ChemInform Abstract: The Formation of Ureas from Cyanamides: Scientific and Technical Remarcable Reactions and Their Practicable Signification

Michaud, Horst; Goll, W.; Hammer, Benedikt; Seyerl, J. Von; Sturm, Werner; Weiß, Stefan; Youngman, Richard J.

doi:10.1002/chin.198913356

Cited by 5 publications

(7 citation statements)

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“…Cyanamide and carbodiimide have been extensively studied in the past, both theoretically and experimentally, as for their equilibrium structures, − torsional-rotational dynamics, and IR frequencies . On the contrary, to our knowledge, tautomerization and hydrolysis of a have never been studied theoretically.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of Hydration of Cyanamide and Carbodiimide

et al. 2003

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The isomerization reaction cyanamide f carbodiimide in vacuo and in the presence of up to six water molecules has been investigated by means of DFT and MP2 calculations, using a flexible basis set. The reliability of such methods has been checked against results of coupled cluster calculations on isolated molecules. The effect of water molecules has also been investigated in the case of the hydrolysis reaction of cyanamide and carbodiimide, leading to isourea. The number of water molecules considered is large enough to give results converged in activation and hydration energies. In addition to the water molecules explicitly described, the effect of water bulk solvent is taken into account according to the polarizable continuum model. The results show that the direct hydrolysis of H 2 NCN is hindered by an activation energy much higher than that for HNCNH, which in turn can be obtained from cyanamide with a relatively easy process.

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Section: Introductionmentioning

confidence: 99%

Theoretical Study of Hydration of Cyanamide and Carbodiimide

et al. 2003

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“…Cyanamides, N⋮CNR 2 (R = H, alkyl or aryl), can be regarded as amino-functionalized nitriles, but despite the well developed coordination chemistry of organonitriles , and of the biological and synthetic interest of such species [in particular cyanamide itself, N⋮CNH 2 , and its dimeric form, cyanoguanidine, NCNC(NH 2 ) 2 ], − only scarce examples of reactions of cyanamide ligands have been reported, and the study of their activation by coordination to a transition metal center still remains virtually unexplored, as well as the effect of the amino moiety on the reactivity of the cyano group. Insertion into a metal−carbon multiple bond, − metathesis with a metal−metal triple bond, nucleophilic addition of an oxime or of an alcohol (in this case to cyanoguanidine) to form a five- or six-membered azametallacycle, respectively, and dehydrogenation of NCNH 2 followed by electrophilic addition , or deprotonation or deamination (of cyanoguanidine) are the most significant reactions reported so far.…”

Section: Introductionmentioning

confidence: 99%

Mixed Dinitrogen−Organocyanamide Complexes of Molybdenum(0) and Their Protic Conversion into Hydrazide and Amidoazavinylidene Derivatives

Cunha¹,

Silva²,

Pombeiro³

2003

Inorg. Chem.

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Organocyanamides, Ntbd1;CNR(2) (R = Me or Et), react with trans-[Mo(N(2))(2)(dppe)(2)] (1, dppe = Ph(2)PCH(2)CH(2)PPh(2)), in THF, to give the first mixed molybdenum dinitrogen-cyanamide complexes trans-[Mo(N(2))(NCNR(2))(dppe)(2)] (R = Me 2a or Et 2b) which are selectively protonated at N(2) by HBF(4) to yield the hydrazide(2-) complexes trans-[Mo(NNH(2))(NCNR(2))(dppe)(2)][BF(4)](2) (R = Me, 3a, or Et, 3b). On treatment with Ag[BF(4)], oxidation and metal fluorination occur, and the ligating cyanamide undergoes an unprecedented beta-protonation at the unsaturated C atom to form trans-[MoF(NCHNR(2))(dppe)(2)][BF(4)](2) (R = Me, 4a, or Et, 4b) compounds which present the novel amidoazavinylidene (or amidomethyleneamide) ligands. Complexes 4 are also formed from the corresponding compounds 3, with liberation of ammonia and hydrazine. The crystal structure of 2b was determined by single-crystal X-ray diffraction analysis which indicates that the N atom of the amide group has a trigonal planar geometry.

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“…In contrast with the rich coordination chemistry exhibited by the NCR (R ) alkyl or aryl) nitriles, 5 that of cyanamides, NtCNR 2 (R ) H or alkyl) is still a field that remains to be explored, despite the biological and synthetic significance of such a type of compounds, in particular cyanamide itself (NtCNH 2 ) [6][7][8] and its dimeric form, cyanoguanidine, NtC-NdC(NH 2 ) 2 . [9][10][11][12] We have previously observed that cyanamide is dehydrogenated by an electron-rich Mo(0) or W(0) center, {M(dppe) 2 } (M ) Mo or W, dppe ) Ph 2 PCH 2 CH 2 PPh 2 ) to form a cyanoimide complex, trans-[M(NCN) 2 (dppe) 2 ], 13 whereas cyanoguanidine at {ReCl(dppe) 2 } can undergo deprotonation or deamination to give the ligating NCNC(NH)NH 2or NCNCN -(dicyanamide) derivatives, respectively. 14 Moreover, at a dicationic Pt(II) center, {Pt(PPh 3 ) 2 } 2+ , cyanoguanidine is activated toward nucleophilic addition which, combined with deprotonation of the guanidine unit and its chelation, forms a sixmembered azametallacycle, i.e., cis-[(PPh 3 ) 2 Pt{NHC(OMe)d NC(NH 2 )dNH}][BPh 4 ] derived from the reaction of cis-[Pt{NCNC(NH 2 ) 2 } 2 (PPh 3 ) 2 ][BPh 4 ] 2 with MeOH.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast with the rich coordination chemistry exhibited by the NCR (R = alkyl or aryl) nitriles, that of cyanamides, N⋮CNR 2 (R = H or alkyl) is still a field that remains to be explored, despite the biological and synthetic significance of such a type of compounds, in particular cyanamide itself (N⋮CNH 2 ) − and its dimeric form, cyanoguanidine, N⋮C−NC(NH 2 ) 2 . − …”

Section: Introductionmentioning

confidence: 99%

Azametallacycles from Ag(I)- or Cu(II)-Promoted Coupling Reactions of Dialkylcyanamides with Oximes at Pt(II)

Ferreira

Silva

et al. 2001

Inorg. Chem.

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The dialkylcyanamide complexes cis-[PtCl(NCNR(2))(PPh(3))(2)][BF(4)] 1 and cis-[Pt(NCNR(2))(2)(PPh(3))(2)][BF(4)](2) 2 (R = Me or Et) have been prepared by treatment of a CH(2)Cl(2) solution of cis-[PtCl(2)(PPh(3))(2)] with the appropriate dialkylcyanamide and one or two equivalents of Ag[BF(4)], respectively. Compounds 2 can also be obtained from 1 by a similar procedure. Their reaction with oximes, HON=CR'R' ' (R'R' ' = Me(2) or C(4)H(8)), in CH(2)Cl(2) and in the presence of Ag[BF(4)] or Cu(CH(3)COO)(2), leads to the novel type of azametallacycles cis-[Pt(NH=C(ON=CR'R")-NR2)(PPh3)2][BF4]2 4 upon an unprecedented coupling of the organocyanamides with oximes, in a process that proceeds via the mixed oxime-organocyanamide species cis-[Pt(NCNR(2))(HON=CR'R' ')(PPh(3))(2)][BF(4)](2) 3, and is catalyzed by either Ag(+) or Cu(2+) which activate the ligating organocyanamide by Lewis acid addition to the amide group. In contrast, in the organonitrile complexes cis-[Pt(NCR)(2)(PPh(3))(2)][BF(4)](2) 5 (R = C(6)H(4)OMe-4 or Et), obtained in a similar way as 2 (but by using NCR instead of the cyanamide), the ligating NCR is not activated by the Lewis acid and does not couple with the oximes. The spectroscopic properties of those complexes are reported along with the molecular structures of 2b (R = Et), 4a1 (R = Me, R'R' ' = Me(2)), and 4b1 (R = Et, R'R' ' = Me(2)), as established by X-ray crystallography which indicates that in the former complex the amide-N-atoms are trigonal planar, whereas in the latter (4a1 and 4b1) the five-membered rings are planar with a localized N=C double bond (imine group derived from the cyanamide) and the exocyclic amide and alkylidene groups (in 4b1) are involved in two intramolecular H-bonds to the oxygen atom of the ring.

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ChemInform Abstract: The Formation of Ureas from Cyanamides: Scientific and Technical Remarcable Reactions and Their Practicable Signification

Cited by 5 publications

References 0 publications

Theoretical Study of Hydration of Cyanamide and Carbodiimide

Theoretical Study of Hydration of Cyanamide and Carbodiimide

Mixed Dinitrogen−Organocyanamide Complexes of Molybdenum(0) and Their Protic Conversion into Hydrazide and Amidoazavinylidene Derivatives

Azametallacycles from Ag(I)- or Cu(II)-Promoted Coupling Reactions of Dialkylcyanamides with Oximes at Pt(II)

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