Abstract:The amphiphilic rhenium carbene complex Cp(CO)2-Re=CDCHzCH2CMe3 undergoes stereospecific addition of HCl to produce a single diastereomer of cis-Cp(C0)zClReCHDCHz-CHzCMe3,I but the absolute stereochemistry of the process could not be determined in part because rotation about the Re=C bond is expected to be fast.2 In the course of synthesizing a rotationally restricted rhenium carbene complex having a twocarbon link between the cyclopentadienyl ligand and the carbene carbon atom, we discovered an equilibrium be… Show more
“…The 13 C resonances of the acyl carbonyl carbon atoms were detected at 276.1 and 278.9 ppm for PPN- 2a and PPN- 2b , respectively. Similar results for the 13 C resonance of the acyl carbon were reported recently by Casey and co-workers for Li + [(η 5 -C 5 H 5 )(CO) 2 Re(CO)(η 5 -C 5 H 4 )Re(CO) 3 ] - and Li + [(CO) 2 Re(CO)CH 2 CH 2 (η 5 -C 5 H 4 )] - . , Recrystallization of PPN- 2b from pure dichloromethane afforded yellow-orange monoclinic crystals suitable for X-ray diffraction analysis (Figure ). 1 ORTEP drawing and atom-numbering scheme of the molecular structure of 2b .…”
Addition of phenyllithium and methyllithium to tetracarbonyl[2-(phenyl-κC
2‘),pyridine-κN]rhenium(I), 1, affords novel anionic acyl species that result from selective nucleophilic addition at the axial carbonyl ligand of the chelated Re(CO)4 species.
“…The 13 C resonances of the acyl carbonyl carbon atoms were detected at 276.1 and 278.9 ppm for PPN- 2a and PPN- 2b , respectively. Similar results for the 13 C resonance of the acyl carbon were reported recently by Casey and co-workers for Li + [(η 5 -C 5 H 5 )(CO) 2 Re(CO)(η 5 -C 5 H 4 )Re(CO) 3 ] - and Li + [(CO) 2 Re(CO)CH 2 CH 2 (η 5 -C 5 H 4 )] - . , Recrystallization of PPN- 2b from pure dichloromethane afforded yellow-orange monoclinic crystals suitable for X-ray diffraction analysis (Figure ). 1 ORTEP drawing and atom-numbering scheme of the molecular structure of 2b .…”
Addition of phenyllithium and methyllithium to tetracarbonyl[2-(phenyl-κC
2‘),pyridine-κN]rhenium(I), 1, affords novel anionic acyl species that result from selective nucleophilic addition at the axial carbonyl ligand of the chelated Re(CO)4 species.
“…Presumably, carbon monoxide was extruded upon irradiation followed by intramolecular amino group coordination; alternatively, THF might fill the vacant site first followed by pendant amino group substitution to give 3 . The terminal carbonyl stretchings of 3 appeared at 1893 and 1816 cm -1 , much lower frequencies than those for CpRe(CO) 2 L compounds (L = THF, N 2 , carbene, alkyne, and thiophene ). This indicates that the Re to CO π* back-bonding for the aminorhenium complex 3 is much stronger than that of the other complexes with ligands other than the amino group.…”
Section: Resultsmentioning
confidence: 75%
“…The alkyl tether of 8 is bent down 6.7° from the cyclopentadienyl ring toward rhenium (C(2)−C(3)−Cp(centroid) = 173.3°). This angle is smaller than that of the tethered methoxycarbene complex (CO) 2 ReC(OCH 3 )CH 2 CH 2 (η 5 -C 5 H 4 ),8b in which the alkyl tether is bent down 9°. This may suggest that the strain introduced by tethering a ligand to the cyclopentadienyl ligand is smaller for a tethered four-legged piano-stool complex, such as 8 , than that of the tethered three-legged piano stool complex, such as (CO) 2 ReC(OCH 3 )CH 2 CH 2 (η 5 -C 5 H 4 ).…”
The aminorhenium complex
(CO)2ReNH(CH3)CH2CH2(η5-C5H4)
(3), in which the ligating
amino group is connected to the cyclopentadienyl ligand, was prepared
by irradiation of
(η5-C5H4CH2CH2NHCH3)Re(CO)3
(2) in THF. Alkylation of the corresponding
anion
[(CO)2ReN(CH3)CH2CH2(η5-C5H4)]-Li+
(4) as well as the neutral aminorhenium complex
3
with a variety of electrophiles has been studied. The anion
4 reacted with electrophiles,
such as CH3I, CH2CHCH2Br,
C6H5CH2Br, and
HC⋮CCH2Br, at the nitrogen center to
provide
(CO)2ReNR(CH3)CH2CH2(η5-C5H4)
(5a−d). However, 4 reacted with
electrophiles
having a carbonyl group or a nitrile group next to the electrophilic
carbon, such as BrCH2CO2CH3,
BrCH2CO2C2H5, and
BrCH2CN, to give rhenium alkylation compounds
[(CO)2(R)ReNH(CH3)CH2CH2(η5-C5H4)]+Br-
(7e−g) after protonation. The neutral
aminorhenium
complex 3 reacted with the electrophiles mentioned above to
provide exclusive Re-alkylation
compounds 7a−g. The structure of the
tetraphenylborate salt of 7c,
[(CO)2(C6H5CH2)ReNH(CH3)CH2CH2(η5-C5H4)]+BPh4
-
(8), has been determined by X-ray diffraction.
“…The IR spectrum of 3 does not change when compound 3 is mixed with 1 equiv of HBF 4 ·OEt 2 , suggesting that there is little Fe−(hydroxy)carbene cation formation. Interestingly anionic (CO) 2 ReC(O)CH 2 CH 2 (η 5 -C 5 H 4 ) - , the isolobal Re analog of neutral 3 , reacts with HBF 4 · OEt 2 to give rise to the corresponding neutral Re−(hydroxy)carbene (CO) 2 ReC(OH)CH 2 CH 2 (η 5 -C 5 H 4 ) that is in equilibrium with the Re−hydride (CO) 2 (H)ReC(O)CH 2 CH 2 (η 5 -C 5 H 4 ) …”
Spiro[2.4]hepta-4,6-diene)tricarbonyliron (2) self-converts to the tethered acyl complex (CO) 2 FeC(O)CH 2 CH 2 (η 5 -C 5 H 4 ) (3) when refluxed for 1 h in common organic solvents. The reaction of 2 with an external electrophile (CPh 3 + , H + ) opens the three-membered ring, resulting in the cation (η 5 -C 5 H 4 CH 2 CH 2 R)Fe(CO) 3 + whose structure was determined by spectroscopic methods and confirmed by X-ray analysis of the PPh 3 derivative (η 5 -C 5 H 4 CH 2 -CH 3 )Fe(CO) 2 (PPh 3 ) + . The reaction of 3 with a strong electrophile (CPh 3 + , Me + ) affords the rotationally restricted Fe-(alkoxy)carbene cation (CO) 2 FedC(OR)CH 2 CH 2 (η 5 -C 5 H 4 ) + , which can be converted to the Fe-(anilino)carbene cation (CO) 2 FedC(NHPh)CH 2 CH 2 (η 5 -C 5 H 4 ) + . 146 °C) originating from 4. If brought to reflux for 1 h, compound 2 in solution is fully converted to 3, whose IR ν(CO) stretching bands are shown in Figure 1d. Compound 3 is not soluble in n-hexane or Et 2 O but is soluble in THF and chlorinated solvents.Reactions of 2 with Lewis and Protic Acids. Scheme 1 shows a proposed, intramolecular, ionic rear-
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