Transition metal complexes containing organoimido (nr) and related ligands

Titanium Imido Complexes with Tetradentate Schiff Base Ligands

New mono- and binuclear titanium imido complexes supported by tetradentate, dianionic N(2)O(2)-donor Schiff base ligands were prepared in good yield from the readily available [Ti(NBu(t))Cl(2)(py)(3)] (1a). Thus treatment of 1a with Na(2)[substituted-salen] gave monomeric [Ti(NBu(t))(substituted-salen)] where substituted-salen = Et(2)salen (2) or Bu(t)(4)salen (4). In contrast, the binuclear complex [Ti(NBu(t)){&mgr;-(MeO)(2)salen}](2) (5) was obtained from 1a and Na(2)[(MeO)(2)salen]. The less sterically crowded compounds 2 and 5 undergo tert-butyl imide/arylamine exchange reactions to form [Ti(N-2,6-C(6)H(3)Me(2))(Et(2)salen)] (3) and [Ti(N-2,6-C(6)H(3)Me(2)){&mgr;-(MeO)(2)salen}](2) (6), respectively, whereas 4 does not exhibit this kind of reactivity. The compound 3 can also be obtained directly from Na(2)[Et(2)salen] and [Ti(N-2,6-C(6)H(3)Me(2))Cl(2)(py)(3)] (1b). Crystal data for 3: triclinic, P&onemacr;, a = 12.216(4) Å, b = 12.312(11) Å, c = 17.246(2) Å, alpha = 90.352(12) degrees, beta = 102.59(2) degrees, gamma = 104.96(2) degrees, V = 2440.3(8) Å(3), Z = 4, R = 0.051, R(w) = 0.066 for 7011 data with I > 2sigma(I). Crystal data for 5.CH(2)()Cl(2)(): orthorhombic, Pbca, a = 14.747(4) Å, b = 17.042(4) Å, c = 20.545(3) Å, V = 5163.5(13) Å(3), Z = 4, R(1) = 0.096, wR(2) = 0.086 for 3765 data with I > 2sigma(I). Crystal data for 6: monoclinic, C2/c, a = 17.902(5) Å, b = 12.411(4) Å, c = 21.068(5) Å, beta = 90.27(2) degrees, V = 4681(2) Å(3), Z = 4, R = 0.034, R(w)() = 0.039 for 3633 data with I > 2sigma(I).

Reactivity of Hydrides FeH(2)(CO)(2)P(2) (P = Phosphites) with Aryldiazonium Cations: Preparation, Characterization, X-ray Crystal Structure, and Electrochemical Studies of Mono- and Binuclear Aryldiazenido Complexes

Mono- and binuclear aryldiazenido complexes [Fe(ArN(2))(CO)(2)P(2)]BPh(4) (1-4) and [{Fe(CO)(2)P(2)}(2)(&mgr;-N(2)Ar-ArN(2))](BPh(4))(2) (5-8) [P = P(OEt)(3), PPh(OEt)(2), PPh(2)OEt, P(OPh)(3); Ar = C(6)H(5), 2-CH(3)C(6)H(4), 4-CH(3)C(6)H(4); Ar-Ar = 4,4'-C(6)H(4)-C(6)H(4), 4,4'-(2-CH(3))C(6)H(3)-C(6)H(3)(2-CH(3)), 4,4'-C(6)H(4)-CH(2)-C(6)H(4)] were prepared by allowing hydride species FeH(2)(CO)(2)P(2) to react with an excess of mono- (ArN(2))(BF(4)) or bis-aryldiazonium (N(2)Ar-ArN(2))(BF(4))(2) salts, respectively, at low temperature. A reaction path involving a hydride-aryldiazene intermediate [FeH(ArN=NH)(CO)(2)P(2)](+), which, through the loss of H(2), affords the final aryldiazenido complexes 1-8, is proposed. The compounds were characterized by (1)H and (31)P{(1)H} NMR spectroscopy (including (15)N isotopic substitution) and X-ray crystal structure determination. The complex [Fe(CO)(2){P(OEt)(3)}(2){&mgr;-4,4'-N(2)(2-CH(3))C(6)H(3)-C(6)H(3)(2-CH(3))N(2)}](BPh(4))(2) (5b) crystallizes in the space group P&onemacr; with a = 15.008(4) Å, b = 17.094(5) Å, c = 10.553(3) Å, alpha = 99.56(1) degrees, beta = 102.80(1) degrees, gamma = 65.30(1) degrees, and Z = 1. The structure is centrosymmetric and consists of binuclear cations with the two iron atoms in a quite regular trigonal bipyramidal environment, with the two CO in the equatorial and the two phosphites in the apical position, respectively. Aryldiazenido complexes 1-8 react with strong acids HX (X = Cl, CF(3)SO(3), CF(3)CO(2)) to give the corresponding aryldiazene derivatives, according to the equilibrium [Fe(ArN(2))(CO)(2)P(2)](+) + HX right harpoon over left harpoon [FeX(ArN=NH)(CO)(2)P(2)](+). Electrochemical studies of both mono- (1-4) and binuclear (5-8) compounds were undertaken, and a mechanism for oxidation and reduction processes is proposed.

Mono- and Bis(hydrazine) Complexes of Osmium(II): Synthesis, Reactions, and X-ray Crystal Structure of the [Os(NH(2)NH(2))(2){P(OEt)(3)}(4)](BPh(4))(2) Derivative

Reaction of OsH(2)P(4) [P = P(OEt)(3), PPh(OEt)(2), PPh(2)OEt] with methyl triflate followed by the treatment with hydrazines gave the [OsH(RNHNH(2))P(4)]BPh(4) (1-3) (R = H, CH(3), C(6)H(5), 4-NO(2)C(6)H(4)) derivatives. Instead, the reaction of OsH(2)P(4) first with methyl triflate, then with triflic acid, and finally with an excess of the appropriate hydrazine afforded the bis(hydrazine) [Os(RNHNH(2))(2)P(4)](BPh(4))(2) (4, 5) (R = H, CH(3), C(6)H(5)) complexes. Also the [Os(NH(2)NH(2)){P(OEt)(3)}(5)](BPh(4))(2) (7) derivative was prepared. All the hydrazine complexes were fully characterized by IR and (1)H and (31)P NMR spectra, and a single-crystal X-ray structure determination of the complex [Os(NH(2)NH(2))(2){P(OEt)(3)}(4)](BPh(4))(2).C(2)H(5)OH (4a) is reported. The compound crystallizes in the space group P2(1)/c with a = 20.550(4) Å, b = 19.663(4) Å, c = 20.843(4) Å, beta = 99.84(9) degrees, and Z = 4. The coordination around the osmium atom is octahedral and the orientation of the ligands in the [Os(NH(2)NH(2))(2){P(OEt)(3)}(4)](2+) cation is determined by several strong hydrogen bonds involving hydrazine nitrogen and phosphite oxygen atoms. Amidrazone complexes [Os{eta(2)-NH=C(R1)N(R)NH(2)}{P(OEt)(3)}(4)](BPh(4))(2) (8, 9) (R = H, CH(3); R1 = CH(3), 4-CH(3)C(6)H(4)) were prepared by allowing nitrile complexes [Os(R1CN)(2)P(4)](BPh(4))(2) to react with hydrazine NH(2)NH(2) or methylhydrazine CH(3)NHNH(2). Reaction of complexes containing substituted hydrazine ligands of the type [OsH(RNHNH(2))P(4)]BPh(4) and [Os(RNHNH(2))(2)P(4)](BPh(4))(2) [P = P(OEt)(3); R = CH(3), C(6)H(5)] with Pb(OAc)(4) at -30 degrees C results in the selective oxidation of the hydrazine affording the corresponding diazene [OsH(RN=NH)P(4)]BPh(4) (10) and [Os(RN=NH)(2)P(4)](BPh(4))(2) (11) derivatives. The first bis(methyldiazene) complex [Os(CH(3)N=NH)(2){P(OEt)(3)}(4)](BPh(4))(2) (11b) was thus prepared.

Terminal Coordination of a Gallium(I) Species to a Transition Metal. Syntheses and Crystal Structures of Ru{GaCl(THF)(2)}{GaCl(2)(THF)}(2)(CO)(3).0.5THF and Ru(2){GaCl(2)(THF)}(2)(CO)(8)

The reaction of Ru(3)(CO)(12) with Ga(2)Cl(4) in the presence of gallium metal in refluxing toluene, followed by crystallization from tetrahydrofuran, produces Ru{GaCl(THF)(2)}{GaCl(2)(THF)}(2)(CO)(3).0.5 THF (1) and Ru(2){GaCl(2)(THF)}(2)(CO)(8) (2) (THF = tetrahydrofuran). The ruthenium atom in 1 has an approximately octahedral coordination environment, with meridinal arrangements of carbonyl ligands and gallium atoms. The GaCl(THF)(2) group is in a position trans to one of the GaCl(2)(THF) groups. The crystal structure of 2 consists of a linear arrangement of metal atoms in which two GaCl(2)(THF) groups are in axial positions with respect to the metal-metal bond of an Ru(2)(CO)(8) unit. Crystal data for 1: monoclinic space group P2(1)/c (No. 14), a = 17.367(3) Å, b = 12.054(2) Å, c = 16.049(3) Å, beta = 95.18(1) degrees, Z = 4, R = 0.0527, R(w) = 0.0718. Crystal data for 2: monoclinic space group P2(1)/c (No. 14), a = 11.980(1) Å, b = 6.944(1) Å, c = 16.097(3) Å, beta = 96.81(1) degrees, Z = 2, R = 0.0300, R(w) = 0.0510. The title complexes are the first compounds to contain ruthenium-gallium bonds, and compound 1 is the second structurally-characterized example of a complex in which a gallium(I) species is terminally coordinated to a transition metal.

Osmium Hydrazido and Dinitrogen Complexes

[Os(tpy)(bpy)(NH(3))](PF(6))(2) (1) was oxidized electrochemically in the presence of a series of amines in aqueous solutions buffered to pH 7. With secondary aliphatic amines, electrolysis gave [Os(tpy)(bpy)(NNR(2))](PF(6))(3) (3); number of electrons n = 4.6-5.0. 3 was reduced to [Os(tpy)(bpy)(NNR(2))](PF(6))(2) (2) in aqueous and nonaqueous solutions with n = 1.0. The structures of 2 were determined by X-ray crystallography for NR(2) = diethylamide (2a) and morpholide (2c) and were found to exhibit bent hydrazido(2-) coordination (Os-N-N = 137 degrees ). The salts crystallized in the triclinic system, space group P&onemacr;. For 2a, a = 9.004(1) Å, b = 9.796(1) Å, c = 20.710(2) Å, alpha = 88.78(2) degrees, beta = 85.43(2) degrees, gamma = 86.22(2) degrees, and Z = 2. For 2c, a = 9.632(8) Å, b = 21.229(9) Å, c = 9.039(5) Å, alpha = 97.41(4) degrees, beta = 94.28(5) degrees, gamma = 85.07(5) degrees, and Z = 2. Solutions of 2 were protonated in strongly acidic media to give hydrazido(1-) complexes. The pK(a) of the protonated form of 2a is 0.90 +/- 0.01. Reduction of 2 in aqueous solutions of pH <1 gave 1 and NH(2)R(2)(+) with n = 4.0. At higher pH, there is evidence for an Os(II) hydrazine intermediate. Oxidation of 3 by one electron afforded transiently stable species which decomposed to give [Os(tpy)(bpy)(NCCH(3))](3+) in acetonitrile solution. Pseudo-first-order rate constants of 8.1 +/- 0.9 s(-)(1) and 0.200 +/-.005 s(-)(1) were estimated by cyclic voltammetry on solutions of 2a and 2b(NR(2) = piperidide), respectively. Oxidation of 1 at pH 7, in the presence of primary aliphatic amines or ammonia, occurred with n = 5.9-6.2, and generated [Os(II)(tpy)(bpy)(N(2))](PF(6))(2) (4).

Synthesis and Characterization of (2,4,6-Trimethylphenylimido)molybdenum Complexes. X-ray Crystal Structures of (L(OEt))Mo(Nmes)(2)Cl, (L(OEt))Mo(Nmes)Cl(2), and MoCl(3)(Nmes)(depe) (mes = 2,4,6-Trimethylphenyl, L(OEt) = (eta-C(5)H(5))Co{P(O)(OEt)(2)}(3), depe = Et(2)PCH(2)CH(2)PEt(2))

The bis(imido) complex MoCl(2)(Nmes)(2)(dme) (1) (mes = 2,4,6-trimethylphenyl, dme = 1,2-dimethoxyethane) has been used as the starting material for the preparation of the compounds (L(OEt))Mo(Nmes)(2)Cl (2) (L(OEt) = (eta-C(5)H(5))Co{P(O)(OEt)(2)}(3)) and Mo(Nmes)(2)(acac)(2) (5), as well as for the synthesis of the mixed oxo-imido MoCl(2)(Nmes)(O)(dme) (6), the latter reaction involving conproportionation of 1 and MoCl(2)(O)(2)(dme). Similarly, the paramagnetic mono(imido) species Mo(Nmes)Cl(3)(dme) (11) can also be obtained from 1 by interaction with MoCl(4)(THF)(2) (THF = tetrahydrofuran) in refluxing dme. Compounds 6 and 11 are suitable sources for the synthesis of other diamagnetic mixed oxo-imido and paramagnetic mono(imido) compounds, respectively. Three of the newly synthesized complexes, namely, (L(OEt))Mo(Nmes)(2)Cl (2), (L(OEt))Mo(Nmes)Cl(2) (12), and MoCl(3)(Nmes)(depe) (14) (depe = Et(2)PCH(2)CH(2)PEt(2)) have been characterized by X-ray crystallography.