Iridium Chemistry of 1,6-Bis((<i>tert</i>-butylphosphino)methyl)-1,3,5-cycloheptatriene

Nemeh, S.; Flesher, Robert J.; Gierling, Karlheinz; Maichle‐Mößmer, Cäcilia; Mayer, Hermann A.; Kaska, William C.

doi:10.1021/om980045x

Cited by 49 publications

(33 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Of such Z 1 -bound cycloheptatrienyl complexes only three examples in transition metal chemistry and some more involving tin have been crystallographically characterised so far. [23][24][25][26][27][28][29][30] A Z 1 -cycloheptatrienyl complex has also been proposed as a short-lived intermediate in the reaction of CHT complexes with nucleophiles. 20 In agreement with previous reports, the seven-membered ring adopts a distinct boat-conformation as required by the tetrahedral environment of the alkyl-bound carbons C1 and C23, which feature bond lengths of Pd1-C1 = 2.023(7) Å, C1-C2 = 1.482(15) Å, C1-C7 = 1.496(12) Å, Pd2-C23 = 2.008(9) Å, C23-C24 = 1.500 (14) Å and C23-C29 = 1.489(12) Å.…”

mentioning

confidence: 99%

A hybrid carbocyclic/N-heterocyclic carbene ligand

Jandl

Pöthig

2017

Chem. Commun.

View full text Add to dashboard Cite

We report the synthesis and characterisation of the first complex bearing a bidentate carbocyclic/N-heterocyclic carbene ligand, which represents an unprecedented combination of these two carbene classes. Starting from an unsubstituted cycloheptatrienylidene-Pd complex, the ligand was built up in an on-site synthesis at the metal center. DFT calculations were employed to understand the crucial allyl-to-alkyl rearrangement of the carbocycle in this sequence and all its binding modes during the reaction cascade were crystallographically characterised.

show abstract

mentioning

confidence: 99%

A hybrid carbocyclic/N-heterocyclic carbene ligand

Jandl

Pöthig

2017

Chem. Commun.

View full text Add to dashboard Cite

show abstract

“…Synthesis and complexation chemistry of a higher homologue 2 based on cycloheptatriene has already been reported. 3 For these reasons we are interested in the synthesis of the ferrocene analogue 3, and report its successful completion together with some preliminary reactions that demonstrate the access to pincer-type ligation.General methods for the preparation of 1,3-disubstituted ferrocenes are severely lacking. 4 In order to synthesise a suitable precursor, we prepared compound 4 according to published procedures, involving the photochemical displacement of p-xylene from CpFe[p-xylene] + BF 4 2 in the presence of 3-methoxycarbonyl-6-dimethylaminofulvene.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Synthesis and reactivity of a ferrocene-derived PCP-pincer ligand

et al. 2002

View full text Add to dashboard Cite

The 1,3-bis(diphosphinomethyl)ferrocene 3 readily reacts with [(C 2 H 4 ) 2 RhCl] 2 to form an equilibrating pair of diastereomers 8a and 8b by C-H insertion into the ferrocene.Pincer-type ligands have played a significant role in homogeneous catalysis. 1 With the recent development of effective catalysts for dehydrogenation that involve Rh, or more especially Ir, complexes related to compound 1, interest in their application has been heightened. 2 Among the factors that contribute to their reactivity in the critical C-H activation step will be the chelate bite angle and the electronic character of both the s-and n-bonding entities. Synthesis and complexation chemistry of a higher homologue 2 based on cycloheptatriene has already been reported. 3 For these reasons we are interested in the synthesis of the ferrocene analogue 3, and report its successful completion together with some preliminary reactions that demonstrate the access to pincer-type ligation.General methods for the preparation of 1,3-disubstituted ferrocenes are severely lacking. 4 In order to synthesise a suitable precursor, we prepared compound 4 according to published procedures, involving the photochemical displacement of p-xylene from CpFe[p-xylene] + BF 4 2 in the presence of 3-methoxycarbonyl-6-dimethylaminofulvene. 5,6 This was cleanly reduced by LiAlH 4 in refluxing THF to the primary diol 5a in 89% yield. 7 Attempts to form the diacetate 5b by conventional means (Ac 2 O, py, DMAP) were unsuccessful, but it was demonstrated that direct S N 1 reaction in AcOH at 80 °C proceeded cleanly, according to precedent. 8 Rather than isolate the diacetate according to conventional phosphination procedures, 9 diol 5a was converted directly into the desired diphosphine 3 by heating with HPBu t 2 (2 equiv.) in AcOH (80°C , 1 h), isolating the product † in 62% yield by precipitation from MeOH.The new ligand was surveyed for its reactivity towards simple unsaturated metal complexes under mild conditions. A model reaction was first established, using ligand 1b. By NMR (C 6 D 6 , 65 °C, 30 min), displacement of the pincer diamine ligand 10 in 6 by the diphosphine was observed. The formation of complex 7 was inferred, ‡ although it was not isolated. Repeating this reaction with ligand 3 gave no evidence of complexation, however. Reaction of the ferrocene-derived ligand 3 with (PPh 3 ) 3 RuCl 2 or (MeCN) 2 PdCl 2 likewise failed to give characterisable products.When ligand 3 was reacted with [(C 2 H 4 ) 2 RhCl] 2 in CD 2 Cl 2 at ambient temperature a clean transformation occurred within minutes, the product being characterised by NMR and MS. † Initially, two sets of resonances were observed in the 1 H NMR spectrum, in particular two distinct Rh-H signals at ca. 227 ppm. Equilibration occurred over 4 h so that the lower field signal, initially the minor component, became strongly predominant. The equilibration could also be followed by 31 P NMR, it being observed that the signal at 87.5 ppm, decreases monotonically over 3 h as the signal at 93.5 ppm increases. ...

show abstract

“…Overall the chemical shifts of the novel BCHT PCP ligand 5 are very similar to the corresponding shifts of the CHT PCP ligand. 18 After treatment of the BCHT PCP ligand 5 with Ir(CO) 3 Cl in THF at slightly elevated temperatures a yellow to orange residue was isolated which gave three singlets in the 31 P{ 1 H} NMR spectrum. The resonances at δ P 61.5, 49.0 and 46.0 integrate to 1 : 15 : 3.…”

Section: Resultsmentioning

confidence: 99%

“…[18][19][20][21] This leads to an easy interconversion between several complexes of different ligand structure and/or metal oxidation states. Several unusual reactions have been reported e.g.…”

Section: Introductionmentioning

confidence: 99%

Benzo annulated cycloheptatriene PCP pincer iridium complexes

et al. 2014

Self Cite

View full text Add to dashboard Cite

The benzo annulated cycloheptatriene PCP pincer ligand was prepared in five steps. Treatment of with Ir(CO)3Cl gave the meridional cyclometalated chlorohydrido carbonyl iridium complexes which differ in their arrangement of the H, Cl, and CO ligands around iridium. Storing in THF led to isomerization processes. Hydrogen shifts from the sp(3)-CH carbon bound to iridium into the ligand backbone produced the three isomers . Reductive elimination of HCl from these complexes resulted in the square planar Ir(i) carbonyl complexes . Abstraction of the hydrogen from the sp(3)-CH-Ir fragment could be achieved either by treatment of with Ph3CBF4 or by the elimination of H2 which is initiated by CF3SO3H. The mass spectrometric characterisation of using fast atom bombardment reveals a complex fragmentation pattern. These different "fragment" ions were further investigated by electro-spray ionisation (tandem) mass spectrometry in high and low resolution. The identified compounds were attributed to structures by DFT calculations.

show abstract

Iridium Chemistry of 1,6-Bis((tert-butylphosphino)methyl)-1,3,5-cycloheptatriene

Cited by 49 publications

References 31 publications

A hybrid carbocyclic/N-heterocyclic carbene ligand

A hybrid carbocyclic/N-heterocyclic carbene ligand

Synthesis and reactivity of a ferrocene-derived PCP-pincer ligand

Benzo annulated cycloheptatriene PCP pincer iridium complexes

Contact Info

Product

Resources

About