Transition metal complexes containing organoimido (nr) and related ligands

Mixed dinitrogen-organocyanamide complexes of molybdenum(0) and their protic conversion into hydrazide and amidoazavinylidene derivatives

Organocyanamides, Ntbd1;CNR(2) (R = Me or Et), react with trans-[Mo(N(2))(2)(dppe)(2)] (1, dppe = Ph(2)PCH(2)CH(2)PPh(2)), in THF, to give the first mixed molybdenum dinitrogen-cyanamide complexes trans-[Mo(N(2))(NCNR(2))(dppe)(2)] (R = Me 2a or Et 2b) which are selectively protonated at N(2) by HBF(4) to yield the hydrazide(2-) complexes trans-[Mo(NNH(2))(NCNR(2))(dppe)(2)][BF(4)](2) (R = Me, 3a, or Et, 3b). On treatment with Ag[BF(4)], oxidation and metal fluorination occur, and the ligating cyanamide undergoes an unprecedented beta-protonation at the unsaturated C atom to form trans-[MoF(NCHNR(2))(dppe)(2)][BF(4)](2) (R = Me, 4a, or Et, 4b) compounds which present the novel amidoazavinylidene (or amidomethyleneamide) ligands. Complexes 4 are also formed from the corresponding compounds 3, with liberation of ammonia and hydrazine. The crystal structure of 2b was determined by single-crystal X-ray diffraction analysis which indicates that the N atom of the amide group has a trigonal planar geometry.

The effect of substituents on the phenyl portion of the imido ligand on the structure and properties of molybdenum(VI) imido complexes

Anilines with alkyl substituents on the phenyl ring (ArNH2 = 2,4,6-trimethylaniline; 2,3-, 2,4-, 2,6-, and 3,4-dimethylaniline; and 2,6-diisopropylaniline) react with MoO(X)2(dtc)2 (X = Cl or Br; dtc = diethyldithiocarbamate) in methanol in the presence of 2 equiv of triethylamine to form ionic imido complexes of the type [MoNAr(dtc)3]2[Mo6O19] or MoNAr(dtc)3]4[Mo8O26]. The same reaction in THF with butyllithium as base yields imido complexes of the type MoNAr(X)2(dtc)2. The structures of three ionic, five chloro, and two bromo complexes have been determined by X-ray crystallography. In all complexes, the molybenum center is a distorted pentagonal bipyramid. While the structures are similar, the angles of the imido linkages differ. The effect of the substituents on the phenyl ring of the imido ligand on the 95Mo NMR chemical shifts was determined. The Mo nucleus becomes more deshielded with the substituents in the following order: 3,4-Me2 < 2,3-Me2 < 2,4-Me2 < 2,6-Me2 < 2,4,6-Me3 < 2,6 isopropyl. Complexes with more deshielded 95Mo centers tend to have angles of the imido linkage that are closer to 180 degrees.

Chemistry of the strong electrophilic metal fragment [(99)Tc(N)(PXP)](2+) (PXP = diphosphine ligand). A novel tool for the selective labeling of small molecules

Monosubstituted [M(N)Cl(2)(POP)] [M = Tc, 1; Re, 2] and [M(N)Cl(2)(PNP)] [M = Tc, 3; Re, 4] complexes were prepared by reaction of the precursors [M(N)Cl(4)](-) and [M(N)Cl(2)(PPh(3))(2)] (M = Tc, Re) with the diphosphine ligands bis(2-diphenylphosphinoethyl)ether (POP) and bis(2-diphenylphosphinoethyl)methoxyethylamine (PNP) in refluxing dichloromethane/methanol solutions. In these compounds, the diphosphine acted as a chelating ligand bound to the metal center through the two phosphorus atoms. Considering also the weak interaction of the heteroatom (N or O) located in the middle of the carbon backbone connecting the two P atoms, we found that the coordination arrangement of the diphosphine ligand could be viewed as either meridional (m) or facial (f), and the resulting geometry as pseudooctahedral. The heteroatom of the diphosphine ligand was invariably located trans to the nitrido linkage, as established by X-ray diffraction analysis of the representative compounds 2m and 4f. Density functional theoretical calculations showed that in POP-type complexes the mer form is favored by approximately 6 kcal mol(-1), whereas mer and fac isomers are almost isoenergetic in PNP-type complexes. A possible role of noncovalent interactions between the phosphinic phenyl substituents in stabilizing the fac-isomer was also highlighted. The existence of fac-mer isomerism in this class of complexes was attributed to the strong tendency of the two phosphorus atoms to occupy a reciprocal trans-position within the pseudooctahedral geometry. The switching of P atoms between cis- and trans-configurations was confirmed by the observation that the fac isomers, 1f and 2f, were irreversibly transformed, in solution, into the corresponding mer isomers, 1m and 2m, thus suggesting that fac complexes are more reactive species. Theoretical calculations supported this view by showing that the lowest unoccupied orbitals of the fac isomers are more accessible to a nucleophilic attack with respect to those of the mer ones. Furthermore, the large participation of the Cl orbitals to the HOMO, which is a metal-ligand pi* antibonding in the complex basal plane, shows that the Tc-Cl bonds are labile. As a consequence, facial isomers could be considered as highly electrophilic intermediates that were selectively reactive toward substitution by electron-rich donor ligands. Experimental evidence was in close agreement with this description. It was found that fac-[M(N)Cl(2)(PXP)] complexes easily underwent ligand-exchange reactions with bidentate donor ligands such as mercaptoacetic acid (NaHL(1)), S-methyl 2-methyldithiocarbazate (H(2)L(2)), diethyldithiocarbamate sodium salt (NaL(3)), and N-acetyl-L-cysteine (H(2)L(4)) to afford stable asymmetrical heterocomplexes of the type fac-[M(N)(L(n))(POP)](+/0) (5-8) and fac-[M(N)(L(n))(PNP)](+/0) (9-14) comprising two different polydentate chelating ligands bound to the same metal center. In these reactions, the bidentate ligand replaced the two chloride atoms on the equatorial plane of the distorted octahedron, leaving the starting fac-[M(N)(PXP)](2+) (X = O, N) moieties untouched. No formation of the corresponding symmetrical complexes containing two identical bidentate ligands was detected over a broad range of experimental conditions. Solution-state NMR studies confirmed that the structure in solution of these heterocomplexes was identical to that established in the solid state by X-ray diffraction analysis of the prototype complexes fac-[M(N)(HL(2))(POP)][BF(4)] [M = Tc, 7; Re, 8] and fac-[Tc(N)(HL(2))(PNP)][BF(4)], 11. In conclusion, the novel metal fragment fac-[M(N)(PXP)](2+) could be utilized as an efficient synthon for the preparation of a large class of asymmetrical, nitrido heterocomplexes incorporating a particular diphosphine ligand and a variety of bidentate chelating molecules.

Reversible intramolecular hydride transfer between tantalum and an aromatic ring: an eta(5)-cyclohexadienyl complex as a masked hydride

The methyl triflate complex (2,6-Mes2C6H3N=)(2,6-Mes2C6H3NH)TaMe(OSO2CF3) reacts cleanly with H2 to give the eta5-cyclohexadienyl complex 3. Complex 3 therefore results from the insertion of an arene ring into an M-H bond, which has been proposed as the first step in catalytic arene hydrogenations. This insertion is reversible, such that 3 behaves as a "masked hydride" in its reaction chemistry.

Pyridylazole chelation of oxorhenium(V) and imidorhenium(V). Rates and trends of oxygen atom transfer from Re(V)O to tertiary phosphines

The concerned azoles are 2-(2-pyridyl)benzoxazole (pbo) and 2-(2-pyridyl)benzthiazole (pbt). These react with ReOCl(3)(PPh(3))(2) in benzene, affording Re(V)OCl(3)(pbo) and Re(V)OCl(3)(pbt), which undergo facile oxygen atom transfer to PPh(2)R (R = Ph, Me) in dichloromethane solution, furnishing Re(III)(OPPh(2)R)Cl(3)(pbo) and Re(III)(OPPh(2)R)Cl(3)(pbt). The oxo species react with aniline in toluene solution, yielding the imido complexes Re(V)(NPh)Cl(3)(pbo) and Re(V)(NPh)Cl(3)(pbt). The X-ray structures of pbt, ReOCl(3)(pbt), Re(OPPh(3))Cl(3)(pbt), and Re(NPh)Cl(3)(pbo) are reported. The lattice of pbt consists of stacked dimers. In all the complexes the azole ligand is N,N-chelated and the ReCl(3) moiety is meridionally disposed. In ReOCl(3)(pbt) the metal-oxo bond length is 1.607(9) A. The second-order rates and the associated activation parameters of the oxygen atom transfer reactions of the Re(V)O chelates with PPh(2)R are reported. The large and negative entropy of activation (approximately -24 eu) is consistent with an associative pathway involving nucleophilic phosphine attack. The rate increases with phosphine basicity (PPh(2)Me > PPh(3)) and azole heteroatom electronegativity (O(pbo) > S(pbt)). Logarithmic rate constants for ReOCl(3)(pbo), ReOCl(3)(pbt), and ReOCl(3)(pal) are found to correlate linearly with Re(VI)O/Re(V)O reduction potentials (pal is pyridine-2-(N-p-tolyl)aldimine). The relatively low rate constant of ReOCl(3)(pbt) compared to that of ReOCl(3)(pal) is consistent with the observed shortness of the metal-oxo bond in the former. Crystal data are as follows: (pbt) empirical formula C(12)H(8)N(2)S, crystal system orthorhombic, space group Pca2(1), a = 13.762(9) A, b = 12.952(8) A, c = 11.077(4) A, V = 1974(2) A(3), Z = 8; (ReOCl(3)(pbt)) empirical formula C(12)H(8)Cl(3)N(2)OSRe, crystal system monoclinic, space group P2(1)/c, a = 11.174(7) A, b = 16.403(10) A, c = 7.751(2) A, beta = 99.35(4) degrees, V = 1401.8(13) A(3), Z = 4; (Re(NPh)Cl(3)(pbo)) empirical formula C(18)H(13)Cl(3)N(3)ORe, crystal system monoclinic, space group P2(1)/c, a = 9.566(6) A, b = 16.082(8) A, c = 11.841(5) A, beta = 94.03(4) degrees, V = 1817(2) A(3), Z = 4.

Syntheses, reactivity, and pi-donating ligand metathesis reaction of five-coordinate sixteen-electron manganese(I) complexes: crystal structures of [Mn(CO(3)(-TeC(6)H(4)-o-NH-)](-), [(Mn(CO)(3))2(mu-SC(6)H(4)-o-S--S--C(6)H(4)-o-mu-S--)], [(CO)(3)Mn(mu-SC(6)H(4)-o-NH(2)-)]2, and [(CO)(3)Mn(mu-SC(8)N(2)H(4)-o-S-)](2)(2-)

The preparation of the varieties of five-coordinate sixteen-electron manganese(I) complexes [Mn(CO)(3)(-EC(6)H(4)-o-E'-)](-) (E = Te, Se, S, O; E' = NH, S, O) by (a) oxidative addition of 2-aminophenyl dichalcogenides to anionic manganese(0)-carbonyl, (b) pi-donating ligand metathesis reaction of complex [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-), and (c) reduction /deprotonation of the neutral dimetallic [(Mn(CO)(3))(2)(mu-SC(6)H(4)-o-S-S-C(6)H(4)-o-mu-S-)]/[(CO)(3)Mn(mu-SC(6)H(4)-o-NH(2)-)](2) proved successful approaches in this direction. The IR nu(CO) data of the coordinatively and electronically unsaturated [Mn(CO)(3)(-EC(6)H(4)-o-E'-)](-) (E = Te, Se, S, O; E' = NH, S, O) complexes suggest the relative order of pi-donating ability of the series of bidentate ligands being [TeC(6)H(4)-o-NH](2)(-) > [SeC(6)H(4)-o-NH](2)(-) > [SC(6)H(4)-o-NH](2)(-) > [SC(6)H(4)-o-S](2)(-) > [SC(6)H(4)-o-O](2)(-) > [OC(6)H(4)-o-O](2)(-). Proton NMR spectra of the [Mn(CO)(3)(-EC(6)H(4)-o-NH-)](-) (E = Te, Se, S) derivatives show the low-field shift of the amide proton ((1)H NMR (C(4)D(8)O): delta 9.66 (br) ppm (E = Te), 9.32 (br) ppm (E = Se), 8.98 (br) ppm (E = S)). The formation of the dimetallic [(CO)(3)Mn(mu-SC(8)N(2)H(4)-o-S-)](2)(2-) can be interpreted as coordinative association of two units of unstable mononuclear [(CO)(3)Mn(-SC(8)N(2)H(4)-o-S-)](-) and reflects the pi-donating ability of the bidentate ligand is responsible for the formation of pentacoordinate, sixteen-electron manganese(I) carbonyl complexes. The neutral bimetallic manganese(I)-bismercaptophenyl disulfide complex [(Mn(CO)(3))(2)(mu-SC(6)H(4)-o-S-S-C(6)H(4)-o-mu-S-)] with internal S-S bond length of 2.222(1) A and the five-coordinate sixteen-electron complex [Mn(CO)(3)(-SC(6)H(4)-o-S-)](-) are chemically interconvertible. In a similar fashion, treatment of complex [Mn(CO)(3)(-SC(6)H(4)-o-NH-)](-) with HBF(4) yielded neutral dinuclear complex [(CO)(3)Mn(mu-SC(6)H(4)-o-NH(2)-)](2) and showed that the amine deprotonation is reversible. Investigations of pi-donating ligand metathesis reactions of complex [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-) revealed that the stable intermediate, not the pi-donating ability of bidentate ligands, is responsible for the final protonation/oxidation product. This argument is demonstrated by reaction of [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-) with 1,2-benzenedithiol, hydroxythiophenol, and catechol, respectively leading to the formation of [Mn(CO)(3)(-EC(6)H(4)-o-E'-)](-) (E = S, O; E' = S, O), although any pi-donor containing the amido group is a more effective donor than any other pi-donor lacking an amido group. Also, the reactions of [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-) with electrophiles occurring at the more electron-rich amide site support that the more electron-rich amide donor of the chelating 2-tellurolatophenylamido occupies an equatorial site as indicated by a shorter Mn(I)-N bond length of the distorted trigonal bipyramidal [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-).

Synthesis, characterization, and C—N bond cleavage of tungsten(VI)arylimido-calix[4]arene complexes

The tetradentate, partially flattened cone tungsten(VI) imido-calix[4]arene derivative [W(NC6H5)(t-BucalixH)]+Cl–, (4), is formed in good yield from reaction of p-tert-butyl-calix[4]arene (t-BucalixH4), and W(NC6H5)Cl4. A reaction mechanism involving a putative, bidentate calixarene intermediate W(NC6H5)(t-BucalixH2)Cl2 (3), which partitions by reversible cleavage of the imido group to give the known tetradentate calixarene complex W(t-Bucalix)Cl2 (2), and elimination of HCl to form the thermodynamic imido product 4 is proposed. A series of iso structural [W(NAr)(t-BucalixH)]+Cl– (Ar = C6H5 or o,m,p-C6H4CH3) imido derivatives (4–7), which adopt a partially flattened cone conformation in solution has been prepared by reaction of dichloride 2 with H2NAr (Ar = C6H5, o,m,p-C6H4CH3). Reaction of W(t-Bucalix)Cl2 with aliphatic amines affords a red product formulated as the nitrido complex, 9, which results from facile cleavage of the imido C—N bond.Key words: calix[4]arene complex, imido complex, nitrido complex, C—N bond cleavage, conformation, metallocalixarene.

Oxygen atom transfer from nitrogenous ReVO reagents to diphosphines and subsequent transformations. Rhenium(III) products and reaction models

The concerned diphosphines are Ph2P(CH2)nPPh2 (1), abbreviated PnP, and the ReVO reagents are ReOCl3L (2) and ReOCl3L' (3), where L and L' are the azopyridine and pyridine-imine ligands p-ClC6H4N=NC5H4N and p-MeC6H4N=CHC5H4N, respectively. One atom transfer from 2 to 1 has afforded Re(OPnP)Cl3L (4a, n = 1; 4b, n = 2; 4c, n = 3). Of these 4b and 4c are stable, but 4a undergoes spontaneous isomerization to Re(PlPO)Cl3L (5) in solution. Two-atom transfer studied with both 2 and 3 has afforded binuclear LCl3Re(OPnPO)ReCl3L (8a, n = 2; 8b, n = 3) and L'Cl3Re(OPnPO)ReCl3L' (9a, n = 2; 9b, n = 3) for n = 2, 3 and mononuclear Re(OP1PO)Cl3L (11) and Re(OP1PO)Cl3L' (12) for n = 1. The mixed system L'Cl3Re(OP2PO)ReCl3L (10) has been prepared from 3 and 4b. The complex Re(PPh3)Cl3L (7a) is furnished by the reaction of Re(OPPh3)Cl3L (6a) or 4b or 11 with PPh3. The species have been characterized with the help of spectral, electrochemical, and X-ray structural data. All the complexes have mer geometry except 5 and 7a, which have fac geometry. The latter is best suited for concurrent Re-N and Re-P back-bonding. Variable-temperature rate data of the reaction 4a-->5 are consistent with an intramolecular strongly associative transition state (delta S++, -22.6 eu) in which the dangling phosphine function lies close to the metal. Two-atom transfer to P1P is believed to proceed via a transient binuclear intermediate which undergoes cleavage at one end due to steric crowding, affording 11 and 12. Crystal data for the complexes are as follows: 5.1.5 C6H6, empirical formula C45H39Cl4N3OP2Re, crystal system triclinic, space group P1, a = 10.034(2) A, b = 10.737(2) A, c = 20.357(4) A, alpha = 89.38(3) degrees, beta = 87.79(3) degrees, gamma = 80.22(3) degrees, V = 2159.7(7) A3, Z = 2; 7a.CH2Cl2, empirical formula C30H25Cl6N3PRe, crystal system monoclinic, space group P2(1)/n, a = 11.695(6) A, b = 17.745(7) A, c = 15.459(9) A, beta = 100.94(5) degrees, V = 3150(3) A3, Z = 4; 9a, empirical formula C52H48Cl6N4O2P2Re2, crystal system monoclinic, space group C2/c, a = 19.769(12) A, b = 12.864(6) A, c = 22.20(2) A, beta = 101.76(6) degrees, V = 5530(6) A3, Z = 4; 11, empirical formula C36H30Cl4N3O2P2Re, crystal system monoclinic, space group I2/a, a = 16.866(6) A, b = 12.583(6) A, c = 34.78(2) A, beta = 99.22(4) degrees, V = 7285(7) A3, Z = 8.

Computational study of analogues of the uranyl ion containing the -N=U=N- unit: density functional theory calculations on UO2(2+), UON+, UN2, UO(NPH3)3+, U(NPH3)2(4+), [UCl4[NPR3]2] (R = H, Me), and [UOCl4[NP(C6H5)3]]

The electronic and geometric structures of the title species have been studied computationally using quasi-relativistic gradient-corrected density functional theory. The valence molecular orbital ordering of UO2(2+) is found to be pi g < pi u < sigma g << sigma u (highest occupied orbital), in agreement with previous experimental conclusions. The significant energy gap between the sigma g and sigma u orbitals is traced to the "pushing from below" mechanism: a filled-filled interaction between the semi-core uranium 6p atomic orbitals and the sigma u valence level. The U-N bonding in UON+ and UN2 is significantly more covalent than the U-O bonding in UON+ and UO2(2+). UO(NPH3)3+ and U(NPH3)2(4+) are similar to UO2(2+), UON+, and UN2 in having two valence molecular orbitals of metal-ligand sigma character and two of pi character, although they have additional orbitals not present in the triatomic systems, and the U-N sigma levels are more stable than the U-N pi orbitals. The inversion of U-N sigma/pi orbital ordering is traced to significant N-P (and P-H) sigma character in the U-N sigma levels. The pushing from below mechanism is found to destabilize the U-N f sigma molecular orbital with respect to the U-N d sigma level in U(NPH3)2(4+). The uranium f atomic orbitals play a greater role in metal-ligand bonding in UO2(2+), UN2, and U(NPH3)2(4+) than do the d atomic orbitals, although, while the relative roles of the uranium d and f atomic orbitals are similar in UO2(2+) and U(NPH3)2(4+), the metal d atomic orbitals have a more important role in the bonding in UN2. The preferred UNP angle in [UCl4(NPR3)2] (R = H, Me) and [UOCl4(NP(C6H5)3)]- is found to be close to 180 degrees in all cases. This preference for linearity decreases in the order R = Ph > R = Me > R = H and is traced to steric effects which in all cases overcome an electronic preference for bending at the nitrogen atom. Comparison of the present iminato (UNPR3) calculations with previous extended Hückel work on d block imido (MNR) systems reveals that in all cases there is little or no preference for linearity over bending at the nitrogen when R is (a) only sigma-bound to the nitrogen and (b) sterically unhindered. The U/N bond order in iminato complexes is best described as 3.

Formation of ammonia in the reactions of a tungsten dinitrogen with ruthenium dihydrogen complexes under mild reaction conditions

Treatment of cis-[W(N2)2(PMe2Ph)4] (5) with an equilibrium mixture of trans-[RuCl(eta 2-H2)(dppp)2]X (3) with pKa = 4.4 and [RuCl(dppp)2]X (4) [X = PF6, BF4, or OTf; dppp = 1,3-bis(diphenylphosphino)propane] containing 10 equiv of the Ru atom based on tungsten in benzene-dichloroethane at 55 degrees C for 24 h under 1 atm of H2 gave NH3 in 45-55% total yields based on tungsten, together with the formation of trans-[RuHCl(dppp)2] (6). Free NH3 in 9-16% yields was observed in the reaction mixture, and further NH3 in 36-45% yields was released after base distillation. Detailed studies on the reaction of 5 with numerous Ru(eta 2-H2) complexes showed that the yield of NH3 produced critically depended upon the pKa value of the employed Ru(eta 2-H2) complexes. When 5 was treated with 10 equiv of trans-[RuCl(eta 2-H2)(dppe)2]X (8) with pKa = 6.0 [X = PF6, BF4, or OTf; dppe = 1,2-bis(diphenylphosphino)ethane] under 1 atm of H2, NH3 was formed in higher yields (up to 79% total yield) compared with the reaction with an equilibrium mixture of 3 and 4. If the pKa value of a Ru(eta 2-H2) complex was increased up to about 10, the yield of NH3 was remarkably decreased. In these reactions, heterolytic cleavage of H2 seems to occur at the Ru center via nucleophilic attack of the coordinated N2 on the coordinated H2 where a proton (H+) is used for the protonation of the coordinated N2 and a hydride (H-) remains at the Ru atom. Treatment of 5, trans-[W(N2)2(PMePh2)4] (14), or trans-[M(N2)2(dppe)2] [M = Mo (1), W (2)] with Ru(eta 2-H2) complexes at room temperature led to isolation of intermediate hydrazido(2-) complexes such as trans-[W(OTf)(NNH2)(PMe2Ph)4]OTf (19), trans-[W(OTf)(NNH2)(PMePh2)4]OTf (20), and trans-[WX(NNH2)(dppe)2]+ [X = OTf (15), F (16)]. The molecular structure of 19 was determined by X-ray analysis. Further ruthenium-assisted protonation of hydrazido(2-) intermediates such as 19 with H2 at 55 degrees C was considered to result in the formation of NH3, concurrent with the generation of W(VI) species. All of the electrons required for the reduction of N2 are provided by the zerovalent tungsten.

An unexpected '4+2' [N(3)S]:[NS] rhenium(IV) complex formed upon cleavage of a Re(V) imido bond

The reaction of [Re(NMe)Cl(3)(PPh(3))(2)] with the pentadentate [N(3)S(2)] ligand pyN(2)H(2)S(2)-H(2) [2,6-bis(2-mercaptophenylamino)dimethylpyridine] (1) in the presence of triethylamine did not yield the anticipated six-coordinate complex [Re(NMe)(eta(5)-pyN(2)HS(2))] (2), but rather resulted in cleavage of the Re(V)=NMe bond. A novel six-coordinate Re(IV) [N(3)S]/[NS] complex [Re(eta(4)-SC(6)H(4)-2-NCH(2)-C(5)H(3)N-C=NC(6)H(4)-2-S)(eta(2)-NHC(6)H(4)-2-S)] (4) was thus obtained with the simultaneous coordination of 2-aminothiophenol, a dianionic bidentate [NS] donor resulting from the decomposition of the parent ligand and ligand 3, a dianionic tetradentate [N(3)S] donor formed by partial self-condensation and subsequent oxidation of the parent ligand 1. Crystal data for 4: C(25)H(18)N(4)S(3)Re.CH(2)Cl(2), monoclinic, space group P2(1)/n, a = 9.255(2) A, b = 11.181(2) A, c = 25.316(4) A, beta = 97.434(3) degrees , V = 2587.8(7) A(3) and Z = 4.

Macrocycle-supported titanium complexes with chelating imido ligands: analogues of ansa-metallocenes

Reactions of 1,4-dimethyl-1,4,7-triazacyclononane (L1a) and 1,4-diisopropyl-1,4,7-triazacyclononane (L1b) to form 1-aminopropyl-4,7-di-R-1,4,7-triazacyclononane [R = Me (H2L3a) or Pri (H2L3b)] and 1-(2-aminobenzyl)-4,7-di-R-1,4,7-triazacyclononane [R = Me (H2L5a) or Pri (H2L5b)] are reported. Reaction of H2L3a and H2L5a with [Ti(NMe2)2Cl2] gives the ansa-linked macrocycle-imido complexes [Ti(kappa 4-L3a)Cl2] (5a) and [Ti(kappa 4-L5a)Cl2] (6a), respectively, and NHMe2. Reaction of H2L3a with [Ti(NBut)Cl2(py)3] gives [Ti(NBut)(kappa 3-H2L3a)Cl2] (7), which possesses a pendant alkylamine group that does not undergo amine/tert-butylimido group exchange to give 5a and ButNH2. However, reaction of H2L3b and H2L5b with [Ti(NBut)Cl2(py)3] does give amine/tert-butylimido group exchange to form [Ti(kappa 4-L3b)Cl2] (5b), [Ti(kappa 4-L5b)Cl2] (8b), and ButNH2. The compounds 5a,b and 6a,b are isolobal analogues of group 4 ansa-metallocene complexes and relatives of titanium cyclopentadienyl-amido constrained geometry olefin polymerization catalysts. Reaction of 5b with AgOTf affords [Ti(kappa 4-L3b)(OTf)Cl] (8) as the major product, the crystal structure of which has been determined. Alkylation of 6b by RLi gives the dialkyl derivatives [Ti(kappa 4-L5b)(R)2] [R = Me (9) or CH2SiMe3 (10)]. The ethylene polymerization capability of the compounds 5a,b, 6a,b, and 10 in the presence of methylaluminoxane has been determined and compared to that of [Ti(NBut)(kappa 3-L1a,b)Cl2] (11a,b); in all instances, low yields of high-molecular-weight polymer are obtained.

Ruthenium(II) ammine and hydrazine complexes with [N(Ph2PQ)2]- (Q = S, Se) ligands

Reactions of coordinatively unsaturated Ru[N(Ph2PQ)2]2(PPh3) (Q = S (1), Se (2)) with pyridine (py), SO2, and NH3 afford the corresponding 18e adducts Ru[N(Ph2PQ)2]2(PPh3)(L) (Q = S, L = NH3 (5); Q = Se, L = py (3), SO2 (4), NH3 (6)). The molecular structures of complexes 2 and 6 are determined. The geometry around Ru in 2 is pseudo square pyramidal with PPh3 occupying the apical position, while that in 6 is pseudooctahedral with PPh3 and NH3 mutually cis. The Ru-P distances in 2 and 6 are 2.2025(11) and 2.2778(11) A, respectively. The Ru-N bond length in 6 is 2.185(3) A. Treatment of 1 or 2 with substituted hydrazines L or NH2OH yields the respective adducts Ru[N(Ph2PQ)2]2(PPh3)(L) (Q = S, L = NH2NH2 (12), t-BuNHNH2 (14), l-aminopiperidine (C5H10NNH2) (15); Q = Se, L = PhCONHNH2 (7), PhNHNH2 (8), NH2OH (9), t-BuNHNH2 (10), C5H10NNH2 (11), NH2NH2 (13)), which are isolated as mixtures of their trans and cis isomers. The structures of cis-14 and cis-15 are characterized by X-ray crystallography. In both molecular structures, the ruthenium adopts a pseudooctahedral arrangement with PPh3 and hydrazine mutually cis. The Ru-N bond lengths in cis-14.CH2Cl2 and cis-15 are 2.152(3) and 2.101(3) A, respectively. The Ru-N-N bond angles in cis-14.CH2Cl2 and cis-15 are 120.5(4) and 129.0(2) degrees, respectively. Treatment of 1 with hydrazine monohydrate leads to the isolation of yellow 5 and red trans-Ru[N(Ph2PS)2]2(NH3)(H2O) (16), which are characterized by mass spectrometry, 1H NMR spectroscopy, and elemental analyses. The geometry around ruthenium in 16 is pseudooctahedral with the NH3 and H2O ligands mutually trans. The Ru-O and Ru-N bond distances are 2.118(4) and 2.142(6) A, respectively. Oxidation reactions of the above ruthenium hydrazine complexes are also studied.

The syntheses and structures of '3+2' and '2+2+1' oxorhenium mixed-ligand complexes employing 8-hydroxy-5-nitroquinoline as the bidentate N,O donor ligand

The syntheses and structural characterizations of a series of novel '3+2' and '2+2+1' mixed-ligand complexes carrying 8-hydroxy-5-nitroquinoline (HL) as the bidentate N,O donor atom system are reported. Thus one-pot reactions of [ReOCl(3)(PPh(3))(2)] with dianionic tridentate ligands H(2)L(n) (where H(2)L(1)=HOC(6)H(4)-2-CH=NC(6)H(4)-2-OH; H(2)L(2)=HOC(6)H(4)-2-CH=N-C(6)H(4)-2-SH; H(2)L(3)=HOC(6)H(4)-2-CH=NN=C(NHC(6)H(5))-SH; H(2)L(4)=2-CH(2)OH-C(5)H(3)N-6-CH(2)SH; and H(2)L(5)=2-CO(2)H-C(5)H(3)N-6-CO(2)H) and HL afforded a series of '3+2' oxorhenium complexes of the type [ReO(H(2)L(n))(L)] 2-6, which exhibit distorted octahedral geometries. Crystals of 1 are monoclinic space group C2/c, a=16.702(1), b=14.275(1), c=22.363(2) A, beta=108.083(1) degrees V=5068.2(7) A(beta) and Z=8; those of 2 are monoclinic space group P2(1)/n, a=8.5093(4) b=38.518(2), c=11.6092(5) A, beta=97.708(1) degrees , V=3770.7(3) A(3) and Z=8; those of 5 are triclinic, space group P1-, a=7.5899(8), b=10.322(1), c=11.905(1) A, alpha=78.636(2) degrees , beta=74.229(2) degrees , gamma=71.391(2) degrees , V=844.3(2) A(3), and Z=2. Upon reaction of 2,6-pyridinedimethanol (H(2)L(6)) with the intermediate complex [ReOCl(2)(L)(PPh(3))] (1), only one of the two methylene hydroxy group was deprotonated and a new '2+2+1' complex [ReO(OCH(3))(HL(6))(L)].CH(3)OH (7) was obtained. Crystal data for 7: monoclinic P2(1)/n, a=12.0579(6), b=11.0993(6), c=14.9262(8) A, beta=107.872(1) degrees , V=1901.2(2) A(3), and Z=8. In the preparation of complex 3, cleavage of the C=N bond of the Schiff base H(2)L(2) was observed and the '2+2+1' complex 8 [ReO(PPh(3))(eta(2)-NHC(6)H(4)-2-S)(L)].CH(2)Cl(2) having 2-aminothiophenol as a dianionic bidentate ligand was isolated. Crystals of 8 are monoclinic space group C2/c, a=25.627(2), b=8.1305(6) c=31.404(2) A beta=96.147(1) degrees , V=6505.7(8) A(3), and Z=8. Reduction of HL to 8-hydroxy-5-aminoquinoline was realized during the formation of complex 6, and a new complex 9 was thus isolated involving the coordination of two sets of N,O donor atoms from L and 8-hydroxy-5-aminoquinoline while a methoxy oxygen atom completes the octahedral coordination geometry. Crystals of 9 are monoclinic space group P2(1)/n, a=7.5330(6), b=15.095(1), c=16.394(1) A, beta=99.690(2) degrees , V=1837.7(3) A(3), and Z=4.

Azido derivatives of low-valent group 14 elements: synthesis, characterization, and electronic structure of [(n-Pr)2ATI]GeN3 and [(n-Pr)2ATI]SnN3 featuring heterobicyclic 10-pi-electron ring systems

Treatment of THF solutions of [(n-Pr)2ATI]MCl (where [(n-Pr)2ATI]- = N-(n-propyl)-2-(n-propylamino)troponiminate; M = Ge and Sn) with sodium azide affords the compounds [(n-Pr)2ATI]MN3 in excellent yield. X-ray analyses revealed that these Ge(II) and Sn(II) compounds feature linear azide moieties and planar heterobicyclic C7N2M ring systems. Germanium and tin atoms adopt a pyramidal geometry. IR spectra of [(n-Pr)2ATI]GeN3 and [(n-Pr)2ATI]SnN3 display a nu asym(N3) band at 2048 and 2039 cm-1, respectively. DFT calculations on the corresponding methyl-substituted species demonstrate that the geometrical and electronic structure of these two species are very similar, and the dominant canonical form of the metal-azide moiety is M-N-N identical to N. The tin system is, as expected, slightly more ionic. A comparative CASSCF/DFT study on the model system H-Sn-N3 illustrates that the DFT approach is viable for the calculation of the structures of these species.

Copper and silver complexes containing organic azide ligands: syntheses, structures, and theoretical investigation of [HB(3,5-(CF3)2Pz)3]CuNNN(1-Ad) and [HB(3,5-(CF3)2Pz)3]AgN(1-Ad)NN (where Pz = pyrazolyl and 1-Ad = 1-adamantyl)

Treatment of [HB(3,5-(CF3)2Pz)3]Na(THF) with CF3SO3Cu followed by 1-azidoadamantane affords [HB(3,5-(CF3)2Pz)3]CuNNN(1-Ad) in 65% yield. The solid state structure shows that the copper atom is coordinated to the terminal nitrogen atom (NT) of the azidoadamantane ligand. The related silver(I) adduct can be prepared in 80% yield by the treatment of [HB(3,5-(CF3)2Pz)3]Ag(THF) with 1-azidoadamantane. However, [HB(3,5-(CF3)2Pz)3]AgN(1-Ad)NN shows a different bonding mode where the silver atom coordinates to the alkylated nitrogen atom (NA) of the azidoadamantane ligand. Asymmetric stretching bands of the azido group for copper and silver adducts appear at 2143 and 2120 cm-1, respectively. Theoretical investigation shows that steric effects do not play a dominant role in determining the bonding mode of the azide ligand in these two metal complexes. Although the copper(I) ion affinity for the two coordinating sites NT and NA is nearly identical, copper-azide back-bonding interactions favor the copper-NT mode of bonding over the copper-NA mode. Silver (a very poor back-bonding metal) prefers the NA site for coordination. The NA site has a significantly higher proton affinity and slightly higher sodium ion affinity. Important structural parameters for [HB(3,5-(CF3)2Pz)3]CuNNN(1-Ad) and [HB(3,5-(CF3)2Pz)3]AgN(1-Ad)NN are as follows: Cu-NT 1.861(3) A, NT-N 1.136(4) A, N-NA 1.219(4) A, NT-N-NA 173.1(3) degrees; Ag-NA 2.220(5) A, NT-N 1.143(12) A, N-NA 1.227(10) A, NT-N-NA 176.8(12) degrees. Overall, the azidoadamantane ligand does not undergo any significant changes upon coordination to Cu(I) or Ag(I) ions.

Bis axial ligation of simple imine and methyleneamido groups by ruthenium porphyrins

Bis(N-ethylideneethanamine)ruthenium(ii) porphyrins, [Ru11(Por)(N(Et)=CHMe)2] (Por=TTP, 4-Cl-TPP), were prepared by the reaction of dioxoruthenium(VI) porphyrins with triethylamine in approximately 85% yields. The reaction between dioxoruthenium(VI) porphyrins and benzophenone imine afforded bis(diphenylmethyleneamido)ruthenium(IV) porphyrins, [Ru(IV)(Por)(N=CPh2)2] (Por=TTP, 3,4,5-MeO-TPP), in approximately 65% yields. These new classes of metalloporphyrins were characterized by 1H NMR, UV/Vis, and IR spectroscopy as well as by mass spectrometry and elemental analysis. The X-ray crystallographic structures of [Ru(II)(TTP)(N(Et)=CHMe)2] and [Ru(IV)(3,4,5-MeO-TPP)(N=CPh2)2] revealed an axial Ru-N bond length of 2.115(6) A for the imine complex and 1.896(8) A for the methyleneamido complex. Each of the N=CPh2 axial groups in [Ru(IV)(3,4,5-MeO-TPP)(N=CPh2)2] adopts a linear coordination mode with a corresponding Ru-N-C angle of 175.9(9)degrees. Spectral and structural studies revealed essentially single bonding character for the bis(imine) complexes but a multiple bonding character for the bis(methyleneamido) complexes with respect to their axial Ru-N bonds.

Preparations, structures, and electrochemical studies of aryldiazene complexes of rhenium: syntheses of the first heterobinuclear and heterotrinuclear derivatives with bis(diazene) or bis(diazenido) bridging ligands

The mono- and binuclear aryldiazene complexes [Re(C6H5N=NH)(CO)5-nPn]BY4 (1-5) and [(Re(CO)5-nPn)2-(mu-HN=NAr-ArN=NH)](BY4)2 (6-12) [P = P(OEt)3, PPh(OEt)2, PPh2OEt; n = 1-4; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-(2-CH3)C6H3-C6H3(2-CH3), 4,4'-C6H4-CH2-C6H4; Y = F, Ph) were prepared by reacting the hydride species ReH(CO)5-nPn with the appropriate mono- and bis(aryldiazonium) cations. These compounds, as well as other prepared compounds, were characterized spectroscopically (IR; 1H, 31P, 13C, and 15N NMR data), and 1a was also characterized by an X-ray crystal structure determination. [Re(C6H5N=NH)(CO)(P(OEt)3)4]BPh4 (1a) crystallizes in space group P1 with a = 15.380(5) A, b = 13.037(5) A, c = 16.649(5) A, alpha = 90.33(5) degrees, beta = 91.2(1) degrees, gamma = 89.71(9) degrees, and Z = 2. The "diazene-diazonium" complexes [M(CO)3P2(HN=NAr-ArN identical to N)](BF4)2 (13-15, 17) [M = Re, Mn; P = PPh2OEt, PPh2OMe, PPh3; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-C6H4-CH2-C6H4] and [Re(CO)4(PPh2OEt)(4,4'-HN=NC6H4-C6H4N identical to N)](BF4)2 (16b) were synthesized by allowing the hydrides MH(CO)3P2 or ReH(CO)4P to react with equimolar amounts of bis(aryldiazonium) cations under appropriate conditions. Reactions of diazene-diazonium complexes 13-17 with the metal hydrides M2H2P'4 and M2'H(CO)5-nP"n afforded the heterobinuclear bis(aryldiazene) derivatives [M1(CO)3P2(mu-HN=NAr-ArN=NH)M2HP'4](BPh4)2 (ReFe, ReRu, ReOs, MnRu, MnOs) and [M1(CO)3P2(mu-HN=NAr-ArN=NH)M2'(CO)5-nP"n](BPh4)2 (ReMn, MnRe) [M1 = Re, Mn; M2 = Fe, Ru, Os; M2' = Mn, Re; P = PPh2OEt, PPh2OMe; P',P" = P(OEt)3, PPh(OEt)2; Ar-Ar = 4,4'-C6H4-C6H4, 4,4'-C6H4-CH2-C6H4; n = 1, 2]. The heterotrinuclear complexes [Re(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N=NH)M(P(OEt)3)4(mu-4,4'-HN=NC6H4- C6H4N=NH)Mn(CO)3(PPh2OEt)2](BPh4)4 (M = Ru, Os) (ReRuMn, ReOsMn) were obtained by reacting the heterobinuclear complexes ReRu and ReOs with the appropriate diazene-diazonium cations. The heterobinuclear complex with a bis(aryldiazenido) bridging ligand [Mn(CO)2(PPh2OEt)2(mu-4,4'-N2C6H4-C6H4N2)Fe(P(OEt)3)4]BPh4 (MnFe) was prepared by deprotonating the bis(aryldiazene) compound [Mn(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N=NH)Fe(4- CH3C6H4CN)(P(OEt)3)4](BPh4)3. Finally, the binuclear compound [Re(CO)3(PPh2OEt)2(mu-4,4'-HN=NC6H4-C6H4N2)Fe(CO)2(P(OPh)3)2](BPh4)2 (ReFe) containing a diazene-diazenido bridging ligand was prepared by reacting [Re(CO)3(PPh2OEt)2(4,4'-HN=NC6H4-C6H4N identical to N)]+ with the FeH2(CO)2(P(OPh)3)2 hydride derivative. The electrochemical reduction of mono- and binuclear aryldiazene complexes of both rhenium (1-12) and the manganese, as well as heterobinuclear ReRu and MnRu complexes, was studied by means of cyclic voltammetry and digital simulation techniques. The electrochemical oxidation of the mono- and binuclear aryldiazenido compounds Mn(C6H5N2)(CO)2P2 and (Mn(CO)2P2)2(mu-4,4'-N2C6H4-C6H4N2) (P = PPh2OEt) was also examined. Electrochemical data show that, for binuclear compounds, the diazene bridging unit allows delocalization of electrons between the two different redox centers of the same molecule, whereas the two metal centers behave independently in the presence of the diazenido bridging unit.

Chemistry of the rhenium-azopyridine family: an oxo parent and derivatives thereof including a novel oxo-imido dimer

The concerned azo ligands are 2-(phenylazo)pyridine (HL) and 2-((p-chlorophenyl)azo)pyridine (ClL). The reaction of KReO4 with HL in hot concentrated HCl is attended with metal reduction and ligand chlorination affording the oxo complex ReVOCl3(ClL), 2, which furnishes ReIII(OPPh3)Cl3(ClL), 3, upon treatment with PPh3. Aromatic amines, ArNH2, convert 2 to the imido complex ReV(NAr)Cl3(ClL), 5, and the unusual oxo-imido dimer (ClL)-Cl2(O)ReVOReV(NAr)Cl2(ClL), 7. The complex ReIII(OPPh3)Cl3(HL), 4, has been generated from ReVOCl3(PPh3)2 and HL. Reaction of 4 with HL has yielded ReV(NPh)Cl3(HL), 6, via azo splitting. The complexes have been characterized with the help spectral, magnetic, and X-ray structural data (2, 3, 5c (Ar = pClC6H4) and 7.CH2Cl2 (Ar = pMeC6H4)). In 2, 3, and 5c the ReCl3 fragment is meridionally disposed, and in 7 the ReCl2 fragments have a trans configuration. The Re-O(oxo) bond, 1.663(6) A, in 2 and Re-N(imido) bond, 1.719(5) A, in 5c are triple bonds. The corresponding bonds are slightly longer in 7 wherein the (O)Re(1)-O(2)-Re(2)(NAr) bridge is angular (151.0(5) degrees) and unsymmetrical, the Re(1)-O(2) bond, 1.849(7) A, having a large double-bond character (Re(2)-O(2), 1.954(7) A). In effect, cis-ReVO2 acts as a monodentate oxygen ligand toward ReVNAr in 7. In all cases the pyridine nitrogen binds trans to the oxo, OPPh3, or NAr donor. Bond length data are consistent with the presence of substantial d(Re)-pi*(azo) back-bonding. In acetonitrile solution the complexes display electrochemical one-electron metal (ReVI/ReV or ReIV/ReIII) and azo redox. The imido ligand in 5 stabilizes the ReVI state (E1/2 approximately 1.4 V) better than the oxo ligand in 2 (approximately 1.9 V). Parallely it is more difficult to reduce the azo group in 5 (approximately -0.4 V) than in 2 (approximately 0.0 V). In 7 the metal (approximately 1.0 V) and azo (approximately -0.4 V) couples correspond to the imido and oxo halves, respectively. The significantly higher (by 0.2-0.6 V) metal reduction potentials of the azopyridine compared to pyridine-2-aldimine complexes is ascribed to the superior pi-acidity and electron-withdrawing character of the azo function relative to the aldimine function. This also makes the transfer of the ReVO oxygen function much more facile under azopyridine chelation as in 2. For the same reason, ReOCl3(PPh3)2 reacts with HL affording only 4 while it reacts with pyridine-2-aldimines furnishing oxo species. Crystal data for the complexes are as follows: 2, empirical formula C11H8Cl4N3ORe, crystal system triclinic, space group P1, a = 7.118(4) A, b = 8.537(4) A, c = 13.231(9) A, alpha = 79.16(5) degrees, beta = 78.03(5) degrees, gamma = 70.96(4) degrees, V = 737.2(7) A3, Z = 2; 3, empirical formula C29H23Cl4N3OPRe, crystal system monoclinic, space group P2(1)/n, a = 11.264(2) A, b = 15.221(3) A, c = 17.628(4) A, beta = 94.21(3) degrees, V = 3014(1) A3, Z = 4; 5c, empirical formula C17H12Cl5N4Re, crystal system triclinic, space group P1, a = 9.683(3) A, b = 10.898(3) A, c = 11.522(3) A, alpha = 63.67(2) degrees, beta = 71.24(2) degrees, gamma = 86.79(2) degrees, V = 1026(1) A3, Z = 2; 7.CH2Cl2, empirical formula C30H25Cl8N7O2Re2, crystal system triclinic, space group P1, a = 12.522(6) A, b = 12.857(8) A, c = 13.182(7) A, alpha = 67.75(4) degrees, beta = 88.30(4) degrees, gamma = 82.09(4) degrees, V = 1945(2) A3, Z = 2.