Unprecedented Hybrid Scorpionate/Phosphine Ligand Able To Be Anchored to Carbosilane Dendrimers

Hack, Verena; Camerano, José A.; Ciriano, Miguel A.; Tejel, Cristina; Oro, Luis A.

doi:10.1021/ic051279t

Cited by 26 publications

(27 citation statements)

References 22 publications

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“…[10] In solution, both complexes are fluxional and have a single signal for the olefinic carbon atoms and protons of the cod ligand and the equivalence of the pyrazolyl rings in the 13 C{ 1 H} and 1 H NMR spectra at room temperature. [10] Although the pyrazolyl rings and the cod carbon atoms are nonequivalent in the solid-state structure of the rhodium complex, the equivalences found in solution can be easily explained on the basis of the lack of stereochemical rigidity associated with pentacoordination or the known turnover mechanism.…”

Section: Resultsmentioning

confidence: 99%

“…Complex 1 was prepared according to published procedures. [10] All of the other chemicals used in this work were purchased from Aldrich Chemicals and used as received. Carbon and hydrogen analyses were performed by using a Perkin-Elmer 2400 microanalyzer.…”

Section: Methodsmentioning

confidence: 99%

“…This modified scorpionate ligand also bears an allyl group directly connected to boron, which has allowed it to be covalently linked to carbosilane dendrimers. [10] We have already anticipated that such a system could lead to new reactivity patterns and open up new possibilities for scorpionate ligands. [11] In this paper we report the results of a study of a series of iridium complexes produced with this ligand system, paying special attention to the possibilities of coordination through the four arms, and their reactions with protic acids, which reflect the versatility of this hybrid scorpionate when attached to an iridium center.…”

Section: H T U N G T R E N N U N G {(Allyl)b-a C H T U N G T R E N N mentioning

confidence: 99%

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Coordination Features of a Hybrid Scorpionate/Phosphane Ligand Exemplified with Iridium

Camerano¹,

Ciriano²,

Tejel³

et al. 2008

Chemistry A European J

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Although the pentacoordinated complex [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(cod)] (1; pz=pyrazolyl, cod=1,5-cyclooctadiene), isolated from the reaction of [{Ir(mu-Cl)(cod)}(2)] with [Li(tmen)][B(allyl)(CH(2)PPh(2))- (pz)(2)] (tmen=N,N,N',N'-tetramethylethane-1,2-diamine), shows behavior similar to that of the related hydridotris(pyrazolyl)borate complex, the carbonyl derivatives behave in a quite different way. On carbonylation of 1, the metal--metal-bonded complex [(Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}CO)(2)(mu-CO)] (2) that results has a single ketonic carbonyl bridge. This bridging carbonyl is labile such that upon treatment of 2 with PMe(3) the pentacoordinated Ir(I) complex [Ir(CO){(pz)B(eta(2)-CH(2)CH=CH(2))(CH(2)PPh(2))(pz)}(PMe(3))] (3) was isolated. Complex 3 shows a unique fac coordination of the hybrid ligand with the allyl group eta(2)-bonded to the metal in the equatorial plane of a distorted trigonal bipyramid with one pyrazolate group remaining uncoordinated. This unusual feature can be rationalized on the basis of the electron-rich nature of the metal center. The related complex [Ir(CO){(pz)B(eta(2)-CH(2)CH=CH(2))(CH(2)PPh(2))(pz)}(PPh(3))] (4) was found to exist in solution as a temperature-dependent equilibrium between the cis-pentacoordinated and trans square planar isomers with respect to the phosphorus donor atoms. Protonation of 3 with different acids is selective at the iridium center and gives the cationic hydrides [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(CO)H(PMe(3))]X (X=BF(4) (5), MeCO(2) (6), and Cl (7)). Complex 7 further reacts with HCl to generate the unexpected product [Ir(CO)Cl{(Hpz)B(CH(2)PPh(2))(pz)CH(2)CH(Me)}(PMe(3))]Cl (9; Hpz=protonated pyrazolyl group) formed by the insertion of the hydride into the Ir-(eta(2)-allyl) bond. In contrast, protonation of complex 4 with HCl stops at the hydrido complex [Ir{(allyl)B(CH(2)PPh(2))(pz)(2)}(CO)H(PPh(3))]Cl (8). X-ray diffraction studies carried out on complexes 2, 3, and 9 show the versatility of the hybrid scorpionate ligand in its coordination.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: H T U N G T R E N N U N G {(Allyl)b-a C H T U N G T R E N N mentioning

confidence: 99%

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Coordination Features of a Hybrid Scorpionate/Phosphane Ligand Exemplified with Iridium

Camerano¹,

Ciriano²,

Tejel³

et al. 2008

Chemistry A European J

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“…P, 12 S, 13 and C 14 ) providing different electronic environments to the metals, which has made possible the observation of unusual reactivity patterns. 12d,15 With the idea of bringing together mixed donor sets 'N 2 P', we reported the synthesis 16 documented the related 'P 2 N' hybrid system [PhB(CH 2 P t Bu 2 ) 2 (Pz)] . Aimed by the rich reactivity and coordination chemistry displayed by the iridium complexes stabilized by the 'PN 2 ' tripodal system, which showed the allyl arm not to be innocent, 18 we decided to take a step further in the design of such hybrid architectures and now we wish to report the synthesis of a new ligand with a flexible scaffold, provided with a set of three different donors based on hard (N) and soft (P, C) atoms of composition shown by its rhodium and iridium complexes.…”

Section: Introductionmentioning

confidence: 99%

Rhodium and Iridium Complexes with a New Scorpionate Phosphane Ligand

2013

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“…Access to the required bis(phosphino)pyrazolylborate 7 ligand is achieved by initial preparation of the bis(phosphino)borane precursor PhB(CH 2 P t Bu 2 ) 2 (1) via metathesis between PhBCl 2 and two equivalents of LiCH 2 P t Bu 2 (Scheme 1). Reaction of [pz]Li with 1 (pz = pyrazolyl), followed immediately by salt metathesis with TlPF 6 , leads to the clean formation of solid white [PhBP tBu 2 (pz)]Tl (2a) in 66% isolated yield.…”

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Characterization of the Terminal Iron(IV) Imides {[PhBP^t^Bu₂(pz‘)]Fe^IV⋮NAd}⁺

2006

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New hybrid bis(phosphine)(pyrazole)borate tripodal ligands ([PhBP tBu 2 (pz')] − ) are reported that support pseudotetrahedral iron in the oxidation states +1, +2, +3, and +4. The higher oxidation states are stabilized by a terminal Fe≡NR linkage. Of particular interest is the generation and thorough characterization of an S = 1 Fe IV ≡NR + imide cation using this new ligand system. The latter species can be observed electrochemically and spectroscopically, and its solid-state crystal structure is reported.Although implicated as intermediates in group transfer reactions,1 mid-to-late first row transition metals (e.g., Mn, Fe, Co, Ni) featuring terminal imido/nitrene functionalities are rare. 5 To the best of our knowledge the single report of a complex that can be formulated as an Fe(IV) imide concerns Lee's tetranuclear cluster Fe 4 (µ 3 -N t Bu) 4 (N t Bu)Cl 3 , isolated in only 1-2% yield. 6 Mössbauer data for this species were consistent with a cluster featuring three Fe(III) centers and one Fe (IV) center, the latter most likely indicative of the Fe IV =N t Bu terminal linkage. Herein we describe a new hybrid pyrazolyl/phosphino-borate ligand that can support pseudotetrahedral iron in the +1, +2, +3, and +4 oxidation states. The +3 and +4 oxidation states are stabilized by the terminal Fe≡NR imide linkage.Access to the required bis(phosphino)pyrazolylborate 7 ligand is achieved by initial preparation of the bis(phosphino)borane precursor PhB(CH 2 P t Bu 2 ) 2 (1) via metathesis between PhBCl 2 and two equivalents of LiCH 2 P t Bu 2 (Scheme 1). Reaction of [pz]Li with 1 (pz = pyrazolyl), followed immediately by salt metathesis with TlPF 6 , leads to the clean formation of solid white [PhBP tBu 2 (pz)]Tl (2a) in 66% isolated yield. 8 The use of the bulky LiCH 2 P t Bu 2 carbanion is critically important in the preparation of this type of hybrid borate ligand because (i) effective di-rather than tri-substitution at boron can be achieved, which could not be realized using less hindered carbanions such as LiCH 2 P i Pr 2 and LiCH 2 PPh 2 ; (ii) the borane product, PhB (CH 2 P t Bu 2 ) 2 (1), does not appear to dimerize to an appreciable degree in solution. This fact allows the efficient introduction of a third donor arm. Metathesis of 2a with FeCl 2 leads to the clean formation of the high spin (S = 2) complex [PhBP tBu 2 (pz)]FeCl (3a), isolated in 69% yield as a yellow crystalline solid. Solution 1 H NMR data for 3a are suggestive of a monomeric structure in solution, in accord with the calculated solution Evans' method magnetic moment at 295 K (5.2 µ B ). 9 However, the 100 K X-ray crystal structure of 3a establishes a dimeric structure with bridging chlorides and a crystallographic center of symmetry in the solid-state (see SI for details).Following an overall methodology that proved effective for the synthesis of Fe(III) imides previously, one-electron reduction of 3a with sodium/mercury amalgam in the presence of excess PMe 3 generates the high spin d 7 precursor [PhBP tBu 2 (pz)]Fe(PMe 3 ) (4a) a...

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Unprecedented Hybrid Scorpionate/Phosphine Ligand Able To Be Anchored to Carbosilane Dendrimers

Cited by 26 publications

References 22 publications

Coordination Features of a Hybrid Scorpionate/Phosphane Ligand Exemplified with Iridium

Coordination Features of a Hybrid Scorpionate/Phosphane Ligand Exemplified with Iridium

Rhodium and Iridium Complexes with a New Scorpionate Phosphane Ligand

Characterization of the Terminal Iron(IV) Imides {[PhBP^t^Bu₂(pz‘)]Fe^IV⋮NAd}⁺

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Unprecedented Hybrid Scorpionate/Phosphine Ligand Able To Be Anchored to Carbosilane Dendrimers

Cited by 26 publications

References 22 publications

Coordination Features of a Hybrid Scorpionate/Phosphane Ligand Exemplified with Iridium

Coordination Features of a Hybrid Scorpionate/Phosphane Ligand Exemplified with Iridium

Rhodium and Iridium Complexes with a New Scorpionate Phosphane Ligand

Characterization of the Terminal Iron(IV) Imides {[PhBPtBu2(pz‘)]FeIV⋮NAd}+

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Characterization of the Terminal Iron(IV) Imides {[PhBP^t^Bu₂(pz‘)]Fe^IV⋮NAd}⁺