The carbene-alkyne chelated tungsten complexes (W(CO)
4{=C(OEt)(o-C
6H
4C≡CTMS)}, 2.5; W(CO)
4{=C(OEt)[C(nPr)=C(nPr)C≡CTMS]}, 2.6, and W(CO)
4{=C(OEt)(o-C
6H
4C≡CCH
3)}, 2.7), have been synthesized. The PMe
3 supported carbene-alkyne chelated tungsten complex (W(CO)
3(PMe
3){=C(OEt)(o-C
6H
4C≡CTMS)}, 2.10) has been isolated from the reaction of the complex 2.5 with PMe
3. The oxidation of the complex 2.10 with PhICl
2 afforded the 16e
- carbene complex (W(Cl)
2(CO)
2(PMe
3){=C(OEt)(o-C
6H
4C≡CTMS)}). The reaction of the complex 2.10 with secondary amine and K
2CO
3 led to the formation of the η
1-ylidic enamine carbene complex W(CO)
3(PMe
3){=C(OEt)[o-C
6H
4CH=CH(NMeCH
2CH
2NMe
2)]}. The tungsten carbyne complexes (TpW(CO)
2≡CN(
iPr)
2, Tp*W(CO)
2≡CN(
iPr)
2, TpWI
2(CO)≡CN(
iPr)
2, (triphos)WBr(CO)
2≡CN(
iPr)
2, and [(NP3)W(CO)
2≡CN(
iPr)
2]Br) have been synthesized and systematically investigated for their reactivity towards alkynes. Several new tungsten carbyne complexes including WBr
3(IDipp)≡C(3,5-(CH
3)
2C
6H
3, WBr
2(OSiPh
3)(IDipp)≡C(3,5-(CH
3)
2C
6H
3, WBr
2(N[TMS]Mes)(IDipp)≡C(3,5-(CH
3)
2C
6H
3, and WBr
2(IDipp)
2≡C(3,5-(CH
3)
2C
6H
3 supported by a bulky N-heterocyclic carbene ligand have also been synthesized and characterized. The reaction of the high valent tungsten benzylidyne complex WBr
2(OSiPh
3)(IDipp)≡C(3,5-(CH
3)
2C
6H
3 with H
2O and the Lewis acid B(C
6F
5)
3 provided tungsten oxo-benzylidene complexes WBr{O(H)B(C
6F
5)
3}(IDipp)=CH(3,5-(CH
3)
2C
6H
3 and WBr
2(=O)(IDipp)=CH(3,5-(CH
3)
2C
6H
3. The tungsten carbyne complex WBr
2(OSiPh
3)(IDipp)≡C(3,5-(CH
3)
2C
6H
3 in combination with KBAr
F4 was found to be catalytically active for internal alkynes polymerization. The tungsten (V) benzylidyne complex WBr
2(IDipp)
2≡C(3,5-(CH
3)
2C
6H
3 was isolated from the reduction reaction of WBr
3(DME)≡C(3,5-(CH
3)
2C
6H
3 by magnesium in the presence of IDipp. Furthermore, pyrrolide-diphosphine (PNP) lithium could react with the PMe
3-ligated tungsten benzylidyne complex WBr(PMe
3)
4≡C(3,5-(CH
3)
2C
6H
3 to provide the PNP pincer ligand supported complex (PNP)W(PMe
3)
2≡C(3,5-(CH
3)
2C
6H
3. Various alkynes were found to displace two of the trimethylphosphine ligands in the complex (PNP)W(PMe
3)
2≡C(3,5-(CH
3)
2C
6H
3 to provide tungsten alkyne-benzylidyne complexes (PNP)W(alkyne)≡C(3,5-(CH
3)
2C
6H
3. The tungsten alkyne-benzylidene complex (PNP)WI(alkyne)=CH(3,5-(CH
3)
2C
6H
3 was isolated from the reaction of the tungsten alkyne-benzylidyne complex (PNP)W(3-hexyne)≡C(3,5-(CH
3)
2C
6H
3 with methyl iodide and H
2O. Several new organic precursors (phosphonium salts ([o-C
6H
4(PPh
3CH
2)C≡CTMS]BPh
4; and [o-C
6H
4(PMe
3CH
2)C≡CTMS]BPh
4) and isoindolium salts ([1-(TMSC≡C)-2-(HC=N[2,6-
iPrC
6H
3]C(Ph
2)C
6H
3)]OTf) have been synthesized and their reactivity with transition metal complexes have also been briefly investigated. The alkyne complex mer-[W(PMe
3)Cl
2(o-C
6H
4(C≡CTMS)(CH
2PMe
3)]Cl has been isolated from the reaction of the ylide o-C
6H
4(PPh
3=CH)C≡CTMS with WCl
2(PMe
3)
4. The reaction of the o-bromoaryliminium salt [o-C
6H
4(Br)(CH=NMeCH
2CH
2NMe
2)]OTf with W(CO)
3(EtCN)
3 yielded the complex (W(CO)
3OTf[o-C
6H
4(Br)(CH=NMeCH
2CH
2NMe
2)] as a consequence of oxidative addition of the iminium group. Interestingly, [o-C
6H
4(Br)(CH=NEt
2)]OTf undergoes
sp2C-Br oxidative addition with Pd(PPh
3)
4 to yield (PPh
3)
2PdBr(o-C
6H
4(CH=NEt
2). Additionally, platinum carbene complexes ([(PPh
3)
2ClPt=CH(NMe
2)]Cl) and ([(IMes)
2ClPt=CH(NMe
2)]Cl) have been isolated from the oxidative addition of low valent platinum complexes (Pt(PPh
3)
4 and Pt(IMes)
2) with chloromethylenedimethyliminium chloride.
| Date of Award | 2017 |
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| Original language | English |
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| Awarding Institution | - The Hong Kong University of Science and Technology
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