M4X4 Structures in Transition Metal Chemistry:  Cubane-like or Planar? A DFT Study of Some Clusters Containing the M4X4 Core (M = Ti, V, Mo; X = N, P, As)

Sarasa, Jose-Pedro; Poblet, Josep M.; Bénard, Marc

doi:10.1021/om990986p

“…The computed geometry for complex 6 is in good agreement with the crystallographic data (see the http://www.wiley-vch.de/contents/jc_2002/2007/z604677_s.pdf) and its formation from the monoalkynyl derivative 3 is calculated to be exothermic by 75 kJ mol −1 . Analysis of the frontier orbitals of 3 and 6 reveals that the titanium centers in 3 remain totally oxidized, as in previously studied hetero‐9 and homotitanocubanes,5, 21 but the formation of 6 is accompanied by a two‐electron reduction of the Ti 3 core. The highest occupied molecular orbital (HOMO) in 6 may be described as a bonding combination of titanium d orbitals (86 %) with other smaller contributions (see the http://www.wiley-vch.de/contents/jc_2002/2007/z604677_s.pdf for details).…”

Section: Methodssupporting

confidence: 69%

Addition of Terminal Alkynes to a Molecular Titanium–Zinc Nitride

Carbó

¹

,

Martı́n

²

,

Mena

³

et al. 2007

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Dedicated to Professor Gerhard Erker on the occasion of his 60th birthdayTransition-metal nitrido complexes have been studied extensively in the past few decades. [1, 2] While nitrido complexes of Group 6-8 metals usually bear the nitrido ligands as a terminal functionality, M N, [3] the analogous derivatives of early transition metals exhibit polynuclear structures, with m nnitrido ligands bridging two or more metal centers. [2,4,5] The reactivity of terminal nitrido ligands has received increasing attention because of their potential to show either nucleophilic or electrophilic character. [1,3,6] The net result of the latter is usually a two-electron reduction of the metal center and a reduced bond order between the metal and the nitrogen atom [Eq. (1)]. Recently a similar behavior has been pro-posed for the nucleophilic attack of a phosphine to a bridging dinitride species; in that case the reduction leads to a complex with a metal-metal bond.[7]Over the last few years we have been studying the reactivity of the trinuclear imido-nitrido titanium derivative [{Ti(h 5 -C 5 Me 5 )(m-NH)} 3 (m 3 -N)] [8] (1) towards metal complexes and have reported the coordination of 1 to these metals through the imido groups to give the cube-type adducts [1·ML n ].[9] The elimination of organic molecules and the formation of nitrido groups that bridge the metal centers occur if the NÀH bonds of the organometallic ligand 1 are activated by metal-imido, metal-amido, or metal-alkyl linkages.[10] However, none of those processes involves the triply bridging apical nitrido ligand of 1. Herein we present the first example of a reaction at this nitrido ligand, which leads to an alkynylimido ligand by C À N bond formation. We have studied this "apparent" nucleophilic attack of an acetylide at the apical nitrido ligand by density functional calculations and propose a plausible reaction mechanism.Our synthetic route is outlined in Scheme 1. Treatment of the amido zinc derivative 2 [11] with one equivalent of terminal alkyne RCCH in toluene gives the expected zinc acetylides [{(RCC)Zn}(m 3 -N)(m 3 -NH) 2 {Ti(h 5 -C 5 Me 5 )} 3 (m 3 -N)], with R = SiMe 3 (3), CMe 3 (4), or Ph (5), as brown or red solids in good yields (71-87 %). Because of the light sensitivity of 2 in solution, the reactions were performed in amber-stained glassware. Complexes 3 and 4 were obtained at room temperature, while 5 had to be prepared at 90 8C to obtain a pure sample. Reaction of 2 with two equivalents of Me 3 SiCCH led to a complex which was shown by X-ray diffraction to be the zinc acetylide [{(RCC)Zn}(m 3 -NH) 3 {Ti-(h 5 -C 5 Me 5 )} 3 (m 3 -NCCR)], with R = SiMe 3 (6). The analogous reaction with PhCCH gave the complex with R = Ph (7). Both 6 and 7 were obtained as black solids in good yields (81 and 91 %, respectively). In contrast, the reaction of 2 with more than two equivalents of tert-butylacetylene at a variety of temperatures only produced a mixture of 4 and the unreacted alkyne. [D 6 ]Benzene solutions of 6 are stable at different temperatures, wh...

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“…The computed geometry for complex 6 is in good agreement with the crystallographic data (see the http://www.wiley-vch.de/contents/jc_2001/2007/z604677_s.pdf) and its formation from the monoalkynyl derivative 3 is calculated to be exothermic by 75 kJ mol −1 . Analysis of the frontier orbitals of 3 and 6 reveals that the titanium centers in 3 remain totally oxidized, as in previously studied hetero‐9 and homotitanocubanes,5, 21 but the formation of 6 is accompanied by a two‐electron reduction of the Ti 3 core. The highest occupied molecular orbital (HOMO) in 6 may be described as a bonding combination of titanium d orbitals (86 %) with other smaller contributions (see the http://www.wiley-vch.de/contents/jc_2001/2007/z604677_s.pdf for details).…”

Section: Methodssupporting

confidence: 69%

Addition of Terminal Alkynes to a Molecular Titanium–Zinc Nitride

Carbó

¹

,

Martı́n

²

,

Mena

³

et al. 2007

Angewandte Chemie

5

0

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Dedicated to Professor Gerhard Erker on the occasion of his 60th birthdayTransition-metal nitrido complexes have been studied extensively in the past few decades. [1, 2] While nitrido complexes of Group 6-8 metals usually bear the nitrido ligands as a terminal functionality, M N, [3] the analogous derivatives of early transition metals exhibit polynuclear structures, with m nnitrido ligands bridging two or more metal centers. [2,4,5] The reactivity of terminal nitrido ligands has received increasing attention because of their potential to show either nucleophilic or electrophilic character. [1,3,6] The net result of the latter is usually a two-electron reduction of the metal center and a reduced bond order between the metal and the nitrogen atom [Eq. (1)]. Recently a similar behavior has been pro-posed for the nucleophilic attack of a phosphine to a bridging dinitride species; in that case the reduction leads to a complex with a metal-metal bond.[7]Over the last few years we have been studying the reactivity of the trinuclear imido-nitrido titanium derivative [{Ti(h 5 -C 5 Me 5 )(m-NH)} 3 (m 3 -N)] [8] (1) towards metal complexes and have reported the coordination of 1 to these metals through the imido groups to give the cube-type adducts [1·ML n ].[9] The elimination of organic molecules and the formation of nitrido groups that bridge the metal centers occur if the NÀH bonds of the organometallic ligand 1 are activated by metal-imido, metal-amido, or metal-alkyl linkages.[10] However, none of those processes involves the triply bridging apical nitrido ligand of 1. Herein we present the first example of a reaction at this nitrido ligand, which leads to an alkynylimido ligand by C À N bond formation. We have studied this "apparent" nucleophilic attack of an acetylide at the apical nitrido ligand by density functional calculations and propose a plausible reaction mechanism.Our synthetic route is outlined in Scheme 1. Treatment of the amido zinc derivative 2 [11] with one equivalent of terminal alkyne RCCH in toluene gives the expected zinc acetylides [{(RCC)Zn}(m 3 -N)(m 3 -NH) 2 {Ti(h 5 -C 5 Me 5 )} 3 (m 3 -N)], with R = SiMe 3 (3), CMe 3 (4), or Ph (5), as brown or red solids in good yields (71-87 %). Because of the light sensitivity of 2 in solution, the reactions were performed in amber-stained glassware. Complexes 3 and 4 were obtained at room temperature, while 5 had to be prepared at 90 8C to obtain a pure sample. Reaction of 2 with two equivalents of Me 3 SiCCH led to a complex which was shown by X-ray diffraction to be the zinc acetylide [{(RCC)Zn}(m 3 -NH) 3 {Ti-(h 5 -C 5 Me 5 )} 3 (m 3 -NCCR)], with R = SiMe 3 (6). The analogous reaction with PhCCH gave the complex with R = Ph (7). Both 6 and 7 were obtained as black solids in good yields (81 and 91 %, respectively). In contrast, the reaction of 2 with more than two equivalents of tert-butylacetylene at a variety of temperatures only produced a mixture of 4 and the unreacted alkyne. [D 6 ]Benzene solutions of 6 are stable at different temperatures, wh...

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“…This interesting observation lies in line with this one, pointed out by Sarasa et al for M 4 X 4 structures in transition metal chemistry (M = Ti, V; X = N, P, As). [15] The Bi-µ 1 -Fe bonds in 2a are slightly more elongate with regard to the Bi-µ 3 -Fe bonds and consequently weaker. The bonding to four µ 1 -Fe(CO) 4 4 groups are involved in 2c-2e bonding to threevalent Bi atoms, here.…”

Section: Synthesismentioning

confidence: 96%

Cubane‐Like Bismuth‐Iron Cluster: Synthesis, X‐ray Crystal Structure and Theoretical Characterization of the [Bi₄Fe₈(CO)₂₈]^4– Anion

Monakhov

¹

,

Zessin

²

,

Linti

³

2010

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The reaction of cyclo‐Bi4[Si(SiMe3)3]4 (1) with Na2[Fe(CO)4] in the presence of nBu4NCl leads to the formation of the cage compound [nBu4N]4[Bi4Fe8(CO)28] (2). According to X‐ray single‐crystal structure analysis, the faces of the tetrahedral Bi4 core are capped by Fe(CO)3 moieties in a μ3 fashion to give a cubanoid Bi4Fe4 framework. The four Fe(CO)4 fragments are μ1‐coordinated to bismuth, each. With 12 skeletal electron pairs the [Bi4Fe8(CO)28]4– anion (2a) is a Bi4Fe4 cubane. The negative charge is localized within cluster 2a according to the NBO analysis of its derivatives. The strength of metal–ligand interactions Bi–μ3‐Fe(CO)3 is responsible for the size of the cluster's cubic core. NICS computations at the cage centers of considered molecules show that 2a has paratropic character, whereas removal of four μ1‐Fe(CO)4 fragments from latter causes spherical aromaticity of the modified clusters [Bi4Fe4(CO)12]4– (2aa) and [Bi4Fe4(CO)12]2+ (2ab), mediated by a Bi4 cluster π orbital.

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M₄X₄ Structures in Transition Metal Chemistry: Cubane-like or Planar? A DFT Study of Some Clusters Containing the M₄X₄ Core (M = Ti, V, Mo; X = N, P, As)

Cited by 20 publications

References 53 publications

Addition of Terminal Alkynes to a Molecular Titanium–Zinc Nitride

Addition of Terminal Alkynes to a Molecular Titanium–Zinc Nitride

Addition of Terminal Alkynes to a Molecular Titanium–Zinc Nitride

Cubane‐Like Bismuth‐Iron Cluster: Synthesis, X‐ray Crystal Structure and Theoretical Characterization of the [Bi₄Fe₈(CO)₂₈]^4– Anion

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M4X4 Structures in Transition Metal Chemistry: Cubane-like or Planar? A DFT Study of Some Clusters Containing the M4X4 Core (M = Ti, V, Mo; X = N, P, As)

Cited by 20 publications

References 53 publications

Addition of Terminal Alkynes to a Molecular Titanium–Zinc Nitride

Addition of Terminal Alkynes to a Molecular Titanium–Zinc Nitride

Addition of Terminal Alkynes to a Molecular Titanium–Zinc Nitride

Cubane‐Like Bismuth‐Iron Cluster: Synthesis, X‐ray Crystal Structure and Theoretical Characterization of the [Bi4Fe8(CO)28]4– Anion

Contact Info

Product

Resources

About

M₄X₄ Structures in Transition Metal Chemistry: Cubane-like or Planar? A DFT Study of Some Clusters Containing the M₄X₄ Core (M = Ti, V, Mo; X = N, P, As)

Cubane‐Like Bismuth‐Iron Cluster: Synthesis, X‐ray Crystal Structure and Theoretical Characterization of the [Bi₄Fe₈(CO)₂₈]^4– Anion