Ronald F. See

Structural considerations of terdentate ligands: crystal structures of 2,2′ : 6′,2″-terpyridine and 2,6-bis(pyrazol-1-yl)pyridine

The crystal structures of the terdentate ligands 2,2′ : 6′,2″-terpyridine (terpy) and 2,6-bis(pyrazol-1-yl)pyridine (bppy) were determined by single-crystal diffraction studies. The compound terpy crystallizes in the non-centrosymmetric orthorhombic space group P212121 with a= 3.947(1), b= 16.577(7) and c= 17.840(6)A; the structure was refined to R= 0.0745 for all 1087 independent data and R= 0.0470 for those 609 data with F > 6σ(F). The compound bppy crystallizes in the centrosymmetric orthorhombic space group Pnma with a= 11.929(3), b= 21.320(3) and c= 3.889(0)A; this structure was refined to R= 0.0409 for all 896 independent data and R= 0.0300 for those 723 reflections with F > 6σ(F). The structures of the free terpy and bppy ligands were compared directly with the structures of the co-ordinated terpy and bppy ligands in the [RuL(NO2)(PMe3)2][ClO4] complexes (L = terpy 1 or bppy 2) in order to determine if any ligand structural changes occur upon co-ordination to ruthenium. To act as terdentate ligands, it was observed that both terpy and bppy must adopt the cis,cis ligand configuration as opposed to the trans,trans configuration found in the solid state and as the equilibrium configuration in solution. Both terpy and bppy distort upon co-ordination to ruthenium. The greatest distortions for terpy occur primarily at the central pyridine ring. Large distortions were observed for bppy at both in the central pyridine ring and in the terminal pyrazole rings.

Syntheses and crystal structures of 1,2:5,6:9,10:13,14:17,18:21,22-hexabenzo-3,7,11,15,19,23-hexadehydro[24]annulene (HBC), 1,2:5,6:9,10:13,14-tetrabenzo-3,7,11,15-tetradehydro[16]annulene (QBC) and a tetracobalt complex of QBC. The first example of a transition metal complex of QBC

1,2:5,6:9,10:13,14-Tetrabenzo-3,7,11,15-tetradehydro[16]annulene, or tetrabenzocyclyne (QBC) and 1,2:5,6:9,10:13,14:17,18:21,22-hexabenzo-3,7,11,15,19,23-hexadehydro[24]annulene (HBC) have been structurally characterized by X-ray. crystallography. QBC crystallizes in two different space groups; P21/c with a = 10.652(3) A, b = 10.624(2) A, c = 19.549(4) A, β = 93.83(2)°, V = 2207.4(8) A3, and Z = 4 and P41212 with a = 9.330(1) A, c = 25.497(8) A, V = 2219.6(12) A, and Z = 4. HBC crystallizes in monoclinic P21/n with a = 14.763(3) A, b = 10.296(2) A, c = 22.057(4) A, β = 108.61(3), V = 3177.4(11) A3, T = 133 K, and Z = 4. Reaction of QBC with dicobaltoctacarbonyl has produced a tetracobalt complex which has been characterized by X-ray crystallography. This complex crystallizes in monoclinic P21/c with a = 14.699(3) A, b = 17.188(3) A, c = 17.254(3) A, β = 112.63(3)°, V = 4023.5(13) A3, and Z = 4. Only two of the four CC triple bonds of QBC bind to dicobalthexacarbonyl moieties even when excess dicobaltoctacarbonyl is used.

Reaction of (η1-allenyl)dicarbonyl(η5-cyclopentadienyl)ruthenium with nonacarbonyldiiron: synthesis and characterization of iron-ruthenium mixed-metal products

Reaction of Cp(CO)2RuCHCCH2 with Fe2(CO)9 in hexane at reflux affords four iron-ruthenium products: Cp(CO)2Ru(μ3-η1,η2,η3-C(O)CHCCH2)Fe2(CO)6(3), CO)3Fe(μ2-CO)RuCp(μ2-CO)Fe(CO)3(μ3-η1-CCHCH2) (4), Cp(CO)2Ru(μ4-η1,η3,η3η1-CH2CCHC(CH)CH2)(CO)3FeFe(CO)2(μ2-CO) Ru(CO)Cp (5) and (CO)3FeRu(CO)CpFe(CO)3(μ3-η1,η1,η3-CCHCH2) (6), which were isolated and characterized. Complex 3 reacts with PPh3 to yield the monosubstitution derivative Cp(CO)2Ru(μ3-η1,η3,η3-C(O)-CHCCH2)Fe2(CO)5(PPh3) (10); both 3 and 10 were characterized spectroscopically and are thought to contain a Ru-bonded allenylcarbonyl ligand, which is attached to Fe2(CO)5L (L=CO,PPh3) through the oxygen atom and the two CC double bonds. The trinuclear 4 is structurally analogous to the previously prepared (C.E. Shuchart, A. Wojcicki, M. Calligaris, P. Faleschini and G. Nardin, Organometallics, 13 (1994) 1999), from Cp(CO)2RuCH2CCPh and Fe2(CO)9, (CO)3Fe(μ2-CO)RuCp(μ2-CO)Fe(CO)3(μ3-η1-CCHCHPh) (1) and contains a μ3-η1-CCHCH2 ligand capping an Fe2Ru metal core. In solution, 4 and 1 undergo partial conversion to 6 and (CO)3FeRu(CO)CpFe(CO)3(μ3-η1,η1,η3-CCHCHPh) (2), respectively, in which the CCHCHR (R = H, Ph) ligand bridges the Fe2Ru triangle in a μ3-η1,η1,η3 mode. Complexes 6 and 2 also equilibrate to mixtures of 6 and 4 and of 2 and 1, respectively, upon storage in solution. 1 reacts with 2 equiv. of PEt3 in the presence of Me3NO to afford the disubstituted (CO)(PEt3)2Fe(μ2-CO)RuCp(μ2-CO)Fe(CO)3(μ3-η1-CCHCHPh) (4bd9), in which the bridging CCHCHPh ligand retains its μ3-η1 bonding mode. In contrast, reactions of 1 and 4 with PPh3 yield (CO)2(PPh3)Fe(μ2-CO)RuCp(μ2-CO)Fe(CO)3(μ3-η1,η1,η3-CCHCHPh) (8) and (CO)2(PPh3)Fe(μ2-CO)RuCp(μ2-CO)Fe(CO)3(μ3-η1,η1,η3-CCHCH2) (7), respectively, which contain μ3-η1,η1,η3-CCHCHR (R=H,Ph). The tetranuclear Fe2Ru2 complex 5 results from the coupling of two FeRu allenyl or related species between a terminal and a central carbon atom of their C3 fragments. The structures of 4 and 8 (as 8·0.5CH2Cl2) were determined by X-ray diffraction analysis. 4: monoclinic, P21/n, a = 9.038(1) A, b = 15.062(6) A, c = 13.485(4) A, β = 99.16(1)°, Z = 4, R = 2.8%, Rw = 2.9%; 8·0.5CH2Cl2: monoclinic, C2/c, a = 39.851(9) A, b = 9.319(2) A, c = 21.156(5) A, β = 112.91(2)°, Z = 8, R = 4.02%, Rw = 4.81%.

Crystal structures of trans-[Ru(dppe)2(CO)(Cl)](BF4)·2(toluene) and trans-[Ru(dppm)2(CO)(Cl)](BF4)·CH2Cl2: a study of the steric and electronic ligand effects of trans-positioned diphosphine ligands

Abstract Single-crystal X-ray diffraction studies were carried out on the complexes trans-[Ru(dppe)2(CO)(Cl)](BF4) ·2(toluene) (1) (where dppe = 1,2-bis(diphenylphosphino)ethane) and trans-[Ru(dppm)2(CO)(Cl)](BF4) ·CH2Cl2 (2) (where dppm = bis(diphenylphosphino)methane). Complex 1 crystallizes in the orthorhombic space group P21212 with a = 14.366(3), b = 17.075(3), c = 12.433(2) A , V = 3049.8(10) A 3 and Z = 2 . The structure was refined to R = 3.02% for 3233 reflections above 6σ (R = 4.46% for all 3991 point-group independent data); the Ru-cation lies on a site of C2 symmetry, leading to disorder of the Cl and CO ligands. Complex 2 crystallizes in the orthorhombic space group Pna2 1 , with a = 22.425(7), b = 11.515(4), c = 19.511(10) A , V = 5038(3) A 3 and Z = 4 . The structure was refined to R = 4.43% for 4770 reflections above 6σ (R = 7.09% for all 6631 point-group independent data). The crystal structure data suggest increased intramolecular interligand interactions with the trans-bis(dppe) complexes relative to the trans-bis(dppm) complexes. In order to furth assess the steric ligand effects of dppm and dppe on the redox chemistry of ruthenium complexes, the electrochemical data for complexes 1 and 2 as well as for trans-Ru(dppe)2(Cl)2 and trans-Ru(dppm)2(Cl)2 were analyzed. The Epa value for the oxidation of complex 1 was more positive than the Epa value for the oxidation of complex 2; similarly, the E 1 2 value for the oxidation of trans-Ru(dppe)2(Cl)2 was more positive than the E 1 2 value for the oxidation of trans-Ru(dppm)2(Cl)2. The increase in the redox potentials for the oxidation of the dope complexes may be due to the enhanced intramolecular interligand interactions of the dppe ligands, which is in agreement with the crystal structure data.

Synthesis, characterization and crystal structure of trans-[2,6-bis(3-phenylpyrazol-1-yl-κN2)pyridine-κN]chloro-bis(trimethylphosphine)ruthenium(II) perchlorate: evidence for meridional steric crowding

The synthesis, characterization, and crystal structure of trans-[RuL(Cl)(PMe3)2]ClO4[L = 2,6-bis(3-phenylpyrazol-1-yl)pyridine] are reported. The complex crystallizes in the non-centrosymmetric trigonal space group P3121 (no. 152) with a= 14.158(2), c= 14.493(3)A, and Z= 3. Both the RuII-containing cation and the perchlorate anion (which is disordered) lie on a crystallographic two-fold axis. This represents the first structural characterization of a transition-metal complex which utilizes a member of the family of bis(pyrazolyl)pyridine ligands. In addition, the crystal structure yields evidence that the ligand L may be sterically more suitable for co-ordination to a ruthenium(II) centre than the analogous diphenyl-substituted terpyridine ligand, dpt (6,6″-diphenyl-2,2′ : 6′2″-terpyridine). For both tridentate ligands, the donor nitrogen atoms take up three meridional sites and the phenyl substituents are directed toward the fourth equatorial co-ordination site; however, due to the large distance between the two phenyl arms of L (relative to the dpt), the former ligand can be utilized in synthesising the present ruthenium(II) complex whereas the analogous dpt complex cannot readily be prepared.

Crystal structure of Fe(η6-C5H5BCMe3)2 a “problem structure”

The complex Fe(η6-C5H5CMe3)2 crystallizes in the centrosymmetric triclinic space group P1(Ci1; No. 2) with unit cell dimensions of a 8.770(1) A, b 8.878(1) A, c 11.991(1) A, α 107.56(1)°, β 90.85(1)°, γ 90.13(1)°, V 890.0(2) A3 and Z = 2. A full sphere of data was collected on a four-circle diffractometer. The structure was solved and refined to R 7.93% for all 3155 independent reflections and R 4.98% for those 2002 data with | F0 | > 6σ. | F0 |. The molecules lie on crystallographic inversion centers at 0, 0, 0 and 1/2, 0, 1/2; the crystallographic asymmetric unit therefore consists of two independent half molecules. The molecule centered at 0, 0, 0 (molecule “A”) is ordered and well-defined; that centered on 1/2, 0, 1/2 (molecule “B”)is probably disordered, as indicated by larger “thermal parameters” and a greater range of apparent interatomic distances. Discussion em phasizes the geometry of molecule A, which has precise Ci symmetry with Fe(1A)-B(1A) 2.297(4) A and Fe(1A)-C(ring) distances ranging from 2.057(6) A to 2.138(4) A.

Structure of (η5-C5H5) 2Ru2Fe2(CO) 8(μ2-CO)(μ4-η6-C6H6): an unusual mixed-metal compound containing a bridging diallyl ligand derived by unsymmetrical coupling of two allenyl groups☆

The heteronuclear compound (η5-C5H5)2Ru2Fe2(CO)8(μ2-CO)(μ4-η6-C6H6) (1), obtained by reaction of (η5-C5H5)(CO)2RuCH=C=CH2 with Fe2(CO)9, displays unusually complex 1H and 13C NMR spectra. All nine CO ligands, as well as all six carbon and hydrogen atoms of C6H6, afford separate resonance signals. The structure of 1 was determined by X-ray diffraction techniques. The complex crystallizes from hexane (as a 3:1 cluster: solvate complex) in the centrosymmetric triclinic space group P1 with a = 7.852(1) A, b = 23.487(5) A, c = 24.144(4) A, α = 74.47(2)°, β = 84.79(1)°, γ=86.69(1)°, V=4269.8(14)A3. The unit cell contains six polynuclear Ru2Fe2-containing molecules and two molecules of hexane. X-ray diffraction data (Mo K α, 2σ = 7.0–40.0°) were collected with a Siemens R3m/V diffractometer and the structure was refined to R = 6.56% for all 7987 independent reflections (R = 2.90% for those 4844 reflections with ¦o¦ > 6σ (¦o¦)). The organometallic molecule is based upon an unusual ∗CH-C(CH2)-CH-C∗-CH2 fragment which is derived from a β-γ coupling of two allenyl moieties and which forms π-allyl linkages to the two iron atoms and σ-bonds (via the starred carbon atoms) to (η5-C5H5)Ru moieties. The metal atoms are arranged as a linear Ru(1)-Fe(2)-Fe(3) system and a lone Ru(4) atom. Dimensions in the three independent molecules are internally consistent, with carbonyl-bridged Ru(1)-Fe(2) distances of 2.687(1), 2.679(1) and 2.687(1) A and Fe(2)-Fe(3) distances of 2.895(2), 2.871(2) and 2.906(2) A.

Synthesis and characterization of ruthenium complexes which utilize a new family of terdentate ligands based upon 2,6-bis(pyrazol-1-yl)pyridine

To demonstrate the synthetic utility of a new family of terdentate ligands based on 2,6-bis(pyrazol-1-yl)pyridine (bpp), reaction conditions were developed to generate a variety of [RuL(NO2)(PMe3)2]+ complexes [L = bpp, 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine(bdmpp), 2,6-bis(3-phenylpyrazol-1-yl)pyridine (bppp) or 2,6-bis(3-p-chlorophenylpyrazol-1-yl)pyridine (bcppp)]. These complexes were characterized by elemental analysis, 1H and 13C NMR, infrared and UV/VIS spectroscopies, cyclic voltammetry, and single-crystal X-ray diffraction studies. The substituents of the terdentate bpp ligands sterically affected the Ru–N(pyrazole) bond lengths, the displacement of the nitrogen atoms of the nitro ligands from the RuL plane, and the twisting of the N–O vectors of the nitro ligand from that plane. Also the substituents affected the potentials and peak-current ratios of the RuIII–RuII couples. The log (ipc/ipa) values (ipc= cathodic peak current, ipa= anodic peak current) are linearly correlated with the steric size of the substituents as estimated by Tolmans cone angles and with the distance of the nitro ligand out of the RuL plane. A linear correlation was also found between the differences in infrared absorbances due to the N–O symmetric and asymmetric stretches and the ratio of the N–O bond distances observed from the four crystal structures.