Nucleophilic additions to pseudohalides in the coordination sphere of transition metal ions and coligand isomerism

Hvastijová, Mária; Kohout, Jiřı́; Buchler, Johann W.; Boča, Roman; Kožı́šek, Jozef; Jäger, Lothar

doi:10.1016/s0010-8545(98)00208-2

Cited by 57 publications

(12 citation statements)

References 51 publications

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“…The dcnm anion has previously been reported to react with water and methanol to yield the anionic species ccnm and cmnm, respectively (Scheme 2a). 10,31 These reactions take place rapidly at room temperature in the presence of a transition metal. For instance, the reaction of Cu(ClO 4 ) 2 with Na(dcnm) in methanol yields the mononuclear complex [Cu(cmnm) 2 (MeOH) 2 ], cmnm = cyano[imino(methoxy)methyl]nitrosomethanide, as a crystalline product within an hour.…”

Section: Reactivity and Derivatised Anions Reactions Of Nitrile Group...mentioning

confidence: 99%

The chemistry and complexes of small cyano anions

et al. 2011

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The chemistry of the anions dicyanamide and tricyanomethanide (dca and tcm, respectively) has produced a plethora of discoveries over the past few decades, particularly in relation to transition-metal coordination polymers with magnetic coupling. Over recent years there have been an increasing number of reports of heterofunctionalised cyano-containing anions, typically derivatives of dicyanomethanide. Our own group has been particularly concerned with the amide- and nitroso-functionalised anions carbamoyldicyanomethanide (cdm) and dicyanonitrosomethanide (dcnm), respectively. This feature article examines the fascinating diversity of materials and complexes that can be obtained using small cyano anions, ranging from coordination polymers to heterometallic clusters and hydrogen bonding networks. In particular, we focus on results from our own laboratories in the past few years. The magnetic properties of these materials are briefly discussed.

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Section: Reactivity and Derivatised Anions Reactions Of Nitrile Group...mentioning

confidence: 99%

The chemistry and complexes of small cyano anions

et al. 2011

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“…This experimental evidence supports the reports in the literature that the addition of alcohols to the dcnm anion only proceeds in the presence of a transition metal cation. 31,[33][34][35][36][37][38][39] Optimized geometries of the methanol addition products are shown in Figure 9, and the reaction enthalpies for both steps of methanol addition are presented in Table 4. In the case of the first methanol addition the reaction enthalpies are less exothermic by about 30 kJ mol -1 compared to those of water.…”

Section: Table 2: Reaction Enthalpies (In Kj Mol -1 ) Of Water Additimentioning

confidence: 99%

“…[20][21][22][23][24][25][26] The dicyanonitrosomethanide anion (dcnm, [C(CN) 2 (NO)] -) [27][28][29] has been demonstrated to have an even greater propensity to undergo this reaction. For the dcnm anion, the reaction has been shown to occur under three distinct sets of conditions: (1) in the presence of a transition metal, which may promote the addition of water, an alcohol or an amine, [30][31][32][33][34][35][36][37][38][39][40] (2) in the presence of an acid, which may promote the addition of an amine, [41][42][43] or (3) by heating an aqueous reaction solution containing the dcnm anion with a nonmetallic countercation to reflux, which has been shown to result in the addition of water, giving the carbamoylcyanonitrosomethanide anion (ccnm, [C(CN)(CONH 2 )(NO)] -), as shown in Figure 1. 44 Despite numerous literature reports, certain aspects of this reaction are yet to be adequately understood, namely why the addition of an amine may occur to both of the nitrile groups of the dcnm anion while water or alcohols have been observed to react only with one nitrile group.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and Experimental Insights into the Mechanism of the Nucleophilic Addition of Water and Methanol to Dicyanonitrosomethanide

et al. 2010

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In this work the nucleophilic addition of water and methanol to the dicyanonitrosomethanide anion (dcnm, [C(CN)(2)(NO)](-)) in the absence of the usual transition metal promoters was investigated. Experimentally it was shown that a quantitative conversion of the dcnm anion to carbamoylcyanonitrosomethanide (ccnm, [C(CN)(CONH(2))(NO)](-)) by the addition of 1 equiv of water to a nitrile group is complete in 48 h at 100 °C, or in 1.5 h at 150 °C when the reaction is conducted in a microwave reactor. Attempts to add a second equivalent of water to the anion failed with thermal degradation of the anion occurring at 200 °C. Ab initio calculations show that the reaction proceeds via three distinct transition states: (1) the transfer of a proton from a water molecule to the nitrile group, (2) the subsequent attack of the generated hydroxide anion on the carbon atom of the nitrile group, and (3) a rapid proton transfer to form a carbamoyl group. The attacking water molecule is shown to be a stronger proton donor when modeled as part of a hydrogen-bonded three water molecule chain, leading to a significant reduction in the reaction barrier. Only the anti-ccnm anion is formed in the reaction. There is a high-energy barrier to the formation of the syn isomer by the rotation of the nitroso group. While the syn isomer of ccnm is shown to be the more thermodynamically stable conformation, examination of the HOMO-1 molecular orbital that arises during the second transition state of the reaction indicates the addition of the hydroxide anion to the carbon atom is forbidden due to orbital symmetry, with a similar effect responsible for the failure of a second equivalent of water to add to the ccnm anion. Under analogous reaction conditions the addition of 1 equiv of methanol to dcnm to form cyano(imino(methoxy)methyl)nitrosomethanide (cmnm, [C(CN)(C(OMe)NH)(NO)](-)) failed, although ab initio calculations initially indicated the reaction should proceed more readily than the addition of water. When the energy required to break the hydrogen-bonded cyclic hexamers in methanol is taken into consideration, the energy barrier to the first transition step is greatly increased. The addition of a second equivalent of methanol to cmnm is unlikely to occur even in the presence of a transition metal as the resultant anion would be marginally thermodynamically unstable.

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“…[13] Subsequent carbonylation furnished oxamidide ([N 2 C 2 O 2 ] 4À ) ligands [16] while treatment with cyclooctyne at ambient temperature resulted in NÀC bond formation by cycloaddition. These results suggested that terminal isocyanates, which are often viewed as pseudohalides and typically inert in transition-metal compounds, [17][18][19] are potential platforms for additional N À C bond forming chemistry. Likewise, organic nitriles underwent insertion into the bridging hafnium nitride, and the resulting carbodiimide ligand engaged in additional NÀC bond formation with the terminal isocyanate ligand.…”

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confidence: 98%