PX4+, P2X5+, and P5X2+ (X=Br,I) salts of the superweak Al(OR)4- anion [R=C(CF3)3

PX(4) (+)[Al(OR)(4)](-) (X=I: 1 a, X=Br: 1 b) was prepared from X(2), PX(3), and Ag[Al(OR)(4)] [R=C(CF(3))(3)] in CH(2)Cl(2) at -30 degrees C in 69-86 % yield. P(2)X(5) (+) salts were prepared from 2 PX(3) and Ag[Al(OR)(4)] in CH(2)Cl(2) at -30 degrees C yielding almost quantitatively P(2)X(5) (+)[Al(OR)(4)](-) (X=I: 3 a, X=Br: 3 b). The phosphorus-rich P(5)X(2) (+) salts arose from the reaction of cold (-78 degrees C) mixtures of PX(3), P(4), and Ag[Al(OR)(4)] giving P(5)X(2) (+)[Al(OR)(4)](-) (X=I: 4 a, X=Br: 4 b) with a C(2v)-symmetric P(5) cage. Silver salt metathesis presumably generated unstable PX(2) (+) cations from PX(3) and Ag[Al(OR)(4)] (X=Br, I) that acted as electrophilic carbene analogues and inserted into the Xbond;X (Pbond;X/Pbond;P) bond of X(2) (PX(3)/P(4)) leading to the highly electrophilic and CH(2)Cl(2)-soluble PX(4) (+) (P(2)X(5) (+)/P(5)X(2) (+)) salts. Reactions that aimed to synthesize P(2)I(3) (+) from P(2)I(4) and Ag[Al(OR)(4)] instead led to anion decomposition and the formation of P(2)I(5)(CS(2))(+)[(RO)(3)Al-F-Al(OR)(3)](-) (5). All salts were characterized by variable-temperature solution NMR studies (3 b also by (31)P MAS NMR), Raman and/or IR spectroscopy as well as X-ray crystallography (with the exception of 4 a). The thermochemical volumes of the Pbond;X cations are 121 (PBr(4) (+)), 161 (PI(4) (+)), 194 (P(2)Br(5) (+)), 271 (P(2)I(5) (+)), and 180 A(3) (P(5)Br(2) (+)). The observed reactions were fully accounted for by thermochemical calculations based on (RI-)MP2/TZVPP ab initio results and COSMO solvation enthalpy calculations (CH(2)Cl(2) solution). The enthalpies of formation of the gaseous Pbond;X cations were derived as +764 (PI(4) (+)), +617 (PBr(4) (+)), +749 (P(2)I(5) (+)), +579 (P(2)Br(5) (+)), +762 (P(5)I(2) (+)), and +705 kJ mol(-1) (P(5)Br(2) (+)). The insertion of the intermediately prepared carbene analogue PX(2) (+) cations into the respective bonds were calculated, at the (RI-)MP2/TZVPP level, to be exergonic at 298 K in CH(2)Cl(2) by Delta(r)G(CH(2)Cl(2))=-133.5 (PI(4) (+)), -183.9 (PBr(4) (+)), -106.5 (P(2)I(5) (+)), -81.5 (P(2)Br(5) (+)), -113.2 (P(5)I(2) (+)), and -114.5 kJ mol(-1) (P(5)Br(2) (+)).     

Structures and stabilities of group 13 adducts [(NHC)(EX3)] and [(NHC)2(E2X(n))] (E=B to In; X=H, Cl; n=4, 2, 0; NHC=N-heterocyclic carbene) and the search for hydrogen storage systems: a theoretical study

Quantum chemical calculations using density functional theory at the BP86/TZVPP level and ab initio calculations at the SCS-MP2/TZVPP level have been carried out for the group 13 complexes [(NHC)(EX(3))] and [(NHC)(2)(E(2)X(n))] (E=B to In; X=H, Cl; n=4, 2, 0; NHC=N-heterocyclic carbene). The monodentate Lewis acids EX(3) and the bidentate Lewis acids E(2) X(n) bind N-heterocyclic carbenes rather strongly in donor-acceptor complexes [(NHC)(EX(3))] and [(NHC)(2)(E(2)X(n))]. The equilibrium structures of the bidentate complexes depend on the electronic reference state of E(2)X(n), which may vary for different atoms E and X. All complexes [(NHC)(2)(E(2)X(4))] possess C(s) symmetry in which the NHC ligands bind in a trans conformation to the group 13 atoms E. The complexes [(NHC)(2)(E(2)H(2))] with E=B, Al, Ga have also C(s) symmetry with a trans arrangement of the NHC ligands and a planar CE(H)E(H)C moiety that has a E=E π bond. In contrast, the indium complex [(NHC)(2)(In(2) H(2))] has C(i) symmetry with pyramidal-coordinated In atoms in which the hydrogen atoms are twisted above and below the CInInC plane. The latter C(i) form is calculated for all chloride systems [(NHC)(2)(E(2)Cl(2))], but the boron complex [(NHC)(2)(B(2)Cl(2))] deviates only slightly from C(s) symmetry. The B(2) fragment in the linear coordinated complex [(NHC)(2)(B(2))] has a highly excited (3)(1)Σ(g)(-) reference state, which gives an effective B≡B triple bond with a very short interatomic distance. The heavier homologues [(NHC)(2)(E(2))] (E=Al to In) exhibit a anti-periplanar arrangement of the NHC ligands in which the E(2) fragments have a (1)(1) Δ(g) reference state and an E=E double bond. The calculated energies suggest that the dihydrogen release from the complexes [(NHC)(EH(3))] and [(NHC)(2)(E(2)H(n))] becomes energetically more favourable when atom E becomes heavier. The indium complexes should therefore be the best candidates of the investigated series for hydrogen-storage systems that could potentially deliver dihydrogen at close to ambient temperature. The hydrogenation reaction of the dimeric magnesium(I) compound [LMgMgL] (L=β-diketiminate) with [(NHC)(EH(3))] becomes increasingly exothermic with the trend B相似文献   

Luminescent homo- and heteropolynuclear platinum(II) chalcogenido aggregates based on [Pt2E2(P empty set N)4] units (E=S,Se)

A series of homodinuclear platinum(II) complexes containing bridging chalcogenido ligands, [Pt(2)(mu-E)(2)(P empty set N)(4)] (P empty set N=dppy, E=S (1), Se (2); P empty set N=tBu-dppy, E=S (3)) (dppy=2-(diphenylphosphino)pyridine, tBu-dppy=4-tert-butyl-2-(diphenylphosphino)pyridine) have been synthesized and characterized. The nucleophilicity of the [Pt(2)E(2)] unit towards a number of d(10) metal ions and complexes has been demonstrated through the successful isolation of a number of novel heteropolynuclear platinum(II)-copper(I), -silver(I), and -gold(I) complexes: [[Pt(2)(mu(3)-E)(2)(dppy)(4)](2)Ag(3)](PF(6))(3) (E=S (4); Se (5)) and [Pt(2)(dppy)(4)(mu(3)-E)(2)M(2)(dppm)]X(2) (E=S, M=Ag, X=BF(4) (6); E=S, M=Cu, X=PF(6) (7); E=S, M=Au, X=PF(6) (8); E=Se, M=Ag, X=PF(6) (9); E=Se, M=Au, X=PF(6) (10)). Some of them display short metal.metal contacts. These complexes have been found to possess interesting luminescence properties. Through systematic comparison studies, the emission origin has been probed.     

Preparation of stable AsBr4+ and I2As-PI3+ salts. Why didn't we succeed to prepare AsI4+ and As2X5+? A combined experimental and theoretical study

In analogy to our successful "PX2+" insertion reactions, an "AsX2+" insertion route was explored to obtain new arsenic halogen cations. Two new salts were prepared: AsBr4+[Al(OR)4]-, starting from AsBr3, Br2 and Ag[Al(OR)4], and I2As-PI3+[Al(OR)]4 from AsI3, PI3 and Ag[Al(OR)4](R=C(CF3)3). The first cation is formally a product of an "AsBr2+" insertion into the Br2 molecule and the latter clearly a "PI2+" insertion into the As-I bond of the AsI3 molecule. Both compounds were characterized by IR and NMR spectroscopy, the first also by its X-ray structure. Reactions of Ag[Al(OR)4] with AsI3 do not lead to ionization and AgI formation but rather lead to a marginally stable Ag(AsI3)2+[Al(OR)]4 salt. Despite many attempts we failed to prepare other PX-cation analogues such as AsI4+, As2X5+ and P4AsX2+(X=Br, I). To explain these negative results the thermodynamics of the formation of EX2+, EX4+ and E2X5+(E = As, P; X = Br, I) was carefully analyzed with MP2/TZVPP calculations and inclusion of entropy and solvation effects. We show that As2Br5+ is in very rapid equilibrium with AsBr2+ and AsBr3(DeltaGo((CH2Cl2))=+30 kJ mol(-1)). The extremely reactive AsBr2+ cation available in the equilibrium accounts for the observed decomposition of the [Al(OR)4]- anion. By contrast, the stability of AsI3 against Ag[Al(OR)4] appears to be kinetic and, if prepared by a suitable route, As2I5+ would be expected to have a stability intermediate between the known P2I5+ and P2Br5+.     

Molecular orbital investigation of the protonated H2X2AlNHn(CH3)3-n+ (X = F, Cl, and Br; n = 0-3) complexes

Structures of protonated alane-Lewis base donor-acceptor complexes H2X2AlNHn(CH3)(3-n)+ (X = F, Cl, and Br; n = 0-3) as well as their neutral parents were investigated. All the monocations H2X2AlNHn(CH3)(3-n)+ are Al-H protonated involving hypercoordinated alane with a three-center two-electron bond and adopt the C(s) symmetry arrangement. The energetic results show that the protonated alane-Lewis complexes are more stable than the neutral ones. They also show that this stability decreases on descending in the corresponding periodic table column from fluorine to bromine atoms. The calculated protonation energies of HX2AlNHn(CH3)(3-n) to form H2X2AlNHn(CH3)(3-n)+ were found to be highly exothermic. The possible dissociation of the cations H2X2AlNHn(CH3)(3-n)+ into X2AlNHn(CH3)(3-n)+ and molecular H2 is calculated to be endothermic.     

Structural isomerism in tris-tolyl halo-phosphonium and halo-arsonium tri-halides, [(CH3C6H4)3EX][X3], (E = P, As; X = Br, I)

The group 15 ligands (o-CH(3)C(6)H(4))(3)P, (m-CH(3)C(6)H(4))(3)P, (p-CH(3)C(6)H(4))(3)P, Ph(3)As, (o-CH(3)C(6)H(4))(3)As and (p-CH(3)C(6)H(4))(3)As have been reacted with two equivalents of di-iodine or di-bromine to yield complexes of formula R(3)EX(4) (E = P, As; X = I, Br). These halogenated group 15 compounds are ionic, [R(3)EX][X(3)] consisting of halo-phosphonium or halo-arsonium cations and trihalide anions. These adducts exhibit structural isomerism and may exist either as simple 1:1 ion pairs, [R(3)EX][X(3)], isomer (A), which display a weak XX interaction between cation and anion, or as a 2:1 complex, which consists of a [{R(3)EX}(2)X(3)](+) cationic species made up of two [R(3)EX](+) cations interacting with one [X(3)](-) anion. The overall charge is balanced by a second [X(3)](-) anion. These 2:1 species also exhibit structural isomerism due to subtle differences in the connectivity of the [{R(3)EX}(2)X(3)](+) fragment, as the {R(3)EX}(+) units may either interact at the same end of the [X(3)](-) ion, to give a Y-shaped motif, isomer (B), or at opposite ends, giving a Z-shaped motif, isomer (C). The type of structural isomer formed is related to the way in which [Ar(3)EX](+) cations pack together via aryl embraces. Isomer (A) and (C) structures form chains of side-to-side, anti-parallel embracing cations. In (A) and (C) structures a square-like stacking motif of cations is observed. In contrast, isomer (B) structures feature side-to-side, parallel embracing cations, and do not exhibit the square motif.     

Cationic P-S-X cages (X=Br, I)

The first condensed-phase preparation of ternary P-Ch-X cations (Ch=O-Te, X=F-I) is reported: [P5S3X2]+, [P5S2X2]+, and [P4S4X]+ (X=Br, I). [P5S3X2]+ is formed from the reaction of the Ag+/PX3 reagent with P4S3. The [P5S3X2]+ ions have a structure that is related to P4S5 by replacing P=S by P+--X and S in the four-membered ring by P(X). We provide evidence that the active ingredient of the Ag+/PX3 reagent is the (H2CCl2)Ag-X-PX2+ cation. The latter likely reacts with the HOMO of P4S3 in a concerted HOMO-LUMO addition to give the P5S3X2+ ion as the first species visible in situ in the low-temperature 31P NMR spectrum. The [P5S3X2]+ ions are metastable at -78 degrees C and disproportionate at slightly higher temperatures to give [P5S2X2]+ and [P4S4X]+, probably with the extrusion of 1/n (PX)n (X=Br, I). All six new cage compounds have been characterized by multinuclear NMR spectroscopy and, in part, by IR or Raman spectroscopy. The [P5S2X2]+ salts have a nortricyclane skeleton and were also characterized by X-ray crystallography. The structure of the [P4S4X]+ ion is related to that of P4S5 in that the exo-cage P=S bond is replaced by an isoelectronic P+--X moiety.     

Theoretical study of valence photoelectron spectra of Re(CO)5X (X=Cl, Br, and I): a spin-orbit DK3 symmetry-adapted cluster/symmetry-adapted cluster-configuration interaction study

The valence photoelectron spectra of Re(CO)(5)X (X=Cl, Br, and I) are studied theoretically using symmetry-adapted cluster (SAC)/SAC-configuration interaction (SAC-CI) theory. The relativistic effects are included by the third-order Douglas-Kroll (DK3) method, and the spin-orbit coupling is also considered. Both electron correlation and relativistic effects are significant in assigning the valence photoelectron spectra of Re(CO)(5)X (X=Cl, Br, and I). DK3-SAC/SAC-CI provides values for the relative peak positions in a reasonable agreement with the observed photoelectron spectra. The sequence of ionization energies for Re(CO)(5)Cl, Re(CO)(5)Br, and Re(CO)(5)I are calculated as e(')[a(1)(Cl)]>e(')[e(Re+Cl)] approximately e(")[e(Re+Cl)]>e(")[b(2)(Re)]>e(')[e(Re-Cl)]>e(")[e(Re-Cl)], e(')[a(1)(Br)]>e(')[e(Re+Br)]>e(")[e(Re+Br)+b(2)(Re)]>e(")[b(2)(Re)+e(Re+Br)]>e(')[e(Re-Br)]>e(")[e(Re-Br)], and e(')[e(Re+I)+a(1)(I)]>e(")[b(2)(Re)+e(Re+I)] approximately e(')[a(1)(I)+e(Re+I)]>e(")[e(Re+I)+b(2)(Re)]>e(')[e(Re-I)]>e(")[e(Re-I)], respectively. These assignments are quite new and different from previous assignments.     

Reduction of the host cationic framework charge by isoelectronic substitution: synthesis and structure of Hg7Ag2P8X6 (X = Br, I) and Hg6Ag4P8Br6

The first compounds, Hg(7)Ag(2)P(8)X(6) (X = Br, I) and Hg(6)Ag(4)P(8)Br(6), featuring the partial isoelectronic substitution of Hg(2+) for Ag(1+) in mercury-pnicogen frameworks have been obtained and structurally characterized. The new compounds are the supramolecular assemblies built of the covalently bonded metal-pnicogen frameworks trapping guests of different complexity. The frameworks feature the perfect ordering of Hg(2+) and Ag(1+) cations and contain P(2)(4)(-) and P(6)(6)(-) phosphorus clusters. The substitution of Hg(2+) with Ag(1+) leads to the reduction in charge of the host cluster-containing cationic matrix and concomitant replacement of the monatomic X(-) guest by a lesser amount of the AgBr(3)(2)(-) anions.     

Copper(I) coordination polymers [{Cu(mu-X)}2{RP(mu-NtBu)}2]n (R = OC6H4OMe-o; X = Cl, Br, and I) and their reversible conversion into mononuclear complexes [CuX{(RP(mu-NtBu)2}2]: synthesis and structural characterization

The reactions of cyclodiphosphazane cis-[tBuNP(OC6H4OMe-o)]2 (1) with 2 equiv of CuX in acetonitrile afforded one-dimensional Cu(I) coordination polymers [Cu2X2{tBuNP(OC6H4OMe-o)}2]n (2, X = Cl; 3, X = Br; 4, X = I). The crystal structures of 2 and 4 reveal a zigzag arrangement of [P(mu-N)(2)P] and [Cu(mu-X)(2)Cu] units in an alternating manner to form one-dimensional Cu(I) coordination polymers. The reaction between 1 and CuX in a 2:1 ratio afforded mononuclear tricoordinated copper(I) complexes of the type [CuX{(tBuNP(OC6H4OMe-o))2}2] (5, X = Cl; 6, X = Br; 7, X = I). The single-crystal structures were established for the mononuclear copper(I) complexes 5 and 6. When the reactant ratios are 1:1, the formation of a mixture of polymeric and mononuclear products was observed. The Cu(I) polymers (2-4) were converted into the mononuclear complexes (5-7) by reacting with 3 equiv of 1 in dimethyl sulfoxide. Similarly, the mononuclear complexes (5-7) were converted into the corresponding polymeric complexes (2-4) by reacting with 3 equiv of copper(I) halide under mild reaction conditions.     

New halide-centered discrete Ag(I)(8) cubic clusters containing diselenophosphate ligands, [Ag(8)(X)[Se(2)P(OR)(2)](6)](PF(6)) (X = Cl, Br; R = Et, Pr, (i)Pr): syntheses, structures, and DFT calculations

Six clusters Ag(8)(micro(8)-X)[Se(2)P(OR)(2)](6)(PF(6)) (R = Et, X = Cl, 1a, X = Br, 1b; R = Pr, X = Cl, 2a, X = Br, 2b; R = (i)Pr, X = Cl, 3a, X = Br, 3b) were isolated from the reaction of [Ag(CH(3)CN)(4)](PF(6)), NH(4)[Se(2)P(OR)(2)], and Bu(4)NX in a molar ratio of 4:3:1 in CH(2)X(2). Positive FAB mass spectra show m/z peaks at 2573.2 for 1a, 2617.3 for 1b, 2740.9 for 2a, 2786.9 for 2b, 2742.3 for 3a, and 2787.0 for 3b due to respective molecular cation, (M - PF(6))(+). (31)P NMR spectra of 1a-3b display a singlet at delta 82.3, 81.5, 82.9, 81.7, 76.3, and 75.8 ppm with a set of satellites (J(PSe) = 661, 664, 652, 652, 656, and 656 Hz, respectively). The X-ray structure (1a-2b) consists of a discrete cationic cluster in which eight silver ions are linked by six diselenophosphate ligands and a central micro(8)-Cl or micro(8)-Br ion with a noncoordinating PF(6)(-) anion. The shape of the molecule is a halide-centered distorted Ag(8) cubic cluster. The dsep ligand exhibits a tetrametallic tetraconnective (micro(2), micro(2)) coordination pattern, and each caps on a square face of the cube. Each silver atom of the cube is coordinated by three selenium atoms and the central chloride or bromide ion. Additionally, molecular orbital calculations at the B3LYP level of the density functional theory have been carried out to study the Ag-micro(8)-X (X = Cl, Br) interactions for cluster cations [Ag(8)(micro(8)-X)[Se(2)P(OR)(2)](6)](+). Calculations show very weak bonding interactions exist between micro(8)-X and Ag atoms of the cube.     

Ultrafast photochemical dissociation of an equatorial CO ligand from trans(X,X)-[Ru(X)2(CO)2(bpy)] (X = Cl, Br, I): a picosecond time-resolved infrared spectroscopic and DFT computational study

Ultrafast photochemistry of the complexes trans(X,X)-[Ru(X)(2)(CO)(2)(bpy)] (X = Cl, Br, I) was studied in order to understand excited-state reactivity of equatorial CO ligands, coordinated trans to the 2,2'-bipyridine ligand (bpy). TD-DFT calculations have identified the lowest electronic transitions and singlet excited states as mixed X -->bpy/Ru --> bpy ligand to ligand/metal to ligand charge transfer (LLCT/MLCT). Picosecond time-resolved IR spectroscopy in the region of nu(CO) vibrations has revealed that, for X = Cl and Br, subpicosecond CO dissociation is accompanied by bending of the X-Ru-X moiety, producing a pentacoordinated intermediate trans(X,X)-[Ru(X)(2)(CO)(bpy)]. Final movement of an axial halide ligand to the vacant equatorial position and solvent (CH(3)CN) coordination follows with a time constant of 13-15 ps, forming the photoproduct cis(X,X)-[Ru(X)(2)(CO)(CH(3)CN)(bpy)]. For X = I, the optically populated (1)LLCT/MLCT excited state undergoes a simultaneous subpicosecond CO dissociation and relaxation to a triplet IRuI-localized excited state which involves population of an orbital that is sigma-antibonding with respect to the axial I-Ru-I bonds. Vibrationally relaxed photoproduct cis(I,I)-[Ru(I)(2)(CO)(CH(3)CN)(bpy)] is formed with a time constant of ca. 55 ps. The triplet excited state is unreactive, decaying to the ground state with a 155 ps lifetime. The experimentally observed photochemical intermediates and excited states were assigned by comparing calculated (DFT) and experimental IR spectra. The different behavior of the chloro and bromo complexes from that of the iodo complex is caused by different characters of the lowest triplet excited states.     

Influence of ligand polarizability on the reversible binding of O2 by trans-[Rh(X)(XNC)(PPh3)2] (X = Cl, Br, SC6F5, C2Ph; XNC = xylyl isocyanide). Structures and a kinetic study

The complexes trans-[Rh(X)(XNC)(PPh 3) 2] (X = Cl, 1; Br, 2; SC 6F 5, 3; C 2Ph, 4; XNC = xylyl isocyanide) combine reversibly with molecular oxygen to give [Rh(X)(O 2)(XNC)(PPh 3) 2] of which [Rh(SC 6F 5)(O 2)(XNC)(PPh 3) 2] ( 7) and [Rh(C 2Ph)(O 2)(XNC)(PPh 3) 2] ( 8) are sufficiently stable to be isolated in crystalline form. Complexes 2, 3, 4, and 7 have been structurally characterized. Kinetic data for the dissociation of O 2 from the dioxygen adducts of 1- 4 were obtained using (31)P NMR to monitor changes in the concentration of [Rh(X)(O 2)(XNC)(PPh 3) 2] (X = Cl, Br, SC 6F 5, C 2Ph) resulting from the bubbling of argon through the respective warmed solutions (solvent chlorobenzene). From data recorded at temperatures in the range 30-70 degrees C, activation parameters were obtained as follows: Delta H (++) (kJ mol (-1)): 31.7 +/- 1.6 (X = Cl), 52.1 +/- 4.3 (X = Br), 66.0 +/- 5.8 (X = SC 6F 5), 101.3 +/- 1.8 (X = C 2Ph); Delta S (++) (J K (-1) mol (-1)): -170.3 +/- 5.0 (X = Cl), -120 +/- 13.6 (X = Br), -89 +/- 18.2 (X = SC 6F 5), -6.4 +/- 5.4 (X = C 2Ph). The values of Delta H (++) and Delta S (++) are closely correlated (R (2) = 0.9997), consistent with a common dissociation pathway along which the rate-determining step occurs at a different position for each X. Relative magnitudes of Delta H (++) are interpreted in terms of differing polarizabilities of ligands X.     

Gleichgewichtsmessungen mit den Systemen PdX2,f + Al2X6,g = PdAl2X8,g (X = Cl,Br, I)

Equilibrium Measurements with the Systems PdX_2.f + Al₂X_6.g = PdAl₂X_8.g; (X = Cl, Br, I) The equilibria mentioned on the title have been measured by a simple flow method. In contrast with the data measured with X = Cl or Br, for X = I only less accurate, informing values could be obtained. Even so differences in the stability of chloride and bromide complexes on one hand and iodide complexes on the other hand can be traced back on differences in the structures of the solid dihalides.     

Highly luminescent complexes [Mo6X8(n-C3F7COO)6]2- (X=Br, I)

New complexes (Bu(4)N)(2)[Mo(6)X(8)(n-C(3)F(7)COO)(6)] (X = Br, I) display extraordinarily bright long-lived red phosphorescence both in solution and solid phases, with the highest emission quantum yields and the longest emission lifetimes among hexanuclear metal cluster complexes of Mo, W and Re, hitherto reported.     

Photodissociation of Mg+-XCH3 (X=F, Cl, Br, and I) complexes. I. Electronic spectra and dissociation pathways

Photodissociation spectra of Mg+-XCH3 (X=F, Cl, Br, and I) complexes have been measured in the ultraviolet region (225-415 nm). Several fragment ions with and without charge transfer (CT), Mg+, XCH3+, MgX+, MgCH3+, CH3+, and X+, were formed by evaporation (intermolecular bond dissociation) and intracluster reaction (intramolecular bond dissociation) via excited electronic states. Branching ratios of these ions were found to depend both on absorption bands and on halogen atoms. The ground states of the complexes were calculated to have geometries in which the Mg atom lies next to X atom of methyl halide molecules. Positive charges of the complexes are confirmed to be almost localized on Mg. Observed absorption bands were assigned to the transitions of the Mg+2P-2S atomic line perturbed by interactions with methyl halide molecules. Branching ratios of fragment ions can be partly explained by the stability of fragment ions and neutral counterparts. From the excited state potential energy curves along the Mg-X bond distance, dissociation reaction after CT was concluded to proceed predissociatively; potential curve crossings between the initially excited states and repulsive CT states may have a crucial role in the formation of CH3+, XCH3+, and X+. In particular, XCH3+ ions were formed via repulsive CT states having a character of electron excitation from Xnp to Mg+3s.     

Linear Trinuclear Pt.Mo-Mo Complexes [Mo(2)PtX(2)(pyphos)(2)(O(2)CR)(2)](2) (X = Cl, Br, I; R = CH(3), C(CH(3))(3); pyphos = 6-(Diphenylphosphino)-2-pyridonate) with an Axial Interaction between the Quadruply Bonded Mo(2) Moiety and the Platinum Atom

An example of a direct axial interaction of a platinum(II) atom with a Mo(2) core through a uniquely designed tridentate ligand 6-(diphenylphosphino)-2-pyridonate (abbreviated as pyphos) is described. Treatment of PtX(2)(pyphosH)(2) (2a, X = Cl; 2b, X = Br; 2c, X = I) with a 1:1 mixture of Mo(2)(O(2)CCH(3))(4) and [Mo(2)(O(2)CCH(3))(2)(NCCH(3))(6)](2+) (3a) in dichloromethane afforded the linear trinuclear complexes [Mo(2)PtX(2)(pyphos)(2)(O(2)CCH(3))(2)](2) (4a, X = Cl; 4b, X = Br; 4c, X = I). The reaction of [Mo(2)(O(2)CCMe(3))(2)(NCCH(3))(4)](2+) (3b) with 2a-c in dichloromethane afforded the corresponding pivalato complexes [Mo(2)PtX(2)(pyphos)(2)(O(2)CCMe(3))(2)](2) (5a, X = Cl; 5b, X = Br; 5c, X = I), whose bonding nature is discussed on the basis of the data from Raman and electronic spectra as well as cyclic voltammograms. The linear trinuclear structures in 4b and 5a-c were confirmed by NMR studies and X-ray analyses: 4b, monoclinic, space group C2/c, a = 34.733(4) ?, b = 17.81(1) ?, c = 22.530(5) ?, beta = 124.444(8) degrees, V = 11498(5) ?(3), Z = 8, R = 0.060 for 8659 reflections with I > 3sigma(I) and 588 parameters; 5a, triclinic, space group P&onemacr;, a = 13.541(3) ?, b = 17.029(3) ?, c = 12.896(3) ?, alpha = 101.20(2) degrees, beta = 117.00(1) degrees, gamma = 85.47(2) degrees, V = 2599(1) ?(3), Z = 2, R = 0.050 for 8148 reflections with I > 3sigma(I) and 604 parameters; 5b, triclinic, space group P&onemacr;, a = 12.211(2) ?, b = 20.859(3) ?, c = 10.478(2) ?, alpha = 98.88(1) degrees, beta = 112.55(2) degrees, gamma = 84.56(1) degrees, V = 2433.3(8) ?(3), Z = 2, R = 0.042 for 8935 reflections with I > 3sigma(I) and 560 parameters; 5c, monoclinic, space group P2(1)/n, a = 13.359(4) ?, b = 19.686(3) ?, c = 20.392(4) ?, beta = 107.92(2) degrees, V = 5101(2) ?(3), Z = 4, R = 0.039 for 8432 reflections with I > 3sigma(I) and 560 parameters.     

Synthesis and ligand-based mixed valency of cis- and trans-Cr(III)(X(4)SQ)(X(4)Cat)(L)(n) (X = Cl and Br,n = 1 or 2) complexes: effects of solvent media on intramolecular charge distribution and ligand dissociation of Cr(III)(X(4)SQ)(3)

The treatment of Cr(III)(X(4)SQ)(3) (SQ = o-semiquinonate; X = Cl and Br) with acetonitrile affords trans-Cr(III)(X(4)SQ)(X(4)Cat)(CH(3)CN)(2) (X = Cl (1) and Br (2)). In the presence of 2,2'-bipyridine (bpy) or 3,4,7,8-tetramethyl-1,10-phenanthrene (tmphen), the reaction affords Cr(III)(X(4)SQ)(X(4)Cat)(bpy).nCH(3)CN (X = Cl, n = 1 (3); X = Br, n = 0.5 (4)) or Cr(III)(X(4)SQ)(X(4)Cat)(tmphen) (X = Cl (5) and Br (6)), respectively. All of the complexes show a ligand-based mixed-valence (LBMV) state with SQ and Cat ligands. The LBMV state was confirmed by the presence of the interligand intervalence charge-transfer band. Spectroscopic studies in several solvent media demonstrate that the ligand dissociation included in the conversion of Cr(III)(X(4)SQ)(3) to 1-6 occurs only in solvents with relatively high polarity. On the basis of these results, the effects of solvent media were examined and an equilibrium, Cr(III)(X(4)SQ)(3) <--> Cr(III)(X(4)BQ)(X(4)SQ)(X(4)Cat) (BQ = o-benzoquinone), is proposed by assuming an interligand electron transfer induced by solvent polarity.     

Resonance Raman Spectra of [M(6)X(8)Y(6)](2)(-) Cluster Complexes (M = Mo, W; X, Y = Cl, Br, I)

Resonance Raman spectra of the cubic metal-halide complexes having the general formula [M(6)X(8)Y(6)](2)(-) (M = Mo or W; X, Y = Cl, Br, or I) are reported. The three totally symmetric fundamental vibrations of these complexes are identified. The extensive mixing of the symmetry coordinates that compose the symmetric normal modes expected in these systems is not observed. Instead the "group-frequency" approximation is valid. Furthermore, the force constants of both the apical and face-bridging metal-halide bonds are insensitive to the identity of either the metal or the halide. Raman spectra of related complexes with methoxy and benzenethiol groups as ligands are reported along with the structural data for [Mo(6)Cl(8)(SPh)(6)][NBu(4)](2). Crystal data for [Mo(6)Cl(8)(SPh)(6)][NBu(4)](2) at -156 degrees C: monoclinic space group P2(1)/c; a = 12.588(3), b = 17.471(5), c = 20.646(2) ?; beta = 118.53(1) degrees, V = 3223.4 ?(3); d(calcd) = 1.664 g cm(-)(3); Z = 2.     

Thermal and electrochemical C-X activation (X = Cl,Br, I) by the strong Lewis acid Pd3(dppm)3(CO)2+ cluster and its catalytic applications

The stoichiometric and catalytic activations of alkyl halides and acid chlorides by the unsatured Pd(3)(dppm)(3)(CO)(2+) cluster (Pd(3)(2+)) are investigated in detail. A series of alkyl halides (R-X; R = t-Bu, Et, Pr, Bu, allyl; X = Cl, Br, I) react slowly with Pd(3)(2+) to form the corresponding Pd(3)(X)(+) adduct and "R(+)". This activation can proceed much faster if it is electrochemically induced via the formation of the paramagnetic species Pd(3)(+). The latter is the first confidently identified paramagnetic Pd cluster. The kinetic constants extracted from the evolution of the UV-vis spectra for the thermal activation, as well as the amount of electricity to bring the activation to completion for the electrochemically induced reactions, correlate the relative C-X bond strength and the steric factors. The highly reactive "R(+)" species has been trapped using phenol to afford the corresponding ether. On the other hand, the acid chlorides react rapidly with Pd(3)(2+) where no induction is necessary. The analysis of the cyclic voltammograms (CV) establishes that a dissociative mechanism operates (RCOCl --> RCO(+) + Cl(-); R = t-Bu, Ph) prior to Cl(-) scavenging by the Pd(3)(2+) species. For the other acid chlorides (R = n-C(6)H(13), Me(2)CH, Et, Me, Pr), a second associative process (Pd(3)(2+) + RCOCl --> Pd(3)(2+.....)Cl(CO)(R)) is seen. Addition of Cu(NCMe)(4)(+) or Ag(+) leads to the abstraction of Cl(-) from Pd(3)(Cl)(+) to form Pd(3)(2+) and the insoluble MCl materials (M = Cu, Ag) allowing to regenerate the starting unsaturated cluster, where the precipitation of MX drives the reaction. By using a copper anode, the quasi-quantitative catalytic generation of the acylium ion ("RCO(+)") operates cleanly and rapidly. The trapping of "RCO(+)" with PF(6)(-) or BF(4)(-) leads to the corresponding acid fluorides and, with an alcohol (R'OH), to the corresponding ester catalytically, under mild conditions. Attempts were made to trap the key intermediates "Pd(3)(Cl)(+)...M(+)" (M(+) = Cu(+), Ag(+)), which was successfully performed for Pd(3)(ClAg)(2+), as characterized by (31)P NMR, IR, and FAB mass spectrometry. During the course of this investigation, the rare case of PF(6)(-) hydrolysis has been observed, where the product PF(2)O(2)(-) anion is observed in the complex Pd(3)(PF(2)O(2))(+), where the substrate is well-located inside the cavity formed by the dppm-Ph groups above the unsatured face of the Pd(3)(2+) center. This work shows that Pd(3)(2+) is a stronger Lewis acid in CH(2)Cl(2) and THF than AlCl(3), Ag(+), Cu(+), and Tl(+).