Marco J.A. Kraakman

CC coupling and CH activation occurring in reactions of FeRu(CO)6(iPr-Pyca) (ipr-PycaC5H4N-2-CHN-iPr) with activated alkynes RCCR′ (RR′C(O)OMe; RH, R′C(O)Me)

Abstract Reaction of FeRu(CO)6(iPr-Pyca) (5) with the alkynes RCCC(O)OMe (RC(O)OMe (a); RH (b)) leads to the formation of FeRu(CO)5(iPr-Pyca)(μ-η1,η3-MeOC(O)CC(R)C(O)) (RC(O)OMe (6a); RH (6b)). In the case of the monosubstituted alkyne HCCC(O)OMe (b) the CC coupling reaction between the alkyne and the carbonyl ligand proved to be highly regioselective. However, in contrast to literature reports, the CC coupling exclusively takes place at the unsubstituted alkyne C atom, which indicates that substituent effects are dominant. An X-ray single crystal structure of complex 6a has been determined. Red crystals of 6a are monoclinic, space group P21/n, Z = 4, with unit cell dimensions a = 9.277(2), b = 20.112(4), c = 15.964(2) A and β = 99.267(15)°. The structure refinement converged to R = 0.040 for 4123 observed reflections. Thermal conversion of the complexes 6a, b leads to the formation of FeRu(CO)5(C5H4N-2-CHNC(Me)2)(μ,η2-RCCHR′) (RR′C(O)OMe (7a); RH, R′C(O)OMe (7b); RC(O)OMe, R′H (7b′)) in which, as a result of H migration of the isopropyl H atom from the iPr-Pyca ligand to the alkyne, a μ,η2-vinyl fragment is present which is σ-bonded to Ru and η2-bonded to Fe. The former imine C atom is σ-bonded to the Fe centre. The conversion of 6b leads to an unseparable mixture of the complexes 7b and 7b′ suggesting that during the H migration reaction the alkyne C atoms may change their positions and are both capable of abstracting a proton from the iPr-Pyca ligand. Given the fact that the formation of 7b is strongly favoured over the formation of 7b′ substituent effects appear to be important in determining the product distribution of the H migration reaction.

Preparation of the new heteronuclear α-diimine complexes FeRu(CO)6(R-Pyca) and Fe2Ru(CO)10(R-Pyca)(R-PycaC5H4N-2-CHNR); 13C NMR study of the fluxional behaviour of the carbonyl ligands in Fe2Ru(CO)10(R-Pyca)

Abstract Ru 2 (CO) 4 (L) 2 (LR-Pyca, R i Pr ( 1a ); R c Hex ( 1b ); R  t Bu ( 1c )) reacts with Fe 2 (CO) 9 ( 2 ) at room temperature to give the new complexes FeRu(CO) 6 (R-Pyca) ( 3a–c ) and Fe 2 Ru(CO) 10 (R-Pyca) ( 4a–c ). Although the reaction proceeds also for LR-DAB, it is synthetically useful only for L  R-Pyca. The complexes 3a–c can also be prepared by thermal conversion of 4a-c at 70 °C in nearly quantitative yields. X-ray single crystal structures of the complexes 3a and 4a have been determined. Red crystals of 3a (FeRuC 15 H 12 N 2 O 6 , m r  473.2, Z = 4) are monoclinic, space group P 2 1 / n and have cell constants a = 16.945(3), b = 13.796(6), c = 7.687(2) A and β = 97.66(2)°. A total of 3174 reflections was used in the refinement which converged to a final R value of 0.038. Dark purple crystals of 4a (Fe 2 RuC 19 H 12 N 2 O 10 , M r = 641.1, Z = 4) are monoclinic, space group P 2 1 /a and have cell constants a = 14.800(2), b = 14.705(2), c = 11.034(1) A and β = 92.87(2)°. A total of 4781 reflections was used in the refinement which converged to a final R value of 0.033. The carbonyl ligands of complexes 4a–c were found to be involved in fluxional movements on the NMR timescale. From the spectroscopic data it can be concluded that several processes are occurring, of which the possible mechanisms are discussed.

Synthesis of the monohydride complexes HRu2(X)(CO)5(iPr-NCHCHN-iPr) (X=Cl, I); hydrogenation of the central CC bond of the coordinated α-diimine ligands. X-ray. single crystal structure of HRu2(Cl)(CO)5(iPr-NCHCHN-iPr)

Abstract Reaction of H 2 Ru 2 (CO) 5 ( i Pr-DAB{H,R}) (RH ( 1a ); RMe ( 1b )), which contains one terminal and one bridging hydride, with CX 4 (XCl; XI) afforded HRu 2 (X)(CO) 5 ( i Pr-DAB{H,R}) (XCl, RH ( 3a ); X= CI, R=Me ( 3b ); XI, RH ( 3c )). As confirmed by a single crystal X-ray structure determination, complex 3a contains a bimetallic unit bridged by a hydride and a 6e σ-N,μ2-N′,η 2 -CN′ bonded DAB ligand, whereas the chloride is terminally bonded. Crystals of 3a are monoclinic, space group P 2 1 / c , a = 12.421(2), b = 12.003(2), c = 13.227(1) A, β = 90.22(1)°, Z = 4. The structure was refined to R = 0.043 for 2947 observed reflections. Reaction of 3a with D 2 at 70 °C afforded DRu 2 (Cl)(CO) 5 ( i Pr-DAB) ( 3a′ ), whereas 3a′ could be reconverted to 3a by reaction with H 2 . To rationalize these results it is suggested that in the first step of the reaction, e.g. of 3a with D 2 , the D 2 molecule attacks the empty position created by rupture of the Ru-η 2 -CN′ bond. Exchange of H by D may occur via an intermediate containing a HD 2 species coordinated to the bimetallic moiety. Raising the reaction temperature to 90 °C leads subsequently to the reduction of the coordinated DAB ligand, whereby 3a and 3c are converted to HRu 2 (X)(CO) 5 ( i Pr-N-CH 2 CH 2 -N- i pr)(XCl ( 4a ); XI ( 4c ), together with small amounts of the side product Ru 2 (CO) 6 ( i Pr-N-CH 2 CH 2 -N- 1 Pr) ( 5a ). The latter was formed from 4a , as established by refluxing complexes 4 in toluene which yielded 5a . However, in contrast to 3a and 3c , reaction of 3b with hydrogen at 90 °C afforded only Ru 2 (CO) 6 ( i Pr-N-C(H)(Me)CH 2 -N- i pr) ( 5b ). Complexes 4 could also be prepared by reacting H 2 Ru 2 (CO) 5 ( i Pr-N-CH 2 CH 2 -N- i pr) ( 2a ) with CX 4 . Interestingly, for example, reaction of DRu 2 (Cl)(CO) 5 ( i Pr- DAB{H,R}) with D 2 at 90 °C showed in the final product the presence of D at all sites of the reduced central CC bond of R-DAB with an average varying between 0.5 and 1 proton on this moiety, indicating the occurrence of intramolecular CH/CD bond making and bond breaking steps during the hydrogenation process. Reaction of 3a with AgOTF yielded [OTF][HRu 2 (CO) 5 ( i Pr-DAB)] ( 6 ), which subsequently could be converted to [OTF][HRu 2 (CO) 5 (L)( i Pr-DAB)] (LCO ( 8 ); L=′Bu-NC ( 9 )) and to [HRu 2 (X)(CO) 5 ( i Pr-DAB)] (XCo(CO) 4 ( 3d ); XMn(CO) 5 ( 3e ); XCN ( 3f )). Whereas the DAB ligand of 6 could be reduced, complexes 3d-f, 8 and 9 could not be hydrogenated.

Preparation and properties of FeRu(CO)5(L)(α-diimine) (α-diimineR-DAB, R-Pyca; LPR3, CO); the reduction of the coordinated 1,4-diaza-1,3-butadiene to dianionic 1,2-diaminoethane by reaction with hydrogen

FeRu(CO)6(iPr-Pyca) (1a) reacts with hydrogen to give the highly reactive species H2FeRu(CO)5(iPr-Pyca) (2), which contains a bridging and a terminal hydride atom. Treatment of 2 with CX4 affords HFeRu(X)(CO)5(iPr- Pyca) (XCl (3a); I (3b)) in which the terminal hydride has been substituted. Complex 2 reacts back with carbon monoxide to give FeRu(CO)6(iPr-Pyca) (1a), whereas treatment of 2 with PMe2Ph gives FeRu(CO)5(PMe2Ph)(iPr-Pyca) (4b). Complexes 4 can easily be prepared from the hexacarbonyl complexes FeRu(CO)6(α-diimine) (α-diimineiPr-Pyca (1a); iPR-DAB (1b)) and the appropriate phosphine, giving FeRu(CO)5(PR3)(α-diimine) (α-diimineiPr-Pyca, PR3PPh3 (4a); α-diimineiPr-Pyca, PR3PMe2Ph (4b); α- diimineiPr-DAB, PR3PPh3 (4c); α-diimineiPr-DAB, PR3PMe2Ph (4d)) in high yields. Reaction of FeRu(CO)5(PPh3)(iPr-DAB) (4c) with hydrogen at 90 °C yields FeRu(CO)5(PPh3)(iPr-N-CH2CH2-N-iPr) (5). The use of deuterium showed that the reduction proceeds stereoselectively, giving solely the trans-addition product FeRu(CO)5(PPh3)(iPr-N-C(H)(D)C(H)(D)-N-iPr) (5′). Complex 5 can easily be converted by carbon monoxide to FeRu(CO)6(iPr-N-CH2CH2-N-iPr) (8). The conversion of 8 to 5 can be performed also, albeit less facile than the conversion of 5 to 8. The hydrogenation of both 1b and 4c was inhibited by carbon monoxide and free triphenylphosphine. In the latter case the new complexes FeRu(CO)4(PPh3)2(α-diimine) (α-diimineiPr-Pyca (6a); iPr-DAB (6b)) were formed. A single crystal X-ray structure determination of 6a was obtained. Red crystals of 6a (C49H42N2O4P2FeRu, Mr=941.8, Z=2) are triclinic, space group P and have cell constants a=11.625(3), b=14.269(3), c=15.963(2) A, α=90.95(1), β=100.23(1) and γ=101.95(2)°. A total of 5886 reflections was used in the refinement which converged to a final R value of R=0.064. Reaction of MRu(CO)6(iPr-DAB)(MFe (1b); Ru (1c)) with 40 bar of carbon monoxide at 90 °C afforded Ru(CO)3(iPr-DAB) and M(CO)5 (MFe, Ru). Interestingly it was found that reaction of Ru(CO)3(DAB) with H2Fe(CO)4 also produced FeRu(CO)6(iPr-N-CH2CH2-N-iPr) (8), whereas D2Fe(CO)4 afforded only the trans deuterated compound FeRu(CO)6(iPr-N-C(H)(D)C(H)(D)-N-iPr) (8). Finally attention has been focussed on the elucidation of the mechanism of this trans addition of H2/D2 to the central CC bond of the coordinated 1,4-diaza-l,3-butadiene.