The neutral ruthenium complexes Cp'Ru(PR3)(2)Cl [Cp' = Cp, PR3 = PPh3, PMe3, or 1/2 dppe; Cp' = Cp*, PR3 = PMe3] react with [p-MeOC6H4N2][BF4] in acetone to give new cyclopentadienyl ruthenium aryldiazenido dicationic complexes [Cp'Ru(PR3)(2)(N2C6H4OMe)]-[BF4](2) [Cp' = Cp, PR3 = PPh3 (1), PMe3 (2), or 1/2 dppe (3); Cp' = Cp*, PR3 = PMe3 (4)] in good yields. The dicationic complexes 1-3 may also be conveniently isolated in better yield by treatment of the acetonitrile ruthenium complexes [CpRu(PR3)(2)(NCMe)][BF4] with the arenediazonium salt. When the reaction of Cp'Ru(PPh3)(2)Cl (Cp' = Cp or Cp*) with [p-MeOC6H4N2][BF4] is carried out in toluene, the product is instead the cyclopentadienyl ruthenium aryldiazenido monocationic complex [Cp'RuCl(PPh3)(N2C6H4OMe)][BF4] [Cp' = Cp (5) or Cp* (6)]. Further, if the reaction of Cp*Ru(PPh3)(2)Cl with diazonium salt is carried out in acetone, the binuclear complex [Cp*RuCl(N2C6H4OMe)](2)[Cl](2) (7) can be isolated in low yield in addition to 6. All new complexes 1-7 were fully characterized by NMR, FT-IR, and mass spectroscopies. The structure of [CpRu(PPh3)(2)(N2C6H4OMe)][BF4](2). 0.93CHCl(3) (1 . 0.93CHCl(3)) was determined by single-crystal ii-ray diffraction. The structure exhibits a near-linear Ru-N-N-C geometry for the coordinated aryldiazenido group, with the NNC angle having a value of 159 degrees, compared to the "sp(2)" value of approximately 120 degrees commonly exhibited by other "singly bent" aryldiazenido complexes. On the basis of NMR spectroscopic data, 1 reacts with NaBH4 at low temperature to give an arylhydrazido(2-) complex [CpRu(PPh3)(2)-{NN(H)C6H4OMe}][BF4], which readily converts to the corresponding aryldiazene complex [CpRu(PPh3)(2)(NH=NC6H4OMe)][BF4] by a hydrogen shift; at room temperature, the only product is the hydride complex CpRuH(PPh3)(2).

The rhenium hydrido allyl complex Cp*Re(η3-C3H5)(CO)(H) (1) reacted with NOBF4 or [p-N2C6H4OMe][BF4] at −78°C to give [Cp*Re(η2-C3H6)(CO)(NO)][BF4] (2) or [Cp*Re(η2-C3H6)(CO)(N2C6H4OMe)][BF4] (3), respectively. In these reactions addition of the electrophile is accompanied by transfer of the hydride ligand to the allyl group to form the propene ligand. Complex 1 reacted with [Ph3C][BF4] in CH3CN at −78°C to abstract the hydride ligand and form the allyl acetonitrile complex [Cp*Re(η3-C3H5)(CO)(CH3CN)][BF4] (4). Complex 1 reacted with CF3CO2H or CF3SO3H to form the hydrido propene complexes Cp*Re(η2-C3H6)(H)(CO)(CF3CO2) (5) or Cp*Re(η2-C3H6)(H)(CO)(CF3SO3) (6). Studies with CF3CO2D demonstrated that both Cp*Re(η2-C3H6)(D)(CO)(CF3CO2) and Cp*Re(η2-C3H5D)(H)(CO)(CF3CO2) are formed. This is consistent with a mechanism in which D+ attacks the metal followed by transfer of either D or H to the allyl group. Complex 1 was found not to react with C2H4, hexene, cyclohexene, MeCCMe, PhCCMe, CH3CN or PMe3.

Reaction of Cp*Re(CO)(2)I-2 with methylcopper affords cis-Cp*Re(CO)(2)(Me)I, which converts to the trans isomer on prolonged reaction or in the presence of neutral alumina. The X-ray structure of the trans isomer has been determined. The related chloro complexes Cp*Re(CO)(2)(Me)Cl and Cp*Re(CO)(2)(p-tolyl)Cl are formed in the photolyses of compounds 3 and 1 (below) in CCl4. Photolysis of Cp*Re(CO)(2)(Me)R (R p-tolyl (1), Ph (2), Me (3)) in the presence of CO has been carried out in hydrocarbons, CCl4, and benzene-d(6). In hydrocarbons, 1 and 2 produce Cp*Re(CO)(3), CH4, and either toluene or benzene, respectively; 3 produces Cp*Re(CO)(3) and CH4. In benzene-d(6) 1 gave CH3D and toluene-4-d, and 3 gave mainly CH3D. These results are consistent with a general scheme involving successive homolysis of the metal-methyl and metal-aryl bonds to give methyl and aryl radicals that abstract H or D from the solvent and carbonylation of the rhenium dicarbonyl fragment. Products known or expected to arise from further photolysis of Cp*Re(CO)(3) in benzene-d(6), such as Cp*Re-2(2)(CO)(3), Cp*Re-2(2)(CO)(5), and Cp*Re(CO)(2)(eta(2)-C6D6), were also found. Photolysis of 1 in CCl4 in the presence or absence of CO gave CH3Cl and Cp*Re(CO)(2)(p-tolyl)Cl, but no p-chlorotoluene, indicating the preferential homolysis of the Re-Me bond and the rapid scavenging of the subsequent radicals by the chlorinated solvent. Photolysis of the dimethyl complex 3 gave CH3Cl and some evidence of a small amount of Cp*Re(CO)(2)(Me)Cl, but the major rhenium product was Cp*Re(CO)(2)Cl-2, consistent with the more facile homolysis of both Re-Me bonds in 3. Production of small amounts of CH2D2 (in benzene-d(6)) and CH4 and CH2Cl2 (in CCl4) are discussed in terms of a competing pathway. Notably, in none of these photolyses were there observed other than trace amounts of products such as p-xylene, which would be expected to be major products if reductive elimination were to occur.

The phenyl chloride complexes Cp*Re(CO)(L)(Ph)Cl (L = P(OEt)(3) (6), Pc (7), P(OMe)(3) (8), and PMe2Ph (9)) have been prepared by irradiation of the corresponding rhenium dinitrogen complex Cp*Re(CO)(L)(N-2) in chlorobenzene. In the case of L = P(OPh)(3) the result was instead the formation of the cyclometalated complex Cp*Re(CO){eta(2)-P(OC6H4)(OPh)(2)}H (10), arising from intramolecular C-H oxidative addition of a phenyl group of the phosphine orxide ligand.

Results are reported for the UV photolysis of the rhenium dinitrogen phosphite and phosphine complexes Cp*Re(CO)(L)(N2) (L = P(OEt)3 (1), P(OPh)3 (2), P(OCH2)3CCH3 (3), P(OMe)3 (4), PPh3 (5)) in hydrocarbon solvents. Irradiation of 1 in hexane yielded cis and trans isomers of the cyclometalated complex Cp*Re(CO){η2-P(OCH2CH2)(OEt)2}H (6) and a third product identified as agostic-6, in which a methyl C−H bond of one of the ethoxy groups forms an agostic interaction with the metal. This complex decayed to give the other two isomers of 6 over time. Irradiation of 1 in benzene afforded the above compounds plus two isomers of a benzene C−H activation product Cp*Re(CO){P(OEt)3}(Ph)H (7). The latter isomers and the agostic complex all decayed over time to leave only the cis and trans isomers of 6. The final observed ratio of cis(P,H)-6 to trans(P,H)-6 was 76:24. Irradiation of 2 in hexane, cyclohexane, or benzene produced no evidence of any intermolecular C−H activation product. In each case, two products result...

Results are reported for the UV photolysis of the rhenium dinitrogen phosphite and phosphine complexes Cp*Re(CO)(L)(N2) (L = P(OEt)3 (1), P(OPh)3 (2), P(OCH2)3CCH3 (3), P(OMe)3 (4), PPh3 (5)) in hydrocarbon solvents. Irradiation of 1 in hexane yielded cis and trans isomers of the cyclometalated complex Cp*Re(CO){η2-P(OCH2CH2)(OEt)2}H (6) and a third product identified as agostic-6, in which a methyl C−H bond of one of the ethoxy groups forms an agostic interaction with the metal. This complex decayed to give the other two isomers of 6 over time. Irradiation of 1 in benzene afforded the above compounds plus two isomers of a benzene C−H activation product Cp*Re(CO){P(OEt)3}(Ph)H (7). The latter isomers and the agostic complex all decayed over time to leave only the cis and trans isomers of 6. The final observed ratio of cis(P,H)-6 to trans(P,H)-6 was 76:24. Irradiation of 2 in hexane, cyclohexane, or benzene produced no evidence of any intermolecular C−H activation product. In each case, two products result...

The nucleophilic addition of oxygen, sulfur, nitrogen and carbon nucleophiles to [Cp∗Re(η3-C3H5)(CO)2][BF4] (1) has been investigated. In all cases, addition of the nucleophile to the allyl ligand in 1 was observed to result, giving the substituted propene complexes with general formula Cp∗Re(CO)2(η2-C3H5R) (RCH3CO2, C2H5S, C6H5S, NH2, CHMe2 and C6H5) and [Cp∗Re(CO)2]2(η2;η2-C3H5S(CH2)3SC3H5). No product of attack at the central carbon was observed for any of the nucleophiles. In the cases where the nucleophile was NH2− or C6H5Li, nucleophilic addition occurred either at the η3-allyl or at a CO ligand. At low temperature (−78-0°C) the CO was attacked and complexes with general formula Cp∗Re(η3-C3H5)(CO)(COR) (R  NH2 and C6H5) were produced. When R is C6H5, the product was stable and was observed along with the substituted propene complex in solution, but when NH2− was used, the carbamoyl complex converted completely to the substituted propene complex at room temperature. A by-product of the method used to synthesize Cp∗Re(η2-C3H5SC6H5)(CO)2 was a small amount of Cp∗Re(η3-C3H5)(CO)(O2CSC6H5) (7). The X-ray crystal structure of 7 has been determined.

The rhenium η3-allyl chloro complex Cp*Re(η3-C3H5)(CO)Cl (5) has been synthesized from the photolysis of Cp*Re(CO)3 and allyl chloride, or from the reaction of the cationic complex [Cp*Re(η3-C3H5)(CO)2]+ with PhIO and Me4NCl. Complex 5 is readily converted to the η3-allyl hydrido complex Cp*Re(η3-C3H5)(CO)H by reaction with LiBEt3H, and to the phenyl or alkyl derivatives Cp*Re(η3-C3H5)(CO)Ph or Cp*Re(η3-C3H5)(CO)R by treatment with LiPh or Grignard reagents.

Reaction of CpIr(CO)(2) (3, Cp = eta(5)-C(5)Me(5)) with [N(2)Ar][BF(4)] (Ar = p-C(6)H(4)OMe) in acetone at -78 degrees C affords the nitrogen extrusion product [CpIr(CO)(2)(Ar)][BF(4)] (5), but in dichloromethane it yields a dinuclear product [Cp(CO)(2)Ir-Ir(Cl)(CO)Cp][BF(4)] (6). By carrying out this very reaction in ethanol solution, a nitrogen-retained product [CpIr(CO)(OEt)(NHNAr)][BF(4)] (7) is obtained, containing an aryldiazene ligand. Deprotonation of 7 gives quantitatively the neutral doubly-bent aryldiazenido complex CpIr(CO)(OEt)(N(2)Ar) (8). The IR nu(CO) absorptions measured for the dinuclear compound 6 indicate no bridging carbonyl, but a (13)C NMR study in solution shows that 6 is stereochemically nonrigid at ambient temperature; its three carbonyl ligands are all involved in a fast exchange process, and this process is frozen at -86 degrees C. Exchange of the CO groups via a terminal-bridging-terminal process accompanied by rotation about the Ir-Ir axis is suggested. The molecular structure of 6 in the solid state has been established by single crystal X-ray crystallographic analysis and is consistent with the solution spectra. By reaction of [N(2)Ar][BF(4)] with the dinuclear complex [CpIr(CO)](2) (4) in acetone, the complex [{CpIr(CO)}(2)(1-eta(1)-1,2-eta(2)-p-C(6)H(4)OMe)][BF(4)] (9) with a rare sigma,pi-bridging aryl group has been obtained and crystallized. The molecular structure containing an asymmetric bridging aryl group is established for 9 in the solid state by a single crystal X-ray crystallographic analysis. However, the identical (1)H NMR features observed at ambient temperature and -90 degrees C in solution (i.e., a singlet resonance for the two Cp ligands and a symmetric AA'BB' pattern for the p-C(6)H(4)OMe) indicate a static or time-averaged symmetrical molecular geometry for 9. Compound 6 crystallizes in the monoclinic space group P2(1)/c with a = 10.583(2) Å, b = 14.256(3) Å, c= 16.818(4) Å, beta = 95.91 (2) degrees, V = 2523.9 Å(3), and Z = 4. Refinement yielded R(F)() = 0.027 and R(w)(F)() = 0.033 for 3299 observed reflections (I(o) >/= 2.5sigma(I(o))) of 4427 unique reflections. Compound 9 crystallizes in the monoclinic space group P2(1)/n with a = 11.695(2) Å, b = 19.911(3) Å, c= 12.539(2) Å, beta = 96.54(1) degrees, V = 2900.8 Å(3), and Z = 4. Refinement yielded R(F)() = 0.025 and R(w)(F)() = 0.035 for 3444 observed reflections (I(o) >/= 2.5sigma(I(o))) of 4526 unique reflections.

Reaction of Cp*Ir(CO)(2) (3, Cp* = eta(5)-C(5)Me(5)) with [N2Ar][BF4] (Ar = p-C(6)H(4)OMe) in acetone at -78 degrees C affords the nitrogen extrusion product [Cp*Ir(CO)(2)(Ar)][BF4] (5), but in dichloromethane it yields a dinuclear product [Cp*(Co)(2)Ir-Ir(Cl)(CO)Cp*][BF4] (6). By carrying out this very reaction in ethanol solution, a nitrogen-retained product [Cp*Ir(CO)(OEt)(NHNAr)][BF4] (7) is obtained, containing an aryldiazene ligand. Deprotonation of 7 gives quantitatively the neutral doubly-bent aryldiazenido complex Cp*Ir(CO)(OEt)(N2Ar) (8). The IR nu(CO) absorptions measured for the dinuclear compound 6 indicate no bridging carbonyl, but a C-13 NMR study in solution shows that 6 is stereochemically nonrigid at ambient temperature; its three carbonyl ligands are all involved in a fast exchange process, and this process is frozen at -86 degrees C. Exchange of the CO groups via a terminal-bridging-terminal process accompanied by rotation about the Ir-Ir axis is suggested. The molecular structure of 6 in the solid state has been established by single crystal X-ray crystallographic analysis and is consistent with the solution spectra. By reaction of [N2Ar][BF4] with the dinuclear complex [Cp*Ir(CO)](2) (4) in acetone, the complex [{Cp*Ir(CO)}(2)(1-eta(1)-1,2-eta(2)-p-C(6)H(4)OMe)][BF4] (9) with a rare sigma,pi-bridging aryl group has been obtained and crystallized. The molecular structure containing an asymmetric bridging aryl group is established for 9 in the solid state by a single crystal X-ray crystallographic analysis. However, the identical H-1 NMR features observed at ambient temperature and -90 degrees C in solution (i.e., a singlet resonance for the two Cp* ligands and a symmetric AA'BB' pattern for the p-C(6)H(4)OMe) indicate a static or time-averaged symmetrical molecular geometry for 9. Compound 6 crystallizes in the monoclinic space group P2(1)/c with a = 10.583(2) Angstrom, b = 14.256(3) Angstrom, c = 16.818(4) Angstrom, beta = 95.91 (2)degrees, V = 2523.9 Angstrom(3), and Z = 4. Refinement yielded R(F) = 0.027 and R(wF) = 0.033 for 3299 observed reflections (I-o greater than or equal to 2.5 sigma(I-o)) of 4427 unique reflections. Compound 9 crystallizes in the monoclinic space group P2(1)/n with a = 11.695(2) Angstrom, b = 19.911(3) Angstrom, c = 12.539(2) Angstrom, beta = 96.54(1)degrees, V= 2900.8 Angstrom(3), and Z = 4. Refinement yielded R(F) = 0.025 and R(wF) = 0.035 for 3444 observed reflections (I-o greater than or equal to 2.5 sigma(I-o)) of 4526 unique reflections.

By replacing one or both of the CO groups in [Cp∗Re(η3-C3H5)(CO)2][BF4] (1) by MeCN to give [Cp∗Re(η3-C3H5)(CO)(NCMe)][BF4] (3) or [Cp∗Re(η3-C3H5)(NCMe)2][BF4] (4), it was anticipated that the MeCN groups would be labile and would promote ligand substitutior reactions, leading to a variety of new rhenium η3-allyl half-sandwich derivatives. Instead, MeCN is found to be difficult to substitute, and nucleophiles often result in products that arise from attack at either the MeCN or allyl ligands. Complex 1 reacted with NaBH4 to give the propene complex Cp∗Re(η3-CH2CHCH3)(CO)2 (2), with NaOMe to give the methoxycarbonyl complex Cp∗(η3-C3H5)(CO)(COOMe) (6) and the 3-methoxypropene complex Cp∗Re(η2-CH2CHCH2OMe)(CO)2 (5), and with PMe3 to give [Cp∗Re(η2-CH2CHCH2PMe3)(CO)2][BF4] (7). Complex 3 gave the ethylamine complex [Cp∗C3H5(CO)(NH2Et)][BF4] (8) when reacted with NaBH4, [Cp∗Re(η2-CH2CHCH2PMe3)(CO)(NCMe)][BF4] (9) with PMe3, and Cp∗Re(η-3-C3H5)(CO)(NHCOMe) (10) with NaOH. Complex 4 similarly yielded the bis-ethylamine complex [Cp∗Re(η3-C3H5)(NH2Et)in2][BF4] (11) when reacted with NaBH4, but with PMe3 ligand substitution occurred, resulting in [Cp∗Re(η3-C3H5)(NCMe)(PMe3)][BF4 (12). Treating 12 with NaBH4, or 11 wiht PMe3, yielded the ethylamine complex [Cp∗Re(η3-C3H5)(PMe3)(NH2Et)][BF4] (13). The X-ray crystal structure of [endo-Cp∗Re(η3-C3H5)(NH2Et)2][ReO4].solv has been determined. This compound crystallizes in the space group Pnma with a = 8.6554(8) Å, b = 11.729(2) Å, c = 26.928(3) Å, V = 2733.7 Å3, and Z = 4. The structure was refined to RF = 0.028 for 1444 data (I0 ⩾ 2.5 σ(I0), 2θmax = 46°) and 158 variables. The cation has a crystallographic mirror plane that relates the two EtNH2 ligands and bisects the endo-η3-allyl and Cp∗ ligands. Selected distances and angles are ReN = 2.228(7) Å, ReC(6) = 2.177(9) Å (allyl terminal carbon), ReC(7) = 2.090(13) Å (allyl central carbon), NC(4) = 1.470(10) Å, ReNC(4) = 125.2(6) Å, and C(6)-C(7)-C(6) = 114.1(13) Å

The singly N-15-labeled dinitrogen complexes Cp'Re(CO)(L)((NN)-N-15-N-14) (Cp' = eta(5)-C5H5, L = CO (1,N-15(alpha)) and Cp' = eta(5)-C(5)Me(5), L = CO (2-N-15(alpha)), PMe(3) (3-N-15(alpha)), or P(OMe)(3) (4-N-15(alpha))) were synthesized from the corresponding aryldiazenido complex [Cp'Re(CO)(L)((15)N(14)NC(5)H(4)OMe)]-_ [BF4] by treatment with Ph(3)C, Cp(2)Co, Na/Hg, or NaBH4. When these dinitrogen complexes are freshly synthesized, the N-15 label is exclusively retained in the metal-bound (N-alpha) position irrespective of the reagent used. At 291 K 1-N-15(alpha) isomerizes in acetone to give a 1:1 mixture of 1-N-15(alpha) and 1-N-15(beta), as indicated by the intensities of the N-15(alpha) and N-15(beta) resonances in the N-15 NMR spectra, with rate constant K-obs = (48 +/- 6) x 10(-6) s(-1) and Delta G(double dagger) = 95.3 +/- 0.5 kJ mol(-1). For 2-N-15(alpha) isomerization occurs similarly, and the temperature dependence over the range 274-291 K yielded Delta G(291)(double dagger) = 92.6 +/- 0.4 kJ mol(-1), Delta H-double dagger = 105.3 +/- 6.0 kJ mol(-1), Delta S-double dagger = 43.5 +/- 21.2 J mol(-1) K-1, E(a) = 106.8 +/- 5.4 kJ mol(-1), and A = (2.1 +/- 1.3) x 10(-15) s(-1). As a consequence of the linkage isomerization, samples of 1-N-15 and 2-N-15 obtained from any of the above syntheses following normal isolation and purification proceduresare inevitably 1:1 mixtures of the N-15(alpha) and N-15(beta) isotopomers. The dinitrogen complexes 3-N-15(alpha) and 4-N-15(alpha) do not isomerize at ambient temperature, and isolated samples are the pure N-15(alpha) isotopomer. However, at higher temperatures both 3-N-15(alpha) (at 333 K) and 4-N-15(alpha) (at 320 K) isomerize to 1:1 N-15(alpha) and N-15(beta) mixtures. Neither 1-N-15 nor 2-N-15 exchanged with bulk N-14(2) under pressure at room temperature, nor did 3-N-15 or 4-N-15 at 333 or 320 K, respectively, over several half-lives for the isomerization. A mixture of unlabeled 1 and 2-N-15 showed no evidence of formation of the cross products (unlabeled 2 and 1-N-15) at room temperature, and a mixture of unlabeled 4 and 3-N-15 showed no cross-product formation at 333 K. It is concluded that linkage isomerization of the dinitrogen ligand is nondissociative and intramolecular. The proposed mechanism is end-to-end rotation through the intermediacy of a side-on (eta(2)) dinitrogen complex.

The dinitrogen complex Cp*Re(PMe(3))(2)(N-2) (1) undergoes protonation at rhenium but not at the rhenium-bound dinitro(:en ligand under conditions described here. Protonation by using CF3CO2H, HBF4 . OEt(2), or CF3SO3H at 213 K afforded the respective rhenium hydride dinitrogen complexes cis-[Cp*ReH(N-2)(PMe(3))(2)][CF3CO2] (cis-2(CF3CO2)), cis-[Cp*ReH(N-2)-(PMe(3))(2)][BF4] (cis-2(BF4)), and cis-[Cp*ReH(N-2)(PMe(3))(2)][CF3SO3] (cis-2(CF3SO3). These complexes isomerized smoothly to the corresponding trans isomers as the temperature was raised to 273 K. The cis and trans isomers have been fully characterized by using a combination of IR and H-1, P-31, and N-15 NMR spectroscopy, with the dinitrogen ligand singly-labeled in either the Na or Ng positions. The trans isomers are all thermally unstable at room temperature, but trans-2(CF3CO2) is significantly more stable than its analogs, indicating that the counteranion may play a role in stabilizing these cationic rhenium hydride dinitrogen complexes.

The variable temperature H-1 NMR spectra of Cp*ReH(CO)(p-N(2)C(6)H(4)OMe) (1) and Cp*Re-(CH3(CO)p-N(2)C(6)H(4)OMe) (3) and the variable temperature P-31{H-1} NMR spectra of Cp*ReCl-(PR(3))(p-N(2)C(6)H(4)OMe) [R = Me (4), OMe (5), Ph (7)] are presented and discussed. The spectra of 1 and 3-5 show that at low temperature two isomers are present in each case and that these isomers interconvert on the NMR time scale. The isomers are interpreted to occur because the p-N(2)C(6)H(4)OMe ligand adopts two different orientations where the aryl group is oriented syn to either the X or Y ligand in these chiral complexes of general formula Cp*ReXY(p-N(2)C(6)H(4)OMe). The bulky PPh(3) ligand in 7 results in an overwhelming preference for orientation only syn to the Cl group and thus only one observable isomer, The activation parameters for the conformational isomerization of the aryldiazenido ligand in these neutral complexes have been obtained from NMR line shape analyses and are compared with data obtained previously for related cationic rhenium aryldiazenido complexes.

The complex [(eta(5)-C(5)Me(5))Ir(C2H4)(p-N(2)C(6)H(4)OMe)][BF4] (1) reacts with X(-) = I- and Br- to give neutral [(eta(5)-C(5)Me(5))IrX](2)(mu-eta(2)-p-N(2)C(6)H(4)OMe)(mu-eta(1)-p-N(2)C(6)H(4)OMe) where X = I (2) and Br (3), respectively. The spectroscopic data for 2 and 3, as well as their N-15(alpha) derivatives 2a and 3a, establish that 2 and 3 are isostructural in solution and each contains diiridium centers that are bridged by two coordinatively different aryldiazenido ligands, i.e., mu-eta(2)- and mu-eta(1)-p-N(2)C(6)H(4)OMe groups. This structural feature has also been unequivocally confirmed in the solid state by a single-crystal X-ray crystallographic analysis of 2. The NMR studies of the protonation reactions of 2a and 3a indicate that protonation occurs solely at the N-alpha atom of the mu-eta(2)-p-N(2)C(6)H(4)OMe ligand in both cases. When 1 reacts with the metal base complex (eta(5)-C(5)Me(5))Ir(CO)(2) in ethanol at reflux, the monobridging aryldiazenido complex [{(eta(5)-C(5)Me(5))Ir(CO)}(2)(mu-eta(2)-p-N(2)C(6)H(4)OMe][BF4] (6) results. The molecular structure of 6 in the solid state, established by a single-crystal X-ray crystallographic analysis, is consistent with its spectroscopic properties in solution. On the basis of an EHMO calculation and a fragment orbital interaction analysis, a rationale is suggested to explain how the electronic nature of the substituent ligand influences the outcome of substitution reactions of 1. Complex 2 crystallized in the space group <P(1)over bar> with a = 8.937(2) Angstrom, b = 10.036(2) Angstrom, c = 10.893(2) Angstrom, a = 79.98(1)degrees, beta 79.52(1)degrees, gamma = 70.36(1)degrees, and Z = 1. The structure of 2 was refined to R(F) = 0.021 and R(wF) = 0.029 on the basis of 3077 observed independent reflections with I-o greater than or equal to 2.5 sigma(I-o) and 189 variables in the range 28 = 4-52 degrees. Complex 6 crystallized in the space group Pc2lb with a = 8.821(1) Angstrom, b = 20.237(2) Angstrom, c = 34.808(5) Angstrom, and Z = 8. The structure of 6 was refined to R(F) = 0.044 and R(wF) = 0.049 on the basis of 1661 observed independent reflections with I-0 greater than or equal to 2.5 sigma(I-0) and 259 variables in the range 2 theta = 4-50 degrees.

By replacing one or both of the CO groups in [Cp∗Re(η3-C3H5)(CO)2][BF4] (1) by MeCN to give [Cp∗Re(η3-C3H5)(CO)(NCMe)][BF4] (3) or [Cp∗Re(η3-C3H5)(NCMe)2][BF4] (4), it was anticipated that the MeCN groups would be labile and would promote ligand substitutior reactions, leading to a variety of new rhenium η3-allyl half-sandwich derivatives. Instead, MeCN is found to be difficult to substitute, and nucleophiles often result in products that arise from attack at either the MeCN or allyl ligands. Complex 1 reacted with NaBH4 to give the propene complex Cp∗Re(η3-CH2CHCH3)(CO)2 (2), with NaOMe to give the methoxycarbonyl complex Cp∗(η3-C3H5)(CO)(COOMe) (6) and the 3-methoxypropene complex Cp∗Re(η2-CH2CHCH2OMe)(CO)2 (5), and with PMe3 to give [Cp∗Re(η2-CH2CHCH2PMe3)(CO)2][BF4] (7). Complex 3 gave the ethylamine complex [Cp∗C3H5(CO)(NH2Et)][BF4] (8) when reacted with NaBH4, [Cp∗Re(η2-CH2CHCH2PMe3)(CO)(NCMe)][BF4] (9) with PMe3, and Cp∗Re(η-3-C3H5)(CO)(NHCOMe) (10) with NaOH. Complex 4 similarly yielded the bis-ethylamine complex [Cp∗Re(η3-C3H5)(NH2Et)in2][BF4] (11) when reacted with NaBH4, but with PMe3 ligand substitution occurred, resulting in [Cp∗Re(η3-C3H5)(NCMe)(PMe3)][BF4 (12). Treating 12 with NaBH4, or 11 wiht PMe3, yielded the ethylamine complex [Cp∗Re(η3-C3H5)(PMe3)(NH2Et)][BF4] (13). The X-ray crystal structure of [endo-Cp∗Re(η3-C3H5)(NH2Et)2][ReO4].solv has been determined. This compound crystallizes in the space group Pnma with a = 8.6554(8) Å, b = 11.729(2) Å, c = 26.928(3) Å, V = 2733.7 Å3, and Z = 4. The structure was refined to RF = 0.028 for 1444 data (I0 ⩾ 2.5 σ(I0), 2θmax = 46°) and 158 variables. The cation has a crystallographic mirror plane that relates the two EtNH2 ligands and bisects the endo-η3-allyl and Cp∗ ligands. Selected distances and angles are ReN = 2.228(7) Å, ReC(6) = 2.177(9) Å (allyl terminal carbon), ReC(7) = 2.090(13) Å (allyl central carbon), NC(4) = 1.470(10) Å, ReNC(4) = 125.2(6) Å, and C(6)-C(7)-C(6) = 114.1(13) Å

The complex [(η5-C5Me5)Ir(C2H4)(p-N2C6H4OMe)][BF4] (1) reacts with X- = I- and Br- to give neutral [(η5-C5Me5)IrX]2(μ-η2-p-N2C6H4OMe)(μ-η1-p-N2C6H4OMe) where X = I (2) and Br (3), respectively. The spectroscopic data for 2 and 3, as well as their 15Nα derivatives 2a and 3a, establish that 2 and 3 are isostructural in solution and each contains diiridium centers that are bridged by two coordinatively different aryldiazenido ligands, i.e., μ-η2- and μ-η1-p-N2C6H4OMe groups. This structural feature has also been unequivocally confirmed in the solid state by a single-crystal X-ray crystallographic analysis of 2. The NMR studies of the protonation reactions of 2a and 3a indicate that protonation occurs solely at the Nα atom of the μ-η2-p-N2C6H4OMe ligand in both cases. When 1 reacts with the metal base complex (η5-C5Me5)Ir(CO)2 in ethanol at reflux, the monobridging aryldiazenido complex [{(η5-C5Me5)Ir(CO)}2(μ-η2-p-N2C6H4OMe)][BF4] (6) results. The molecular structure of 6 in the solid state, established by a single-crystal X-ray crystallographic analysis, is consistent with its spectroscopic properties in solution. On the basis of an EHMO calculation and a fragment orbital interaction analysis, a rationale is suggested to explain how the electronic nature of the substituent ligand influences the outcome of substitution reactions of 1. Complex 2 crystallized in the space group P1̄ with a = 8.937(2) Å, b = 10.036(2) Å, c = 10.893(2) Å, α = 79.98(1)°, β = 79.52(1)°, γ = 70.36(1)°, and Z = 1. The structure of 2 was refined to RF = 0.021 and RwF = 0.029 on the basis of 3077 observed independent reflections with Io ≥ 2.5σ(Io) and 189 variables in the range 2θ = 4−52°. Complex 6 crystallized in the space group Pc21b with a = 8.821(1) Å, b = 20.237(2) Å, c = 34.808(5) Å, and Z = 8. The structure of 6 was refined to RF = 0.044 and RwF = 0.049 on the basis of 1661 observed independent reflections with Io ≥ 2.5σ(Io) and 259 variables in the range 2θ = 4−50°.

[CP*Ir(C2H4)(N2Ar)][BF4] (1; Ar = p-C(6)H(4)OMe) reacts with PMe(3) to give [Cp*Ir(PMe(3))(2)(N2Ar)][BF4] (4), which has been shown by an X-ray structure determination and by N-15 NMR spectroscopy to possess the aryldiazenido ligand bound with doubly-bent geometry. As is the case in 1, the complexes [Cp*Ir(PPh(3))(N2Ar)][BF4] (2) and [Cp*Ir{P(p-tol)(3)}(N2Ar)][BF4] (3) have the N2Ar ligand bound with singly-bent geometry. This has been demonstrated by an X-ray structure determination for 3. Complexes 2 and 3 react with PMe(3) to give [Cp*Ir(PPh(3))(PMe(3))(N2Ar)][BF4] (5) and [Cp*Ir{P(p-tol)(3)}(PMe(3))(N2Ar)][BF4] (6), and 2 reacts with CO or CN- to give [Cp*Ir(CO)(PPh(3))(N2Ar)][BF4] (7) or Cp*Ir(CN)(PPh(3))(N2Ar) (8). All these reactions are shown by N-15 NMR to involve the transformation of the N2Ar ligand from singly-bent to doubly-bent as a consequence of coordination by the incoming ligand. Diphos (Ph(2)P(CH2)(2)PPh(2)) reacts with 1 to give [Cp*Ir(diphos)(N2Ar)][BF4] (9), but no complex of stoichiometry [Cp*Ir(PPh(3))(2)(N2Ar)][BF4] could be obtained from 1 or 2 with excess PPh(3); this complex is presumably sterically disfavored. Crystal structures: 3, T = 295 K, orthorhombic, space group P2(1)2(1)2(1), 2 = 4; a = 12.974(2) Angstrom; b = 13.449(2) Angstrom, c = 16.213(4) Angstrom, V = 2829.0 Angstrom(3), R(F) = 0.032 for 2974 data (I-0 greater than or equal to 2.5 sigma (I-0)) and 241 variables; 4, T = 295 K, monoclinic, space group P2(1)/n, Z = 4; a = 9.906(2) Angstrom, b = 12.084(3) Angstrom, c = 30.545(6) Angstrom, beta = 93.296(13)degrees, V = 3650.2 Angstrom(3), R(F) = 0.029 for 3606 data (I-0 greater than or equal to 2.5 sigma (I-0)) and 422 variables.

[Cp*Ir(C2H4)(N2Ar)][BF4] (1BF4; Ar = p-N2C6H4OMe) has been synthesized by reacting [ArN2] [BF4] with Cp*Ir(C2H4)2 at low temperature. An initial electrophilic attack of the incoming diazonium ion at iridium, followed by expulsion of C2H4, is postulated to account for the mild reaction conditions that are in sharp contrast to the usual inertness of the bis(ethylene) compound toward ligand substitution. The IR and nitrogen NMR data for 1BF4 and its 15Nα derivative unambiguously establish that the ArN2 ligand has the singly bent geometry in this complex in solution. The X-ray crystal structure confirms this for the solid state, and establishes that the plane of the aryldiazenido ligand is approximately perpendicular to the plane defined by the Ir atom and the centers of mass of the Cp* and ethylene ligands. An extended Hückel molecular orbital analysis of the singly bent aryldiazenido ligand has been carried out and satisfactorily accounts for the observed orientation of the ArN2 ligand. An analysis of the variable-temperature 1H and 13C NMR of 1BF4 indicates that both restricted rotation of the C2H4 ligand and a conformational isomerization of the aryldiazenido ligand are occurring, and ΔG≠270 for the ethylene rotation barrier is estimated at ≤ 51.5 ± 0.4 kJ mol−1. This is lower than the barrier of ΔG≠353 = 68.7 ± 0.2 kJ mol−1 determined previously for the analogous nitrosyl complex [Cp*Ir(C2H4)(NO)] [BF4] (2BF4) and it is suggested that in these half-sandwich complexes both NO and ArN2 function as single-faced π-acceptors, and in these circumstances ArN2 is the better π-acceptor. The ethylene in 1BF4 is readily displaced by PPh3 to give [Cp*Ir(PPh3)(N2Ar)][BF4] (3BF4). This reacts with NaBH4 to yield Cp*IrH(PPh3)(N2Ar) (4) in which the ArN2 ligand has switched to the doubly bent geometry, on the basis of the 15Nα NMR chemical shift data. Attempts to synthesize the corresponding chloro analogue 5 resulted in only the chloride salt of the singly bent ArN2 cation 3. For example, reaction of 3BF4 with HCl yields the aryldiazene complex [Cp*IrCl(PPh3)(NHNAr)] [BF4] (6), but deprotonation of this with Et3N yields 3Cl, not 5. Compound 1BF4 crystallized in the space group P21/n with a = 8.5780(10) Å, b = 20.5310(23) Å, c = 12.0310(15) Å, β = 93.500(10)°, and Z = 4. The structure was refined to Rf = 0.0281 on the basis of 2611 observed reflections with I°> 2.5σ(Io) in the range 2θ = 0–50° (Mo-Kα). Keywords: iridium, cyclopentadienyl, aryldiazenido, nitrosyl, ethylene.