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In this communication, we reinvestigate the structural and magnetic properties of the title compound K2Mn3(H2O)6[ Mo(CN)7] $_{2}\cdot $6H2O. We show that this material crystallises in the space group $C2/c$(monoclinic no.15), instead of $C2$(monoclinic no.5) reported by J. Larianova et al.in J. Am. Chem. Soc., 121(1999) 3349 - 3356. The C2/c and C2 unit cells are closely related. The presence of an inversion center in the C2/c unit cell implies the doubling of the cparameter in comparison to the $C2$unit cell. Magnetic measurements show a transition from a paramagnetic state to a ferrimagnetic ordered state at 39 K, in agreement to neutron diffraction experiments. Key words.X-ray diffraction – Ferrimagnet – Heptacyanomolybdenate.

The reaction of benzyne with 3,4-dimethylphosphole pentacarbonylmolybdenum complexes affords the corresponding 2,3-benzo-7-phosphanorbornadiene complexes through [4+2] cycloaddition. The condensation takes place on the less hindered side of the phosphole ring corresponding to the phosphorus substituent as shown by the X-ray crystal structure analysis of the phenyl derivative (2). The strain at the bridge of 2 (C−P−C angle ca. 80°) induces a variety of splitting reactions. Upon decomplexation by dppe at 110 °C in toluene, phenylphosphinidene is generated and recovered as phenylphosphine. Upon sulfurization under the same conditions, [PhPS2] is formed and trapped as a [4+2] adduct with 2,3-dimethylbutadiene. Potassium tert-butylate attacks the bridge in THF at −78 °C and, after methylation and hydrolytic workup, yields [Ph(Me)P(OH)Mo(CO)5].

The transient phosphinidene complex [PhP−Mo(CO)5], as generated from the appropriate 7-phosphanorbornadiene complex at 110 °C in toluene, selectively reacts with the C&tbd1;C triple bond of 4-phenyl-3-butyn-1-ol to give the corresponding phosphirene complex 4. Upon further heating, this phosphirene evolves via two pathways. The minor pathway involves the formal addition of the OH bond of the alcohol function onto the phosphirene P−C ring bond to give the 3-benzylidene-1,2-oxaphospholane complex 5. The major pathway involves the reaction of a second molecule of [PhP−Mo(CO)5] with the OH group of 4, giving an intermediate phosphirene with an additional secondary alkoxyphosphine functionality (7). An intramolecular hydrophosphination of one P−C bond of the phosphirene ring then immediately takes place to give the cis-1,2-bis(phosphino)ethene [Mo(CO)4] complex 8 as a mixture of two diastereomers. After methylation of the PH group of 8, decomplexation can be efficiently achieved by reaction with sulfur. Structures have been ascertained by X-ray analysis for 5, 8, and the disulfide 10.

The reaction between [VCp2], BPh3, or BCl3 and the nitrile F3CC6H4C&tbd1;N gives the borane adduct of vanada(IV)azirine complex [VCp2{η²:C,N-F3CC6H4C&dbd;N·BR3}] (R = Ph (2), Cl (3)). Using B(C6F5)3 and dicyano compounds such as 1,4-benzene dicarbonitrile N&tbd1;C(C6H4)C&tbd1;N and adiponitrile N&tbd1;C(CH2)4C&tbd1;N, an access to homobimetallic vanadium complexes was obtained and complexes [(VCp2)2{η²:C,N-(C6F5)3B·N&dbd;C(C6H4)C&dbd;N·B(C6F5)3}] (6) and [(VCp2)2{η²:C,N-(C6F5)3B·N&dbd;C(CH2)4C&dbd;N·B(C6F5)3}] (8) are formed. Malononitrile N&tbd1;CCH2C&tbd1;N in the presence of 2 equiv of B(C6F5)3 and 1 or 2 equiv of [VCp2] gave the monometallic complex [(VCp2){η²:C,N-(C6F5)3B·N&dbd;CCH2C&tbd1;N·B(C6F5)3}] (7). Complexes 2, 3, 7, and 8 were characterized by X-ray structure determination. All these complexes are paramagnetic to one electron per vanadium.

The new thioether C5H5FeC5H4C&tbd1;CSC&tbd1;CSiMe3 affords the compound [Ru3(CO)9(μ3-η²:η⁴:η³-Me3SiCC(C2Fc)SC(Fc)CSC&tbd1;CSiMe3)], among others, by reaction with Ru3(CO)12.

Three new azulene-based substituted pyridinium cations, azulene-1-azo(N-methyl-4‘-pyridinium) (1⁺), azulene-1-[(E)-2-(N-methyl-4‘-pyridinium)ethenyl] (2⁺), and azulene-1-azo[(N-methyl-5‘-quinolinium)] (3⁺) were synthesized, and their crystal structures solved by X-ray diffraction. A set of crystallographic, spectroscopic, and computational investigations reveals that, while the pyridinium is a very strong acceptor unit, the azulene counterpart acts as an extremely efficient electron donor in these chromophores. The static quadratic hyperpolarizabilities (β0), measured by the hyper Rayleigh scattering method, are equal to 67 × 10^-30, 108 × 10^-30, and 80 × 10^-30 cm⁵ esu^-1, for 1⁺, 2⁺, and 3⁺, respectively. Interestingly, these values are slightly reduced versus those recorded on the related stilbazolium derivatives built up from the less efficient (dimethylamino)phenyl donor substituent. This observation suggests that the donor strength of azulene is beyond the point which maximizes β in the “push−pull” (arylethenyl)pyridinium series. An important charge delocalization in the ground state is suggested to account for the reduced β value in these chromophores, in agreement with the calculated charge-transfer properties, Mulliken charges, and experimental solvatochromism. These investigations suggest that azulene could attract an additional interest in the design of chromophores with cubic optical nonlinearities.

The reaction of the vanadium(II) carbonyl [Cp2V(CO)] and B(C6F5)3 resulted in formation of zwitterionic, ring-borylated vanadium(III) complexes [(Cp)(C5H4B(C6F5)3)V] (3) and [(Cp)(C5H4B(C6F5)3)V(CO)2] (4) and of the salt [Cp2V(CO)2][HB(C6F5)3] (5). All were characterized by crystallography. Formation of a hydride vanadium(IV) [(Cp)(C5H4B(C6F5)3)VH(CO)] obtained by the electrophilic addition of the borane at the Cp-ring followed by redox and disproportionation reaction is suggested to account for these results.

A series of ortho-metalated ruthenium hydrido dihydrogen complexes of the form RuH(H2)(X)(PⁱPr3)2 (X = 2-phenylpyridine (ph-py) (2), benzoquinoline (bq) (3), phenylpyrazole (ph-pz) (4)) were prepared by adding 1 equiv of the corresponding substrate X−H and 2 equiv of PⁱPr3 to Ru(COD)(COT) under 3 bar of H2. The analogous complex RuH(H2)(ph-py)(PCy3)2 (1) was prepared by adding 1 equiv of 2-phenylpyridine to RuH2(H2)2(PCy3)2. The ortho-metalated X ligand is coordinated to ruthenium via the nitrogen of one ring and the ortho carbon of a second ring as a result of C−H activation. 2 and 3 were characterized by X-ray diffraction. They are the first examples of complexes displaying exchange couplings between the hydride and the dihydrogen ligands. NMR studies and DFT calculations are used to understand this phenomenon. The series of ortho-metalated model complexes RuH(H2)(X)(PH3)2 was investigated by DFT at the B3PW91 level. The coherent (quantum-mechanical) as well as the incoherent (classical) exchange rates have been determined by line shape analysis, and the activation energies hardly depend on the nature of the X ligand:  Ea(coherent) = ca. 10 kJ mol^-1, Ea(incoherent) = ca. 40 kJ mol^-1 (ca. 50 kJ mol^-1 by DFT). The corresponding transition states (2q^TSQEC−4q^TSQEC) for the classical exchange process have been located by DFT at the B3PW91 level. The dihydrogen ligand is now trans to N and perpendicular to the plane of the chelating ligand. These states connect to the isomer with the dihydrogen trans to C through coupled rotation of H2 and proton transfer from H2 to H. The dihydrogen ligand can be substituted easily, and the corresponding complexes RuH(L)(ph-py)(PⁱPr3)2 with L = N2 (5), O2 (6), CO (7), C2H4 (8) have been isolated and fully characterized by NMR and by crystal structure analyses in the case of 6 and 8. The model systems RuH(L)(ph-py)(PH3)2 (5q−8q) have been optimized at the DFT level (B3PW91). In the case of 8, we could not detect any ethylene insertion in either the Ru−H or the Ru−C bond. Theoretical calculations explain the differences we observed with the Murai type catalysts, which are highly reactive to ethylene insertion.

A novel phosphine−phosphonium ylide ligand bearing a chiral sulfinyl moiety was prepared by reaction of (o-diphenylphosphinophenyl)diphenylphosphonium methylide with (S)-menthyl p-tolylsulfinate. Reaction of this ylide with [Rh(cod)2][PF6] gave stable cationic disymmetrically P,C-chelated rhodium complexes with an asymmetric ylidic carbon atom anchored to the metal center. The configuration of this carbon is controlled by the S-configuration of the adjacent sulfinyl group. The stereoselectivity of the complexation is reversed from 9:1 at 20 °C to 1:9 at −45 °C. An X-ray diffraction analysis of the thermodynamic complex shows that the stereoselectivity is not directed by chelation of the SO group which lies at a nonbonding distance from the rhodium center. In the presence of triethylamine, epimerization occurs via a putative neutral P,C-chelated complex bearing an yldiide ligand. In the presence of HPF6 and PPh3, cleavage of the ylidic carbon−rhodium bond takes place simultaneously with displacement of the phosphino−phosphonium ligand by PPh3. The phosphine end of the ligand is intended to preserve at least one phosphine−rhodium bond, which is a common feature of all the rhodium catalysts derived from the Wilkinson complex. Indeed, we found that the phosphino−phosphonium ylide complexes are active&sbd;though poorly enantioselective&sbd;as catalysts for hydrogenation of (Z)-α-acetamidocinnamic acid and hydrosilylation of acetophenone.

Room-temperature stoichiometric reaction of the bis(dihydrogen) complex [RuH2(η²-H2)2(PCy3)2] (1) with thiophene leads to the formation of a new complex that has been isolated and characterized as an η⁴-thioallyl complex [RuH(η⁴(S,C)-SC4H5)(PCy3)2] (2). This complex easily regenerates 1 upon treatment with dihydrogen and can be successfully used as a catalyst precursor in thiophene hydrogenation to 2,3,4,5-tetrahydrothiophene (THT). The reaction of 1 with 2-acetylthiophene leads to a regioselective 1,5-C−S bond splitting with formal hydrogenation of two double C&dbd;C bonds and coordination of a new 2-hexen-2-olato-3-thiolato ligand in an η²(O,S) mode to form [RuH2{η²(O,S)-C6H10OS}(PCy3)2] (3). The new complex 3 has been characterized by ¹H, ³¹P, and ¹³C NMR studies including ¹H DPFGSE TOCSY, 2D-¹H−¹H{³¹P} COSY DQF, and the correlated ¹³C−¹H HMQC LR spectra. The solid state molecular structure of 3 has been unequivocally determined by single-crystal X-ray structure analysis. The bis(dihydrogen) complex 1 is an effective catalyst precursor for the homogeneous hydrogenation of thiophene (T) to 2,3,4,5-tetrahydrothiophene (THT), 2-methylthiophene (2-MeT) to 2-methyltetrahydrothiophene (2-MeTHT), 2-acetylthiophene (2-AcT) to 1-(2-thienyl)ethanol (1-(2-Tyl)E), 2-thiophenecarboxaldehyde (2-TA) to 2-thiophenemethanol (2-TM), and benzo[b]thiophene (BT) to 2,3-dihydrobenzo[b]thiophene (DHBT) under mild conditions (80 °C, 3 bar H2). Dibenzo[b,d]thiophene (DBT) is not reduced under these conditions due to the formation of the S-coordinated dihydrogen complex [RuH2(η²-H2){η¹(S)-C12H8S}(PCy3)2] (4).

The system combining the new ferrocenyl tetraphosphine 1,1‘,2,2‘-tetrakis(diphenylphosphino)-4,4‘-di-tert-butylferrocene (called Fc(P)4^tBu, 1) and [PdCl(η³-C3H5)]2 has been found to be an active catalyst for the cross-coupling of aryl halides with aryl boronic acids (i.e., Suzuki reaction) and for the vinylation of aryl halides with alkenes (Heck reaction). A variety of chlorides reacts in good yield with aryl boronic acids in the presence of 1−0.01% catalyst. The more reactive aryl bromides were reacted with aryl boronic acids or alkenes in the presence of 0.01−0.0001% catalyst. This system compares well with other catalytic systems that have been described for Suzuki or Heck reactions. ¹H, ¹³C, and ³¹P NMR studies in solution were conducted with the view to obtain a better understanding of the interaction involving the palladium dimeric precursor and the tetraphosphine. The initial formation of kinetic and then different thermodynamic species was evidenced. A dynamic evolution from labile Pd(π-allyl)/tetraphosphine species toward the well-defined, stable, and nonfluxional complexes [PdCl2{Fc(P)4^tBu}] (3) and [Pd2Cl4{Fc(P)4^tBu}] (4) is observed. This behavior is different from the other known active tetraphosphine Tedicyp [cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane]. The palladium mononuclear 3 and dinuclear 4 complexes were isolated and fully characterized in the solid state by X-ray diffraction analysis and in solution by multinuclear NMR. The blocked conformation in solution of compounds 1, 3, and 4 respectively leads to original AA‘BB‘, ABMX, and A2B2 ³¹P NMR spin-systems for the four phosphorus atoms.

The substituted cyclopentadienyl zirconium complex [Cp‘ ‘‘2ZrMe2] (1; Cp‘ ‘‘ = η⁵-C5H2-1,2,4-(SiMe3)3) reacts with tris(perfluorophenyl)borane, B(C6F5)3, in pentane to give the two species [Cp‘ ‘‘2ZrMe][MeB(C6F5)3] (2) and [Cp‘ ‘‘(η⁵-C5H2-2,4-(SiMe3)2-1-η¹-SiMe2CH2)Zr][MeB(C6F5)3] (3). Complex 3 was characterized by an X-ray structure determination, showing the C−H activation of a SiMe3 group attached to the cyclopentadienyl ligand. Complexes 2 and 3 could be described, respectively, as the active and inactive species which both arise from 1 and B(C6F5)3 in the cationic polymerization.