摘要:

J. CHEM. soc-. DALTON TRANS. 1989 1217 Reactivity of the Iridium Nitrosyl Complex [Ir(NO)(paa)(PPh,),][PF,l, (paa = 2- Pyridinecarbaldehyde Azine) with Nucleophiles: Insertion of NO into a Methinic C-H Bond; Crystal Structure of [Ir{(2-C5H,N)CH=N-N=C( NOH)(2-C5H,N)}{Me- (EtO)C=NH}(PPh,),][PF,],* Mauro Ghedini, Marcello Longeri, and Francesco Neve Dipartimento di Chimica, Universita della Calabria, I 87030 Arcavacata (CS), Italy Anna Maria Manotti Lanfredi and Antonio Tiripicchio lstituto di Chimica Generale ed lnorganica, Universita di Parma, Centro di Studio per la Strutturistica Diffrattometrica del CNR, Viale delle Scienze, I 43 I00 Parma, Italy The nitrosyl complex [Ir( NO) (paa) (PPh,),] [PF,], (paa = 2-pyridinecarbaldehyde azine) reacts either with RCN (R = Me, Ph, or Ph,CH) or X- (X = CI or SCN) at room temperature, to give II cyclometallated compounds containing the Ir-N-N=k-N (OH) moiety.These complexes were characterised by elemental analysis, conductivity measurements, i.r. and n.m.r. spectroscopy. The metallated ring can be envisaged as resulting from intramolecular insertion of the NO group, activated by the iridium co-ordination of RCN or X-, into the methinic C-H bond of the unco- ordinated paa fragment. Addition of ethanol to the compound containing MeCN or PhCN gives imidate complexes. The structure of the acetoimidate complex [ Ir{ (2-C,H,N)CH=N-N=C( NOH) - (Z-C,H,N)}(Me( EtO)C=NH}( PPh,),] [PF,], has been determined by X-ray diffraction. Crystals are monoclinic, space group Cc, with unit-cell dimensions a = 12.405(6), b = 43.836(12), c = 11.1 26(7) A, p = 11 2.1 (2)", and Z = 4.The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by block-matrix least squares to final R and R' values of 0.057 and 0.073 for 3 394 observed reflections. In the cation four N atoms, one from the neutral ethylacetoimidate ligand and the other three from the monoanionic ligand resulting by intramolecular insertion of NO into a methinic C-H bond of the starting paa ligand, are arranged in the equatorial positions of the iridium co-ordination octahedron whose apices are occupied by P atoms from PPh, molecules. The new =&NOH fragment displays a C-N bond length of 1.37(3) A and the OH group is involved in a strong intramolecular hydrogen bond with the unco-ordinated pyridyl nitrogen atom.The synthesis from NO of nitrogen-containing organic molecules is among the purposes of many recent investigations on the chemistry of transition-metal nitrosyl complexes. In these studies, of relevance is the carbon-nitrogen bond formation through NO migration from the metal to the organic moiety, a critical step in the whole process. The reactivity of the ligand NO is strongly affected by its co- ordination mode. Thus, it can behave either as an electrophile, when linear NO+, or as a nucleophile when bent NO-.' Briefly, some examples recently reported in the literature concerning significant progress in this chemistry are: (i) nucleophilic attack on benzyl bromide by a co-ordinated NO group of [Ru- (NO)2(PPh3)2];2 (ii) migratory insertion of NO into cobalt- or ruthenium<arbon bonds;3 (iii) insertion of NO' into a cobalt cluster-carbon bond;4 (iu) insertion of NOf into a carbon- hydrogen bond of the Me group contained in [Cr(q5- We describe here a further example of C-N bond formation.This reaction arises from a nucleophile-promoted migratory insertion of co-ordinated NO into a methinic C-H bond. The starting complex is a derivative of 2-pyridinecarbaldehyde azine (paa), [Ir(NO)(paa)(PPh3)2][PF,I, (l), whose synthesis and c 5 H s )(NO )2 Me]. * ( 1 -Ethoxyethanimine-N)(a-hydroxyamino-2-pyridinecarbaldehyde azinato)bis(triphenylphosphine)iridium(rrr) bis(hexafluorophosphate). Supplemeniary duici cit;ailuble: see Instructions for Authors, J . Chem. SOL.., Dultoti Trans., 1989, Issue 1, pp.xvii-xx. H5 2 + H l3' characterisation have been previously reported.6 In this cation the co-ordination of Ir, as deduced by spectroscopic in- vestigations, is trigonal bipyramidal with two equivalent PPh, molecules in apical positions and the NO group, v(N0) 1 800 cm-*, linearly bound to the iridium centre, in the plane of the paa ligand which forms a five-membered chelate ring. The nucleophilic reagents reacting with (1) are nitriles and the anions C1- or SCN-. A preliminary account of this work has been given.'1218 J. CHEM. SOC. DALTON TRANS. 1989 Table 1. Proton n.m.r. assignments (6)* Compound Chemical shifts (2) Hh, 8.24; H', 6.89 H". 7.20; H3, 6.65 H", 8.33; H':, n.0. H 4 , 7.77; H 3 , 7.25 H', 7.05 MeCN, 2.26 (3) (4) (7) (9) Hh, 8.47; H5, 7.03 H", 7.21; H3.6.59 Hh', 8.36; H". n.0. H"', 7.80; H3', n.0. H7, 6.99 MeCN. 2.20 H', 8.32; H5, 6.96 H", 7.22; H3, 6.68 H". 8.33; H5', n.0. H4', 7.79; H". 7.29 H', 7.09 PhCN, 7.75 ( 1 H), 7.01 (2 H ) Hh, 8.25; H', 6.95 H", n.0.; H3, 6.58 H":, 8.35; H':, n.0. H", 7.80; H" n.0. H', 6.95 Ph,CHCN, 5.84 Ph,CHCN, 7.08 (4 H) H", 7.52; H', 6.31 H", 7.20; H3, 6.86 H"'. 8.37; H', n.0. H"', 7.71; H", 7.00 H', 6.81 H", 7.02; H', 6.31 H', 7.26; H3, 6.93 Hh , 8.32; HS , n.0. H", 7.72; H" 7.07 H7, 6.95 Hh, 8.67: H'. 6.92 H", 7.19; H". 6.67 H" . 8.32; H" n.o. H", 7.77; H 3 , 7.26 H', 7.10 Mc(CH ,CH ,O)CNH, 2.3 5 Me(CH,CH,O)CNH. 1.20 Me(CH ,CH,O)CN H, 3.65 Hh. 9.31; H5, 6.82 H4. 7.10; H3, 6.37 H', 8.32; H". n.0. H"', 7.73; H A , n.0. H'. 7.00 Ph(CH,CH,O)CNH, 6.89 Ph(CH,CH,O)CNH, I .20 Ph(CH,CH,O)CNH, 3.66 Coupling constants J(HhH') = 5.0; J(H5H4) = J(H4H3) = 7.8 J ( H h : H s j = 5.0, J(Hh'H"') = 1.7, J(Hh'H3') = 1.0, J ( H 5 H") = 7.8, J(H"H3') = 1.0, J(H4'H3') 4J(PH) = 3.1 8.0 J(HhH5) = 5.0, J(H'H4) = 1.3, J(H5H3) = 1.5, J(H'H4) = J(H4H3) = 8.0 J(Hh:HS:) = 5.0; J(Hh'H4') = 1.7.J(Hh'H") = 0.9, J ( H S H4 ) = J ( H 4 H3 ) = 8.0 J(HhH5) = 5 . G 6 . 0 , J(H'H4) = 7.8, J(H5H3) = 1.3, J(H4H3) = 8.0 J(Hh'H',) = 4.9. J(Hh'H4') = 1.6, J(H6'H3') = 0.9, J(H5'H") = 7.9, J(H4'H3') = 8.0 4J(PH) = 3.2 J(HhHS) = 5.6, J(H4H3) = 7.9 J(Hh'H':) = 5.0, J ( H ' H4') = 1.7, J(H''H3 ) = 0.9, J(H"H4) = J(H4'H3') = 7.9 J ( H h H 5 ) = 5.8, J(H5H4) = 7.4, J(H'H3) = 1.2, J(H4H3) = 8.0 J(H":H") = 5.0, J(Hh'H4') = 1.7, J(Hh'H3') = 0.9, J ( H 5 H"') = 7.3.J(H4'H") = 8.0 4J(PH) = 2.6 J(H"H5) = 5.8, J(HsHHJ) = 7.5, J(HsH3) = 1.2, J(H4H3) = 8.0 J(Hh'H5') = 5.0. J(H''H4') = 1.7, J(H5'H4') = J(H"'H") = 7.9 "J(PH) = 2.7 J ( H h H s ) = 5.5, J(HsH") = 7.9, J(H4H3) = 7.9 J(Hh'H") = 5.0, J ( H h ' H 4 ) = 1.7, J(Hh'H3') = 0.8, J(H"H"') = J(H4'H3') = 8.0 "J(PH) = 3.2 'J(HH) = 7.1 J(HhHs) = 5.0, J(H5H4) = 7.5, J(H4H3) = 7.9 J ( H h H' = 5.4, J(Hh H") = 1.5, J ( H s ' H 4 ) = 7.8. J ( H 4 H 3 ] = 7.9 'J(PH) = 2.5 'J(HH) = 7.5 * The values (relative to SiMe,) were obtained in CD,CI, solution. J values in Hz. The free-ligand values are given in ref. 6 (Table 1). n.o. = Not observed because superimposed on PPh, protons.J. CHEM. soc. DALTON TRANS. 1989 1219 Table 2. Proton n.m.r. co-ordination shifts (A&)* Compound Hh H5 H4 H3 H6' H '' H4' H3' H7 - 0.49 -0.26 - 0.4 1 - 0.48 - 1.21 - 1.71 - 0.06 + 0.58 - 0.48 -0.34 - 0.4 1 - 0.48 - 1.06 - 1.06 - 0.45 -0.56 - 0.60 -0.59 -0.58 n.c.- 0.60 - 0.54 -0.61 -0.70 - 1.48 -0.40 n.c. - 1.54 -0.37 n.c. - 1.45 -0.40 n.c. -1.55 -0.38 n.c. - 1.27 -0.36 n.c. - 1.20 -0.41 n.c. - 1.46 -0.41 n.c. - 1.76 -0.41 n.c. -0.03 0.00 -0.01 0.00 - 0.09 - 0.08 - 0.03 - 0.07 - 0.88 n.c. n.c. - 0.84 - 1.13 - 1.06 - 0.87 n.c. - 1.65 - 1.71 - 1.61 - 1.76 - 1.89 - 1.75 - 1.60 - 1.70 * A6 = d(comp1e.x) - 6(free), positive values being downfield shifts. n.c. = Not calculated because the relative signal was not assigned. Table 3. Carbon-13 n.m.r. data (6) for the free paa ligand and its nitrile complexes (2) and (4)" 162.1(C7.7') I 50.0(C6.6') 122.5(C5.' ) 1 36.6(C4., ) 125.1(C3.3j 1 51.9(C2.2 ) / 4-3 6=N N-6' / 'y=4/ ( 2 ) 164.57' 160.86' 154.93 145.83b 144.62 140.67 139.20 136.70' 127.36 126.31 126.26 123.44 (4) 164.58' 160.80' 155.18 145.84' 144.64 140.84 139.30 137.02' 127.43 126.65 126.116 123.60 " The values (p.p.m. relative to SiMe,) were obtained in CD,Cl, solution at 20 "C. For the PPh, and RCN signals see Experimental section. ' Quaternary carbon. This signal shows a triplet structure due to 31P coupling C3J(PC) = 4-6 Hz]. I I I 8 7 6 6 Figure 1. Proton n.m.r. spectrum (300 MHz) at 20°C of complex (2) in the aromatic region Results and Discussion Reuctions \r*ith Acetonitrile.-Complex (1) was prepared by reaction between the six-co-ordinated nitrosyl complex [Ir- (No)(MeCN)3(PPh,)2][PF6]2 and paa at room temperature with tetrahydrofuran (thf) as solvent.6 The pale yellow compound (1) when dissolved in acetonitrile gives rise to a purple solution from which, after 12 h, a violet microcrystalline solid, compound (2), can be separated by addition of diethyl ether (957;) yield).The product (2) was characterised by elemental analysis, which accounts for a stoicheiometry [Ir(NO)(MeCN)(paa)- (PPh3)2][PF6]2, conductivity measurements (is a 1 : 2 electro- lyte in nitromethane'), and spectroscopic methods (data in Experimental section and Tables 1-3). Interestingly the i.r. spectrum (KBr) shows two weak absorptions, at 2 325 and 2 300 cm-', attributable to a CEN stretch, and a very low-frequency NO stretch at 1 354 cm-'. The presence of two bands in the v(CN) region at high frequency with respect to free acetonitrile is diagnostic of its end-on co- ~rdination,~ while the NO stretching frequency is in agreement either with a nitrosoalkane ligand M-N(=O)-R3" or with a metal-bonded nitroxide group M-N(R)-0'. O The 31P-( 'H) n.m.r.spectrum displays a single resonance (6 - 7.34 p.p.m.) indicating the equivalence of two mutually truns phosphines co-ordinated to an iridium(Ix1) centre.' ' . I The 'H n.m.r. spectrum of complex (2) is reported in Figure 1. The assignments of the paa ligand signals, performed as previously described,6 and their shifts upon co-ordination are reported in Tables 1 and 2 respectively. Noteworthy, as far as the two N=CH protons present in free paa are concerned, is that only one of them is detectable. Such a proton, observed as a triplet in the spectral region free from PPh, protonic resonances, appears strongly shielded (A& 1.65) and coupled with the phosphorus nuclei with 4J(PH) = 3.1 Hz; it is assigned to the N=CH moiety having the nitrogen atom co-ordinated to the metal.6 The spectral multiplicity of this signal has been confirmed by comparison with the 'H n.m.r.spectrum of the homologous arsino complex, (3) (see Experimental section and Tables 1 and 2), synthesised ad hoc for this experiment. Finally, the MeCN1220 J. CHEM. SOC. DALTON TRANS. 1989 ligand displays the methyl signal slightly downfield with respect to its unco-ordinated situation. The analysis of the 13C-(1H) n.m.r. spectrum (Figure 2) shows that the signals can be divided into three different sets, due to the PPh,, the MeCN, and the paa respectively.The twelve distinct resonances forming the latter set (Table 3), compared with the spectral pattern of unco-ordinated paa, display some interesting features, namely: (i) in the low-field end of the spectrum (6 165.0-145.0 p.p.m.), together with two expected signals at 6 164.57 and 160.86 p.p.m. tentatively I t 160 150 I4 0 130 120 6 1P.P.m Figure 2. Low-field end of the I3C-[lH) n.m.r. spectrum (75 MHz) of complex (2) in CD,CI, solution PPh, / assigned to C2 and C2' respectively (6 152.9 p.p.m. for free paa), a further resonance attributable to a quaternary carbon atom is present at 6 145.83 p.p.m., and (ii) the C7 resonance, a triplet at 6 136.70 p.p.m. with ,J(CP) = 4-6 Hz, is shifted significantly to highfield (A6 z -35). The 'H and 13C-{'H) n.m.r.data permit the assignments of the third quaternary carbon atom present in the skeleton of the complexed paa ligand. The 'H spectrum shows no structural changes in both the pyridyl rings and in the co-ordinated -N=C7-H moiety, hence in complex (2), where the second N=CH proton is not seen, the remaining N=C" carbon atom is quaternary. The structure of the complex cation, of stoicheiometry [1r(NO)(MeCN)(paa)(PPh,),l2 +, will be discussed later. Remtions \iQith Other Nitri1es.-Benzonitrile or diphenyl- acetonitrile reacted with complex (1) in dichloromethane, but over a longer period than with MeCN (24 h and 7 d respectively), giving rise to violet compounds (4) and ( 5 ) (ca. 800/;; yields) similar to complex (2). The new products, identified by elemental analysis, conductivity measurements, i.r., 'H, 31P-('H), and, for (4) only, 13C-{ ' H ) n.m.r.spectroscopy (Experimental section and Tables 1-3) differ from (2) only in the nitrile ligand. Reactions rt'itlz X - (X = C1 or SCN).-The iridium nitrosyl complex (I), dissolved in CH2C12, and the LiX salt (X = C1 or SCN) in ethanolic solution (1 : 5 molecular ratio; reaction time 12 h) react affording violet products (6) and (7) (Experimental section and Tables 1 and 2). Both microanalytical data and the behaviour in nitromethane solutions (1 : 1 electrolytes') are in agreement with the stoicheiometry [Ir(NO)X(paa)(PPh3)2]- [PF,], X = Cl(6) or SCN (7). Their i.r. spectra (KBr) display a NO stretch at 1 350 cm-', moreover the spectrum of (7) shows a strong absorption at 2 105 cm-' assigned to the SCN group, probably S-bonded.', The 31P-[1H] n.m.r.spectra consist of single resonances at c * CH,CH,O I CH,-Ct ,CN - ,-0 - ~ Figure 3. Proton n.m.r. spectrum (300 MHz) at 20 "C of the imidate complex (8). Peaks with an asterisk represent free ethanolJ. CHEM. SOC. DALTON TRANS. 1989 1221 H6‘ 9 8 7 6 4 1 Figure 4. Proton n.m.r. spectrum (300 MHz) at 20 O C of the imidate complex (9) Figure 5. View of the cationic complex (8) with the atomic numbering scheme 6 - 12.15 and -9.16 respectively [two equivalent PPh, co- ordinated to an iridium(m) centre] while the ‘H n.m.r. spectra exhibit patterns very similar to those of (2)-(5), the only difference being enhanced upfield shifts of the H5, H6, and H7 signals (Table 2).The physical properties above reported as a whole indicate that (6) and (7) are isostructural with complexes (2)-(5) with the NO group in a similar bonding situation. Reucctiori of’ Cotnplexes (2) and (4) with Ethand-The reactivity of the nitrile complex (2) was first observed during the many attempts carried out to grow crystals of such a compound from solvent mixtures containing ethanol. As reported in the literature, transition-metal-co-ordinated nitriles M-N-CR react with alcohols R’OH giving rise to M-NH=C(OR’)R cornplexe~.~”~ In the same way, complexes (2) and (4) dissolved in a CH,CI,-EtOH solution (1 : 2, v/v) over a long time (about 2 months) at room temperature afford the corresponding imidate derivatives (8) and (9). These complexes have been characterised by spectroscopic methods.The addition of EtOH to the co-ordinated nitrile has been confirmed by both i.r. (Experimental section) and ‘H n.m.r. data (Tables 1 and 2), while their very similar structural features to the parents (2) and (4) are evident in the general appearance of the i.r. [v(NO) in KBr: (S), 1 350s; (9), 1 358s cm-’1, 3 1 P-{ ’H) [in CH,CI,: (8), 6 -6.96; (9), -8.291, and ‘H n.m.r. spectra (Figures 3 and 4). X-Raj? Crystal Structure of Complex @).-The crystal structure of complex (8) consists of discrete cations CIr((2- C,H,N)CH=N-N=C(NOH)(2-C5H4N)) { Me(EtO)C=NH} - (PPh,),], + and PF,- counter anions. Relevant bond dis- tances and angles in the cation are given in Table 4. A view of the cationic complex is shown in Figure 5 together with the atomic numbering system. The slightly distorted octahedral co- ordination around the iridium centre involves two mutually trans P atoms from PPh, ligands and, in equatorial positions, four N atoms, one from the neutral ethylacetoimidate ligand, N(6), and the other three, N(I), N(3), and N(4), from the monoanionic ligand arising from the insertion of a nitrosyl group into a methinic C-H bond of the starting paa ligand, with the formation of a new C-N bond whose length is 1.37(3) a.The tridentate moiety of this ligand, including the two fused penta-atomic chelating rings and the co-ordinated pyridyl group, is nearly planar [maximum deviation from the mean plane passing also through the Ir and O(1) atoms is 0.15(3) 8, for C(5)] with the unco-ordinated pyridyl group tilted by 22.3(6)”.The C-N [C( I)-N( 1) 1.37(3), C(l)-N(2) 1.34(3), C(2)-N(3) 1.33(3), and C(3)-N(4) 1.41(2) A] and N-N [N(2)-N(3) 1.32(3) A] bond lengths, even if their standard1222 J. CHEM. SOC. DALTON TRANS. 1989 Table 4. Selected bond distances (A) and angles (") in complex (8) N( 1 )-1r-N(3) N( l)-Ir-N(4) N( l)-Ir-N(6) N( 3)-Ir-N(4) N(3)-Ir-N(6) N(4)-Ir-N( 6) P( I )-1r-N(6) P( 1 )-Ir-N(4) Ir-N(6)-C( 13) N(6)-C( 13)-O(2) N(6)-C( I3)-C( 14) C( 1 )-N( 1 )-O( I ) O( 1 )-N( 1 )-Ir C( 1 )-N( 1 )-Ir N( 1)-C( 1)-N(2) N( 1 )-C( 1 )-C(8) N(2)-C( I)-C(8) C( 1 )-N(2)-N(3) N(2)-N(3)-Ir N(2)-N( 3)-C(2) 2.430( 8) 2.00( 2) I .92( 2) I .38(2) 1.37(3) 1.34(3) 1.49( 3) I .23(2) 1.33( 2) 1.34 77.5(8) I 59.4( 8) 104.4( 8) 82.3(7) 177.8(8) 95.8(7) 90.0( 7) 87.5(5) 134i2) 116(2) I27(2) 1 17(2) 132(1) 1 1 l ( 1 ) I 20( 2) I 24( 2) 116(2) I09( 2) 122( 1 ) 120(2) 1.53(3) I r-P( 2) Ir-N(4) Ir-N( 6) N(2)-N(3) N(3)-C(2) C(2)-C( 3 ) N(4)-C(3) O(2)-C( 15) C( 15)-C( 16) P( l)-Ir-N(3) P( 1 )-Ir-N( 1 ) P( 1 )-Ir-P( 2) P(2)-Ir-N( 6) P(2)-Ir-N(4) P(2)-Ir-N(3) P(2)-Ir-N( I ) C(7)-N(4)-Ir O( 2)-C( 13)-C( 14) C( 13)-0(2)-C( 15) C( 1 6)-C( I 5)-O( 2) C( 2)-N( 3)-Ir N(3)-C(2)-C( 3) C(2)-C(3)-N(4) C(2)-C(3)-C(4) N( 4)-C( 3)-C( 4) C( 3)-N(4)-C( 7) C( 3)-N(4)-Ir N(l)-O(l)-H( 1 ) 2.403( 7) 2.04( 1 ) 2.05(2) 1.32(3) 1.33(3) 1.45( 3) i .41(2) 1.49( 3) 1.38(6) 90.9(6) 96.2( 6) 1 76.4( 3) 87.0( 7) 90.q 6) 92.1(7) 86.5(6) 1332) 1 17(2) 1232) 117(3) 117( I ) 1 1 3 2 ) 1 lS(2) 1232) 123(2) 114(2) I l l ( 1 ) 98 electron negatively charged donor have been reported for the complexes [OSC~~(NHOH)(NO)(PP~,)~]'~ and [Zr(q5- The fourth equatorial position in the iridium co-ordination sphere is occupied by the neutral ethylacetoimidate ligand, probably the first structurally characterised example of a N-co- ordinated acyclic imidate ether. However.the Ir-N(6) bond [2.05(2) A] can be compared with that found in the metalla- cycle [Ir(CH,OCMe=NH)( PMe,),][PF,][BF,] [2.080(12) A]. '') Moreover, the structural parameters of the imidate skeleton are in agreement with the expected ones except for the C( 15)-C( 16) distance [ 1.38(6) A], which involves a rather disordered ethyl group. On the other hand the imidate ligand seems to adopt an apparently sterically congested position between the apical PPh, ligands, with a number of atom-atom contacts approaching, or less than, the sum of the van der Waals radii [0(2)-C(23) 3.12(3), 0(2)-C(24) 3.20(4), N(6)-C(23) 3.20(4), and C(13)-C(42) 3.21(4) A].The torsion angle Ir-N(6)-C( 13)-0(2) of 1.7" suggests the configuration for the imidate ether. Steric effects are probably responsible for this unusual configuration in this case.20 The iridium octahedral co-ordination sphere is completed by two f r m s PPh, ligands with Ir-P bonds [Ir-P(l) 2.430(8) and Ir-P(2) 2.403(7) A] which compare well with those observed in similar six-co-ordinated cationic iridium(rI1) complexes.12.2 Of the two independent PF,- anions, the one involving P(4) shows larger thermal parameters than that involving P(3), probably because the latter is involved in shorter contacts (some of them probably hydrogen bonds) with the cations. C,H,),CI(C,H 1 ,NCHNC,H 1 1 )].I8 I 1 3.18(4), N(6)-C(28) 3.21(4), N(6)-C(42) 3.12(2), C(13)-C(23) -O, ,C=N Z 'H deviations are rather high, indicate an extensive conjugation in this moiety.With regard to the Ir-N bond distances in this ligand, it should be noted that the Ir-N(3) bond, sharing the two chelating penta-atomic rings, is significantly shorter [ 1.92(2) A] than the Tr-N(4) [2.04( 1) A] and Ir-N( 1 ) [2.00(2) A] ones. This distance is the shortest found up to now for Ir-N bonds involved in a five-membered Ir-N=C-C=N moiety, while Ir-N(4) is as expected for Ir-N(sp2) co-ordination.12.' For the Ir-N( 1 ) bond no comparison can be made as, to the best of our knowledge, the present case is the first characterised example of - a metal complex containing the Ir-N(0H)-C fragment.The N-0 bond distance [1.38(2) A] agrees well with those found in similar moieties in [Cr(q5-C,H,)(NO),(N(CH,)- OH)]+ [1.392(7) A] and [RuCl,(PhN=NC(NOH)Ph),1 [1.369(11) and 1.372(9) A] l 6 in which the NOH groups, from the formaldoxime or the phenylazo-oxime ligands respectively, are N-co-ordinated to the metal and are also involved in an intermolecular (with the counter anion) or intramolecular (within the complex) hydrogen bond. In the present case the distance between 0 ( 1 ) , from the NOH group, and N(5), from the unco-ordinated pyridyl group, is rather short [O(l) - N(5) 2.56(2) A] and indicative of the presence of a strong intramolecular hydrogen bond.Moreover, the unique peak found between these two atoms in the final AF map might suggest that the hydrogen atom is symmetrically disposed between them [O(l)-H(l) 1.34, N(5)-H( I ) 1.34 A, O( 1)-H( 1)-N(5) 145O1. Thus, the bonding mode displayed by this monoanionic tridentate bis(che1ate) ligand can be described as the result of an a-di-imine chelate moiety fused with a new chelate ring whose closure is achieved through the bond between the Ir atom and the negatively charged N(1) atom. Other examples of a nitrogen atom behaving as a formal two- Conclusions The new complexes (2) and (4)-(7) have been synthesised in good yield from reactions of the five-co-ordinated species (1) with MeCN, PhCN, Ph,CHCN, C1-, and SCN-. Alternatively, (2) and (4) can be prepared in a one-step reaction from [lr(NO)(MeCN)3(PPh3)2][PF,32 and paa ( 1 : 1 mol ratio) in neat n i t r i le so 1 u t ion s ( E x pe rime n t a 1 sect i o n ) .The co - o r d i n at ed nitrile molecule of (2) and (4) at room temperature slowly reacts with EtOH; the same reaction with ( 5 ) (wherein the nitrile is Ph,CHCN) gave in 2 months no product other than the starting complex, therefore under such conditions ( 5 ) appears to be inert toward EtOH. Compounds (2)-(9) display very similar spectroscopic data [e.,q. v ( N 0 ) = 1 350---I 360 cm-' and 6(P) - -6 to -12 p.p.m.1, therefore their molecular structure, except for a unidentate ligand that in turn is MeCN, PhCN, Ph2CHCN, C1-, SCN-, MeC(OEt)NH, or PhC(OEt)NH, seems to be basically the same. Thus the main feature of these complexes is that the nitrogen atom of the IrNO group, by insertion into the niethinic C-H bond of the paa fragment not involved in co- ordination to the metal, forms a new cyclometallated ring Ir-N-N=k-N(0H).I1 Such an insertion, which is promoted by a wide range of nucleophiles either neutral, such as nitriles, or anionic, such as C1- and SCN-, can be summarised as in the Scheme. The formation of complexes (2)--(7) is proposed to proceed in two steps: ( 1 ) co-ordination of the nucleophile to complex (1) with contemporary internal redox Ir' - Ir"' and NOf - NO- and (2) attack of the nitrogen on the methinic carbon; the former seems to be rate determining in view of the fact that only the final insertion products were obtained from the reaction mixtures.J.CHEM. SOC. DALTON TRANS. 1989 insert ion - Insertion product f a s t Scheme. Proposed steps in the formation of complexes (2h(7); Nu = nucleophile Experimental All the reactions were carried out in an oxygen-free nitrogen atmosphere. Solvents were dried and deaerated prior to use. The 'H, 13C-('H) (75.5 MHz, CD,Cl,, standard SiMe,), and 31P-('H) (121.5 MHz, CH,CI,, external standard 85% H3PO4) n.m.r. spectra were recorded on a Bruker WH 300 spectrometer, i.r. spectra for KBr pellets on a Perkin-Elmer 1330 spectro- photometer. Conductivity measurements were performed using an LKB 5300 B Conductolyser conductivity bridge. The melting points are uncorrected. Elemental analyses were carried out by the Microanalysis Laboratory of the Istituto di Farmacia dell'universita di Pisa, Italy.Prepuration o j Compounds.-The ligand 2-pyridinecarbalde- hyde azine (paa) was prepared by a standard procedure.22 The complexes [Ir(NO)(MeCN),(PPh,)2][PF6]223 and &(NO)- (paa)( PPh,),][ PF,]26 were prepared by published procedures; [I~(NO)(M~CN),(ASP~,)~][PF~], was prepared in a similar way to the triphenylphosphine derivative starting from [IrI ,( NO)( ASP^,),].,^ Reaction of [Ir(NO)(paa)(PPh,),][PF& (1) with MeCN: [I r { ( 2-C , H4N)CH=N-N=C( NO H)( 2-C H4N) ] (M eCN)- (PPh3)2][PF6]2 (2). A yellow solution of complex (1) (0.10 g, 0.08 mmol) in MeCN ( 5 cm3) was left overnight after which time a clear violet solution had developed. The volume of solvent was reduced (2 cm3) and diethyl ether was added giving in quantitative yield a microcrystalline violet precipitate of (2), m.p. 243-244°C (Found: C, 45.9; H, 3.3; N, 6.3.C,,H4,- Fl,IrN60P4 requires C, 46.6; H, 3.3; N, 6.5%). Molar conductivity, A = 177.35 52-' cm2 mol-' (lo-, rnol dm-3) in nitromethane. 1.r. (KBr disc): 2 325w and 2 300w (CN), 1 354s cm-' (NO). N.m.r.: 31P-(1H), 6, -7.34 p.p.m.; 13C-(1H}, 6, 134.51 [12 C, t, J(PC) = 5.0, C2,, (PPh,)], 132.86 [6 C, s, C4 (PPh,)], 129.73 [12 C, t, J(PC) = 5.0, C3,, (PPh,)], 126.78 [l C, s, CN (MeCN)], 122.14 [6 C, t, J(PC) = 28.5 Hz, C' (PPh,)], and 4.00 p.p.m. [l C, s, Me (MeCN)]. Reuc'tion uf' [lr(N0)(paa)(A~Ph,)~][PF~]~ with MeCN: [I r( (2-C H,N)CH=N-N=C(NOH)(2-C5H4N)}( MeCN)- g, 0.064 mmol) and paa (0.014 g, 0.064 mmol) were mixed in acetonitrile (4 cm3). The resulting green solution turned violet in ca.10 min. After 3 h the solution was taken to dryness under reduced pressure, the violet residual solid was triturated with diethyl ether, filtered off, and vacuum dried, m.p. 155-156 "C. Yield 0.08 g (94%) (Found: C, 43.3; H, 3.1; N, 6.5. C,oH4,As,F,,~rN,0P, requires C, 43.6; €3, 3.1; N, 6.1%). A = 166.90 R-' cm2 mol-' ( l t 3 mol drn-,) in nitromethane. 1.r. (KBr disc): 2 320w and 2 300w (CN), 1 350s cm-' (NO). Reaction of complex (1) with PhCN: [Ir{(2-C,H4N)- Benzonitrile (0.1 cm3) was added to a solution of complex (1) (0.06 g, 0.047 mmol) in CH,Cl, (3 cm3) and the reaction mixture was left for 24 h, producing a violet solution. The solvent was (ASPh3)21[PF612 (3)* [1r(No)(MeCN)3(AsPh3)2][pF(j]2 (0.08 CH=N-N=C(NOH)(2-C,H4N)}(PhCN)(PPh,),lCPF6]2 (4).1223 removed under vacuum and the solid residue crystallised from CH,Cl,-cyclohexane as violet plates, m.p. 225-226 "C, yield 0.05 g (80%) (Found: C, 49.7; H, 3.4; N, 6.0. C,,H4,F,,~rN60P, requires C, 49.4; H, 3.4; N, 6.3%). A = 172.80 52-' cm2 mol-' (lo-, mol drn-,) in nitromethane. 1.r. (KBr disc): 2 270w (CN) and 1 355s cm-' (NO). N.m.r.: 31P-(1H}, 6 , -7.10 p.p.m.; I3C- {'H}, 6, 136.44 [l C, s, C4 (PhCN)], 134.49 [12 C, t, J(PC) = 5.0, C2*, (PPh,)], 134.22 [2 C, S, C2*, (PhCN)], 132.88 [6 C, S, C4 (PPh,)], 129.88 [12 C, t, J(PC) = 5.0, C3,, (PPh,)], 129.61 [2 C, s, C3q5 (PhCN)], 126.78 [l C, s, CN (PhCN)], 122.18 [6 C, t, J(PC) = 28.8 Hz, C' (PPh,)], and 108.45 p.p.m. [l C, s, C' (PhCN)]. Complexes (2) and (4) were also prepared by reaction of [Ir(N0)(MeCN),(PPh,),][PF6], and paa (mol ratio 1 : 1) in acetonitrile or benzonitrile respectively.Reaction of complex (1) with Ph,CHCN: [1r((2-C,H4N)- (5). Diphenylacetonitrile (0.195 g, 1 mmol) was added to a solution of complex (1) (0.042 g, 0.034 mmol) in CH2C12 (8 cm3) and the reaction mixture stirred for 7 d. The undissolved excess of the nitrile was removed by filtration and the volume of the filtrate reduced under vacuum. Addition of diethyl ether to the violet solution gave a microcrystalline precipitate of (5), m.p. 22OoC, yield 0.038 g (78%) (Found: C, 49.1; H, 3.1; N, 5.2, A = 156.35 R-' cm2 mol-' rnol dm-,) in nitromethane. 1.r. (KBr disc): 2 290w (CN) and 1 348s cm-' (NO). 31P-{'H} N.m.r.: 6, -6.25 p.p.m. Reaction of complex (1) with LiCI: [IrC1((2-C,H4N)- CH=N-N=C( NO H)( 2-C H ,N) ) ( PPh ,),I [ PF,] (6).A solution of LiCl (0.017 g, 0.4 mmol) in EtOH (10 cm3) was added to a solution of complex (1) (0.100 g, 0.078 mmol) in CH2C12 ( 5 cm3). The solution immediately turned blue-violet and a microcrystalline violet solid was formed overnight, m.p. 265- 267 OC, yield 0.082 g (93%) (Found: C, 50.2; H, 3.4; N, 5.8. C4,H4,CIF6~rN,0P, requires C, 50.7; H, 3.5; N, 6.2%). A = 77.10 R-' cm2 mol-' ( lo-, mol dm-3) in nitromethane. 1.r. (KBr disc): 1 350s cm-' (NO). 31P-('H} N.m.r.: 6, - 12.15 p.p.m. Reaction of complex (1) with LiSCN: [1r(SCN)((2-C,H4N)- C H=N-N=C( NO H)( 2-C , H,N) } (P P h , ) ,] [ PF,] ( 7). To a stirred solution of complex (1) (0.05 g, 0.039 mmol) in CH,Cl, (4 cm3) was added a solution of LiSCN (0.013 g, 0.2 mmol) in EtOH (12 cm3).The resulting yellow solution immediately turned blue-violet and a microcrystalline violet precipitate was formed overnight, m.p. 267 "C, yield 0.031 g (67%) (Found: C, N, 7.2%). A = 77.00 R-' cm2 mol-' mol drn-,) in nitromethane. 1.r. (KBr disc): 2 105s (CN) and 1 350s cm-' (NO). 3'P-{'H) N.m.r.: 6, -9.16 p.p.m. Reaction of complex ( 2 ) Mith EtOH: [Ir((2-C,H4N)- CH=N-N=C( NOH)( 2-C ,H4N)) { Me( Et O)C=NH } ( PP h ,),I- [PF,], (8). When a CH,Cl,-EtOH (1 : 2) solution of the nitrile complex (2) was stirred for 40 d a violet solid which was recrystallised from CH,CI,-EtOH (1 : 2) was obtained. After 20 d violet microcrystals of (8) were obtained. 1.r. (KBr disc): 3 330w (NH), 1 638m (CN), and 1 350s cm-' (NO). 31P-(1H) N.m.r.: 6, -6.96 p.p.m. Reaction of complex (4) with EtOH: [Ir{ (2-C5H,N)CH=N- When the nitrile complex (4) was recrystallised from CH,CI,- EtOH (1 :2) after about 30 d needle-like violet crystals of (4) were formed.From the mother-liquor, after another 30 d, flat violet crystals of (9) separated. 1.r. (KBr disc): 3 370w (NH), 1 600m (CN), and 1 358s cm-' (NO). 3'P-('H} N.m.r.: 6, -8.29 p.p.m. CH=N-N=C(NOH)(2-C,H4N)}(Ph,CHCN)(PPh 3)2][PF6]2 C6,H5 F, 21rN60P4*CH2C12 requires c , 49.6; H, 3.5; N, 5.5%). 50.7; H, 3.5; N, 7.2. C4,H40F,IrN60P,S requires c, 50.8; H, 3.5; N=C(NOH)(2-C 5H4N)} { Ph( EtO)C=NH} (PPh3)2] [ PF, J 2 (9). Crjsstal Structure Determination o f Complex (8).-Crq'staldata. C52H49F121rN602P4, M = 1 334.09, monoclinic, space group1224 J. CHEM. SOC.DALTON TRANS. 1989 ~ ~~~ Table 5. Fractional atomic co-ordinates ( x lo4) with estimated standard deviations in parentheses for the non-hydrogen atoms Xlu 0 - 1 443(5) 1 396(4) 4 359(5) -4 738(13) - I 184(13) - 2 574( 12) - 426( 14) 886( 15) 975( 14) 881(13) - 980(20) - 992( 13) 143(20) 1683(19) 1 678( 18) 2 458(23) 2 394(21) 1617(19) 921(18) 29( 19) 920(24) 634(35) -441(43) - 1 114(30) - 1 977(19) -2 616(21) -3 713(26) - 3 678(35) - 742( 17) - 735(20) - 165(27) 412(25) 462( 19) -82(21) - 2 508(20) - 3 700(25) - 4 552(27) -4 206(31) YI h 1278(1) 1087(1) 1499(1) 2 406( 1) 681(3) 1 034(3) 1457(3) 999(4) 676(4) 929(4) I 446(3) 469(4) 1 660(5) 725(5) 940( 5 ) 1 229(4) 1 288(6) 1591(7) 1793(5) 1 709(6) 472(4) 254( 5) 43(5) 44(7) 263(6) 1 705(4) 2 OlO(5) 1 469(7) 1 525(9) 971(5) 1 141(6) 1031(5) 783(7) 6W5) 708( 5) 1366(5) I 319(6) I 546(7) 1811(8) Z / C 2 500 3 303(6) 1 734(5) 8 996(7) - 3 622( 13) - 303( 14) 439( 16) 969( 18) 2 521(19) 4 312(14) 1 804(18) 1300(21) 4 444(22) 5 084(21) 6 355(23) 6 842(22) 6 123(19) 4 893(25) 365( 2 1 ) 532( 3 1) 3 200(17) - 757(22) - 525(36) - 1 659(36) - 1 630(29) 994( 25) 660(3 I ) -677(37) - 1 883(38) 4 974(21) 6 034(23) 7 303(31) 7 464(31) 6 450(24) 5 262(24) 3 254(25) 2 536(29) 2 361(34) 3 094(37) Xju - 3 057( 26) -2 189(19) - 2 293( 17) -2 637(25) - 3 363(20) -3 739(22) - 3 392(21) - 2 654(22) 2 323( 17) 2 958(20) 3 718(22) 3 744(26) 3 147(24) 2 385(22) 840( 16) - 303( 19) - 755(23) - 40( 23) 1055(24) I544(21) 2 309(20) 1913(20) 2 543(27) 3 553(32) 3 983(30) 3 357(21) 3 179(14) 5 027( 18) 5 532( 17) 3 675(21) 4 303( 19) 4 341(20) - 5 328(28) - 5 992(40) - 4 226(38) - 3 530(39) - 4 47 l(29) - 5 286(34) Yjh 1 880(7) 1 664(5) 765(4) 712(6) 460( 5) 255(6) 3 lO(6) 56 I(6) I229(4) 1 020(5) 805( 6) 8 20( 7) 1018(6) 1 227(5) 1 731(4) 1 687(5) 1 870(6) 2 084(6) 2 123(6) 1961(6) 1761(5) 2 063(6) 2 255(7) 2 171(8) 1 902(8) 1 678(6) 2 332(4) 2 238(4) 2 541(5) 2 086( 5) 2 725(5) 824( 6) 528( 12) 81 1( 10) 391(7) 936(9) 2 493(4) 544( 9) Zjc.3 71 2(30) 3 907(23) 2 532(20) 1 185(29) 605(25) 1295(27) 2 649(25) 3 258(26) I 308(22) 2 266(24) 1 999(27) 7 13(3 I ) 136(27) 3 18(20) - 169(28) -615(23) - 1 741(29) - 1 904(26) - 1 118(28) 3 l(25) 2 965(24) 2 913(24) 3 860(33) 4 781(37) 4 764(36) 3 881(25) 7 854( 17) 8 250(20) 10 115(19) 9 795(24) 9 630(23) 8 463(24) - 2 648(37) - 4 424(49) - 4 607(43) -2 719(41) - 2 848(32) -4 363(41) CC, u = 12.405(6), b = 43.836( 12), c = 11.126(7) A, p = 112.1(2)O U = 5 606(9) A3 (by least-squares refinement of the 0 values of 27 accurately measured reflections), Z = 4, h = 0.7107 A, D, = 1.58 g ~ m - ~ , F(OO0) = 2 656, p(Mo-K,) = 25.66 cm-'.A flattened crystal of approximate dimensions 0.06 x 0.40 x 0.65 mm was used for the structure analysis. A correction for absorption25 was applied (maximum and minimum transmission factors 1.2472 and 0.7547 respectively) using the program ABSORB.26 Data collection and processing. Siemens AED diffractometer, 8-28 scan mode, using niobium-filtered Mo-K, radiation; all the reflections with 8 in the range 3-24" were measured. Of 4 649 independent reflections, 3 394, having I > 2 0 ( I ) , were considered observed and used in the analysis.Structure solution and refinement. Patterson and Fourier methods, block-matrix least squares with anisotropic thermal parameters in the last cycles for the non-hydrogen atoms except those of the phenyl rings. All hydrogen atoms were placed at their geometrically calculated positions except that of the NOH group, whose position was determined from a AF map, and introduced in the final structure-factor calculation. Final R and R' values were 0.057 and 0.073. The SHELX system of computer programs was used.27 Atomic scattering factors, corrected for anomalous dispersion of Ir and P atoms, were taken from ref. 28. All calculations were performed on the CRAY X-MP/12 computer of the Centro di Calcolo Elettronico Interuniversitario dell'ltalia Nord-Orientale, Bologna and on the GOULD 32/77 computer of the Centro di Studio per la Strutturistica Diffrattometrica del CNR, Parma.Final atomic co-ordinates for the non-hydrogen atoms are given in Table 5. Additional data available from the Cambridge Crystallo- graphic Data Centre comprises H-atom co-ordinates, thermal parameters, and remaining bond distances and angles. Acknowledgements We thank the Italian Minister0 della Pubblica lstruzione for financial support. References 1 J. A. McCleverty, Cfiem. Rer., 1979, 79, 53. 2 J. A. McCleverty, C. W. Ninnes, and I. Wolochowicz, J. Chem. Soc., Dulron Truns., 1986, 743. 3 (u) W. P. Wainer and R. G. Bergman, J. Am. Cfzmi. Soc., 1983, 105, 3922; ( h ) M.D. Seidler and R. G. Bergman, ibid., 1984, 106,6110; (c) W. P. Weiner, F. J . Hollander, and R. G. Bergman, ihid., p. 7462. 4 A. Goldhaber, K. P. C. Vollhardt, E. C. Walborsky, and M. Wolfgruber, J. Am. Cfiem. Soc., 1986, 108, 516. 5 P. Legzdins and B. Wassiuk, J . Am. Chem. Suc., 1986, 108, 317. 6 M. Ghedini, M. Longeri, and F. Neve, J . Chem. SOC., Dalton Trans., 1986, 2669.J. CHEM. SOC. DALTON TRANS. 1989 7 M. Ghedini. A. M. Manotti Lanfredi, F. Neve, and A. Tiripicchio, J . 8 W. J. Geary, Cooid. Chem. Rev., 1971, 7, 81. 9 B. M. Storhoff and H. C. Lewis, jun., Coord. Chem. Rev., 1977,23, 1. 10 W. Beck, K. Schmidtuer, and H. J. Keller, Chem. Ber., 1967,100,503. I 1 K . Dahl Schramm and J. A. Ibers, Inorg. Chem., 1980, 19, 2435. 12 A. Tiripicchio, A. M. Manotti Lanfredi, M. Ghedini, and F. Neve, f. 13 A. H. Norbury, Ark. Inorg. Chem. Rudiochem., 1975, 17, 232. 14 M. Waada and T. Schimohigashi, Inorg. Chem., 1976, 15, 954. 15 A. Tiripicchio. M. Tiripicchio Camellini, G. Dolcetti, and M. Ghedini, Trm.sition Met. Chem. (Weinhein?, Ger.), 1980, 5, 102. 16 A. R. Chakravarty, A. Chakravorty, F. A. Cotton, L. R. Falvello, B. K. Ghosh. and M. Tomas, Inorg. Chem., 1983, 22, 1892. 17 K. R. Grundy, C. A. Roper, and W. R. Roper, Chem. Commun., 1970, 1501. 18 S. Gambarotta, S. Strologo, C. Floriani, A. Chiesi Villa, and C. Guastini, J . Am. Chem. Soc., 1985, 107, 6278. Chem. Soc,., Chcni. Commun., 1987, 847. Chein. Soc.. Chem. Commun., 1983, 97. 1225 19 D. L. Thorn and J. C . Calabrese, J . Orgunomet. Chem., 1984,272,283. 20 L. G. Marzilli, M. F. Summers, J. H. Ramsden, jun., N. Bresciani- Pahor, and L. Randaccio, f. Chem. Soc., Dalton Trans., 1984, 511. 21 M. Lanfranchi, A. Tiripicchio, G. Dolcetti, and M. Ghedini, Transition Met. Cheni. (Weinheini, Ger.), 1980, 5, 21. 22 W. J. Stratton and D. H Busch, J. Am. Chem. Soc., 1958, 80, 1286. 23 M. Ghedini and G. Dolcetti, Inorg. Synth., 1982, 21, 104. 24 G. R. Crooks and B. F. G. Johnson, J. Cheni. Soc. A, 1970, 1662. 25 N. Walker and D. Stuart, Actu Crystullogr., Sect. A , 1983, 39, 158. 26 F. Ugozzoli, Comput. Chem., 1987, 11, 109. 27 G. M. Sheldrick, SHELX Program for crystal structure determin- 28 ‘International Tables for X-Ray Crystallography,’ Kynoch Press, ation, University of Cambridge, 1976. Birmingham, 1974, vol. 4. Receiced 1 st June 1988; Paper 8/02 17 1 F

ISSN:1477-9226    

DOI:10.1039/DT9890001217

出版商:RSC    

年代:1989

数据来源: RSC