A cumulene is a compound having three or more cumulative (consecutive) double bonds.[1] They are analogous to allenes, only having a more extensive chain. The simplest molecule in this class is butatriene (H2C=C=C=CH2), which is also called simply cumulene. Unlike most alkanes and alkenes, cumulenes tend to be rigid, comparable to polyynes. Cumulene carbenes H2Cn for n from 3 to 6 have been observed in interstellar molecular clouds[2][3] and in laboratory experiments[4] by using microwave and infrared spectroscopy. (The more stable cumulenes H2CnH2 are difficult to detect optically because they lack an electric dipole moment.) Cumulenes containing heteroatoms are called heterocumulenes;[5] an example is carbon suboxide.
The first reported synthesis of a butatriene is that of tetraphenylbutatriene in 1921.[6] The most common synthetic method for butatriene synthesis is based on reductive coupling of a geminaldihalovinylidene.[7] Tetraphenylbutatriene was reported synthesized in 1977 by homocoupling of 2,2-diphenyl-1,1,1-tribromoethane with elemental copper in dimethylformamide.[8]
Structureedit
Cis–trans isomerism of a triene vs axial chirality of an allene
The rigidity of cumulenes arises from the fact that the internal carbon atoms carry double bonds. Their sp hybridisation results in two π bonds, one to each neighbor, which are perpendicular to each other. This bonding reinforces a linear geometry of the carbon chain.
Cumulenes with non-equivalent substituents on each end exhibit isomerism. If the number of consecutive double bonds is odd, there is cis–trans isomerism as for alkenes. If the number of consecutive double bonds is even, there is axial chirality as for allenes.
Transition metal cumulenesedit
The first reported complex containing a vinylidene ligand was (Ph2C2Fe2(CO)8, derived from the reaction of diphenylketene and Fe(CO)5 Structurally, this molecule resembles Fe2(CO)9, wherein one μ-CO ligand is replaced by 1,1-diphenylvinylidene, Ph2C2. The first monometallic vinylidene complex was (C5H5)Mo(P(C6H5)3)(CO)2[C=C(CN)2]Cl.[9]
^Thaddeus, P.; Gottlieb, C.A.; Mollaaghababa, R.; Vrtilek, J.M. (1993). "Free carbenes in the interstellar gas". J. Chem. Soc., Faraday Trans. 89 (13): 2125. doi:10.1039/ft9938902125. ISSN 0956-5000.
^Cabezas, C.; Tercero, B.; Agúndez, M.; et al. (2021). "Cumulene carbenes in TMC-1: Astronomical discovery of I\-H2C5". Astronomy & Astrophysics. 650: L9. doi:10.1051/0004-6361/202141274. ISSN 0004-6361. PMC7611420.
^McCarthy, M. C.; Travers, M. J.; Kovács, A.; et al. (1997). "Detection and Characterization of the Cumulene Carbenes H2C5 and H2C6". Science. 275 (5299): 518–520. doi:10.1126/science.275.5299.518. ISSN 0036-8075.
^Brand, K. (17 September 1921). "Über Untersuchungen in der Tetraarylbutan-Reihe und über das 1.1 4.4-Tetraphenyl-butatrien. (4. Mitteilung über die Reduktion organischer Halogen-verbindungen.)". Berichte der Deutschen Chemischen Gesellschaft (A and B Series). 54 (8): 1987–2006. doi:10.1002/cber.19210540828.
^Leroyer, Léo; Maraval, Valérie; Chauvin, Remi (2012). "Synthesis of the Butatriene C4 Function: Methodology and Applications". Chemical Reviews. 112 (3): 1310–1343. doi:10.1021/cr200239h. ISSN 0009-2665. PMID 22040177.
^Kunieda, Takehisa; Takizawa, Takeo (1977). "Convenient preparation of tetraarylbutatrienes". Chemical & Pharmaceutical Bulletin. 25 (7): 1809–1810. doi:10.1248/cpb.25.1809.
^King, R. Bruce (August 2004). "The beginnings of terminal vinylidene metal complex chemistry through the dicyanomethylene/oxygen analogy: dicyanovinylidene transition metal complexes". Coordination Chemistry Reviews. 248 (15–16): 1533–1541. doi:10.1016/j.ccr.2004.05.003.
January 01, 1970
cumulene, confused, with, cumene, cumulene, compound, having, three, more, cumulative, consecutive, double, bonds, they, analogous, allenes, only, having, more, extensive, chain, simplest, molecule, this, class, butatriene, which, also, called, simply, cumulen. Not to be confused with cumene A cumulene is a compound having three or more cumulative consecutive double bonds 1 They are analogous to allenes only having a more extensive chain The simplest molecule in this class is butatriene H2C C C CH2 which is also called simply cumulene Unlike most alkanes and alkenes cumulenes tend to be rigid comparable to polyynes Cumulene carbenes H2Cn for n from 3 to 6 have been observed in interstellar molecular clouds 2 3 and in laboratory experiments 4 by using microwave and infrared spectroscopy The more stable cumulenes H2CnH2 are difficult to detect optically because they lack an electric dipole moment Cumulenes containing heteroatoms are called heterocumulenes 5 an example is carbon suboxide Butatriene the simplest cumulene Contents 1 Synthesis 2 Structure 3 Transition metal cumulenes 4 See also 5 ReferencesSynthesis editThe first reported synthesis of a butatriene is that of tetraphenylbutatriene in 1921 6 The most common synthetic method for butatriene synthesis is based on reductive coupling of a geminal dihalovinylidene 7 Tetraphenylbutatriene was reported synthesized in 1977 by homocoupling of 2 2 diphenyl 1 1 1 tribromoethane with elemental copper in dimethylformamide 8 Structure edit nbsp Cis trans isomerism of a triene vs axial chirality of an allene The rigidity of cumulenes arises from the fact that the internal carbon atoms carry double bonds Their sp hybridisation results in two p bonds one to each neighbor which are perpendicular to each other This bonding reinforces a linear geometry of the carbon chain Cumulenes with non equivalent substituents on each end exhibit isomerism If the number of consecutive double bonds is odd there is cis trans isomerism as for alkenes If the number of consecutive double bonds is even there is axial chirality as for allenes Transition metal cumulenes editThe first reported complex containing a vinylidene ligand was Ph2C2Fe2 CO 8 derived from the reaction of diphenylketene and Fe CO 5 Structurally this molecule resembles Fe2 CO 9 wherein one m CO ligand is replaced by 1 1 diphenylvinylidene Ph2C2 The first monometallic vinylidene complex was C5H5 Mo P C6H5 3 CO 2 C C CN 2 Cl 9 See also editCyclopropatriene and cyclohexahexaene cyclic cumulenesReferences edit IUPAC Compendium of Chemical Terminology 2nd ed the Gold Book 1997 Online corrected version 2006 cumulenes doi 10 1351 goldbook C01440 Thaddeus P Gottlieb C A Mollaaghababa R Vrtilek J M 1993 Free carbenes in the interstellar gas J Chem Soc Faraday Trans 89 13 2125 doi 10 1039 ft9938902125 ISSN 0956 5000 Cabezas C Tercero B Agundez M et al 2021 Cumulene carbenes in TMC 1 Astronomical discovery of I H2C5 Astronomy amp Astrophysics 650 L9 doi 10 1051 0004 6361 202141274 ISSN 0004 6361 PMC 7611420 McCarthy M C Travers M J Kovacs A et al 1997 Detection and Characterization of the Cumulene Carbenes H2C5 and H2C6 Science 275 5299 518 520 doi 10 1126 science 275 5299 518 ISSN 0036 8075 IUPAC Compendium of Chemical Terminology 2nd ed the Gold Book 1997 Online corrected version 2006 heterocumulenes doi 10 1351 goldbook H02797 Brand K 17 September 1921 Uber Untersuchungen in der Tetraarylbutan Reihe und uber das 1 1 4 4 Tetraphenyl butatrien 4 Mitteilung uber die Reduktion organischer Halogen verbindungen Berichte der Deutschen Chemischen Gesellschaft A and B Series 54 8 1987 2006 doi 10 1002 cber 19210540828 Leroyer Leo Maraval Valerie Chauvin Remi 2012 Synthesis of the Butatriene C4 Function Methodology and Applications Chemical Reviews 112 3 1310 1343 doi 10 1021 cr200239h ISSN 0009 2665 PMID 22040177 Kunieda Takehisa Takizawa Takeo 1977 Convenient preparation of tetraarylbutatrienes Chemical amp Pharmaceutical Bulletin 25 7 1809 1810 doi 10 1248 cpb 25 1809 King R Bruce August 2004 The beginnings of terminal vinylidene metal complex chemistry through the dicyanomethylene oxygen analogy dicyanovinylidene transition metal complexes Coordination Chemistry Reviews 248 15 16 1533 1541 doi 10 1016 j ccr 2004 05 003 Retrieved from https en wikipedia org w index php title Cumulene amp oldid 1170568639, wikipedia, wiki, book, books, library,
