Triple Bridge Research Articles

Metal Tetrahydroborates and Tetrahydroborato Metalates, 17 / Bonding in Cadmium Bis(tetrahydroborate), and the Reaction with Lithium Tetrahydroborate

Cadmium bis(tetrahydroborate) has been prepared from dimethyl cadmium and H3B · THF in tetrahydrofuran. Low temperature 113Cd NMR spectra recorded for THF, monoglyme and diglyme solutions show a septet with 1J(113Cd1H) = 273 Hz. This proves that the BH4⁻ groups are bound to the metal centre via triple hydride bridges. Reaction of Cd(BH4)2 with LiBH4 yields LiCd(BH4)3 quantitatively in diglyme solution.

Syntheses and x-ray crystal structures of [MoO(SCH2CH2-CH2S)2]? and [Mo2O2(?-N3)(SCH2CH2CH2S)3]?. A study of the redox behaviour of [MoO(SCH2CH2S)2]? by cyclic voltammetry using convolution analysis

The complexes [PPh4][MoO{S(CH2)nS}2], n=2 (1) n=3 (3), were synthesised from the MoVI dioxoprecursor complex [MoO2(butane-2,3-diolato)2] and the appropriate thiol in the presence of base. Complex (3) exhibits a square pyramidal geometry. Crystal Data: P21,0, Z=4,a=9.612(2),b=21.202(4),c=15.462(3) A, β=103.06(1)°, V=3043.3A3, F(000)=1364.0, 3687 reflections collected, and 1957 used in solution with R=0.058. [MoO(SCH2CH2CH2S)2]− reacts with hydrazoic acid in methanol to produce [Mo2O2(μ-N3)-(SCH2CH2CH2S)3] (5), crystal data:\(P_{2_{1} 2_{1} 2_{1} } \)a=9.398(3),b=14.650(2),c=27.42(2) (A), α=β=γ=90°, Z=4 V=3775.8A3, F(000)=1872.0, 2563 reflections collected and 1244 were used in the solution with R=0.058. The complex is an asymmetric dimer with a triple bridge comprising two dithiolate sulphurs and a nitrogen of the azide ligand. Convolution analysis of the cyclic voltammetric response of complex (1) confirmed a diffusion controlled one electron reversible reduction process.

A flexible framework obtained from oxidative additions upon the binuclear complex [Ir2(µ-pz)(µ-SBut)(CO)2{P(OMe)3}2]: preparation and X-ray structures of [Ir2(µ-pz)(µ-SBut)(µ-L)(CO)2{P(OMe)3}2] and [Ir2(µ-pz)(µ-SBut)(µ-L)I2(CO)2-{P(OMe)3}2](Hpz = pyrazole, L = dimethyl acetylenedicarboxylate)

The formation and properties of the heterobridged complexes [Ir2(µ-pz)(µ-SBut)(cod)2](1)(cod = cyclo-octa-1,5-diene, pz = pyrazolate) and [Ir2(µ-pz)(µ-SBut)(CO)2{P(OMe)3}2](2) are reported. Compound (2) undergoes stepwise addition of molecular iodine to yield the complexes [Ir2(µ-pz)(µ-SBut)In;(CO)2{P(OMe)3}2][n= 2 (3) and 4 (4)]. Interaction of complex (2) with dimethyl acetylenedicarboxylate affords the triply heterobridged complex [Ir2(µ-pz)(µ-SBut)(µ-MeO2CCCCO2Me)(CO)2{P(OMe)3}2](5). Compound (5) undergoes a further oxidative addition with I2 to form [Ir2(µ-pz)(µ-SBut)(µ-MeO2CCCCO2Me)I2(CO)2{P(OMe)3}2](6). Compound (6) can be also obtained using mercury(II) iodide as oxidant, and similarly, [Ir2(µ-pz)(µ-SBut)(µ-MeO2CCCCO2Me)Cl2(CO)2{P(OMe)3}2](7) using mercury(II) chloride. The structures of (5) and (6) have been determined by X-ray diffraction methods. Crystals of (5) are monoclinic, space group P21/n, with a= 18.040(7), b= 15.986(6), c= 11.085(4)A, β= 92.68(2)°, and Z= 4. Complex (6) is orthorhombic, space group P212121 with a= 13.522(5), b= 20.871 (8), c= 12.649(7)A, with Z= 4. Both complexes are binuclear with the metal atoms held in proximity by a triple bridge: a pyrazolate anion, a ButS group and a dimethyl acetylenedicarboxylate ligand bonded as a cis-dimetallated olefin. The oxidative addition of I2 to (5) originates a remarkable change in the Ir–Ir distance from 2.614(2) to 3.626(2)A, leaving practically unaltered the bridging framework.

Trinuclear angular aggregates of rhodium: synthesis and crystal structures of [Rh3(µ3-SC5H4N)2(CO)6][ClO4](SC5H4N = pyridine-2-thiolate) and [Rh3(µ3-C7H4NS2)2(CO)2(PPh3)2(tfbb)][ClO4](C7H4NS2= benzothiazole-2-thiolate, tfbb = tetrafluorobenzobarrelene)

The binuclear complexes [{Rh(µ-L)L′2}2]{L = pyridine-2-thiolate (SC5H4N–) or benzothiazole-2-thiolate (C7H4NS2–); L′2= cyclo-octa-1,5-diene (cod), norborna-2,5-diene (nbd), tetrafluorobenzobarrelene (tetrafluorobenzo[5,6]bicyclo[2.2.2]octa-2,5,7-triene, tfbb), (CO)2, or (CO)(PPh3)} react with the appropriate species cis-[RhL′2(Me2CO)x]+ to give trinuclear aggregates [Rh3(µ3-L)2(L′2)3][ClO4]. A study of this reaction has led to the controlled synthesis of a single isomer of the complexes [Rh3(µ3-C7H4NS2)2(CO)2(PPh3)2L′2][ClO4]. The trinuclear complexes have been characterized by 1H, 31P n.m.r., and u.v.-visible spectroscopy and in the case of [Rh3(µ3-SC5H4N)2(CO)6][ClO4]·0.5CH2Cl2(4) and [Rh3(µ3-C7H4NS2)2(CO)2(PPh3)2(tfbb)][ClO4](12) by single-crystal X-ray diffraction methods. In both structures trinuclear cationic rhodium complexes are present, in which two pyridine-2-thiolate[(4)] or benzothiazole-2-thiolate[(12)] ligands, acting as triple bridges through the nitrogen and one sulphur atom, interact with all three metal atoms, which are in a bent arrangement. Carbonyl ligands [(4)] and carbonyl, PPh3, and tfbb (through the two double bonds) ligands [(12)] complete the slightly distorted square-planar co-ordination of the Rh atoms.

2′-Deoxyadenosine Adducts with 3d Metal Perchlorates

Abstract Adducts of 2′-deoxyadenosine (L) with 3d metal perchlorates were synthesized by refluxing mixtures of ligand and metal salt in triethyl orthoformate-ethanol. Solid complexes of the following types were obtained: (X = C1O4): M2L3X6.4H2O (M = Cr, Fe), M2L3X,.4H2O (M = Mn, Co, Ni, Zn), FeL2X2.2H2O and Cu2L3X4. The Cu(II) complex is magnetically subnormal and appears to be a dimer of the type {O3CIOCuL3CuOCIO3} (CIO4)2 involving a triple bridge of N1,N7-bound L Iigands. The rest of the new complexes exhibit normal ambient temperature magnetic moments and were characterized as linear chainlike polymers comprising a singlebridged (M-L)n backbone, terminal unidentate L, –OC1O3 and aqua Iigands and ionic perchlorate. Bridging L is also Nl,N7-bound in the latter adducts, while the terminal L Iigands present bind most probably via N7.

Reactivity of binuclear pyrazolate-bridged rhodium complexes with isocyanides. Molecular structure of [Rh2(µ-pz)I2(CNBut)2–(µ-Ph2PCH2PPh2)2]BF4(pz = pyrazolate)

The CO groups of [Rh2(µ-pz)I2(CO)2(µ-dppm)2]ClO4(pz = pyrazolate, dppm = Ph2PCH2PPh2) have been gradually substituted by reaction with isocyanides CNR (R = But or C6H4Me-p) to give [(OC)IRh(µ-pz)(µ-dppm)2Rhl(CNR)]ClO4[R = But(3) or C6H4Me-p(4)]via[(OC)IRh(µ-pz)(µ-CO)(µ-dppm)2Rhl(CNR)]ClO4[R = But(1) or C6H4Me-p(2)] and, finally, [Rh2(µ-pz)I2(CNR)2(µ-dppm)2] ClO4[R = But(7) or C6H4,Me-p(8)]via[Rh2(µ-pz)I2(µ-CO)(CNR)2(µ-dppm)2]ClO4[R = But(5) or C6H4Me-p(6)]. The CO bridging groups of (1), (2), (5), and (6) are ketonic carbonyls according to their spectroscopic properties. The reactivity of [Rh2(µ-pz) I2(CO)2(µ-dpam)2]ClO4(dpam = Ph2AsCH2AsPh2) with isocyanides was studied for comparison. The structure of the BF4–analogue of (7), [Rh2(µ-pz)I2(CNBut)2(µ-dppm)2]BF4(7b), has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P21/n with unit-cell parameters a= 20.347(8), b= 21.221(8), c= 14.514(6)A, β= 94.11(2)°, and Z= 4. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by block-matrix least squares to R= 0.0630 for 4 969 observed reflections. In the cationic complex the two Rh atoms, at a distance of 2.829(3)A, are connected by a triple bridge, involving two dppm ligands and the pyrazolate anion.

Addition and reaction products of triethyl thiophosphate and metal perchlorates at just over ambient and elevated temperatures

Triethyl thiophosphate (tetp) invariably forms adducts with various metal perchlorates (M=Mg 2+, Al 3+, Cr 3+, Mn 2+, Fe 2+, Fe 3+, Co 2+, Ni 2+, Cu 2+, Zn 2+, Cd 2+) at 35–40°C in ethanol-triethyl orthoformate (teof). Only certain of these adducts, which involve S-bonded tetp in the thione form for soft or borderline metal ions and O-bonded tetp in the thiol tautomeric form for hard metal ions, could be isolated in solid form, owing to their tendency to decompose yielding diethylthiophosphato (detp) metal complexes and ethyl perchlorate, at temperatures ranging between ambient and 80–90°C, depending on the metal ion. Several well-defined detp and detpperchlorato metal complexes were obtained by heating solutions of mixtures of tetp and metal perchlorates in ethanol-teof at 80–90°C, and characterized. In most cases, linear polymeric or dimeric complexes involving double or triple bridges of O,S-bonded bidentate detp between adjacent metal ions were isolated. However, in a number of occasions, heavily hydrated monomeric species, containing terminal S-bonded detp were obtained.

An asymmetric triply-bridged Mov complex with bridging azido-ligand. The structures of [Mo2O2(µ-N3){S(CH2)3S}3]–and its precursor [MoO{S(CH2)3S}2]–

The complex [MoO(SCH2CH2CH2S)2]– reacts with HN3 in methanol to give [Mo2O2(µ-N3)(SCH2CH2S)3]–;X-ray crystallography shows the former anion to have tetragonal pyramidal co-ordination about Mo with an apical oxo-group and the latter to be an asymmetric dinuclear complex with a triple bridge comprising two dithiolate sulphurs and a bent azide group linking two distinct pseudo-octahedral molybdenums.

An improved three-phase stepped-voltage inverter

The paper Presents an improved method of generating a three-phase stepped-voltage waveform using ten thyristor power switches. In the proposed method, it is possible to generate one step for every 20 ° of the voltage waveform on all the phases. The waveform has a total harmonic distortion of about 10% and the Predominant harmonies are the 17th and 19th. This is possible by a unique method of magneticcoupling betweena 120° conduction three-phase bridge inverter and a triple frequency single phase bridge inverter. The theoretical results are in close agreement with experimental results.

Binuclear and mononuclear nickel(II) and zinc(II) complexes of the tetradentate ligand 1,4-di(2′-pyridyl)aminophthalazine

Previous studies with the title ligand, PAP, have shown a predominance of binuclear complexes with cobalt and copper in which the ligand-to-metal ratio is 1:2. The nickel complexes produced are more varied in composition; e.g., 1:2 binuclear systems [PAPNi2X(OH)(H2O)4]X2 (X = Cl, Br); 1:1 binuclear systems [PAP2Ni2(H2O)4]X4 (X = Cl, Br), [PAP2Ni2(NCS)3]NCS, [PAP2Ni2(OH)I2]I•2H2O, [PAP2Ni2(OH)(H2O)2]X3 (X = ClO4, BF4, I); and 2:1 mononuclear systems [(PAPH)2Ni(H2O)2]X4 (X = I, BF4). Zinc forms both mononuclear, [PAPZnX2]•H2O (X = Br, I), and a 1:1 binuclear system, [PAP2Zn2Cl4]. Triple bridges are suggested between the nickel atoms in all binuclear systems involving bridging hydroxy groups. Weak antiferromagnetic exchange is observed (−J < 10 cm−1) in two binuclear nickel complexes, which is enhanced in the presence of a hydroxy bridge. Spin–spin coupling is assumed to occur via a superexchange mechanism. In all cases nickel appears to be six-coordinate while for the zinc complexes both four- and six-coordination are observed.

ChemInform Abstract: PREPARATION AND CHARACTERIZATION OF SALTS CONTAINING THE TRIPLY BRIDGED DIMERIC IRIDIUM(III) ION, (H(AR3P)2IR(SAR′)2CLIR(PAR3)2H)+

AbstractDie dimeren Ir(III)‐Komplexe (I) reagieren in halogenierten Lösungsmitteln wie Chloroform oder 1,2‐Dichloräthan unter Bildung der als Dihydrate isolierten, dreifach‐verbrückten Ir(III)‐chloride (IIa) und (IIb).

Preparation and characterization of salts containing the triply bridged dimeric iridium(III) ion, [H(Ar3P)2Ir(SAr′)2ClIr(PAr3)2H]+

The dimeric iridium(III) hydride complexes [IrHCl(SAr′)(PAr3)2]2 where Ar = 4-CH3C6H4 or C6H5 and Ar′ = 4-CH3C6H4, 4-CH3OC6H4, 4-FC6H4, or C6H5 have been shown to react in halogenated solvents such as chloroform or 1,2-dichloroethane to form triply bridged dimeric hydrated complexes of the type, [H(Ar3P)2Ir(SAr′)2ClIr(PAr3)H]Cl•2H2O. When PAr3 = (4-FC6H4)3P, no triple bridge formation was observed. However, the dimeric complexes, [IrHCl(SAr′)(PAr3)2]2 including PAr3 = (4-FC6H4)3P all react with AgClO4 in acetone to form the complexes, [H(Ar3P)2Ir(SAr′)2ClIr(PAr3)2H]ClO4•x(CH3)2CO (x = 0–3). The isolation and characterization of these triply bridged dimeric iridium(III) hydrides are discussed.

The nature of uranium borohydride in its vapour and solid phases from infrared spectra

A preliminary X-ray diffraction study of uranium borohydride, U(BH,),, has recently been reported’. It was concluded that the compound is polymeric in the solid with six BH4 groups associated with each uranium atom. Four of these are involved in U-(BH4)-U bridges and the rest are terminal [U-(BH,) type]. The authors deferred an assessment of the nature of the hydrogen bridging present until neutron diffraction studies were completed, but noted that the X-ray data were not inconsistent with double hydrogen bridges between all bonded uranium and boron atoms. An X-ray structure determination’ of solid (160 “C) zirconium borohydride, Zr(BH ) 4 4r and an electron diffraction study of Zr(BHq)q vapou? were both interpreted in terms of a monomeric structure in which tetrahedrally arranged boron atoms arc bonded through triple hydrogen bridges to the central metal atom. A recent vibrational study of zirconium borohydride and hafnium borohydride in the gas phase and in solution has strongly implied a triple bridge structure of Td molecular symmetry *. We wish to report the infrared spectrum of vapour phase uranium borohydride and compare it with the solid phase spectrum.