the apical vs basal complexation dichotomy
No full textReaction of [(triphos)Re(CO)2(OTf)] (1) [triphos = MeC(CH2PPh2)3; OTf = OSO2CF3] with P4S3 and P4Se3 yields pairs of coordination isomers, namely, [(triphos)Re(CO)2{1-Papical-P4X3}]+ (X = S, 2; Se, 5) and [(triphos)Re(CO)2{1-Pbasal-P4X3}]+ (X = S, 3; Se, 6). The latter represent the first examples of the 1-Pbasal coordination achieved by the P4X3 molecular cage. Further reaction of 2/3 and 5/6 mixtures with 1 affords the dinuclear species [{(triphos)Re(CO)2}2{,1:1-Papical,Pbasal-P4X3}]2+ (X = S, 4; Se, 7) in which the unprecedented M-1-Pbasal/1-Papical-M' bridging coordination of the P4X3 molecule is accomplished. A theoretical analysis of the bonding properties of the two coordination isomers is also presented. The directionality of apical vs basal phosphorus lone pairs is also discussed in terms of MO arguments
Synthesis of heterocyclic ligands by diheterocyclization at the rhenium(I) allenylidene [(triphos)(CO)(2)Re{C=C=CPh2}](OSO2CF3). 1. Reactivity with dipolar N,N-heterocycles
No full text1,2,3-Diheterocyclizations at the allenylidene ligand in the complex [(triphos)(CO)2Re{CdCdCPh2}]-
OTf (1; triphos ) MeC(CH2PPh2)3, OTf ) OSO2CF3) readily occur upon reacting 1 with N,N-heterocycles
such as 1H-benzotriazole, 2-aminopyridine, and 2-aminothiazole. The reaction of 1 with 1H-benzotriazole
leads to [(triphos)(CO)2Re{CdC(H)C(Ph)}]N(C6H4)NdN}]OTf (4). Deprotonation of 4 with sodium
methoxide in tetrahydrofuran at room temperature yields the alkynyl derivative [(triphos)(CO)2Re{Ct
CC(Ph)2(NC6H4NdN)}] (5) via ring opening of the triazaindenyl moiety in 4. Reaction of 1 with
2-aminopyridine or 2-aminothiazole in CH2Cl2 leads to the heterobicyclic compounds [(triphos)(CO)2Re-
{CdC(H)C(Ph)2N(H)C(CH)4N}]OTf (6) and [(triphos)(CO)2Re{CdC(H)C(Ph)2N(H)CS(CH)2N}]OTf
(8), respectively. Both complexes undergo regioselective deprotonation at the N-H heterocycle group
by treatment with sodium methoxide in THF, giving the neutral species [(triphos)(CO)2Re{CdC(H)C-
(Ph)2NC(CH)4N}] (7) and [(triphos)(CO)2Re{CdC(H)C(Ph)2NCS(CH)2N}] (9), respectively. The X-ray
structures of the new organorhenium species 4 and 7-9 have been determined, which have confirmed
that the addition of the NH bond of the N,N-heterocycle occurs always across the Cbeta-Cgamm double bond
of the allenylidene chain
Synthesis, characterisation and molecular structure of Re(III) 2-oxacyclocarbenes stabilised by a benzoyldiazenido ligand
No full textA family of new Fischer-type rhenium() benzoyldiazenido-2-oxacyclocarbenes of formula [(ReCl2{η1-N2C(O)-
Ph}{ C(CH2)nCH(R)O}(PPh3)2] [n = 2, R = H (2), R = Me (3); n = 3, R = H (4), R = Me (5)] have been prepared by
reaction of [ReCl2{η2-N2C(Ph)O}(PPh3)2] (1) with ω-alkynols, such as 3-butyn-1-ol, 4-pentyn-1-ol, 4-pentyn-2-ol,
5-hexyn-2-ol in refluxing THF. The correct formulation of the carbene derivatives 2-5 has been unambiguously
determined in solution by NMR analysis and confirmed for compounds 2–4 by X-ray diffraction methods in the
solid state. All complexes are octahedral with the benzoyldiazenido ligand, Re{N2C(O)Ph}, adopting a “single bent”
conformation. The coordination basal plane is completed by an oxacyclocarbene ligand and two chlorine atoms.
Two triphenylphosphines in trans positions with respect to each other complete the octahedral geometry around
rhenium. The reactivity of 1 towards different alkynes and alkenes including propargyl- and allylamine has been
also studied. With propargyl amine, monosubstituted or bisubstituted complexes, [(ReCl2{η1-N2C(O)Ph}{η1-NH2-
CH2C CH}n(PPh3)3 n] [n = 1 (6); n = 2 (7)], have been isolated depending on the reaction conditions. In contrast, the
reaction with allylamine gave only the disubstituted complex [(ReCl2{η1-N2C(O)Ph}{η1-NH2CH2CH CH2}2(PPh3)]
(8). The molecular structure of the monosubstituted adduct 6 has been confirmed by X-ray analysis in the solid state
Synthesis and chemistry of 2-oxacyclocarbene and 2-cyclovinyl ether ligands supported by the [{MeC(CH2PPh2)(3)}Re(CO)(2)](+) auxiliary
No full textThe rhenium(I) cyclovinyl ether complexes [(triphos)Re(CO)2{C /CHCH2(CH2)nO}]BF4 [triphos./MeC(CH2PPh2)3, n./1, 2]
have been synthesized through the reversible and regioselective deprotonation of the corresponding 2-oxacyclocarbene complexes
[(triphos)Re(CO)2{./CCH2CH2(CH2)nCH2O}]BF4 (n./1, 2). The structure of the octahedral 2-oxacyclohexylidene complex
[(triphos)Re(CO)2(./CCH2CH2CH2CH2O)]BF4 has been determined by a single-crystal X-ray diffraction analysis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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