Chelating Fashion Research Articles

NMR spectral studies of [Me2Sn{XYP(OBun)2}2] (X, Y = O or S)

Abstract The diorganotin compounds, [Me2Sn{OOP(OBun)2}2] (II), [Me2Sn{OSP(OBun)2}2] (III) and [Me2Sn{SSP(OBun)2}2] (IV), have been investigated by 13C, 31P and 119Sn solution state NMR as well as solid state NMR. On the basis of these studies it is suggested that the phosphate ligand acts in a symmetrical chelating fashion in II, while the ligands behave in an anisobidentate manner in III and IV.

Reactions of [RuCl2(PPh3)4] with mixed anhydrides of diphenylphosphinous and acrylic acids; structure of [RuCl{(Ph2PO)2H}(PPh3)(O2CCH2CH2PPh3)]·C4H8O

Reactions of [RuCl2(PPh3)4] with 1 mol equivalent of Ph2PO2CCHCR′R″ produce [RuCl2(PPh3)2(Ph2PO2CCHCR′R″)](R′, R″= H or Me), although for R′= H, R″= H or Me the major product is [RuCl{(Ph2PO)2H}(PPh3)(O2CCH2CHR″PPh3)], which for R″= H has been crystallographically characterized. Using 2 mol equivalents of Ph2PO2CCRCR′R″ the products are [RuCl2(Ph2PO2CCRCR′R″)2](R = H, R′= R″= Me; R = Me, R′= H, R″= Ph) or [RuCl2(PPh3)(Ph2PO2CCHCH2)(Ph2POPPh2)]. The complexes have all been characterized spectroscopically and the mixed anhydride ligands are generally co-ordinated through P and O, apparently for steric reasons. Binding through P and the CC appears to occur in [RuCl2(PPh3)2(Ph2POCH2CHCMe2)], prepared from [RuCl2(PPh3)4] and Ph2POCH2CHCMe2, whilst unidentate binding via the P atom is observed for the mixed anhydride in [RuCl2(PPh3)(Ph2PO2CCHCH2)(Ph2POPPh2)]. Crystal data for [RuCl{(Ph2PO)2H}(PPh3)(O2CCH2CH2PPh3)]: orthorhombic, space group P212121, with a= 15.16(3), b= 23.05(3), c= 17.08(4)A and Z= 4. The structure was obtained from 6558 reflections measured on an automatic diffractometer and refined to an R value of 0.076. The main features of the structure include the zwitterionic triphenylphosphoniopropionate betaine ligand binding via the carboxylate in a chelating fashion and the planar RuPOHPO ring of the bis(diphenylphosphinito)hydrogenate ligand. The O ⋯ O distance in this ligand is 2.382(12)A indicative of strong hydrogen bonding.

The coordination of mono- and diphosphines to the surface of cadmium selenide

Band edge photoluminescence (PL) of single-crystal n-CdSe provides evidence for adduct formation between the solid's surface and various mono- and diphosphines present in toluene solution. Relative to a toluene ambient, solutions of triphenylphosphine (PPh 3), ethyldiphenylphosphine (PEtPh 2), bis(diphenylphosphino)methane (dppm) and bis(diphenylphosphino)ethane (dppe) in toluene enhance the semiconductor's PL intensity. For all of the phosphines, the increases in PL intensity can be fit to a dead-layer model, allowing the estimation of the reduction in depletion width resulting from phosphine exposure; reductions in dead-layer widths are about 300–400 Å for all phosphines except PEtPh 2, which yields a reduction roughly twice as large. Fits of the PL changes to the Langmuir adsorption isotherm model yield formation constants for the phosphine/CdSe adducts of 30±7 M −1 for PPh 3 and 220± 30 M −1 for PEtPh 2; the diphosphines, which do not fit this simple model as well, give adsorption equilibrium constants of ∼ 100–200 M −1. The results suggest that the diphosphines do not coordinate to the surface in a chelating fashion, but in some combination of bridging and monodentate bonding modes at lower effective surface coverages than the monophosphines.

Reaction of bis(dimethylphosphino)ethane with the tetracobalt cluster Co 4(CO) 10(μ 4-PPh) 2; synthesis, structure, and solution dynamics of Co 4(CO) 8(μ 4-PPh) 2(dmpe)

The reaction of the tetracobalt cluster Co 4(CO) 10(μ 4-PPh) 2 ( 1) with the bidentate ligand 1,2-bis(dimethylphosphino)ethane (dmpe) gives the disubstituted cluster Co 4(CO) 8(μ 4-PPh) 2(dmpe) ( 3) in high yield. The dmpe ligand is bound to a single cobalt atom in a chelating fashion as determined by FTIR and NMR ( 31P and 13C) spectroscopy and singlecrystal X-ray crystallography. Co 4(CO) 8(μ 4-PPh) 2(dmpe) · 1 2 toluene crystallizes in the triclinic space group P 1 with a 11.673(1), b 15.986(5), c 20.276(7) Å, α 94.40(3), β 106.28(2), γ 94.89(2)°, V 3599(2) Å 3 and Z  4. Blockcascade least squares refinement yielded R  0.0521 for 6830 reflections. The temperaturedependent 13C NMR spectra of 3 reveal two distinct fluxional processes which serve to equilibrate the carbonyl ligands about the cluster polyhedron. The stability of 3 under different conditions has been examined by Cylindrical Internal Reflectance (CIR) spectroscopy. In benzene solution 3 is stable under 250 psi of H 2 at 150°C; partial decomposition to Co(CO) − 4 is observed using CO and H 2/CO under analogous conditions.

The crystal structures and absolute configurations of the anti-tumor complexes Pt(oxalato)(1R,2R-cyclohexanediamine) and Pt(malonato)(1R,2R-cyclohexanediamine)

The absolute configurations of the anti-tumor complexes [Pt(oxalato)(trans-l-dach)] and [Pt(malonato) (trans-l-dach)] (trans-l-dach = 1R,2R-cyclohexanediamine) have been determined by X-ray anomalous scattering techniques. These complexes are particularly interesting because they show higher anti-tumor activity than the corresponding Pt complexes with other 1,2-cyclohexanediamine(dach) ligands, namely those with trans-d-dach (1S,2S-dach) or cis-dach (1R,2S-dach). The oxalato and malonato ligands are found to bind to the Pt atom in a chelating fashion, through one oxygen atom from each of the two carboxylate groups. Crystallographic details: Pt(oxalato)(trans-l-dach): space group P2 1 (monoclinic); a = 11.230(11) Å, b = 9.914(5) Å, c = 4.716(3) Å, β = 90.86(6)°; R = 4.0% for 1256 reflections. Pt(malonato)(trans-l-dach): space group P2 1 (monoclinic); a = 11.568(5) Å, b = 10.007(5) Å, c = 5.187(3) Å, β = 99.16(4)°; R = 4.8% for 1675 reflections.

ChemInform Abstract: Deoxygenation Reaction of 2-Nitrophenol. Synthesis and X-Ray Crystal Structure of [Ru(OC6H4NO-o)(OC6H4NO2-o)(CO(PPh3)2

By reaction of [Ru(CO)3(PPh3)2] with 2-nitrophenol, the deep brown ruthenium(II) complex, [[graphic omitted]O-o)(OC6H4NO2-o)(CO)(PPh3)2], has been obtained. X-Ray crystallography has shown that the complex contains a o-nitrosophenolate ligand, which co-ordinates to ruthenium in a chelating fashion through its nitroso-nitrogen and phenolic oxygen atoms.

Deoxygenation reaction of 2-nitrophenol. Synthesis and X-ray crystal structure of [Ru(OC6H4NO-o)((OC6H4NO2-o)(CO)(PPh3)2

By reaction of [Ru(CO)3(PPh3)2] with 2-nitrophenol, the deep brown ruthenium(II) complex, [[graphic omitted]O-o)(OC6H4NO2-o)(CO)(PPh3)2], has been obtained. X-Ray crystallography has shown that the complex contains a o-nitrosophenolate ligand, which co-ordinates to ruthenium in a chelating fashion through its nitroso-nitrogen and phenolic oxygen atoms.

Molecular configuration of (Me)2N4Fe(CO)3, a tetrazadiene–tricarbonyliron complex

View Article Online / Journal Homepage / Table of Contents for this issue Published on 01 January 1968. Downloaded by University of California - Irvine on 13/08/2015 00:21:38. CHEMICAL COMIkUIUNICATIONS, Molecular Configuration of (Me),N,Fe(CO),, a Tetrazadiene- Tricarbonyliron Complex By ROBERT J. DOEDENS (Department of Chewistry, Universitv of California, Irvine, Cali foruia 92664) THE iiiost unusual product of the reaction of methyl azide with enneaca rbonyldi-iron1 is a \volatile stable orange-red solid, hle,N,Fe(CO) 3 . On the basis of i.r., n.m.r., and mass spectral data, ;L molecular structure ( I ) analogous to that of butadienetricarbonyliron was suggested by Dekker a n d Iinos for this compound. A single-crystal S-ray structural analysis has now shown that the hIe,K;, ligand is bound in a chelating fashion, resulting in a nearly planar Fe-N, ring. This is the first example of a nietal complex of a tetrazadieiie. RS,R. Crystals of 31e,X4Fe(C0) (supplied by Dr. G. R. Iinox) are orthorhombic, 2 = S, a = 22.00, / J = 12.20, and c = 6.64 The systematic absences, I/ = 212 for h0Z reflections and k # 2n for hhO reflections, are consistent with space groups P2,ah (no.29) and Pwnb (110.57). L4 three- tlimensioiial Patterson map could only be inter- preted in terms of the former, noncentrosyni- metric space-group and thus the asymmetric unit contains two crystallographically independent iiiolecules. Intensity data for reciprocal lattice levels hk0-5 were collected by the multiple-film equi-inclination Weissenberg technique. The structure was solved by Patterson and Fourier methods, and an isotropic full-matrix least- squares refinement led t o a final R of 6.2% for the 336 independent non-zero reflections. Owing to the low value of the d a t a : parameter ratio and the niarginal quality of the crystals, this structure is one of relatively low precision, with a standard deviation of 0.07 -4 €or bond lengths between light atoms. Hence, only average bond lengths of a givcn type will be discussed. a. be (CO), (Ib) The monomeric Me,N,Fe(CO) molecule (see Figure) consists of an Fe(C0) group co-ordinated via a 1,4-1inkage t o the 1,4-dimethyltetrazadiene moiety, a species not known to exist as a free compound. Representations (Ia) and (Ib) for the bonding of this complex are inconsistent with the near-planarity of the five-membered ring apd the fact that N(2) and N(3) are more than 2.6 A away from the iron atom. If the N-Fe bonds are regarded as two-electron dative bonds, the iron atom attains its preferred 36-electron closed-shell configuration. It is reasonable that back-donation from the iron d, orbitals to the n-antibonding orbitals of the tetrazadiene ligand could then serve t o relieve the metal atom of an excess of negative charge. This model u-ould imply a Fe-N bond order greater than one, which is consistent with the mean observed Fe-X bond length of 1.83 & 0-03 -4. In a variety of related compounds,2 the lengths of unequivocal Fe-N single bonds range from 1-95 t o 2-02 A. The observed mean Fe-S FIGURE. The moleculav configwntioti of Me,X,Fe(CO) distance is thus closer to the length of a typical Fe-CO bond, in which the presence of multiple- bond character is generally accepted, than t o that of an Fe-N single bond. The X-N bonds average 1.32 & 0.03 A in length, again a value indicative of the expected multiple-bond character in these bonds. The mean Fe-C, C-0, and C-Tu' distances are 1.76 i. 0.03, 1-18 03, and 1-53 f 0.03 A, respectively ; all unremarkable values. None of the angles about the iron atom is within 20 of being linear, and the co-ordination seems best described as distorted square pyramidal.