Gene B. Carpenter

A coordination network containing metal–organometallic secondary building units based on π-bonded benzoquinone complexes

In DMSO-MeOH solvent the complex [(eta 4-benzoquinone)Mn(CO)3]- (QMTC) reacts with Mn2+ ions to produce the coordination polymer (Mn2[(eta 4-benzoquinone)Mn(CO)3]4(DMSO))n, which consists of dimanganese secondary building units interconnected by QMTC spacers.

Synthesis and structural characterization of non-planar perfluoro phthalonitriles

Abstract Perfluoropropene reacts with 1,2-dicyano-3,4,5,6-tetrafluorobenzene to give the first perfluoroalkyl substituted phthalonitriles. The X-ray structures of the bis- and tris-substituted products reveal planar, undistorted rings and head-to-head and head-to-tail preferred conformations for the isopropyl substituents, respectively. As a result, the CF3 groups impart global non-planar character to the new molecules.

π-Bonded quinonoid transition-metal complexes

Coordination of the carbocyclic ring of hydroquinones to electrophilic transition-metal fragments such as Mn(CO)3+ and Rh(COD)+ produces stable π-bonded η6-complexes that are activated to facile reversible deprotonation of the –OH groups. The deprotonations are accompanied by electron transfer to the transition metal, which acts as an internal oxidizing agent or electron sink. With manganese as the metal, the resulting η5-semiquinone and η4-quinone complexes have been used to synthesize one- two- and three-dimensional polymeric metal–organometallic coordination networks. With rhodium as the metal, the π-quinonoid complexes have been demonstrated to play a unique role in multifunctional C–C coupling catalysis and in the synthesis of new organolithium reagents. Both classes of π-quinonoid complexes appear to have significant applications in nanochemistry by providing an excellent vehicle for templating the directed self-assembly of nanoparticles into functional materials.

η6-Hydroquinone and catechol complexes of manganese tricarbonyl. 0olecular structure of [(η6-hydroquinone) Mn(CO)3]2SiF6

Abstract The reaction of ( η 6 -acenaphthene)Mn(CO) 3 + with hydroquinone and catechol affords the stable π-bonded complexes ( η 6 -hydroquinone)Mn(CO) 3 + ( 1 ) and ( η 6 -catechol)Mn(CO) 3 + ( 2 ). The X-ray structure of [ 1 ] 2 SiF 6 shows an approximately planar arene ligand with the -OH substituents strongly hydrogen bonded to fluorine atoms in the SiF 6 2− anion. Deprotonation of 1 and 2 by NEt 3 yields the corresponding π-bonded semiquinone complexes.

Benzamidoximes: structural, conformational and spectroscopic studies. I

Abstract The synthesis and properties of seven arylamidoximes are reported. 1 H- and 13 C-NMR studies and MO calculations were performed on all seven and an X-ray crystallographic determination was done on one, to determine their structure. The theoretical calculations were done using the AM1 and PM3 methods. From these results it is concluded that, for all of the arylamidoximes studied here, the NH 2 group of the amidoxime ( N -hydroxyamidine) has very little sp 2 character and the aryl ring is not coplanar with the amidoxime group. X-ray crystallographic data for p -chlorobenzamidoxime were compared with the theoretically calculated coordinates. It is interesting to note that, in crystals, the –NH 2 group is coplanar with the CN bond and the aryl ring is out of the plane of the amidoxime group. Molecular mechanics (Biosym) calculations on benzamidoxime yielded better coordinates than either the AM1 or PM3 methods.

Synthesis and structure of new diarene-bridged bi- and polymetallic compounds

Abstract Phenylcyclopentadiene (2) and diphenylcyclopentadiene (10) have been used to make bi- and polymetallic compounds. Compounds 2 and 10 have been used to make Cr–Fe bimetallic (5), Fe–Cr2 trimetallic (6), Cr–Mn–Fe trimetallic (7), Fe–Mn2 trimetallic (8), Mn–Cr bimetallic (12), Cr–Mn2 trimetallic (13), Fe2 bimetallic (15) and Fe–Cr4 pentametallic (17) compounds. The molecular structures of 8 and 12 have been determined by X-ray crystallography.

Intramolecular electron transfer in linear trinuclear complexes of copper(I), silver(I) and gold(I) bound to redox-active cyanomanganese ligands

The reaction of [Cu(NCMe)4][PF6] with 2 equivalents of [Mn(CN)Lx]{Lx=(CO)(dppm)2, cis-or trans-(CO)2[P(OR)3](dppm)(R = Ph or Et, dppm = Ph2PCH2PPh2)} in CH2Cl2 gave [Cu{µ-NC)MnLx}2][PF6]. With 2 equivalents of [Mn(CN)Lx] in toluene, AgPF6 gave [Ag{(µ-NC)MnLx}2]+{Lx=cis- or trans-(CO)2[P(OR)3](dppm)(R = Ph or Et)} but in CH2Cl2cis-[Mn(CN)(CO)2(PEt3)(dppe)](dppe = Ph2PCH2CH2PPh2) or trans-[Mn(CN)(CO)(dppm)2] and AgX (X = BF4–, PF6– or SbF6–) gave the tricationic manganese(II) complexes [Ag{(µ-NC)Mn(CO)(dppm)2}2][PF6]3 and [Ag{(µ-NC)MnLx}2]X3{Lx=trans-(CO)2(PEt3)(dppe)]; the complexes [Ag{(µ-NC)MnLx}2][PF6]3{Lx=trans-(CO)2(P(OR)3](dppm)(R = Ph or Et)} were prepared directly from Ag[PF6] and trans-[Mn(CN)(CO)2{P(OR)3}(dppm)][PF6](R = Ph or Et) in CH2Cl2. Treatment of [AuCl(tht)](tht = tetrahydrothiophene) with [Mn(CN)Lx] in CH2Cl2 in the presence of Tl[PF6] yielded [Au{(µ-NC)MnLx}2][PF6]{Lx=(CO)(dppm)2, cis- or trans-(CO)2[P(OR)3](dppm)(R = Ph or Et)}. X-Ray structural studies on [Ag{(µ-NC)MnLx}2][PF6]{Lx=trans-(CO)2[P(OPh)3](dppm)}, [Au{(µ-NC)MnLx}2][PF6]{Lx=trans-(CO)2[P(OEt)3](dppm)}, and [Ag{(µ-NC)MnLx}2][PF6]3[Lx=(CO)(dppm)2] showed, in each case, near linear Mn–CN–M′–NC–Mn skeletons (M′= Ag or Au); the Mn–P and P–substituent bond lengths are consistent with octahedral MnI and MnII centres in the monocations and trication respectively. Each of the complexes [M′{(µ-NC)MnLx}2][PF6]{M′= Cu or Au, Lx=(CO)(dppm)2; M′= Cu or Ag, Lx=trans-(CO)2[P(OR)3](dppm)(R = Ph or Et)} showed one reversible two-electron oxidation wave at a platinum electrode in CH2Cl2; the trication [Cu{(µ-NC)Mn(CO)(dppm)2}2]3+ was generated in solution by controlled potential electrolysis of [Cu{(µ-NC)Mn(CO)(dppm)2}2]+, and [Au{(µ-NC)Mn(CO)(dppm)2}2][PF6]3 was prepared by chemical oxidation of [Au{(µ-NC)Mn(CO)(dppm)2}2][PF6] with [Fe(cp)2][PF6](cp =η-C5H5) in CH2Cl2. Magnetic and ESR spectroscopic studies provided further evidence for the presence of two isolated low-spin MnII centres in the trications [Ag{(µ-NC)MnLx}2]3+{Lx=(CO)(dppm)2, trans-(CO)2[P(OR)3](dppm)(R = Ph or Et) or trans-(CO)2(PEt3)(dppe)}. By contrast, [Au{(µ-NC)MnLx}2]+{Lx=trans-(CO)2[P(OR)3(dppm)(R = Et or Ph)} showed two reversible one-electron oxidation waves corresponding to the stepwise formation of di- and tri-cations. Electrolytic oxidation of [Au{(µ-NC)MnLx}2]+ in tetrahydrofuran, or chemical oxidation with [N(C6H4Br-p)3]+ or [Fe(η-C5H4COMe)(cp)]+ in CH2Cl2, gave solutions of [Au{(µ-NC)MnLx}2]2+{Lx=trans-(CO)2[P(OEt)3](dppm)}, IR spectroscopic and voltammetric studies on which are compatible with weak interaction between the two manganese centres in the mixed-valence dication.

The synthesis and reactions of A-ring aromatic steroid complexes of manganese tricarbonyl

Abstract Treatment of the A-ring aromatic steroids estrone 3-methyl ether and β-estradiol 3, 17-dimethyl ether with Mn(CO) 5 + BF 4 − in CH 2 Cl 2 yields the corresponding [(steroid)Mn(CO) 3 ]BF 4 salts 1 and 2 as mixtures of α and β isomers. The X-ray structure of [(estrone 3-methyl ether)Mn(CO) 3 ]BF 4 · CH 2 Cl 2 ( 1 ) having the Mn(CO) 3 moiety on the α side of the steroid is reported: space group P 2 1 with a =10.3958(9), b =10.9020(6), c =12.6848(9) A, β=111.857(6)°, Z =2, V =1334.3(2) A 3 , ϱ calc =.481 cm −3 , R =0.0508, and wR =0.0635. The molecule has the traditional ‘piano stool’ structure with a planar arene ring and linear MnCO linkages. The nucleophiles NaBH 4 and LiCH 2 C(O)CMe 3 add to [(β-estradiol 3,17-dimethyl ether)Mn(CO) 3 ]BF 4 ( 2 ) in high yield to give the corresponding α- and β-cyclohexadienyl manganese tricarbonyl complexes ( 3 ). The nucleophiles add meta to the arene -OMe substituent and exo to the metal. The α and β isomers of 3 were separated by fractional crystallization and the X-ray structure of the β isomer with an exo -CH 2 C(O)CMe 3 substituent is reported (complex 4 ): space group P 2 1 2 1 2 1 with a =7.5154(8), b =15.160(2), c =25.230(3) A, Z =4, V =2874.4(5) A 3 , ϱ calc =1.244 g cm −3 , R =0.0529 and wR 2=0.1176. The molecule 4 has a planar set of dienyl carbon atoms with the saturated C(1) carbon being 0.592 A out of the plane away from the metal. The results suggest that the manganese-mediated functionalization of aromatic steroids is a viable synthetic procedure with a range of nucleophiles of varying strengths.

Organometallic crystal engineering of [(1,4- and 1,3-hydroquinone)Rh(P(OPh)3)2]BF4 by charge assisted hydrogen bonding

The ionic complexes [(1,4- and 1,3-hydroquinone)Rh(P(OPh)3)2]BF4 form porous organometallic structures dictated by charge assisted hydrogen bonding.

Regioselectivity in the nucleophilic functionalization of dibenzofuran, dibenzothiophene and xanthene complexes of Mn(CO)3+

The cationic complexes[(η 6 -DBF)Mn(CO) 3 ]BF 4 , [(η 6 -DBT)Mn(CO) 3 ]BF 4 and[(η 6 -XAN)Mn(CO) 3 ]PF 6 (DBF = dibenzofuran, DBT = dibenzothiophene, XAN = xanthene) are prepared. These species react with carbon-based nucleophiles to form exo-substituted cyclohexadienyl complexes. Addition is found exclusively at carbons 1 and 4. The C(1)-functionalized regioisomer predominates, especially for the DBF and XAN complexes, for which 90 to > 95% selectivity is found with stabilized nucleophiles. Preference for C(1) is greatly reduced for unstabilized magnesium and lithium nucleophiles. The origin of this selectivity is discussed. Loss of the aromatic ring from the cationic complexes in the presence of CH 3 CN is found to be extremely facile for the DBF and DBT complexes owing to increased ease of ring slippage. Second-order rate constants for the displacement reactions with CH 3 CN are4.6 ± 0.6 × 10 −5 M −1 ,s −1 (DBF complex, 25°C),4.4 ± 1.0 × 10 −5 ,M −1 ,s −1 (DBT complex, 25°C) and about 1.0 × 10 −5 ,M −1 ,s −1 (XAN complex, 60°C). A crystal structure is presented for the hydride adduct of the DBF complex,[(η 5 -C 12 H 9 O)Mn(CO) 3 ]: space group P 2 1 /c, a = 15.301(2), b = 6.4422(12), c = 12.988(2)A˚, β = 90.888(13)°, V = 1280.1(3)A˚ 3 , Z = 4, D calc = 1.599Mg m −3 , R = 0.0410 and wR 2 = 0.0945 on 2446 reflections with F 2 > 4.0 σ(F 2 ).