Richard L. Short

Crystal structure of NH4[Ni{S2C2(CN)2}2]·H2O, the first equidistant stack d7 monoanion metal dithiolene complex

The X-ray crystal structure of NH4[Ni{S2C2(CN)2}2]·H2O has revealed that the planar [Ni{S2C2(CN)2}2]– anions form an eclipsed equidistant stack structure with a repeat distance of 3.918(8)A. At 98 K the repeat distance in the stack direction is double that at room temperature indicating that the anions are now associated as dimers. The room-temperature structure and low-temperature transition are related to the unusual magnetic properties of this compound.

SYNTHESIS OF TRIMETHYLSILYLATED GERMANOCENES - X-RAY STRUCTURE OF AND STERIC EFFECTS IN HEXAKIS(TRIMETHYLSILYL)GERMANOCENE

Abstract Reaction of GeCl2 · dioxane with mono-, bis- and tris-(trimethylsilyl)cyclopentadienyllithium yields bis-, tetrakis- and hexakis-(trimethylsilyl)germanocene. A single-crystal X-ray diffraction study shows the metallocene species with six silyl groups to consist of nearly parallel C5-units, bound symmetrically to the germanium center. The eclipsed conformation of the rings and the 1,2.4-silyl substitution pattern leave only two silyl groups face to face, effecting a small bending of the molecule. The molecular structure has been examined with the steric energy program EENY2. The conformation found in the crystal is close to the lowest minimum given by the calculations.

Carbon–carbon bond formation through olefin–methylcarbyne linkage at a diruthenium centre: X-ray crystal structure of [Ru2(CO)(µ-CO){µ-η1,η3-C(Me)C(Me)CH2}(η-C5H5)2]

Reaction of [Ru2(CO)2(µ-CO)(µ-CMe)(η-C5H5)2]+ with RCHCH2(R = H or Me) under u.v. radiation provides [Ru2(CO)(µ-CO){µ-η1,η3-C(Me)C(R)-CH2}(η-C5H5)2] which, for RH, may also be obtained by treatment of [Ru2(CO)(C2H4)(µ-CO)2(η-C5H5)2] with MeLi, HBF4 successively; the structure of [Ru2(CO)(µ-CO){µ-η1,η3-C(Me)C(Me)CH2}(η-C5H5)2] has been determined by X-ray diffraction.

Synthesis and characterisation of binuclear and trinuclear organoimido complexes of tungsten-(VI) and -(V) and a binuclear tungsten(V) oxoanion. X-Ray crystal structures of [{WCl4(NEt)}2], [P(CH2Ph)Ph3][W3Cl7(NBut)3(µ-NPh)3], [P(CH2Ph)Ph3][W2Cl7(NR)2](R = Et or Ph), and [P(CH2Ph)Ph3][W2O2Cl7]

The X-ray crystal structure of [{WCl4(NEt)}2] has been determined and shows the molecule to be binuclear with asymmetric chlorine bridges and linear ethylimido groups having a W–N distance of 1.69(1)A. Binuclear, mixed organoimido compounds [{WCl2(NBut)(µ-NR)(NH2But)}2](R = Ph or C6H4Me-p) with asymmetric NR bridges have been converted to the trinuclear anions [W3Cl7(NBut)3(µ-NR)3]–. The X-ray crystal structure of [W3Cl7(NBut)3(µ-NPh)3]– shows it to contain terminal, linear NBut groups with an average W–N distance of 1.70 A, almost symmetrical bridging NPh groups with an average W–N distance of 2.00 A, and a triply bridging chlorine. Carbon-13 and 1H n.m.r. spectra of this anion show that rotation of the phenyl rings in the µ-NPh groups is restricted. Reduction of [WXCl4] with 1 equivalent of sodium amalgam in the presence of chloride ions gave the distorted confacial bioctahedral tungsten(V) anions [W2X2Cl7]–(X = NEt, NPh, or O). X-Ray crystal structures of all three anions have been determined and show the π-bonding ligands to be terminal with average W–N distances of 1.69 (X = NEt) and 1.72 A(X = NPh) and an average W–O distance of 1.67 A. The W–W distances in the three anions are 2.839(4)(X = NEt), 2.835(4)(X = NPh), and 2.849(1)A(X = O).

Comparison of the structures and properties of [N(C2H5)4][Pt{S2C2(CN)2}2] and [H3O]x[NH4]1−x]Pt{S2C2(CN)2}2]•2−xH2O

The crystal structures of [N(C2H5)4][Pt{S2C2(CN)2}2] and [H2O]x[NH4]1–x[Pt{S2C2(CN)2}2]·2 –xH2O are described. Both compounds contain anion dimers. In the former the dimer has a slipped configuration with Pt ⋯ S interactions whereas the latter contains the anions in an eclipsed configuration with a Pt over Pt arrangement. The difference in the structures is related to the size and nature of the cation. The electrical conduction and magnetic properties are related to the structures.

The reaction of cis dioxobis(2,4 pentanedionato)molybdenum (VI) and 2,2′ pyridylbenzoxazole (L), a novel route to β[Mo8O26]4−

MoO 2 (C 5 H 7 O 2 ) 2 , where C 5 H 7 O 2 is 2,4-pentanedione (acac), reacts with 2-2′ pyridylbenzoxazole in acetone to give a product with stoichiometry, Mo 3 C 24 H 16 N 6 O 12 . This product dissolves readily in dimethylformamide to give a brown solution which on standing for several weeks yielded crystals. An X-ray structure determination showed these crystals to contain uncoordinated 2-2′pyridylbenzoxazole and [(CH 3 ) 2 NH 2 ] 4 + [Mo 8 O 26 ] 4− .

Structure and properties of the thiobarbituric acid–malonaldehyde chromogen

An X-ray crystallographic study supported by 1H n.m.r. provides unequivocal evidence that the chromogen formed from the reaction of malonaldehyde with 4,6-dihydroxy-2-mercaptopyrimidine (thiobarbituric acid) is the highly stable delocalised anion (2) from 5,5′-(propane-1,3-diylidene)bis-(2-thioxopyrimidine-4,6-dione).

Reactions of diazo-compounds with the electron-rich germylene Ge[N(SiMe3)2]2. Characterisation and some addition reactions of [(Me3Si)2N]2GeNNC(COOMe)2: crystal and molecular structure of [(Me3Si)2N]2Ge[NHNC(COOMe)2][C(N2)COPh]

Two forms of the stable germyleneazine [(Me3Si)2N]2GeNNC(COOMe)2, formed by addition of the diazo-compound N2C(COOMe)2 to the electron-rich germylene Ge[N(SiMe3)2]2 have been characterised in solution by 1H and 13C n.m.r. spectroscopy. MNDO calculations on the simpler analogue [(H3Si)2N]2GeNNC(COOMe)2 indicate that the two forms have planar transoid and cisoid GeNNC groups respectively, with the cisoid isomer as the more stable: the calculations also indicate that charge-controlled additions of electrophiles will occur at N1, adjacent to germanium, while all nucleophilic addition will occur at Ge. Some adducts of [(Me3Si)2N]2GeNNC(COOMe)2 with weak acids HX are described; in all cases 1,2-addition of HX occurs across the Ge–N1 bond to yield [(Me3Si)2N]2Ge(X)[NHNC(COOMe)2]. Crystals of one such adduct [(Me3Si)2N]2Ge[NHNC(COOMe)2][C(N2)COPh] are triclinic, space group P, with a= 9.627(2), b= 12.672(19), c= 15.702(3)A, α= 101.66(4), β= 85.02(2), γ= 77.65(5)°, and Z= 2. The structure was refined from diffractometer data (5 173 observed reflections) to an R value of 0.046. The structure determination confirms the 1,2-addition of HC(N2)COPh across the Ge–N1 bond of [(Me3Si)2N]2-GeNNC(COOMe)2 and reveals a free diazo-group, sterically unconstrained. Reaction of tosyl azide with Ge[N(SiMe3)2] follows a different course from the reactions involving diazo-compounds; nitrogen is lost and the product is a polygermazane {[(Me3Si)2N]2GeNSO2C6H4Me-p}n, which is insoluble in aqueous media and all common organic solvents, wholly resistant to hot 50% aqueous alkali, but readily hydrolysed by concentrated hydrochloric acid.

Bis(organoimido)-complexes of tungsten(IV): the crystal and molecular structures of tetrachlorobis(t-butylamine)bis(t-butylimido)bis(µ-p-tolylimido)-ditungsten(VI) and tetrachlorobis(µ-phenylimido)-bis(t-butylamine) bis(t-butylimido)ditungsten(VI)

The tungsten(VI) organoimido complexes [{WCl4(NR)}2](R = Ph, C6H4Me-p, Pri, or Me) were treated with the silylamines Me3SiNHR″(R″= Ph, But, Pri, or Et) to form the dimeric complexes [{WCl2(NR)(NR″)(NH2R″)}2], containing terminal and bridging organoimido ligands, cis-oriented chloro ligands, and co-ordinated amine. [{WCl2(NPh)(NBut)(NH2But)}2] was also obtained from the reaction of [{WCl4(NPh)}2] with NH2But. Spectral studies suggest that these complexes arise from two cis-oriented organoimido groups by an inter-ligand proton-transfer process which proceeds regardless of the size of the group R. The structure of [{WCl2(NC6H4Me-p)(NBut)(NH2But)}2] was determined by X-ray crystallography and shown to have distorted edge-shared bioctahedral geometry with terminal t-butylimido groups and bridging unsymmetrical arylimido groups and with the longer W–N bridge bonds trans to the terminal t-butylimido group. The t-butylamine ligands are involved in intramolecular N–H ⋯ Cl bridging within the dimeric unit, which explains some striking features found in the 1H n.m.r. spectrum. Full details are also given of the crystal structure of [{WCl2(NPh)(NBut)(NH2But)}2].

Preparation and magnetic properties of a range of metal and organic cation salts of 2,3-dicyano-1,4-naphthoquinone (DCNQ). X-Ray crystal structure of (methyltriphenylphosphonium)1(DCNQ)1(H2O)1 and 2-dicyanomethylene-indan-1,3-dione (DCID). The rearrangement of DCID to DCNQ

A series of salts (11) formed by the 2,3-dicyano-1,4-naphthoquinone (DCNQ) radical anion with the following counterions has been studied: (a) lithium, (b) methyltriphenylphosphonium, (c) sodium, (d) tetrabutylammonium, (e) tetraphenylarsonium, (f) rubidium, (g) caesium, (h) copper, (i) nickel, (j) cobalt, (k) zinc, (l) tetrathiafulvalene (TTF), and (m) tetramethyl-TTF. A novel method for the preparation of DCNQ salts (11a–c), (11l), and (11m) is described: this involves isomerisation of 2-dicyanomethyleneindan-1,3-dione (7) which is initiated by one-electron transfer to (7) from iodide ion, from sodium metal, or from TTF and TMTTF. DCNQ salts (11b–1) have been prepared from the lithium-DCNQ salt (11a) by cation exchange. The magnetic properties of a selection of these salts have been studied: salts (11a), (11b), (11e), and (11l) are diamagnetic while salts (11d) and (11h) are paramagnetic. The single crystal X-ray structures of the acceptor molecule 2-dicyanomethyleneindan-1,3-dione (7) and the anion radical salt (11b)·H2O have been determined. The anions of salt (11b)·H2O pack in pairs across a centre of symmetry in the crystal lattice. The TTF and TMTTF salts (11l) and (11m) are both semiconductors, σrt= 1.0 and 4 × 10–3 S cm–1, respectively, whereas salts (11a), (11b), (11d), and (11h) are electrical insulators.