The influence of substituents on the geometry of the cyclopropane ring. VII The molecular and crystal structures of bicyclopropylidene (C3H4C3H4) and (dicyclopropylmethylene)cyclopropane [(C3H5)2CC3H4]

Boer, J. S. A. M. de; Stam, C. H.

doi:10.1002/recl.19931121205

Cited by 9 publications

(7 citation statements)

References 9 publications

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“…X-ray quality crystals of 1a were grown by recrystallization from toluene, and an X-ray crystal structure was obtained (Figure ). The BCP CC bond length increased from 1.304(2) Å in the free alkene to 1.427(3) Å in 1a , an increase of 9.4% . This was greater than the 7.4% increase observed for [Co(BCP)(η 5 :η 1 [2-(di- tert -butylphosphanyl- P )ethyl]cyclopentadienyl)], which had a CC bond length of 1.401(5) Å .…”

Section: Resultsmentioning

confidence: 77%

Mono- and Diphosphine Platinum(0) Complexes of Methylenecyclopropane, Bicyclopropylidene, and Allylidenecyclopropane

Hoyte

Spencer

2011

Organometallics

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Bicyclopropylidene (BCP) and methylenecyclopropane (MCP) belong to a class of alkenes that contain cyclopropyl rings with exocyclic double bonds. These alkenes have a rich chemistry and are active toward transition metal catalysts, particularly those of the group 10 metals. 1À4 However, the isolation of transition metal complexes containing these alkenes in η 2 -coordination has not received as much focus as their reactivity. Only a handful of η 2 -MCP complexes have been reported to date, 5À8 while there have been just two of η 2 -BCP, both of first-row transition metals. 7,8 A better understanding of the coordination chemistry of these interesting alkenes could provide valuable insight into their reactivity patterns. Despite the lack of isolated complexes, MCP and BCP are expected to be good ligands toward transition metals, with their high-lying HOMOs capable of effectively donating electron density into empty metal orbitals, 2,7 while alleviation of strain in the highly strained cyclopropyl rings upon coordination is a strong driving force for the formation of stable complexes. As platinum(0) is a strong π-donor, capable of effective back-donation, it is ideal for making the first late transition metal complexes of BCP. The successful synthesis of the Pt(0) complex [Pt(MCP)(PPh 3 ) 2 ] is a strong indication of the viability of such complexes. 5

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Section: Resultsmentioning

confidence: 77%

Mono- and Diphosphine Platinum(0) Complexes of Methylenecyclopropane, Bicyclopropylidene, and Allylidenecyclopropane

Hoyte

Spencer

2011

Organometallics

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“…There are several recent studies of the effect of substituents on the geometry of cyclopropane [25], quantum mechanical analyses of bonding and strain in cyclopropanes [26][27][28], and empirical molecular mechanics [29], but none of these addresses specifically the aryl cyclopropane.…”

Section: Molecular Mechanicsmentioning

confidence: 99%

Crystal structures of phenyl-substituted cyclopropanes. IV. the crystal structure (at 21‡C and −100‡C) and the phenyl ring conformation in 4-cyclopropylacetanilide

et al. 1997

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The crystal structure of 4-cyclopropylacetanilide was investigated at room temperature (21 ~ and at -100~ in order to determine the orientation of the phenyl ring with respect to the cyclopropane moiety and the effect of this substituent on the stereochemistry of the three-membered ring. The compound was chosen because it is one of the few species containing a simple phenyl ring as the sole cyclopropane ring substituent and whose crystals are suitable for X-ray diffraction at room temperature. The substance crystallizes in space group P21/c at either temperature (no phase transitions) with cell constants: (at 21~ a = 9.725(2), b = 10.934(3), and c = 9.636(2) .A., ~ = 106.13(1)~ V = 984.21 ~3 and d(calc; z = 4) = 1.182 g cm -3. The relevant parameters for the -100*C structure are a = 9.557(4), b ---I0.980(2), and c = 9.641(2) ,~,/~ = 106.34(3)~ V = 970.76 ,~3 and d(calc; z = 4) = 1.199 gcm -3. Final values were R(F) = 0.042, Rw = 0.035, using unit weights, and its nonhydrogen atoms were used to phase the low-temperature data, whose final discrepancy indices were R(F) = 0.051, Rw = 0.061. The phenyl substituent is almost exactly in the bisecting conformation with respect to the C--C--C angle at the point of attachment to cyclopropane and conjugative effects are clearly evident in the lengths of the cyclopropane ring [1.494(3), 1.498(3), and 1.474(4) A, the later being the distal bond]. If one omits the terminal methylene fragments at C 10 and C 11, the atoms comprising the acetanilide fragment and the substituted carbon of the cyclopropane ring lie in a nearly perfect plane. Molecular mechanics as well as semiempirical (AM 1) calculations were carried out in order to determine the structure of the energy-minimized configurations in the two computational environments. The molecular conformations thus obtained are close to that experimentally observed from the X-ray diffraction experiment. In both theoretical models, the lowest energy conformation is that in which the plane of the phenyl ring bisects the cyclopropane C--C--C angle as was experimentally observed. Finally, the shape of the conformational barrier as a function of the orientation of the plane of the phenyl ring was computed, giving a maximum barrier to rotation of 2.2 kcal/mol. Similar calculations were carried out for two other aryl cyclopropanes, whose rings (naphthalene and anthracene) cannot adopt the bisecting position. Comparisons of experimental geometrical parameters as well as of the barriers to rotation are presented.

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“…The double-bond has increased s-character due to the presence of the c Pr rings and the carbon atoms are therefore close to sp-hybridised. 29,32,68 As a result of this, in the Xray crystal structure the length of the double-bond is 1.304 Å (Figure 1.5), 30 shorter than the double-bonds in ethene (1.330 Å) 30 and MCP (1.332 Å). 29 It is noteworthy that the presence of one terminal c Pr on a double-bond does not make much of a difference to the bond length, as in the case of MCP, while the presence of two significantly shortens the bond.…”

Section: Transition Metal Complexesmentioning

confidence: 89%

“…While a crystal structure of MCP has not been obtained, the structural properties have been calculated from the microwave spectrum. 29 The length of the double-bond (1.332 Å) is comparable to that of ethene (1.330 Å) 30 and 2-methylpropene (1.330 Å). 29 The proximal (C2-C3) bond lengths (1.457 Å) are shortened relative to the ideal cyclopropane bond lengths of 1.514 Å, 29 while the distal bond length (1.542 Å) is lengthened.…”

Section: Synthesis and Propertiesmentioning

confidence: 97%

“…63 The length of the bonds in the c Pr rings, 1.472 and 1.549 Å for proximal (C1-C2, C1-C3) and distal (C2-C3) respectively, are comparative to the equivalent bonds in MCP, 1.457 and 1.542 Å, although the BCP proximal bond is somewhat longer. 30 As with MCP, the shortening of the proximal bonds relative to the bonds in cyclopropane (1.541 Å) 29 has been attributed to the fact that these bonds are nominally sp 2 -sp 3 , which tend to be shorter than sp 3 -sp 3 bonds. 29 The C2-C1-C3 angle is 63.1 • , 30 approximately the same as that in MCP (63.9 • ) 29 and larger than that in cyclopropane (60 • ).…”

Section: Transition Metal Complexesmentioning

confidence: 99%

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Platinum Complexes of Bicyclopropylidene and Related Ligands

Hoyte¹

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The coordination chemistry of the cyclopropyl-substituted alkenes, bicyclopropylidene (BCP) and methylenecyclopropane (MCP), with platinum was explored. A range of complexes with ŋ²-alkene ligands were synthesised by the displacement of a ligand, typically ethene, from a precursor complex. These complexes are [Pt(L)(P—P)] (L = BCP, MCP; P—P = Ph₂P(CH₂)₃PPh₂, Cy₂P(CH₂)₂PCy₂, ᵗBu₂P(CH₂)₂PᵗBu₂, ᵗBu₂PCH₂(o-C₆H₄)₂PᵗBu₂), [Pt(L)(P—S)] (L = BCP, MCP; P—S = ᵗBu₂PCH₂(o-₆H4)CH₂SᵗBu), [Pt(C₂H4)(L)(PR₃)] (L = BCP, MCP; PR₃ = PPh₃, PCy₃), [Pt(MCP)₂(PR₃)] (PR₃ = PPh₃, PCy₃) and [PtCl₂(L)(L′)] (L = BCP, MCP; L′ = Py, DMSO). These were the first examples of platinum complexes with ŋ²-BCP ligands, and the first bis-MCP Pt complexes. BCP underwent ring-opening reactions with both Pt(0) and Pt(II) complexes to form the 1,3-diene allylidenecyclopropane (ACP). The first transition metal complexes of ACP [Pt(ACP)(P—P)] (P—P = Ph₂P(CH₂)₃PPh₂, Cy₂P(CH₂)₂PCy₂, ᵗBu₂P(CH₂)₂PᵗBu₂) were synthesised. Some of these complexes rearranged to form ŋ²:σ²-metallacyclopentene complexes, the first instances of the formation of ŋ²:σ²-metallacyclopentene complexes from ŋ²:π-diene complexes. With MCP, the ring-opening reaction only occurred with [₂(COD)], as a result of the anti-Markovnikov addition of Pt–H, generated by the β-hydride elimination of an Et group, across the double-bond. The major products of this reaction were the 1-methylcyclopropyl complexes [Pt(C(CH₂)₂CH₃)Et(COD)] and [Pt(C(CH₂)₂CH₃)₂(COD)], the first examples of such complexes. Protonation of [Pt(L)(P—P)] resulted in a ring-opening reaction to form both the 2-substituted and 1-methyl allyl complexes, [Pt(ŋ³-CH₂CRCH₂)(P—P)]⁺ (R = ᶜPr, Me; P—P = Ph₂P(CH₂)₃PPh₂, ᵗBu₂PCH₂(o-C₆H₄)CH₂PᵗBu₂) and [Pt(ŋ³-CR₂CHCHMe)(P—P)]⁺ (R = cPr, Me; P—P = Ph₂P(CH₂)₃PPh₂, ᵗBuPCH₂(o-C₆H₄)CH₂PᵗBu₂). The analogous 1-methyl complexes were also formed from [Pt(L)(P—S)], wherein the alkene reacted with a hydride formed by the ortho-metallation of the P—S ligand. Computational models were used to investigate the formation of the allyl structures and it was found that the activation energy had a more significant effect than complex stability on product distributions. Complexes with β-chloroalkyl ligands [Pt(C(CH₂)₂CR₂Cl)Cl(L)₂] (R = CH₂, H, L = SEt₂, NCᵗBu, Py) were formed by the addition of Pt–Cl across the alkene double bond. Phosphine complexes were formed by the displacement of a ligand from cis–[Pt(C(CH₂)₂CR₂Cl)Cl(Py)₂] (R = CH₂, H). These are the first examples of stable Pt(II) β-haloalkyl complexes. It was found using computational models that the presence of cyclopropyl rings had a stabilising effect on these complexes.

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The influence of substituents on the geometry of the cyclopropane ring. VII The molecular and crystal structures of bicyclopropylidene (C₃H₄C₃H₄) and (dicyclopropylmethylene)cyclopropane [(C₃H₅)₂CC₃H₄]

Cited by 9 publications

References 9 publications

Mono- and Diphosphine Platinum(0) Complexes of Methylenecyclopropane, Bicyclopropylidene, and Allylidenecyclopropane

Mono- and Diphosphine Platinum(0) Complexes of Methylenecyclopropane, Bicyclopropylidene, and Allylidenecyclopropane

Crystal structures of phenyl-substituted cyclopropanes. IV. the crystal structure (at 21‡C and −100‡C) and the phenyl ring conformation in 4-cyclopropylacetanilide

Platinum Complexes of Bicyclopropylidene and Related Ligands

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