Calcium Bis Research Articles

Synthesis and structural characterisation of ‘solvent-free’ lithium–calcium hexamethyldisilazide, [Li{μ-N(SiMe 3) 2} 2Ca{N(SiMe 3) 2}], exhibiting a double ration of agostic H 3C⋯Li and H 3C⋯Ca intramolecular interactions

Addition of lithium hexamethyldisilazide to an equimolar amount of calcium bis(hexamethyldisilazide) in toluene gave ‘solvent-free’, [Li{μ-N(SiMe 3) 2} 2Ca{N(SiMe 3) 2}] ( 1). An X-ray study reveals a dinuclear arrangement based on a planar L iNCaN four-membered ring: both metals engage in additional H 3C⋯M (where M=Li, Ca) interactions with the μ-N(SiMe 3) 2 substituents resulting in a distorted tetrahedral geometry at lithium and a distorted trigonal-bipyramidal geometry at calcium. This contrasts with the previously reported mixed Li–Mg analogue, [Li{μ-N(SiMe 3) 2} 2Mg{N(SiMe 3) 2}], where only the lithium centre engages in such intramolecular agostic H 3C⋯Li interactions.

A Novel and Versatile Calcium-Based Initiator System for the Ring-Opening Polymerization of Cyclic Esters

A novel and efficient calcium alkoxide initiating system, generated in situ from bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] and an alcohol, for the ring-opening polymerization of cyclic esters has been developed. The solution polymerization in THF using mild conditions is living, yielding polyesters of controlled molecular weight and tailored macromolecular architecture. The polymerizations initiated with the 2-propanol−Ca[N(SiMe3)2]2(THF)2 system are first-order in monomer with no induction period. At high 2-propanol/Ca[N(SiMe3)2]2(THF)2 ratios, complete conversion of 2-propanol occurs due to fast and reversible transfer between dormant and active species.

Calcium methoxide initiated ring-opening polymerization of ϵ-caprolactone and L-lactide

A commercial calcium dimethoxide and an in-situ generated calcium methoxide prepared from bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] and methanol, were investigated as initiators for the ring-opening polymerization of e-caprolactone and L-lactide. Commercial calcium dimethoxide initiated rapid e-caprolactone polymerization at 120°C in bulk to give quantitatively a polymer with a polydispersity index around 1.3. Significant racemization was observed for L-lactide polymerization. The In-situ formed calcium methoxide promoted the solution polymerization of both e-caprolactone and L-lactide to high conversion at room temperature over a short time period, yielding the corresponding polyesters with narrow molecular weight distribution. NMR spectra showed that the poly(L-lactide) isolated had a purely isotactic microstructure. The initiator efficiency could be tuned by varying the molar ratio of methanol and bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide].

Fast and Living Ring-Opening Polymerization of l-Lactide Initiated with In-situ –Generated Calcium Alkoxides

The ring-opening polymerization of l-lactide with calcium alkoxides generated in-situ from bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] and 2-propanol are presented. The polymerization in THF at room temperature proceeds rapidly and in a living manner, giving poly(l-lactide)s of controlled molecular weight, low polydispersity, and tailored end-functionalities. Kinetic studies show the absence of an induction period and a pseudo-first order rate constant of 6.41 L mol−1 min−1, which is significantly higher than for related Y5(μ-O)(O i Pr)13− or aluminum alkoxide-initiated polymerizations. The initiation involves a two-step process: (1) alcoholysis of bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] to give the corresponding calcium alkoxide and (2) ring-opening of l-lactide via acyl-oxygen cleavage and insertion into the calcium-alkoxide bond. In the presence of excess alcohol, fast and reversible exchange between free alcohol molecules and coordinated alkoxide ligands takes place. This allows tuning of the poly(l-lactide) molecular weight over a wide range.

Modeling of divalent/monovalent ion selectivity of ion-exchanger-based solvent polymeric membranes doped with coexchanger

It is shown that the addition of a coexchanger does not always improve the selectivity of an ion-selective electrode. As a model case, the selectivity toward divalent primary ions I2+ in the presence of monovalent interference J+ is numerically simulated for membranes based on ion-exchanger R- and doped with a coexchanger (ionic additive) S+. It is, for the first time, demonstrated that the addition of a coexchanger, together with a high mobility of ion-exchanger sites, may be either beneficial or harmful to selectivity. Accordingly, two distinctive representatives of systems, i.e., membrane/solution are discussed. The theory is illustrated with experimental data obtained from PVC membranes based on calcium bis(2ethylhexyl)-phosphate plasticized with tris(2ethylhexyl)phosphate and doped with tetradecylammonium. Electrodes with these membranes exhibit both types of selectivity behavior. Interference from lithium with a calcium response may be sufficiently decreased by the addition of tetradecylammonium, while the interference from potassium and cesium was increased in the doped membranes.

Kinetic study of acamprosate absorption in rat small intestine.

Acamprosate (calcium bis acetyl-homotaurine), a homotaurine derivative, a structural analogue of gamma-aminobutyric acid (GABA) and an upper homologue of taurine, is a relatively new drug used to prevent relapse in weaned alcoholics. When administered orally as enteric-coated tablets at relatively high doses, this drug has a bioavailability of about 11%; however, the intestinal absorption mechanism has not been studied in depth. The present study was therefore planned to characterize the intestinal transport of acamprosate in the rat and the effect of chronic alcohol treatment on this process, quantifying its kinetic parameters and investigating possible inhibitors. Using an in vitro technique, acamprosate absorption was measured in the rat intestine from three different groups: alcohol group [fed a liquid diet containing 5% (w/v) ethanol for 4 weeks], isocaloric pair-fed control, and a solid diet group. Intestinal acamprosate absorption was found to occur mainly by passive diffusion with a diffusive permeability of 0.213+/-0.004 cm/h in control pair-fed animals, 0.206+/-0.001 cm/h in animals receiving chronic alcohol treatment, and 0.193+/-0.001 cm/h in the solid diet group. Inhibition studies showed that at a 10(-3) M acamprosate concentration, some compounds such as GABA, taurine, proline, and glycine at 40 mM each did not affect acamprosate transport. Nevertheless, when a lower concentration of the drug (10(-4) M) was assayed, a significant reduction of acamprosate transport in the presence of taurine or GABA 40 mM was found. These results suggest that acamprosate in the rat jejunum, could be transported, in part, by a carrier system. Further experiments using different concentrations of taurine (10, 20, and 80 mM) showed that the maximum inhibition (32%) is achieved at 20 mM of taurine. These latter results suggest that acamprosate and taurine share, at least, an intestinal carrier system in rat jejunum. From the above results, it can be concluded that there are probably two pathways involved in the intestinal absorption of acamprosate: passive diffusion and mediated transport, with the former being predominant. Moreover, neither chronic ethanol intake nor the type of diet seems to alter the intestinal absorption of the drug.

Fourier transform-IR and 1 H NMR studies on the structure of water solubilized by reverse aggregates of calcium bis(2-ethylhexyl) sulfosuccinate in organic solvents

The structure of water solubilized by reverse aggregates of calcium bis(2-ethylhexyl) sulfosuccinate in deuterobenzene and toluene has been probed by Fourier transform-IR and 1 H NMR spectroscopies. The ν OD band of solubilized HOD (4% D 2 O in H 2 O) has been recorded as a function of the [water]/[surfactant] molar ratio, W/S. Curve fitting of this band showed the presence of a main peak at 2550 ± 13 cm -1 and a small one at 2405 ± 15 cm -1 . As a function of increasing W/S, the frequency of the main peak decreases, its full width at half-height increases, and its area increases linearly. The 1 H NMR chemical shift of solubilized H 2 O-D 2 O mixtures at W/S = 18.1 has been measured as a function of the deuterium content of the aqueous nanodroplet. These data were used to calculate the so-called fractionation factor of the aggregate-solubilized water, the value of which was found to be unity. The results of both techniques show that reverse aggregate-solubilized water, although different from bulk water, does not seem to coexist in layers of different degrees of structure, as suggested, for example by the two-state water-solubilization model.

Formation of Calcium–Carbon Bonds From a Lewis Acid-Base Reaction of Calcium Bis[bis(trimethylsilyl)amide] and Tris(trimethylsilylmethyl)alane

Treatment of calcium bis[bis(trimethylsilyl)amide] with two equivalents of tris(trimethylsilylmethyl)alane yields (Me3SiCH2)2Al–N(SiMe3)2 (1) and the dimer [(Me3Si)2N–Ca(μ–CH2SiMe3)2Al(CH2SiMe3)2]2 (2). The five-coordinate bridging carbon atoms show Ca–C bond lengths of 264 and 268 pm. A similar reaction with calcium bis[bis(trimethylsilyl)phosphanide] gives the dimer [(Me3SiCH2)2Al–P(SiMe3)2]2 (3) with crystallographic C2 symmetry. A calcium-containing species is not isolable, however, in the presence of DME – ether cleavage reactions and the formation of the centrosymmetric dimer [(Me3SiCH2)2Al–OCH2CH2OMe]2 (4) are observed. The central moiety is an Al2O2 cycle with fivefold coordinated aluminium centers.

Formation of Calcium–Carbon Bonds From a Lewis Acid-Base Reaction of Calcium Bis[bis(trimethylsilyl)amide] and Tris(trimethylsilylmethyl)alane

Treatment of calcium bis[bis(trimethylsilyl)amide] with two equivalents of tris(trimethylsilylmethyl)alane yields (Me3SiCH2)2Al–N(SiMe3)2 (1) and the dimer [(Me3Si)2N–Ca(μ–CH2SiMe3)2Al(CH2SiMe3)2]2 (2). The five-coordinate bridging carbon atoms show Ca–C bond lengths of 264 and 268 pm. A similar reaction with calcium bis[bis(trimethylsilyl)phosphanide] gives the dimer [(Me3SiCH2)2Al–P(SiMe3)2]2 (3) with crystallographic C2 symmetry. A calcium-containing species is not isolable, however, in the presence of DME – ether cleavage reactions and the formation of the centrosymmetric dimer [(Me3SiCH2)2Al–OCH2CH2OMe]2 (4) are observed. The central moiety is an Al2O2 cycle with fivefold coordinated aluminium centers.

Percolation phenomenon of calcium bis(2-ethylhexyl) sulfosuccinate water-in-oil microemulsions by conductivity and dielectric spectroscopy measurements.

The sodium counterion (Na+) of the sodium bis(2-ethylhexyl) sulfosuccinate (AOT) surfactant was exchanged with calcium Ca2+ to investigate the counterion charge effect on the structure of water in normal decane microemulsions. Ohmic conductivity and dielectric permittivity measurements were performed on samples at constant water to surfactant mole ratio [water]/[Ca(AOT)(2)]=26.6. Increasing the volume fraction of the dispersed phase phi, a percolation phenomenon was observed at the constant temperature of 25 degrees C. The percolation threshold was found at phi approximately 15% by Ohmic conductivity and static dielectric permittivity studied as a function of phi, and by the frequency dependence of the complex permittivity. Critical exponents typical of the static percolation mechanism (formation of bicontinuous microemulsions) were found below and above threshold. The comparison of these results obtained for the two different counterions, Ca2+ and Na+, in AOT surfactant water in normal decane microemulsions allows detection of an important difference. The percolation below threshold is dynamic for the sodium-based microemulsions, accounting for the formation of clusters of droplets, whereas calcium-based microemulsions show a static percolation. For this system, the coalescence of droplets begins to occur below threshold at phi approximately 12%.

2,5-Diphenyl-3,4-bis(trimethylsilyl)-1-phosphacyclopentadienide as a Ligand at Calcium, Strontium, and Tin(II)

The addition reaction of tetrakis(tetrahydrofuran)calcium or -strontium bis[bis(trimethylsilyl)phosphanide] with diphenylbutadiyne in toluene yields nearly quantitative amounts of slightly yellow tetrakis(tetrahydrofuran)calcium (1) and -strontium bis[2,5-diphenyl-3,4-bis(trimethylsilyl)phosphacyclopentadienide] (2). Due to the fact that the alkaline earth metal bis[bis(trimethylsilyl)amides] do not react with alkynes, colorless (tetrahydrofuran)calcium bis[2,5-bis(tert-butyl)-1-azacyclopentadienide] (3) was prepared by the transmetalation of N-trimethylstannyl-2,5-bis(tert-butyl)-1-azacyclopentadiene with distilled calcium. The metathesis reaction of 1 and 2 with SnCl2 gives yellow tin bis[2,5-diphenyl-3,4-bis(trimethylsilyl)phosphacyclopentadienide] (4).The phosphorus atoms of 1 and 2 are in a planar environment with long M−P distances, whereas in 4 the P atoms comprise a pyramidal coordination sphere. The tin−carbon distances are larger than observed in stannocenes which could be interpreted as a stannylene-like structure with σ-bonded ligands. Crystallographic data for 1: monoclinic, C2/c, a = 2108.9(3) pm, b = 1296.2(2) pm, c = 2735.3(3) pm, β = 93.37(1)°, Z = 4, wR2 = 0.1381 (all data, on F2). Crystallographic data for 2: monoclinic, C2/c, a = 2104.7(1) pm, b = 1296.43(6) pm, c = 2717.8(1) pm, β = 93.189(1)°, Z = 4, wR2 = 0.0954 (all data, on F2). Crystallographic data for 4: triclinic, P1̄, a = 1253.25(4) pm, b = 1312.58(4) pm, c = 1481.61(5) pm, α = 87.667(1)°, β = 79.438(1)°, γ = 72.684(1)°, Z = 2, wR2 = 0.0692 (all data, on F2).

Synthesis and Homomolecular Metalation of Trialkylsilylphosphanides of Calcium and Barium

Metalation of triisopropylsilylphosphane with bis(tetrahydrofuran-O)calcium bis[bis(trimethylsilyl)amide] in tetrahydropyran (thp) in a molar ratio of 3:2 yields (Me3Si)2NCa[μ-P(H)SiiPr3]3Ca(thp)3 (1) containing a trigonal-bipyramidal Ca2P3 core, the metal atoms occupying apical positions. Reaction of two equivalents of triisopropylsilylphosphane or -arsane with bis(tetrahydrofuran-O)barium bis[bis(trimethylsilyl)amide] in tetrahydrofuran gives the corresponding bis(phosphanide) 2 and bis(arsanide) 3, compounds of the type (thf)3Ba[μ-E(H)SiiPr3]Ba(thf)2E(H)SiiPr3 with E = P, As. The equimolar reaction of (tri-tert-butylsilyl)phosphane with (thf)2Ba[N(SiMe3)2]2 in toluene yields heteroleptic dimeric (thf)2Ba[N(SiMe3)2][P(H)SitBu3] (4). Addition of a further equivalent of H2PSitBu3 leads to the formation of homoleptic (thf)nBa[P(H)SitBu3]2 (5). Dissolution of the latter in aromatic hydrocarbons leads to the elimination of H2PSitBu3, yielding dimeric (thf)Ba3(PSitBu3)2[P(H)SitBu3]2 (6). The inner core of 6 consists of the tetramer (BaPSitBu3)4 based on a Ba4P4 heterocubane unit, two opposite faces being capped with (thf)Ba[P(H)SitBu3]2 molecules.

Synthesis and Homomolecular Metalation of Trialkylsilylphosphanides of Calcium and Barium

Metalation of triisopropylsilylphosphane with bis(tetrahydrofuran-O)calcium bis[bis(trimethylsilyl)amide] in tetrahydropyran (thp) in a molar ratio of 3:2 yields (Me3Si)2NCa[μ-P(H)SiiPr3]3Ca(thp)3 (1) containing a trigonal-bipyramidal Ca2P3 core, the metal atoms occupying apical positions. Reaction of two equivalents of triisopropylsilylphosphane or -arsane with bis(tetrahydrofuran-O)barium bis[bis(trimethylsilyl)amide] in tetrahydrofuran gives the corresponding bis(phosphanide) 2 and bis(arsanide) 3, compounds of the type (thf)3Ba[μ-E(H)SiiPr3]Ba(thf)2E(H)SiiPr3 with E = P, As. The equimolar reaction of (tri-tert-butylsilyl)phosphane with (thf)2Ba[N(SiMe3)2]2 in toluene yields heteroleptic dimeric (thf)2Ba[N(SiMe3)2][P(H)SitBu3] (4). Addition of a further equivalent of H2PSitBu3 leads to the formation of homoleptic (thf)nBa[P(H)SitBu3]2 (5). Dissolution of the latter in aromatic hydrocarbons leads to the elimination of H2PSitBu3, yielding dimeric (thf)Ba3(PSitBu3)2[P(H)SitBu3]2 (6). The inner core of 6 consists of the tetramer (BaPSitBu3)4 based on a Ba4P4 heterocubane unit, two opposite faces being capped with (thf)Ba[P(H)SitBu3]2 molecules.

Structure and properties of bis(2-ethyhexyl)phospheric acid microemulsions with a network structure: Effect of counter-ions

Several physicochemical properties were experimentally examined for calcium bis(2-ethylhexyl)phosphate (Ca(DEHP) 2)/water/ n-hexane/calcium chloride systems and compared with sodium bis(2-ethylhexyl)phosphate (NaDEHP)/water/ n-hexane/sodium chloride systems in the Winsor II regime to elucidate the effect of changing counter-ion species on the properties of a microemulsion in the amphiphile-concentrated region characterized by the presence of a network-like structure formed from worm-like molecular assemblies. The measurements of small angle X-ray scattering, shear viscosity, electroconductivity were consistently interpreted in terms of the strong tendency of molecular assemblies to become more elongated for Ca 2+ than for Na +. The dependence of the dynamical correlation length on the volume fraction of molecular assembly obtained from the dynamic light scattering implies that the freely mobile part in the Ca(DEHP) 2 micoemulsion network would be determined by the individual micromechanical property of the worm-like molecular assembly, being different from that in NaDEHP systems determined by the network mesh which becomes more confined with the increase in the volume fraction of the molecular assembly.

The influence of an anionic additive on the properties of cation-exchanger based calcium-selective electrodes

Potentiometric and electrochemical impedance spectroscopic investigations of calcium-selective membranes containing poly(vinylchloride), dioctylphenylphosphonate, calcium (bis[4-(1,1,3,3-tetramethylbutyl)phenyl] phosphate) and different amounts of the lipophilic anionic additive tridodecylmethylammonium chloride were carried out. The addition of the lipophilic additive changes the properties of calcium-selective electrodes, e.g. slope and calcium selectivity. The selectivity for calcium in presence of H+, Na+, K+, NH4 +, Mg2+, Ba2+, Sr2+ and (C2H5)4N+ was measured by three different methods, namely separate solution method, fixed interference method and matched potential method. Membranes with different concentration ratios between the calcium-exchanger and tridodecylmethylammonium chloride were investigated within half a year. The tendency of changing from cationic into anionic response for membranes containing nearly equivalent concentrations of cation- and anion-exchanger was shown. This inversion of the electrode response depends not only upon the concentration ratio of both ion-exchangers but also upon the total concentration of calcium-exchanger. Electrochemical impedance spectroscopy was used for monitoring the development of membrane resistances during a soaking period of one month. Based on these results dielectric constants for the calcium-selective membranes depending on the membrane composition were determined. Furthermore, the dependence of the membrane resistance on the membrane thickness and the concentration of tridodecylmethylammonium chloride was evaluated.

Synthese und Struktur von bis[ η5-(cyclopropyl-cyclopropyliden-methyl)-cylopentadienyl]bis(tetrahydrofuran- O)calcium

The reaction of bis(tetrahydrofuran- O)calcium bis[bis(trimethylsilyl)amide] 1 in tetrahydrofuran with two equivalents of 6,6-di( cyclo-propyl)fulvene at 60°C yields within 150 h bis[ η 5-(cyclopropyl-cyclopropyliden-methyl)cyclopentadienyl]bis(tetrahydrofuran- O)calcium 2. As an intermediate the heteroleptic bis(tetrahydrofuran- O)calcium bis(trimethylsilyl)amide [ η 5-(cyclopropylcyclopropylidenmethyl)cyclopentadienide] 3 is detected by 1H and 13C{ 1H} NMR spectroscopy. In solution an equilibrium involving these three derivatives exists. 2 crystallizes at −20°C from tetrahydrofuran as colorless cuboids (monoclinic, C2/ c; a = 1175,2(1); b = 1182,1(1); c = 2040,0(3) pm; β = 101,015(9)°; Z = 4; wR 2 = 0,1410). The metal center is surrounded distorted tetrahedrally by the four ligands. The cyclopentadienyl group and the propylidene fragment are oriented coplanar.

Evaluation of perchlorate tolerant photo-cured calcium selective electrodes for use in flow injection potentiometry

A photo-cured membrane selective to calcium, based on the calcium bis [4-(1′,1′,3′,3′-tetramethylbutyl)phenyl]phosphate ionophore and incorporating the lipophilic additive, potassium tetraki(4-chlorophenyl)borate, that can tolerate up to 200 nM perchlorate ionic background in the flow injection potentiometry mode has been previously reported (T. Dimitrakopoulos, J.R. Farrell and P.J. Ives, Electroanalysis, 8 (1996) 391). Improvements in the electrode slope and sensitivity of the previously described photo-cured calcium membrane-based electrode were achieved when anhydrous calcium chloride salt was dissolved into the pre-cured membrane composition and then photo-cured. Similar to the previously reported photo-cured calcium ion-selective electrode (ISE), the improved photo-cured calcium ISE can measure calcium in a high perchlorate background in the flow injection potentiometric mode.

Acid Salts of Phosphoenolpyruvic Acid (H3PEP): NaH5(PEP)2.2H2O and KH5(PEP)2

The crystal structures of two new salts of phosphoenolpyruvic acid (H 3 PEP), sodium hydrogen bis[2-(phosphonooxy)propenoate], Na + .C 6 H 9 O 12 P 2 - .2H 2 O, (I), and potassium hydrogen bis[2-(phosphonooxy)propenoate], K + .C 3 H 4 O 6 P - .C 3 H 5 O 6 P, (II), have been determined. In the crystal of (I), the phosphate groups of two PEP residues related by a center of symmetry are joined by a very short disordered hydrogen bond with an O...O distance of 2.456 (2) A. As a result, the bis(phosphoenolpyruvate) monoanion can be distinguished. Crystals of (I) are almost isomorphous with crystals of zinc(II), manganese(II), magnesium and calcium bis(phosphoenolpyruvate) dihydrate and zinc(II) bis(phosphoglycolate) dihydrate. The crystal of (II) was found to be the 1:1 salt co-crystallized with the unionized molecular acid in the crystal chemical unit K + .H 2 PEP - .H 3 PEP. The P-O(ester) bond in the acid molecule [1.578(2) ii is shorter than in the monoanion [1.618(2)A]. In the sodium salt, this bond is 1.612(2)A. In both crystals, there are networks of strong hydrogen bonds.

Synthesis, characterization and the thermal decomposition of calcium(II)bis(oxalato)calcium(II)dihydrate

Calcium(II)bis(oxalato)calcium(II)dihydrate, Ca[Ca(C 2O 4) 2]·2H 2O, has been synthesized and characterized by elemental analysis, and reflectance and IR spectral studies. Thermal decomposition studies (TG, DTG, and DTA) in air showed that the final end product was CaO at 865°C through the intermediate formation of a mixture of CaCO 3 and CaO at approx. 818°C. At around 424°C a mixture of CaO and Ca(C 2O 4) 1.2 is formed by partial decomposition of oxalate which is stable up to 670°C. DSC studies up to 700°C in nitrogen at 10°C min −1 showed both endothermic and exothermic peaks with activation energies of 190 and 458 kJ mol −1, respectively, and compared with values calculated from TG. Some of the decomposition products were identified by spectral, analytical and X-ray powder diffraction studies and a tentative mechanism for the decomposition is proposed.

NMR-spektroskopische und strukturelle charakterisierung der tri- iso-propylsilylphosphanide des calciums

The reaction of (1,2-dimethoxyethane-O,O′)lithium phosphanide with chloro tri- iso-propylsilane yields tri- iso-propylsilylphosphane 1 as well as bis(tri- iso-propylsilyl)phosphane 2. Recrystallisation from an n-pentane solution gives single crystals of 2 (monoclinic, P2 1/ c, a = 1510.5(1), b = 771.18(5), c = 2033.4(1) pm, β = 108.972(6)°, Z = 4, wR2 = 0.0947). The stoichiometry of 1 and calcium bis[bis(tri-methylsilyl)amide] determines the composition of the products. The equimolar ratio leads to dimeric (1,2-dimethoxyethane-O,O′)calcium bis(trimethylsilyl)amide-tri- iso-propylsilylphosphanide 3 with terminal amido ligands and bridging phosphanido substituents (monoclinic, P2 1/ c, a = 1073.8(2), b = 1267.7(3), c = 2228.8(4) pm, β = 100.03°, Z = 2 dimers, wR2 = 0.1459). Choosing a molar ratio of 3 to 2 for the phosphane 1 and Ca[N(SiMe 3) 2] 2, (Me 3Si) 2NCa[μ-P(H)Si iPr 3] 3Ca(thf) 3, 4 forms. Its bicyclic structure with a trigonal bipyramidal Ca 2P 3 core can be deduced from NMR experiments. The large 2 J(PP) coupling constant of 95 Hz is remarkable; however, it is even exceeded by the value of 135 Hz for derivative 3. If phosphane 1 is used in a twofold molar ratio, the characterisation of tetrakis(THF)calcium-bis(tri- iso-propylsilylphosphanide) 5 succeeds (triclinic, P 1 , a = 898.8(2), b = 1141.0(2), c = 1173.0(2) pm α = 79.61(1)°, β = 68.30(1)°, γ = 72.99(2)°, Z = 1, wR2 = 0.1928). In the presence of bis[bis-(trimethylsilyl)amino]stannylene hetero-bi-metallic pentakis(THF)dicalcium-tin(II)-bis(tri- iso-propylsilylphosphanide)-bis(tri- iso-propylsilylphosphandiide) 6 can be isolated; in this derivative the calcium atoms are sixfold, the phosphorus atoms quadruple and the tin atoms threefold coordinated (triclinic, P 1 , a = 1654.4(1), b = 2137.3(2), c = 2170.6(2) pm, α= 82.285(7), β = 89.078(7)°, γ = 86.555(6)°, Z = 4 wR2 = 0.1707). Ab initio SCF calculations prove for the dimetric calcium bis(phosphanide) the preference of the bicyclic structure H 2P-Ca(μ-PH 2) 3Ca, however, for the lighter homologue the monocyclic structure H 2PMg(μ-PH 2) 2MgPH 2 is energetically favoured.