Paula Diaconescu - Academia.edu (original) (raw)
Papers by Paula Diaconescu
Journal of The American Chemical Society, 2010
The C-C coupling of two molecules of 1-methylbenzimidazole was effected by a neutral uranium dibe... more The C-C coupling of two molecules of 1-methylbenzimidazole was effected by a neutral uranium dibenzyl complex supported by a ferrocene 1,1'-diamide ligand. The transformation involves the C-H activation of two heterocycles and the coupling of one eta(2)-N,C-imidazolyl fragment with a coordinated 1-methylbenzimidazole ligand. The solid-state structure of this product was studied by both single-crystal and powder X-ray diffraction methods and confirms the formation of the biheterocyclic moiety. In solution, the C-C coupling event was found to be reversible, as assessed by variable-temperature (1)H and (2)H NMR spectroscopy as well as DFT calculations and reactivity studies.
Nature Chemistry, 2010
Uranium is best known, and feared, for its involvement in nuclear energy. Marisa J. Monreal and P... more Uranium is best known, and feared, for its involvement in nuclear energy. Marisa J. Monreal and Paula L. Diaconescu take a look at how its unique combination of properties is now increasingly attracting the attention of chemists.
Organometallics, 2002
ABSTRACT
Inorganic Chemistry, 2009
A rare example of a cerium(IV) alkoxide catalyst for lactide polymerization is reported. The lact... more A rare example of a cerium(IV) alkoxide catalyst for lactide polymerization is reported. The lactide polymerization activity of the new cerium(IV) complex supported by a ferrocene Schiff base ligand, salfen, is compared to the activity of the yttrium analogue and to that of Ce(O(t)Bu)(4)(THF)(2). The complex Ce(salfen)(O(t)Bu)(2) is less active than Ce(O(t)Bu)(4)(THF)(2) and the corresponding yttrium(III) alkoxide, Y(salfen)(O(t)Bu)(THF). The different activity was correlated with the Mulliken charges calculated by density functional theory for the two complexes.
Organometallics, 2000
SiMe 3 is an active catalyst for alkyne metathesis at room temperature.
Organometallics, 2004
Enolate ligands of formula [OC(Ad)Ar] -(Ad ) 2-adamantylidene; Ar ) 3,5-C 6 H 3 Me 2 1a, Ar ) 2,4... more Enolate ligands of formula [OC(Ad)Ar] -(Ad ) 2-adamantylidene; Ar ) 3,5-C 6 H 3 Me 2 1a, Ar ) 2,4,6-C 6 H 2 Me 3 1b) were designed and prepared as potassium salts to mimic the topology of related N-tert-hydrocarbyl and ketimide ligands. Subsequently, trimethyltantalum bis-enolate complexes TaMe 3 (O-C[Ad]Ar) 2 (Ar ) 3,5-C 6 H 3 Me 2 2a, Ar ) 2,4,6-C 6 H 2 Me 3 2b) were prepared in good yields from a salt metathesis reaction between TaMe 3 Cl 2 and 2 equiv of the corresponding potassium enolate. Complex 2a was structurally characterized and found to be monomeric in the solid state and to exhibit an inner coordination sphere of approximate D 3h symmetry. Reaction between 2a and pyridine in the presence of dihydrogen resulted in an unanticipated pyridine coupling with formation of the bipyridine complex TaMe(O-C[Ad](3,5-C 6 H 3 Me 2 )) 2 (py)(bpy), 3a (py ) pyridyl, bpy ) 2,2′-bipyridyl), which was structurally characterized to confirm its formulation. Labeling experiments using pyridine-d 5 and D 2 suggest that formation of the tantalum(III) complex 3a occurred via C-H activation involving a putative tantalum(III) intermediate, TaMe-(O-C[Ad](3,5-C 6 H 3 Me 2 )) 2 (py) 3 , 4a.
Journal of The American Chemical Society, 2002
Methine (CH) transfer to an open coordination site was achieved in one pot by titanium(III) abstr... more Methine (CH) transfer to an open coordination site was achieved in one pot by titanium(III) abstraction of Cl from 7-chloronorbornadiene, radical capture by Mo, and benzene extrusion. This efficient Mo methylidyne synthesis permitted elaboration to an anionic phosphaisocyanide derivative upon deprotonation, functionalization with dichlorophenylphosphine, and ultimate reduction.
Inorganic Chemistry, 2007
Oxidation of a uranium(IV) bis(1,1'-diamidoferroc... more Oxidation of a uranium(IV) bis(1,1'-diamidoferrocene) gives a compound which is best described as a mixed-valence bisferrocene complex in which uranium mediates the electronic communication.
Journal of The American Chemical Society, 2002
Treatment of IU(DME)(NC[(t)Bu]Mes)(3) (2-I-DME) with 4 equiv of KC(8) and 0.5 equiv of naphthalen... more Treatment of IU(DME)(NC[(t)Bu]Mes)(3) (2-I-DME) with 4 equiv of KC(8) and 0.5 equiv of naphthalene in DME allowed the isolation of a naphthalene-bridged compound, K(2)(mu-eta(6),eta(6)-C(10)H(8))[U(NC[(t)Bu]Mes)(3)](2) (K(2)-2(2)-mu-C(10)H(8)), in 60% yield as a dark brown powder. The twelve U-C distances are rather short, varying from 2.565(11) to 2.749(10) A. Treatment of M(2)-2(2)-mu-C(10)H(8) (M = Na, K) with 2 equiv of 1,3,5,7-cyclooctatetraene afforded a mixture of two products: M-2-COT and 2(2)-mu-COT. Compound 2(2)-mu-COT can be assembled independently in 90% yield by salt elimination upon reaction of M-2-COT with iodide 2-I-DME. The U-C(arene) distance in compound 2(2)-mu-COT is longer than that in its naphthalene counterpart K(2)-2(2)-mu-C(10)H(8)(2.822 vs 2.634 A), in accord with bonding considerations. A DFT study performed on model compounds for both M(2)-2(2)-mu-C(10)H(8) and 2(2)-mu-COT indicates that the delta bonds present in the former compound show better covalent overlap.
Inorganic Chemistry, 2001
A potentially general strategy for accessing the rarely encountered coordination of amidoximates ... more A potentially general strategy for accessing the rarely encountered coordination of amidoximates through both oximato O and amido N atoms was developed. The new amidoxime (Z)-R(1)C(=NOH)NR(2)H (R(1) = mesityl, R(2) = 2-[[dimethylamino]methyl]phenyl), H(2)L, was prepared by reaction of equimolar amounts of the appropriate nitrile oxide and primary amine. Treatment of H(2)L with 1 equiv of AlMe(3) produced the dimeric species (MeAlL)(2) (1) possessing the formally dianionic ligand L(2)(-) bound to the aluminum via the oximato oxygen and the amido and amino nitrogens. The oximato oxygen atoms serve to link the two monomeric organoaluminum units together. Reaction of (ON)Cr(N(i)Pr(2))(3) with H(2)L provided the diamagnetic complex (ON)Cr(N(i)Pr(2))(eta(3)-L) (2). Interaction of 2 with excess methanol led, in particular, to the oxidative loss of NO and yielded the paramagnetic dimer [Cr(LH)(OMe)(mu-OMe)](2) (3) containing the eta(3)-bound amidoximato ligand protonated at its oximato nitrogen. In addition to spectroscopic characterizations of the new substances, single-crystal X-ray structures of H(2)L, 1.(4)/(3)C(6)H(6), and 3.MeOH were obtained.
Organometallics, 2008
... Supporting Information Experimental details for synthesis of 1-I 2 (THF) and 1-Np 2 , X-ray c... more ... Supporting Information Experimental details for synthesis of 1-I 2 (THF) and 1-Np 2 , X-ray crystal structures of 1-I 2 (THF) and 1-Bz 2 , NIR spectra, and DFT calculation details. This ... 19. Shafir, A.; Arnold, J. J. Am. Chem. Soc. ...
Organometallics, 2008
... Colin T. Carver, Marisa J. Monreal and Paula L. Diaconescu*. Department of Chemistry &... more ... Colin T. Carver, Marisa J. Monreal and Paula L. Diaconescu*. Department of Chemistry & Biochemistry, University of California, Los Angeles, California 90095. Organometallics , 2008, 27 (3), pp 363–370. DOI: 10.1021/om7007277. ...
Dalton transactions (Cambridge, England : 2003), Jan 14, 2015
The synthesis and characterization of (bipy)(2)U(N[t-Bu]Ar)(2) (1-(bipy)(2), bipy = 2,2'-bipy... more The synthesis and characterization of (bipy)(2)U(N[t-Bu]Ar)(2) (1-(bipy)(2), bipy = 2,2'-bipyridyl, Ar = 3,5-C(6)H(3)Me(2)), (bipy)U(N[(1)Ad]Ar)(3) (2-bipy), (bipy)(2)U(NC[t-Bu]Mes)(3) (3-(bipy)(2), Mes = 2,4,6-C(6)H(2)Me(3)), and IU(bipy)(NC[t-Bu]Mes)(3) (3-I-bipy) are reported. X-ray crystallography studies indicate that bipy coordinates as a radical anion in 1-(bipy)(2) and 2-bipy, and as a neutral ligand in 3-I-bipy. In 3-(bipy)(2), one of the bipy ligands is best viewed as a radical anion, the other as a neutral ligand. The electronic structure assignments are supported by NMR spectroscopy studies of exchange experiments with 4,4'-dimethyl-2,2'-bipyridyl and also by optical spectroscopy. In all complexes, uranium was assigned a +4 formal oxidation state.
The reactivity of a uranium dibenzyl complex supported by a ferrocene-diamide ligand toward aroma... more The reactivity of a uranium dibenzyl complex supported by a ferrocene-diamide ligand toward aromatic N-heterocycles was investigated. Although ring opening occurred, a complicated behavior was observed with 1-methylbenzimidazole and benzoxazole. On the other hand, when a uranium benzyl h 2 -N,Cbenzimidazole complex reacted with quinoline, alkyl transfer to the pyridine ring was observed.
Organometallics, 2010
... Colin T. Carver, Bryan N. Williams, Kevin R. Ogilby and Paula L. Diaconescu*. Department of C... more ... Colin T. Carver, Bryan N. Williams, Kevin R. Ogilby and Paula L. Diaconescu*. Department of Chemistry & Biochemistry, University of California, Los Angeles, California 90095. Organometallics , 2010, 29 (4), pp 835–846. DOI ...
Metal-Based Drugs, 1998
Metal complexes of dichloro-tetramorpholino-cyclophosphazatriene containing divalent cations such... more Metal complexes of dichloro-tetramorpholino-cyclophosphazatriene containing divalent cations such as Ni(II), Co(II), and Mn(II) have been prepared and characterised by standard physico-chemical procedures (elemental chemical analysis, IR and UV-VIS spectra, conductimetric measurement). The newly synthesised compounds possessed antifungal activity against Aspergillus and Candida spp., some of them showing effects comparable to ketoconazole (with minimum inhibitory concentrations in the range of 2-30 ktg/mL) but being generally less active as compared to the azole. Best activity was detected against C. albicans, and worst activity against A. niger. The mechanism of action of these compounds probably involves inhibition of ergosterol biosynthesis, and interaction with lanosterol-14-o-demethylase (CYP51A 1), since reduced amounts of ergosterol were evidenced by means of HPLC in cultures of the sensitive strain A.
Journal of the American Chemical Society, 2010
Group 3 (Sc, Y, Lu, La) benzyl complexes supported by a ferrocene diamide ligand are reactive tow... more Group 3 (Sc, Y, Lu, La) benzyl complexes supported by a ferrocene diamide ligand are reactive toward aromatic N-heterocycles by mediating their coupling and, in a few cases, the cleavage of their C-N bonds. When these complexes reacted with 2,2′-bipyridine or isoquinoline, they facilitated the alkyl migration of the benzyl ligand onto the pyridine ring, a process accompanied by the dearomatization of the N-heterocycle. The products of the alkyl-transfer reactions act as hydrogen donors in the presence of aromatic N-heterocycles, ketones, and azobenzene. Experimental and computational studies suggest that the hydrogen transfer takes place through a concerted mechanism. An interesting disproportionation reaction of the dearomatized, alkyl-substituted isoquinoline complexes is also reported.
Journal of the American Chemical Society, 2009
Journal of the American Chemical Society, 2004
Nitride NW(N[i-Pr]Ar)3 (1, Ar = 3,5-C6H3Me2) was synthesized in two steps from known NW(O-t-Bu)3 ... more Nitride NW(N[i-Pr]Ar)3 (1, Ar = 3,5-C6H3Me2) was synthesized in two steps from known NW(O-t-Bu)3 (41% overall yield). Complex 1 is the tungsten congener of NMo(N[i-Pr]Ar)3, a known molecule that has been synthesized using N2 as the nitrido nitrogen source, but which undergoes no reaction with pivaloyl chloride. Compound 1 undergoes metathesis with pivaloyl chloride at 25 degrees C to form the corresponding nitrile in 97% yield. Another substrate examined in this work was the labeled acid chloride 1-Ad13C(O)Cl (Ad = adamantyl). The "(O)Cl" moiety is transferred to tungsten forming an oxo-chloride, (Ar[i-Pr]N)3W(O)Cl (3), as the final tungsten product; both 1 and 3 were characterized structurally by X-ray diffraction. An intermediate observed in the nitrile-forming reaction was characterized spectroscopically to be a tungsten acylimido complex. The latter assignment was substantiated by the synthesis and structural characterization of the compound (Ar[i-Pr]N)3W(NC(O)CF3)(O2CCF3) (2m). In addition, density functional theory calculations performed using ADF lent insight into the thermochemistry of the overall process.
Journal of The American Chemical Society, 2010
The C-C coupling of two molecules of 1-methylbenzimidazole was effected by a neutral uranium dibe... more The C-C coupling of two molecules of 1-methylbenzimidazole was effected by a neutral uranium dibenzyl complex supported by a ferrocene 1,1'-diamide ligand. The transformation involves the C-H activation of two heterocycles and the coupling of one eta(2)-N,C-imidazolyl fragment with a coordinated 1-methylbenzimidazole ligand. The solid-state structure of this product was studied by both single-crystal and powder X-ray diffraction methods and confirms the formation of the biheterocyclic moiety. In solution, the C-C coupling event was found to be reversible, as assessed by variable-temperature (1)H and (2)H NMR spectroscopy as well as DFT calculations and reactivity studies.
Nature Chemistry, 2010
Uranium is best known, and feared, for its involvement in nuclear energy. Marisa J. Monreal and P... more Uranium is best known, and feared, for its involvement in nuclear energy. Marisa J. Monreal and Paula L. Diaconescu take a look at how its unique combination of properties is now increasingly attracting the attention of chemists.
Organometallics, 2002
ABSTRACT
Inorganic Chemistry, 2009
A rare example of a cerium(IV) alkoxide catalyst for lactide polymerization is reported. The lact... more A rare example of a cerium(IV) alkoxide catalyst for lactide polymerization is reported. The lactide polymerization activity of the new cerium(IV) complex supported by a ferrocene Schiff base ligand, salfen, is compared to the activity of the yttrium analogue and to that of Ce(O(t)Bu)(4)(THF)(2). The complex Ce(salfen)(O(t)Bu)(2) is less active than Ce(O(t)Bu)(4)(THF)(2) and the corresponding yttrium(III) alkoxide, Y(salfen)(O(t)Bu)(THF). The different activity was correlated with the Mulliken charges calculated by density functional theory for the two complexes.
Organometallics, 2000
SiMe 3 is an active catalyst for alkyne metathesis at room temperature.
Organometallics, 2004
Enolate ligands of formula [OC(Ad)Ar] -(Ad ) 2-adamantylidene; Ar ) 3,5-C 6 H 3 Me 2 1a, Ar ) 2,4... more Enolate ligands of formula [OC(Ad)Ar] -(Ad ) 2-adamantylidene; Ar ) 3,5-C 6 H 3 Me 2 1a, Ar ) 2,4,6-C 6 H 2 Me 3 1b) were designed and prepared as potassium salts to mimic the topology of related N-tert-hydrocarbyl and ketimide ligands. Subsequently, trimethyltantalum bis-enolate complexes TaMe 3 (O-C[Ad]Ar) 2 (Ar ) 3,5-C 6 H 3 Me 2 2a, Ar ) 2,4,6-C 6 H 2 Me 3 2b) were prepared in good yields from a salt metathesis reaction between TaMe 3 Cl 2 and 2 equiv of the corresponding potassium enolate. Complex 2a was structurally characterized and found to be monomeric in the solid state and to exhibit an inner coordination sphere of approximate D 3h symmetry. Reaction between 2a and pyridine in the presence of dihydrogen resulted in an unanticipated pyridine coupling with formation of the bipyridine complex TaMe(O-C[Ad](3,5-C 6 H 3 Me 2 )) 2 (py)(bpy), 3a (py ) pyridyl, bpy ) 2,2′-bipyridyl), which was structurally characterized to confirm its formulation. Labeling experiments using pyridine-d 5 and D 2 suggest that formation of the tantalum(III) complex 3a occurred via C-H activation involving a putative tantalum(III) intermediate, TaMe-(O-C[Ad](3,5-C 6 H 3 Me 2 )) 2 (py) 3 , 4a.
Journal of The American Chemical Society, 2002
Methine (CH) transfer to an open coordination site was achieved in one pot by titanium(III) abstr... more Methine (CH) transfer to an open coordination site was achieved in one pot by titanium(III) abstraction of Cl from 7-chloronorbornadiene, radical capture by Mo, and benzene extrusion. This efficient Mo methylidyne synthesis permitted elaboration to an anionic phosphaisocyanide derivative upon deprotonation, functionalization with dichlorophenylphosphine, and ultimate reduction.
Inorganic Chemistry, 2007
Oxidation of a uranium(IV) bis(1,1'-diamidoferroc... more Oxidation of a uranium(IV) bis(1,1'-diamidoferrocene) gives a compound which is best described as a mixed-valence bisferrocene complex in which uranium mediates the electronic communication.
Journal of The American Chemical Society, 2002
Treatment of IU(DME)(NC[(t)Bu]Mes)(3) (2-I-DME) with 4 equiv of KC(8) and 0.5 equiv of naphthalen... more Treatment of IU(DME)(NC[(t)Bu]Mes)(3) (2-I-DME) with 4 equiv of KC(8) and 0.5 equiv of naphthalene in DME allowed the isolation of a naphthalene-bridged compound, K(2)(mu-eta(6),eta(6)-C(10)H(8))[U(NC[(t)Bu]Mes)(3)](2) (K(2)-2(2)-mu-C(10)H(8)), in 60% yield as a dark brown powder. The twelve U-C distances are rather short, varying from 2.565(11) to 2.749(10) A. Treatment of M(2)-2(2)-mu-C(10)H(8) (M = Na, K) with 2 equiv of 1,3,5,7-cyclooctatetraene afforded a mixture of two products: M-2-COT and 2(2)-mu-COT. Compound 2(2)-mu-COT can be assembled independently in 90% yield by salt elimination upon reaction of M-2-COT with iodide 2-I-DME. The U-C(arene) distance in compound 2(2)-mu-COT is longer than that in its naphthalene counterpart K(2)-2(2)-mu-C(10)H(8)(2.822 vs 2.634 A), in accord with bonding considerations. A DFT study performed on model compounds for both M(2)-2(2)-mu-C(10)H(8) and 2(2)-mu-COT indicates that the delta bonds present in the former compound show better covalent overlap.
Inorganic Chemistry, 2001
A potentially general strategy for accessing the rarely encountered coordination of amidoximates ... more A potentially general strategy for accessing the rarely encountered coordination of amidoximates through both oximato O and amido N atoms was developed. The new amidoxime (Z)-R(1)C(=NOH)NR(2)H (R(1) = mesityl, R(2) = 2-[[dimethylamino]methyl]phenyl), H(2)L, was prepared by reaction of equimolar amounts of the appropriate nitrile oxide and primary amine. Treatment of H(2)L with 1 equiv of AlMe(3) produced the dimeric species (MeAlL)(2) (1) possessing the formally dianionic ligand L(2)(-) bound to the aluminum via the oximato oxygen and the amido and amino nitrogens. The oximato oxygen atoms serve to link the two monomeric organoaluminum units together. Reaction of (ON)Cr(N(i)Pr(2))(3) with H(2)L provided the diamagnetic complex (ON)Cr(N(i)Pr(2))(eta(3)-L) (2). Interaction of 2 with excess methanol led, in particular, to the oxidative loss of NO and yielded the paramagnetic dimer [Cr(LH)(OMe)(mu-OMe)](2) (3) containing the eta(3)-bound amidoximato ligand protonated at its oximato nitrogen. In addition to spectroscopic characterizations of the new substances, single-crystal X-ray structures of H(2)L, 1.(4)/(3)C(6)H(6), and 3.MeOH were obtained.
Organometallics, 2008
... Supporting Information Experimental details for synthesis of 1-I 2 (THF) and 1-Np 2 , X-ray c... more ... Supporting Information Experimental details for synthesis of 1-I 2 (THF) and 1-Np 2 , X-ray crystal structures of 1-I 2 (THF) and 1-Bz 2 , NIR spectra, and DFT calculation details. This ... 19. Shafir, A.; Arnold, J. J. Am. Chem. Soc. ...
Organometallics, 2008
... Colin T. Carver, Marisa J. Monreal and Paula L. Diaconescu*. Department of Chemistry &... more ... Colin T. Carver, Marisa J. Monreal and Paula L. Diaconescu*. Department of Chemistry & Biochemistry, University of California, Los Angeles, California 90095. Organometallics , 2008, 27 (3), pp 363–370. DOI: 10.1021/om7007277. ...
Dalton transactions (Cambridge, England : 2003), Jan 14, 2015
The synthesis and characterization of (bipy)(2)U(N[t-Bu]Ar)(2) (1-(bipy)(2), bipy = 2,2'-bipy... more The synthesis and characterization of (bipy)(2)U(N[t-Bu]Ar)(2) (1-(bipy)(2), bipy = 2,2'-bipyridyl, Ar = 3,5-C(6)H(3)Me(2)), (bipy)U(N[(1)Ad]Ar)(3) (2-bipy), (bipy)(2)U(NC[t-Bu]Mes)(3) (3-(bipy)(2), Mes = 2,4,6-C(6)H(2)Me(3)), and IU(bipy)(NC[t-Bu]Mes)(3) (3-I-bipy) are reported. X-ray crystallography studies indicate that bipy coordinates as a radical anion in 1-(bipy)(2) and 2-bipy, and as a neutral ligand in 3-I-bipy. In 3-(bipy)(2), one of the bipy ligands is best viewed as a radical anion, the other as a neutral ligand. The electronic structure assignments are supported by NMR spectroscopy studies of exchange experiments with 4,4'-dimethyl-2,2'-bipyridyl and also by optical spectroscopy. In all complexes, uranium was assigned a +4 formal oxidation state.
The reactivity of a uranium dibenzyl complex supported by a ferrocene-diamide ligand toward aroma... more The reactivity of a uranium dibenzyl complex supported by a ferrocene-diamide ligand toward aromatic N-heterocycles was investigated. Although ring opening occurred, a complicated behavior was observed with 1-methylbenzimidazole and benzoxazole. On the other hand, when a uranium benzyl h 2 -N,Cbenzimidazole complex reacted with quinoline, alkyl transfer to the pyridine ring was observed.
Organometallics, 2010
... Colin T. Carver, Bryan N. Williams, Kevin R. Ogilby and Paula L. Diaconescu*. Department of C... more ... Colin T. Carver, Bryan N. Williams, Kevin R. Ogilby and Paula L. Diaconescu*. Department of Chemistry & Biochemistry, University of California, Los Angeles, California 90095. Organometallics , 2010, 29 (4), pp 835–846. DOI ...
Metal-Based Drugs, 1998
Metal complexes of dichloro-tetramorpholino-cyclophosphazatriene containing divalent cations such... more Metal complexes of dichloro-tetramorpholino-cyclophosphazatriene containing divalent cations such as Ni(II), Co(II), and Mn(II) have been prepared and characterised by standard physico-chemical procedures (elemental chemical analysis, IR and UV-VIS spectra, conductimetric measurement). The newly synthesised compounds possessed antifungal activity against Aspergillus and Candida spp., some of them showing effects comparable to ketoconazole (with minimum inhibitory concentrations in the range of 2-30 ktg/mL) but being generally less active as compared to the azole. Best activity was detected against C. albicans, and worst activity against A. niger. The mechanism of action of these compounds probably involves inhibition of ergosterol biosynthesis, and interaction with lanosterol-14-o-demethylase (CYP51A 1), since reduced amounts of ergosterol were evidenced by means of HPLC in cultures of the sensitive strain A.
Journal of the American Chemical Society, 2010
Group 3 (Sc, Y, Lu, La) benzyl complexes supported by a ferrocene diamide ligand are reactive tow... more Group 3 (Sc, Y, Lu, La) benzyl complexes supported by a ferrocene diamide ligand are reactive toward aromatic N-heterocycles by mediating their coupling and, in a few cases, the cleavage of their C-N bonds. When these complexes reacted with 2,2′-bipyridine or isoquinoline, they facilitated the alkyl migration of the benzyl ligand onto the pyridine ring, a process accompanied by the dearomatization of the N-heterocycle. The products of the alkyl-transfer reactions act as hydrogen donors in the presence of aromatic N-heterocycles, ketones, and azobenzene. Experimental and computational studies suggest that the hydrogen transfer takes place through a concerted mechanism. An interesting disproportionation reaction of the dearomatized, alkyl-substituted isoquinoline complexes is also reported.
Journal of the American Chemical Society, 2009
Journal of the American Chemical Society, 2004
Nitride NW(N[i-Pr]Ar)3 (1, Ar = 3,5-C6H3Me2) was synthesized in two steps from known NW(O-t-Bu)3 ... more Nitride NW(N[i-Pr]Ar)3 (1, Ar = 3,5-C6H3Me2) was synthesized in two steps from known NW(O-t-Bu)3 (41% overall yield). Complex 1 is the tungsten congener of NMo(N[i-Pr]Ar)3, a known molecule that has been synthesized using N2 as the nitrido nitrogen source, but which undergoes no reaction with pivaloyl chloride. Compound 1 undergoes metathesis with pivaloyl chloride at 25 degrees C to form the corresponding nitrile in 97% yield. Another substrate examined in this work was the labeled acid chloride 1-Ad13C(O)Cl (Ad = adamantyl). The "(O)Cl" moiety is transferred to tungsten forming an oxo-chloride, (Ar[i-Pr]N)3W(O)Cl (3), as the final tungsten product; both 1 and 3 were characterized structurally by X-ray diffraction. An intermediate observed in the nitrile-forming reaction was characterized spectroscopically to be a tungsten acylimido complex. The latter assignment was substantiated by the synthesis and structural characterization of the compound (Ar[i-Pr]N)3W(NC(O)CF3)(O2CCF3) (2m). In addition, density functional theory calculations performed using ADF lent insight into the thermochemistry of the overall process.