On the Bonding in N-Heterocyclic Carbene Complexes of Germanium(II)

Ruddy, Adam J.; Rupar, Paul A.; Bladek, Kamila J.; Allan, Christopher J.; Avery, Jessica C.; Baines, Kim M.

doi:10.1021/om900977g

Cited by 60 publications

(40 citation statements)

References 39 publications

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“…Our results are in good agreement with the work performed by Baines et al. on the lack of a substituent effect on the carbenic carbon–germanium bond length 10g…”

Section: Methodssupporting

confidence: 93%

Stable N‐Heterocyclic Carbene Complexes of Hypermetallyl Germanium(II) and Tin(II) Compounds

Katir

Matioszek

Ladeira³

et al. 2011

Angew Chem Int Ed

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“…Our results are in good agreement with the work performed by Baines et al. on the lack of a substituent effect on the carbenic carbon–germanium bond length 10g…”

Section: Methodssupporting

confidence: 93%

Stable N‐Heterocyclic Carbene Complexes of Hypermetallyl Germanium(II) and Tin(II) Compounds

Katir

Matioszek

Ladeira³

et al. 2011

Angew Chem Int Ed

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“…The optimized Si−C distance of 1.920 Å falls between distances noted by Filippou and co‐workers in their isolated (NHC i Pr )SiI 3 compound (1.91 Å) and that of Rivard and co‐workers in their (NHC i Pr )SiW(CO) 5 compound (1.93 Å). Similarly, the interaction distance calculated for the germanium adduct A , (NHC Me )GeH 2 (2.046 Å), lies between those reported by Rivard and co‐workers (2.00 Å) involving a chloride‐substituted Ge II compound and the mesityl‐substituted germanium compound (2.07 Å) synthesized by Baines . The elongated Ge–NHC interaction found by Frenking, Jones and Stasch could be reasoned by the use of the bulkier NHC i Pr substituent.…”

Section: Resultsmentioning

confidence: 99%

“…Similarly,t he interaction distance calculated for the germanium adduct A,( NHC Me )GeH 2 (2.046 ), lies between those reportedb yR ivard and co-workers [20] (2.00 )i nvolving ac hloride-substituted Ge II compound and the mesityl-substituted germanium compound (2.07 )s ynthesized by Baines. [40] The elongatedG e-NHC interaction found by Frenking, Jones and Stasch [41] could be reasoned by the use of the bulkier NHC iPr substituent. The tin-carbene interaction distance (2.29 )f ound in the organotin complex isolated by Wagner et al [42] also compares well with the theoretical value (2.323 ) for the initial adduct.…”

Section: Group1mentioning

confidence: 98%

Insertion of Group 12–16 Hydrides into NHCs: A Theoretical Investigation

Iversen

Dutton

Wilson

2017

Chemistry An Asian Journal

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Abstract:The endocyclic ring expansiono fN-heterocyclic carbene (NHC) rings by transitionm etal (group 12) and main group (group 13-16) elementh ydrides has been investigated in ac omputational study.I na ddition to previously reported insertion reactivity with Si, B, Be and Zn, similarr eactivity is predicted to be feasible for heavierg roup 13 elements (Al,G a, In, Tl), with the reaction barriersf or Al-Tl calculated to be lower than for boron.I nsertion is not expected with group 15-16 elementh ydrides, as the initial adduct formationist hermodynamically unfavorable. The reaction pathway with group 12 hydrides is calculated to be more favorable with two NHCs rather than as ingle NHC (analogous to Be), however hydride ring insertion with metal dihydrides is not feasible, but ratherareduced NHC is thermodynamically favored. For group 14, ring-insertion reactivityi sp redicted to be feasible with the heavier dihydrides. Trends in reactivity of element hydrides may be related to the protic or hydridic character of the elementhydrides.

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“…anal. calcd for C 26 Synthesis of 5. To the solution of (S,S)-[Me 2 Ga(μ-OCH(CH 3 )C-(O)OMe)] 2 (226 mg, 0.56 mmol) in toluene (8 mL), 4 mL of a toluene solution of IMes (339 mg, 1.11 mmol) was added at room temperature, and the solution was stirred for 0.5 h. Then, toluene was removed under vacuum to give a pale yellow solid.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…25 Although strongly basic properties of NHCs allow for their use as ligands for the synthesis of main group metal alkoxides, there is still paucity of data concerning synthesis, structure, and the catalytic activity of main group metal alkoxides stabilized with NHCs. 26 As an extension of our initial studies on the Me 2 GaOR(NHC) complexes, which constitute a new class of group 13 complexes, we present here the results concerning the effect of NHC and the alkoxide group on their synthesis, structure, and catalytic properties in the polymerization of rac-LA.…”

Section: ■ Introductionmentioning

confidence: 95%

Dialkylgallium Alkoxides Stabilized with N-Heterocyclic Carbenes: Opportunities and Limitations for the Controlled and Stereoselective Polymerization of rac-Lactide

et al. 2015

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The structure of a series of Me 2 GaOR(NHC) complexes with N-heterocyclic carbenes (1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) and 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes)) have been characterized using spectroscopic and X-ray techniques and discussed in view of their reactivity in the polymerization of rac-lactide (rac-LA). Both structure studies and density functional theory (DFT) calculations show the significant influence of NHC and OR on the structure of investigated complexes and has indicated that the Ga−C NHC bond (32.6− 39.6 kcal mol −1 ) is strong enough to form stable Me 2 GaOR-(NHC) complexes in the form of monomeric species. The reactivity of Me 2 Ga((S)-OCH(Me)CO 2 Me)(SIMes) (1) and Me 2 Ga((S)-OCH(Me)CO 2 Me)(IMes) (5) toward Lewis acids such as CO 2 and GaMe 3 has resulted in breaking of the Ga−C NHC bond with the formation of (NHC)CO 2 and Me 3 Ga(NHC) (8 and 10) and [Me 2 Ga(μ-(S)-OCH(Me)CO 2 Me)] 2 . Different results have been obtained for l,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene (SIPr), which coordinates more weakly to gallium, as demonstrated by the Ga−C NHC bond strength for model Me 3 GaSIMes, Me 3 GaIMes (8), and Me 3 GaSIPr (10) adducts. The reaction of SIPr with [Me 2 Ga(μ-OR)] 2 has not allowed for the breaking of Ga 2 O 2 bridges and the formation of monomeric Me 2 GaOR(SIPr) complexes, contrary to SIMes and IMes. In the case of the reaction with [Me 2 Ga(μ-(S)-OCH(Me)CO 2 Me)] 2 , the ionic compound [Me 2 Ga(OCH(Me)-CO 2 )] − [SIPrH] + (9) has been isolated. The investigated Me 2 GaOR(NHC) complexes are highly active and stereoselective in the ring-opening polymerization of rac-lactide from −20°C to room temperature, due to the insertion of rac-LA exclusively into the Ga−O alkoxide bond, leading to isotactically enriched polylactide (PLA) (P m = 0.65−0.78). It has been shown that the polymerization of lactide at low temperature is influenced by the chelate interaction of (S)-OCH(Me)CO 2 Me or (OCH(Me)C(O)) 2 OR resulting from the primary insertion of rac-LA into the Ga−O alkoxide bond, with the Ga center, which can be responsible for the low control over the molecular weight of the obtained PLA. The latter effect can be eliminated by the initial synthesis of Me 2 Ga((PLA) n OR)(NHC) with short PLA chains, which allows for controlled polymerization. Although the adverse chelate effect can be also eliminated by the polymerization of rac-LA at room temperature, the stereoselectivity of rac-LA polymerization is strongly affected by transesterification reactions. Out of investigated Me 2 GaOR(SIMes) and Me 2 GaOR(IMes) complexes, only the latter allowed for the immortal ring opening polymerization of rac-LA in the presence of i PrOH.

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On the Bonding in N-Heterocyclic Carbene Complexes of Germanium(II)

Cited by 60 publications

References 39 publications

Stable N‐Heterocyclic Carbene Complexes of Hypermetallyl Germanium(II) and Tin(II) Compounds

Stable N‐Heterocyclic Carbene Complexes of Hypermetallyl Germanium(II) and Tin(II) Compounds

Insertion of Group 12–16 Hydrides into NHCs: A Theoretical Investigation

Dialkylgallium Alkoxides Stabilized with N-Heterocyclic Carbenes: Opportunities and Limitations for the Controlled and Stereoselective Polymerization of rac-Lactide

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