On the Structure and Role of Avian Eggshells: A 31P, 1H, and 13C Solid-State NMR Study.

The eggshell is a composite and highly ordered structure formed by biomineralization. Besides other functions, it has a vital and intricate role in the protection of an embryo from various potentially harsh environmental conditions. Solid-state nuclear magnetic resonance (SSNMR) has been used for detailed structural investigations of the chicken, tinamou, and flamingo eggshell materials. 31P NMR spectra reveal that hydroxyapatite and ß-tricalcium phosphate in the ratio 3:2 represent major constituents of phosphate species in the eggshells. All three eggshells exhibit similar spectra, except for the line widths, which implies different structural order of phosphate species in the chicken, tinamou, and flamingo eggshells. 1H NMR spectra for these materials are comparable, differentiating overlapped peaks in three spectral regions at around 7, 4-5, and 1-2 ppm. These spectral regions have been attributed to protons from NH or CaHCO3, water, and possibly isolated monomeric water molecules or hydroxyl groups in calcium-deficient hydroxyapatite. 1H-13C CP MAS NMR revealed the presence of organic matter in the form of lipids and proteins. Two overlapped resonances in the carbonyl region at around 173 and 169 ppm are assigned to the carbonyls of the peptide bonds and the bicarbonate unit in calcite, respectively. Fourier-transform infrared spectroscopy (FTIR) spectra confirmed the presence of structural units detected in the NMR spectra.

Solvent-assisted solid-state synthesis: separating the chemical from the mechanical in mechanochemical synthesis.

High-yielding syntheses involving reactions in the diffusion zone between solid reactants are demonstrated in studies of complex formation between copper(i) thiocyanate and ethylenethiourea.

Structural and infrared spectroscopic studies of some novel mechanochemically accessed adducts of silver(I) oxoanion salts with thiourea.

An investigation of the silver(I) nitrate/thiourea ("tu") system, exploiting the uniquely powerful access provided by the recently developed combination of mechanochemical synthesis coupled with vibrational spectroscopy, has resulted in the identification of solid adducts AgNO3/tu (x:y) for x:y = 1:1, 1:1.5, 15:23 (= 1:1.5333), and 1:3. This contrasts with previously published claims for the existence of 1:2 and 1:4 complexes and was confirmed in the case of the 1:3 and 15:23 complexes by X-ray crystal structure determinations on samples prepared by crystallization from aqueous solution. The 1:3 sulfate and perchlorate complexes were also prepared for comparison with the corresponding nitrate compound. In the 1:3 nitrate complex, the one independent silver atom major component (0.78(1)) is closely trigonal planar AgS3 (Ag-S 2.518(2)-2.592(1) A, Sigma(S-Ag-S) 359.7(0) degrees); there are minor nearby components (0.11(1)) which may be regarded as four-coordinate, forming a putative one-dimensional polymer. The sulfate, obtained as its tetrahydrate, has a cation of the familiar binuclear form [{(tu)2Ag(mu-S-tu)}2](SO4) x 4 H2O, while the perchlorate, previously also characterized with the binuclear cation in the anhydrate, has now been isolated as the hemihydrate, having a single-stranded polymeric cation, [...Ag(tu)2(mu-S-tu)...](infinity|infinity)(ClO4) x 0.5 H2O, similar to that observed in CuX/tu (1:3) (X = Cl, Br, I). The remarkable 15:23 nitrate complex (shown to be distinct from the 1:1.5 complex) may be regarded as essentially ionic [Ag15(tu)23(ONO2)](infinity|infinity)(14+)(NO3(-)-)14 (the cation incorporating one O-nitrate ion loosely associated) and comprising one-dimensional polymer strands made up of four-, six-, and eight-membered Ag(2n)S(2n) rings, cross-linked by the sulfur of one of the tu ligands. The nu(CS) and nu(alpha)(CN) bands in the infrared spectra of the complete series of adducts show a monotonic wavenumber decrease and increase, respectively, with decreasing tu content of the adduct, indicating a decrease in the C-S bond strength and a concomitant increase in the C-N bond strength with increasing Ag-S bond strength. The increase in Ag-S bond strength with decreasing tu content is also indicated by an increase in the wavenumbers of the bands assigned to nu(AgS) in the 140-200 cm(-1) region in the far-IR. These and the structural data for the 1:3 and 15:23 complexes provide the basis for establishing a correlation between nu(AgS) and the Ag-S bond length d(AgS) for silver complexes involving the tu ligand.

Crystal structures and vibrational spectroscopy of copper(I) thiourea complexes.

Several synthetic strategies using copper(I) starting materials or copper(II) compounds and an in situ sulfite reductant have been used to systematically explore the chemistry of copper(I) complexes with thiourea and substituted thiourea ligands. This has resulted in the discovery of several new complexes and methods for the bulk synthesis of some previously reported complexes that had been prepared adventitiously in small quantity. The new complexes are (tu = thiourea, dmtu = N,N'-dimethylthiourea, etu = ethylenethiourea): [I(4)Cu(4)(tu)(6)].H(2)O, [Cu(4)(tu)(10)](NO(3)).tu.3H(2)O, [BrCu(dmtu)(3)], [ICu(dmtu)(3)](2), [BrCu(etu)(2)](2), [ICu(etu)(2)], [ICu(etu)(2)](3). [I(4)Cu(4)(tu)(6)].H(2)O has an adamantanoid structure, with four terminal iodide ligands and six doubly bridging tu ligands. In contrast to this, [Cu(4)(tu)(10)](NO(3)).tu.3H(2)O contains a tetranuclear cluster in which four of the tu ligands are terminal and the other six are doubly bridging. [BrCu(dmtu)(3)] is a mononuclear complex with tetrahedral coordination of copper by one bromide and three dmtu ligands, whereas [Cu(dmtu)(3)](2)I(2) has a centrosymmetric dimeric cation with two uncoordinated iodides, four terminal dmtu and two doubly bridging dmtu ligands, [(dmtu)(2)Cu(mu-S-dmtu)(2)Cu(dmtu)(2)]I(2). A reversal of this monomer to dimer trend from bromide to iodide is seen for the etu counterparts: [BrCu(etu)(2)](2) is a centrosymmetric dimer with two doubly bridging etu ligands, [(etu)BrCu(mu-S-etu)(2)CuBr(etu)], whereas [ICu(etu)(2)] is a trigonal planar monomer, although the novel [I(3)Cu(3)(etu)(6)] is also defined. Infrared and Raman spectra of the synthesized complexes were recorded and the metal-ligand vibrational frequencies have been assigned in many cases. The results confirm previously observed correlations between the vibrational frequencies and the corresponding bond lengths for complexes of the unsubstituted tu ligand. A mechanochemical/infrared method was used to synthesize [I(3)Cu(3)(etu)(6)] from CuI and etu, and to demonstrate the polymorphic transition from [ICu(etu)(2)] to [I(3)Cu(3)(etu)(6)].

Correction: Unexpected arene ligand exchange results in the oxidation of an organoruthenium anticancer agent: the first X-ray structure of a protein-Ru(carbene) adduct.

Correction for 'Unexpected arene ligand exchange results in the oxidation of an organoruthenium anticancer agent: the first X-ray structure of a protein-Ru(carbene) adduct' by Matthew P. Sullivan et al., Chem. Commun., 2018, 54, 6120-6123.

Unexpected arene ligand exchange results in the oxidation of an organoruthenium anticancer agent: the first X-ray structure of a protein-Ru(carbene) adduct.

The first X-ray structures of adducts formed between a RuII(N-heterocyclic carbene)(η6-p-cymene) compound and a protein are reported. Coordination to the protein induced the cleavage of the cymene ligand and EPR spectroscopy demonstrated the oxidation of the Ru centre.

Electrochemical detection of DNA hybridization amplified by nanoparticles.

Detection of specific oligonucleotide (ODN) fragments has become an important field in many areas of biomedicine. We describe a novel ODN sensor based on electropolymerization of a conducting polymer (polypyrrole) in the presence of a sample containing ODN(s). The resulting trapped ODN(s) are then probed by addition of complimentary sequence ODN. By incorporating CdS nanoparticles with the probe, a significant improvement in sensor sensitivity was observed. Impedance spectroscopy suggested that optimal detection of hybridization occurred at frequencies>or=3000 Hz (for a 0.07 cm2 85 nm thick film). At these frequencies, the impedance signal was almost linear with the logarithm of ODN concentration in the range 3.7-370 nM with a detection limit of approximately 1 nM ODN (for the sensor fabricated). Importantly, the sensor could be regenerated by removing hybridized ODN with NaOH suggesting possibility of the sensor re-use.

Fast proton spin-lattice relaxation time in the rotating frame during the application of time averaged precession frequency.

A relatively rapid phase alternation of the effective field in the time averaged precession frequency (TAPF) sequence results in averaging of the proton RF spin-lock field. The spin-locking of the proton magnetization becomes less efficient and thus shortens T(1rho)(H), the proton spin-lattice relaxation time in the rotating frame. The relaxation time also depends on the ratio of tau(1) and tau(2) intervals i.e. tau(1)/tau(2) and not only on the number of tau(c)=tau(1)+tau(2) blocks, i.e. the number of the phase transients. Experiments are performed on solid samples of ferrocene and glycine and for some time intervals, T(1rho)(H) is shortened by factors of 9-100 compared to the relaxation times obtained in the standard experiment.

Label-free electrochemical DNA sensor based on functionalised conducting copolymer.

A simple and label-free electrochemical sensor for recognition of the DNA hybridization event was prepared based on a new functionalised conducting copolymer, poly[pyrrole-co-4-(3-pyrrolyl) butanoic acid]. This precursor copolymer can be easily electrodeposited on the electrode surface and shows high electroactivity in an aqueous medium. An amino-substituted oligonucleotide (ODN) probe was covalently grafted onto the surface of the copolymer in a one step procedure and tested on hybridization with complementary ODN segments. The cyclic voltammogram of ODN probe-modified copolymer showed very little change when incubated in presence of non-complementary ODN, while a significant, and reproducible, modification of the voltammogram was observed after addition of complementary ODN. The AC impedance spectrum showed an increased charge transfer resistance (Rct) and double layer capacitance of the sensor film after hybridisation. Sensors with thinner films showed higher sensitivity than thicker films, suggesting that hybridisation at or near the surface of the film produces a larger change in electrical properties than that within the body of the film.

Transient oscillations under strongly mismatched Hartmann-Hahn conditions.

Based on the standard 2D Polarization inversion experiment, a new pulse sequence (PI-TAPF) is proposed. It represents a combination of Polarization Inversion and TAPF (time averaged precession frequency) sequences. The depolarization period consists of phase-alternating intervals of different duration in the I channel. The pulse sequence yields transient oscillations under the strongly mismatched HH conditions where the required power for the dilute spins is reduced by a factor of 5. Experimental results recorded for a sample of ferrocene powder are well reproduced by numerical simulations.

Crystal Structures of AuCN and AgCN and Vibrational Spectroscopic Studies of AuCN, AgCN, and CuCN.

The crystal structures of AuCN and AgCN have been determined by powder neutron diffraction measurements. The structure of AuCN consists of rows of linear AuCN chains parallel to [001] with alternating long Au-C = 2.06(2) and short Au-N = 1.82(2) Å. The Au atoms form sheets and are bonded to 6 other Au atoms at a distance of 3.396(2) Å, so that the local environment of each Au atom can be described as a compressed scalehedron. The Au- - -Au distance is within the range expected for an "aurophilic attraction" between these atoms. The AgCN structure is very similar to that for AuCN, in that it consists of rows of AgCN chains with alternating long Ag-C = 2.15(6) and short Ag-N = 1.86(8) Å. The major difference is that the Ag- - -Ag separation within the Ag sheets is noticeably longer, 3.881(5) Å, so that there are no significant Ag- - -Ag interactions. The IR spectra of MCN show nu(CN) at 2170, 2164, 2236; nu(MC,MN) at 591, 480, 598; delta(MCN) at 326, 272, 358; and delta(NMC) = 168, 112, 224 cm(-)(1) for M = Cu, Ag, and Au, respectively. This pattern of band positions strongly suggests that CuCN has the same infinite linear chain structure as AgCN and AuCN. Anomalies in the previously reported IR spectrum of CuCN are shown to be due to the formation of an unusual CuCN/KBr/H(2)O product in KBr disks, which is possibly an intercalation compound involving incorporation of KBr and H(2)O between the chains in the CuCN structure.

Solid-State (199)Hg MAS NMR and Vibrational Spectroscopic Studies of Dimercury(I) Compounds.

The solid-state (199)Hg MAS NMR spectra of Hg(2)X(2) (X = Cl, SCN, NCO, CH(3)CO(2), CF(3)CO(2)) have been measured, and the infrared and Raman spectra of these compounds have been recorded and analyzed to further characterize them and to assist in the interpretation of the NMR data. Spinning-sideband analysis has been used to determine the (199)Hg shielding anisotropy and asymmetry parameters Deltasigma and eta from the solid-state (199)Hg MAS NMR spectra. In contrast to the case of the corresponding mercury(II) compounds, the shielding anisotropy is found to be relatively insensitive to the nature of the X group. This is consistent with the view that the electronic environment of the Hg atom in the mercury(I) compounds is dominated by the Hg-Hg bond. The changes in the (199)Hg shielding parameters from the mercury(II) to the corresponding mercury(I) compounds, as well as the changes in these parameters in the mercury(I) compounds with changes in X, can be interpreted in terms of variations in the local paramagnetic contribution to the shielding tensor.

A Density Functional Study of Metal-Ligand Bonding in [(PR(3))(2)M](+) and [PR(3)MCl] (M = Ag, Au; R = H, Me) Complexes.

Relativistic and nonrelativistic electronic structure calculations were carried out on [(PR(3))(2)M](+)and [PR(3)MCl] (M = Ag, Au; R = H, Me) complexes using the all-electron linear combination of Gaussian-type orbitals density functional (LCGTO-DF) method. The calculated relativistic metal-ligand bond lengths show good agreement with experimental values. The relativistic contraction of the M-P bonds in [(PR(3))(2)M](+) is about 8 and 22 pm for M = Ag and Au, respectively, resulting in Au-P bonds that are about 10 pm shorter than the Ag-P bonds in these species, in good agreement with recent crystallographic results for the cations [(PMes(3))(2)M](+) (M = Ag, Au). The relativistic contraction of the Au-Cl bond in [PR(3)AuCl] is significantly less than that of the Au-P bond, and this explains the experimentally observed differential Au-X and Au-P bond length contractions from [PR(3)AgX] to [PR(3)AuX]. The calculated relativistic bond lengths for corresponding PH(3) and PMe(3) complexes are very similar, confirming a previous conclusion that PH(3) is a good model for structural properties of larger tertiary phosphine ligands. However, the bond lengths for the PMe(3) complexes are all slightly longer than those for the corresponding PH(3) complexes, whereas the M-P dissociation energies are 20-40% higher for the PMe(3) complexes. These findings provide computational support for the concept of "longer but stronger bonds", which was recently proposed on the basis of experimental studies of transition metal complexes involving various substituted phosphine ligands.

Electrospray Mass Spectrometry of Thiophenolate-Capped Clusters of CdS, CdSe, and ZnS and of Cadmium and Zinc Thiophenolate Complexes: Observation of Fragmentation and Metal, Chalcogenide, and Ligand Exchange Processes.

Electrospray mass spectrometry provides a rapid, convenient technique for characterizing and studying the chemistry of anionic metal sulfide thiolate clusters. Negative-ion electrospray mass spectra have been recorded for the thiophenolate-capped clusters [Me(4)N](4)[E(4)Cd(10)(SPh)(16)] (E = S, Se), [Me(4)N](4)[S(4)Zn(10)(SPh)(16)], and [Me(4)N](2)[S(4)Cd(17)(SPh)(28)] and of the metal thiophenolate complexes [Me(4)N](2)[M(SPh)(4)], [Me(4)N](2)[M(4)(SPh)(10)] (M = Cd, Zn), and [Et(4)N](2)[Cd(4)X(4)(SPh)(6)] (X= Cl, Br, I). The exchanges of M, E, and X which occur in various mixtures of these clusters and complexes and the fragmentation processes have been investigated. In the clusters the M-E bonds involving the sulfide or selenide core remain intact during the observed fragmentation at low cone voltages. At high cone voltages, monoions are ultimately formed by loss of charged species and neutral M(SPh)(2), resulting in almost complete removal of the SPh(-) ligands from the cluster core. Fragmentation of the ME core unit itself occurs only at very high voltages. The exchange of X in [Et(4)N](2)[Cd(4)X(4)(SPh)(6)] (X = Br, I) gives peaks due to the ions [Cd(4)I(n)()Br(m)()(SPh)(10)(-)(()(n)()(+)(m)()())](2)(-) (n + m = 0-4) and fragment ions with mixed ligands. The nature of the detected species suggests that the halides only exist as terminal ligands. The exchange of M in [Me(4)N](2)[M(4)(SPh)(10)] and [Me(4)N](4)[S(4)M(10)(SPh)(16)] results in the mixed-metal complexes [Cd(4)(-)(n)()Zn(n)()(SPh)(10)](2)(-) (n = 0-4) and the mixed-metal clusters [S(4)Cd(10)(-)(n)()Zn(n)()(SPh)(16)](4)(-) (n = 0-10). The exchange follows random statistics in [M(4)(SPh)(10)](2)(-) but is biased toward equilibrium association of the same metal in [S(4)M(10)(SPh)(16)](4)(-). The rates of exchange within the different structural elements of [S(4)M(10)(SPh)(16)](4)(-) and [S(4)M(17)(SPh)(28)](2)(-) decrease for the atoms located toward the center of the clusters.

Vibrational Spectra and Molecular Association of Titanium Tetraisopropoxide.

The Fourier transform-infrared (FT-IR) and polarized FT-Raman spectra of titanium tetraisopropoxide (tetraisopropoxytitanium, TPT), in pure and diluted forms, and of 2-propanol have been investigated in conjunction with previous assignments for related compounds to obtain a comprehensive assignment of the vibrational spectra. Evidence was obtained for the presence of both monomeric and associated species of TPT. The latter are formed by coordination expansion through bridging isopropoxy ligands. For both monomeric and associated TPT species, vibrational modes of isopropoxy ligands with nu(C-O) mode character were coupled to nu(s)(Ti-O) and nu(as)(Ti-O) modes (interligand coupling). The symmetrically coupled ligand modes gave rise to intense, strongly polarized bands in the Raman spectrum. The antisymmetrically coupled ligand modes gave rise to strong bands in the IR spectrum at lower wavenumbers than the corresponding Raman bands. Molecular association of TPT produced negligible shifts in the ligand modes coupled to the nu(s)(Ti-O) mode in the Raman spectrum. In contrast, the degeneracy of the strong ligand modes coupled to the nu(as)(Ti-O) mode was lifted upon molecular association, yielding band shifts and splittings in the IR spectrum of neat TPT.

Solvent-assisted mechanochemistry.

The literature on solvent-assisted mechanochemistry is reviewed with a view to linking observations concerning the applicability of the technique to theories of its mechanism, and summarizing the advantages and limitations of the technique when applied to a variety of different reaction types. Previously unnoticed links between "solvent-free" and solvent-assisted reaction mechanisms are presented, and reasons why the method should be considered more widely by synthetic chemists are given.

Oligo-nuclear silver thiocyanate complexes with monodentate tertiary phosphine ligands, including novel 'cubane' and 'step' tetramer forms of AgSCN : PR3 (1:1)4.

Adducts of a number of tertiary pnicogen ligands ER(3) (triphenyl-phosphine and -arsine (PPh(3),AsPh(3)), diphenyl,2-pyridylphosphine (PPh(2)py), tris(4-fluorophenyl)phosphine (P(C(6)H(4)-4F)(3)), tris(2-tolyl)phosphine (P(o-tol)(3)), tris(cyclohexyl)phosphine (PCy(3))), with silver(I) thiocyanate, AgSCN are structurally and spectroscopically characterized. The 1:3 AgSCN : ER(3) complexes structurally defined (for PPh(3),AsPh(3) (diversely solvated)) take the form [(R(3)E)(3)AgX], the thiocyanate X = NCS being N-bound, thus [(Ph(3)E)Ag(NCS)]. A 1:2 complex with PPh(2)py, takes the binuclear form [(pyPh(2)P)(2)Ag()Ag(PPh(2)py)(2)] with an eight-membered cyclic core. 1:1 complexes are defined with PPh(2)py, P(o-tol)(3) and PCy(3); binuclear forms [(R(3)P)Ag()Ag(PR(3))] are obtained with P(o-tol)(3) (two polymorphs), while novel isomeric tetranuclear forms, which may be envisaged as dimers of dimers, are obtained with PPh(2)py, and, as further polymorphs, with PCy(3); these latter may be considered as extensions of the 'cubane' and 'step' forms previously described for [(R(3)E)AgX](4) (X = halide) complexes. Solvent-assisted mechanochemical or solvent-assisted solid-state synthesis methods were employed in some cases, where complexes could not be obtained by conventional solution methods, or where such methods yielded a mixture of polymorphs unsuitable for solid-state spectroscopy. The wavenumbers of the ν(CN) bands in the IR spectra are in broad agreement with the empirical rule that distinguishes bridging from terminal bonding, but exceptions occur for compounds that have a double SCN bridged dimeric structure, and replacement of PPh(3) with PPh(2)py apparently causes a significant decrease in ν(CN) to well below the range expected for bridging SCN in these structures. (31)P CP MAS NMR spectra yield additional parameters that allow a correlation between the structures and spectra.

Mechanochemical and solution synthesis, and crystal structures and IR and solid-state (CPMAS) NMR spectroscopy of some bis(triphenylphosphine)silver(I) mono- and di-hydrogencitrate systems.

The complex [(Ph(3)P)(2)Ag(H(2)cit)]·EtOH (1; H(2)cit(-) = dihydrogencitrate = C(6)H(7)O(7)(-)) contains [(Ph(3)P)(2)Ag(H(2)cit)] molecules in which the silver atom is coordinated to two PPh(3) molecules and the two oxygen atoms of one of the 'terminal'/1-carboxylate groups of the dihydrogencitrate group. The molecules form centrosymmetric hydrogen-bonded dimers in the solid. In [{(Ph(3)P)(2)Ag}(2)(Hcit)], (2), unsymmetrical deprotonation of the citrate grouping is found, from the 1- and 3- (i.e. terminal and central) carboxylates: [(Ph(3)P)(2)Ag(O(2)CCH(2)C(OH) (CH(2)COOH)CO(2))Ag(PPh(3))(2)]. The above complexes, as well as [(Ph(3)P)(3)Ag(H(2)cit)] (3) were prepared via conventional solution methods, involving the reaction of trisilver(I) citrate, citric acid and triphenylphosphine, and by a mechanochemical method involving the reaction of silver(I) oxide, citric acid and triphenylphosphine. IR studies of 1-3 show the presence of coordinated carboxylate and free carboxylic acid groups in the mono- and di-hydrogencitrate ligands, and the formation of 2 from 1 shows that dihydrogencitrate deprotonation can occur upon dissolution of 1 in protic solvents. High-field (9.40 T) (31)P CPMAS NMR spectra were recorded and analysed, yielding heteronuclear (1)J((107/109)Ag,(31)P) and homonuclear (2)J((31)P,(31)P) spin-spin coupling constants.

Mechanochemical and solution synthesis, X-ray structure and IR and 31P solid state NMR spectroscopic studies of copper(I) thiocyanate adducts with bulky monodentate tertiary phosphine ligands.

A number of adducts of copper(I) thiocyanate with bulky tertiary phosphine ligands, and some nitrogen-base solvates, were synthesized and structurally and spectroscopically characterised. CuSCN:PCy3 (1:2), as crystallized from pyridine, is shown by a single crystal X-ray study to be a one-dimensional polymer ...(Cy3P)2CuSCN(Cy3P)2CuSCN... (1) with the four-coordinate copper atoms linked end-on by S-SCN-N bridging thiocyanate groups. A second form (2), obtained from acetonitrile, was also identified and shown by IR and 31P CPMAS NMR spectroscopy to be mononuclear, with the magnitude of the dν(Cu) parameter measured from the 31P CPMAS and the ν(CN) value from the IR clearly establishing this compound as three-coordinate [(Cy3P)2CuNCS]. Two further CuSCN/PCy3 compounds CuSCN:PCy3 (1:1) (3), and CuSCN:PCy3:py (1:1:1) (4) were also characterized spectroscopically, with the dν(Cu) parameters indicating three- and four-coordinate copper sites, respectively. Attempts to obtain a 1:2 adduct with tri-t-butylphosphine have yielded, from pyridine, the 1:1 adduct as a dimer [(Bu(t)3P)((SCN)(NCS))Cu(PBu(t)3)] (5), while similar attempts with tri-o-tolylphosphine (from acetonitrile and pyridine (= L)) resulted in solvated 1:1:1 CuSCN:P(o-tol)3:L forms as dimeric [{(o-tol)3P}LCu((SCN)(NCS))CuL{P(o-tol)3}] (6 and 8). The solvent-free 1:1 CuSCN:P(o-tol)3 adduct (7), obtained by desolvation of 6, was characterized spectroscopically and dν(Cu) measurements from the 31P CPMAS NMR data are consistent with the decrease in coordination number of the copper atom from four (for 6) (P,N(MeCN)Cu,S,N) to three (for 7) (PCuS,N) upon loss of the acetonitrile of solvation. These results are compared with those previously reported for mononuclear and binuclear PPh3 adducts which demonstrate a clear tendency for the copper centre to remain four-coordinate. The IR spectroscopic measurements on these compounds show that bands in the far-IR spectra provide a much more definitive criterion for distinguishing between bridging and terminal bonding than does an often-used empirical rule based on ν(CN) in the mid-IR, which leads to the wrong conclusion in some cases.

Solution and mechanochemical syntheses, and spectroscopic and structural studies in the silver(I) (bi-)carbonate: triphenylphosphine system.

Syntheses of a number of adducts of silver(I) (bi-)carbonate with triphenylphosphine, both mechanochemically, and from solution, are described, together with their infra-red spectra, (31)P CP MAS NMR and crystal structures. Ag(HCO(3)):PPh(3) (1:4) has been isolated in the ionic form [Ag(PPh(3))(4)](HCO(3))·2EtOH·3H(2)O. Ag(2)CO(3):PPh(3) (1:4) forms a binuclear neutral molecule [(Ph(3)P)(2)Ag(O,µ-O'·CO)Ag(PPh(3))(2)](·2H(2)O), while Ag(HCO(3)):PPh(3) (1:2) has been isolated in both mononuclear and binuclear forms: [(Ph(3)P)(2)Ag(O(2)COH)] and [(Ph(3)P)(2)Ag(µ-O·CO·OH)(2)Ag(PPh(3))(2)] (both unsolvated). A more convenient method for the preparation of the previously reported copper(I) complex [(Ph(3)P)(2)Cu(HCO(3))] is also reported.