Selective Substitution of One of the Substituents on Germanium in

Article pubs.acs.org/Organometallics

Selective Substitution of One of the Substituents on Germanium in Coordinatively Unsaturated Ruthenium Germyl Complexes Peter D. W. Boyd, Michael C. Hart, Julian R. F. Pritzwald-Stegmann, Warren R. Roper, and L. James Wright* School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand S Supporting Information *

ABSTRACT: The coordinatively unsaturated tri-p-tolylgermyl complex RuCl(Ge[p-tolyl]3)(CO)(PPh3)2 (1) is obtained in good yield through the reaction between HGe(p-tolyl)3 and RuCl(Ph)(CO)(PPh3)2. On treatment of 1 with 1 equiv of NaS2CNR′2 (R′ = Et, Me), the chloride ligand is displaced and the corresponding coordinatively saturated complexes Ru(κ2S2CNR′2)(Ge[p-tolyl]3)(CO)(PPh3)2 (2a, R′ = Et; 2b, R′ = Me) are formed. One of the PPh3 ligands in 2a is labile and undergoes substitution readily on addition of CO to give the cis-dicarbonyl complex Ru(κ 2 -S 2 CNEt 2 )(Ge[p-tolyl] 3 )(CO)2(PPh3) (3). On addition of NaS2CNMe2 to 2b, a PPh3 ligand is displaced by one sulfur atom while the other sulfur atom displaces one of the p-tolyl groups on germanium to give Ru(κ2(Ge,S)-Ge[p-tolyl]2S2CNMe2)(κ2-S2CNMe2)(CO)(PPh3) (4). Complex 4 is also formed on addition of excess NaS2CNMe2 to 1. Treatment of 1 with pyridine and ethanol under ambient conditions also results in cleavage of one of the germyl p-tolyl groups, and the product formed is the coordinatively unsaturated, ethoxy-substituted germyl complex RuCl(Ge[OEt][p-tolyl]2)(CO)(PPh3)2 (5). The ethoxy group in 5 is labile, and on contact with n-propanol in solution, alkoxy group exchange slowly occurs to give RuCl(Ge[OnPr][p-tolyl]2)(CO)(PPh3)2 (6). This reaction is reversible, and treatment of 6 with ethanol returns 5. In a related reaction, treatment of 5 with water gives the hydroxy−germyl analogue RuCl(Ge[OH][p-tolyl]2)(CO)(PPh3)2 (7). The single-crystal X-ray structures of 1, 2a, 3, and 4 are presented.

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ment of 1 with excess NaS2CNMe2 to give Ru(κ2(Ge,S)Ge[p-tolyl]2S2CNMe2)(κ2-S2CNMe2)(CO)(PPh3) (4), in which one of the p-tolyl groups on germanium has been substituted by a dithiocarbamate sulfur atom while the other sulfur atom of this ligand coordinates to ruthenium, (iv) treatment of a solution of 1 with pyridine and ethanol resulting in substitution of one of the p-tolyl groups on germanium by ethoxide to give the coordinatively unsaturated germyl complex RuCl(Ge[OEt][p-tolyl]2)(CO)(PPh3)2 (5), (v) exchange of the ethoxy group in 5 occurring readily with n-propoxide or hydroxide to give the analogues RuCl(Ge[OnPr][p-tolyl]2)(CO)(PPh3)2 (6) and RuCl(Ge[OH][p-tolyl]2)(CO)(PPh3)2 (7), respectively, and (vi) the single-crystal X-ray structures of 1, 3, and 4.

INTRODUCTION Transition-metal germyl complexes have been known for a long time,1−3 and more recently germylene4−8 and even germylyne9−15 transition-metal complexes have been isolated and studied. Significant interest in germyl complexes continues unabated, in part because of the relevance these compounds have to materials chemistry16−18 and the catalytic germylation of organic compounds.19−24 One important characteristic of organogermyl complexes is that the metal can have a pronounced activating effect on the germanium organo or hydrido substituents.4,5,16,25−27 The synthesis of some germylene complexes and the catalytic demethanative coupling of HGeMe3 to form polygermanes are both processes that utilize this activation in key steps. In this paper we describe our studies on the selective activation and substitution of germanium organo groups and alkoxy groups in ruthenium germyl complexes. In particular we report (i) a convenient, high-yielding synthesis of the coordinatively unsaturated tri-ptolylgermyl complex RuCl(Ge[p-tolyl]3)(CO)(PPh3)2 (1), (ii) the addition of 1 equiv of NaS2CNEt2 to 1 displacing chloride to give coordinatively saturated Ru(κ2-S2CNEt2)(Ge[p-tolyl]3)(CO)(PPh3)2 (2a) and subsequent treatment of 2a with CO displacing a labile phosphine to give the cis-dicarbonyl complex Ru(κ2-S2CNEt2)(Ge[p-tolyl]3)(CO)2(PPh3) (3), (iii) treat© 2012 American Chemical Society

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RESULTS AND DISCUSSION The coordinatively unsaturated phenyl complexes MCl(Ph)(CO)(PPh3)2 (M = Ru, Os)28,29 have proven to be remarkably useful synthons, from which coordinatively unsaturated Special Issue: F. Gordon A. Stone Commemorative Issue Received: December 13, 2011 Published: March 19, 2012 2914

dx.doi.org/10.1021/om201239a | Organometallics 2012, 31, 2914−2921

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silyl,30−35 stannyl,35−41 and boryl42−44 complexes can be simply prepared. The complex RuCl(Ph)(CO)(PPh3)2 can also be used to form coordinatively unsaturated germyl complexes, and reaction with HGe(p-tolyl)3 proceeds smoothly on heating under reflux in benzene to give the red RuCl(Ge[p-tolyl]3)(CO)(PPh3)2 (1) in good yield (Scheme 1). It was ascertained Scheme 1. Syntheses and Reactions of Ruthenium Germyl Complexes 1−7

Figure 1. ORTEP diagram of 1 showing 50% probability displacement ellipsoids. Hydrogen atoms have been removed for clarity.

analogous five-coordinate complexes RuCl(p-tolyl)(CO)(PPh3)2,29 RuCl(SiMe3)(CO)(PPh3)2,46 RuCl(SnMe3)(CO)(PPh3)2,36 and RuCl(GeMe3)(CO)(PPh3)2.22 The Ru−Ge distance of 2.4591(3) Å in 1 is unexceptional (the average Ru−Ge distance for terminal germyl complexes is 2.508 Å, SD 0.050, nr. obs. 23, CCDC) and only slightly longer than the Ru−Ge distance in the closely related compound RuCl(GeMe3)(CO)(PPh3)2 (2.4455(4) Å).22 On addition of 2 equiv of NaS2CNEt2 or NaS2CNMe2 to 1 in the presence of 5 equiv of triphenylphosphine, the chloride is displaced and the corresponding coordinatively saturated complexes Ru(κ2-S2CNR′2)(Ge[p-tolyl]3)(CO)(PPh3)2 (2a, R′ = Et; 2b, R′ = Me) are formed (Scheme 1). Unlike 1, 2a,b are somewhat air sensitive in solution and decompose over several hours to unidentified products. This decomposition can be effectively suppressed either by working in an oxygen-free environment or through the addition of 5 equiv or more of PPh3 to solutions of these compounds that are exposed to air. This latter observation suggests that PPh3 dissociation in solution is the source of the air sensitivity. 1H NMR spectra of 2a,b can be conveniently obtained in the presence of oxygen if excess PPh3 is added to the deuterated solvent. In the 1H NMR spectrum of 2a obtained under these conditions, the two inequivalent CH3 groups of the ethyl substituents are observed as triplets at 0.64 and 0.73 ppm and the p-tolyl methyl groups are observed as a singlet at 2.23 ppm. In the 31P{1H} NMR spectrum obtained in the presence of added PPh3, a single resonance is observed for the two equivalent phosphorus atoms of the PPh3 ligands at 40.18 ppm. However, when the 31P{1H} NMR spectrum is obtained in the absence of oxygen with no added PPh3, additional weak singlet signals are observed at −4.61 ppm (assigned to free PPh3) and at 47.45 ppm (tentatively assigned to the compound formed on dissociation of PPh3 from 2a). This observation lends support to the proposal that 2a dissociates PPh3 in solution and this results in the observed oxygen sensitivity. The coordination geometry of 2a depicted in Scheme 1 is consistent with the NMR data and has been confirmed by an X-ray crystal structure determination. The molecular structure of 2a is shown in Figure 2. The coordination geometry about ruthenium is essentially octahedral, with the two PPh3 ligands disposed mutually trans. With the introduction of the sulfur donor trans to the germyl ligand the Ru−Ge distance (2.5244(7) Å) in 2a is longer than the

that complex 1 can also be synthesized through the reaction between RuHCl(CO)(PPh 3 ) 3 and (CH 2 CH)Ge(ptolyl)3,22,38,45 although this was found to be a less convenient synthetic route. In the IR spectrum of 1 ν(CO) is observed at 1913 cm−1 , which is at a lower frequency than the corresponding band for RuCl(Ph)(CO)(PPh 3 ) 2 (1922 cm−1)29 but is very similar to the ν(CO) bands observed for analogous silyl and stannyl complexes.30,36,38 The three p-tolyl methyl groups in 1 are observed in the 1H NMR spectrum as a singlet resonance at 2.21 ppm. A singlet is also observed in the 31 1 P{ H} NMR spectrum for the phosphorus atoms of the two triphenylphosphine ligands, indicating that in solution these nuclei are also equivalent on the NMR time scale. Details of the spectral and other characterization data for 1 and the other new compounds are recorded in the Experimental Section. The crystal structure of 1 has been determined, and the molecular structure is shown in Figure 1. The crystal data and refinement details for 1 and the other crystal structures reported in this paper are available in the Supporting Information, and a summary is provided in Table 1. The overall geometry is approximately square pyramidal with the germyl ligand in the apical position. The angles C(1)−Ru− Cl(1) (167.30(9)°), P(1)−Ru−P(2) (163.17(2)°), Ge−Ru− P(1) (98.71(2)°), Ge−Ru−C(1) (83.90(9)°), and P(1)−Ru− C(1) (89.01(9)°) demonstrate the regularity of the structure. In this respect the structure is very similar to those of the 2915


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Table 1. X-ray Structure Summary for 1, 2a, 3, and 4 1 formula formula wt temp (K) wavelength (Å) cryst syst space group unit cell dimens a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z calcd density (Mg/m3) abs coeff (mm−1) F(000) cryst size (mm3) θ range for data collecn (deg) no. of rflns collected no. of indep rflns (R(int)) max, min transmissn no. of data/restraints/params goodness of fit on F2 final R indices (I > 2σ(I))a R indices (all data) largest diff peak, hole (e Å−3) a

2a

3

4

C59H53Cl3GeOP2Ru 1119.96 90(2) 0.710 73 monoclinic P21/c

C64.50H63Cl2.38GeNOP2RuS2 1249.07 90(2) 0.710 73 monoclinic C2/c

C46 H46GeNO2PRuS2 913.59 90(2) 0.710 73 monoclinic P21/n

C40H43Cl2GeN2OPRuS4 971.53 90(2) 0.710 73 monoclinic P21/n

12.9682(2) 21.4121(4) 18.5070(3) 90 95.8290(10 90 5112.39(15) 4 1.455 1.144 2288 0.37 × 0.24 × 0.12 1.46−27.95 67 277 12 205 (0.0414) 0.872, 0.738 12 205/0/607 1.017 R1 = 0.0350, wR2 = 0.0723 R1 = 0.0544, wR2 = 0.0793 1.122, −0.976

36.9885(9) 12.5842(3) 26.2957(6) 90 β= 94.613(2) 90 12 200.2(5) 8 1.360 1.006 5135 0.29 × 0.14 × 0.09 1.55−28.08 72 219 14 710 (0.1329) 0.913, 0.706 14 710/0/687 0.942 R1 = 0.0630, wR2 = 0.1186 R1 = 0.1389, wR2 = 0.1385 1.036, −1.010

10.6616(2) 16.7869(3) 24.0182(4) 90 100.6410(10) 90 4224.74(13) 4 1.436 1.244 1872 0.34 × 0.17 × 0.11 1.49−27.95 52 040 10 092 (0.0313) 0.872, 0.710 10 092/0/492 1.025 R1 = 0.0241, wR2 = 0.0563 R1 = 0.0323, wR2 = 0.0601 0.458, −0.351

16.0430(5) 15.8195(5) 16.6513(5) 90 106.478(2) 90 4052.4(2) 4 1.592 1.527 1976 0.34 × 0.11 × 0.09 1.81−27.72 34 251 9331 (0.0706) 0.872, 0.651 9331/0/475 1.004 R1 = 0.0422, wR2 = 0.0844 R1 = 0.0789, wR2 = 0.0964 0.741, −0.807

R1 = ∑||Fo| − |Fc||/∑|Fo|; wR2 = {∑[w(Fo2 − Fc2)2]/∑[w(Fo2)2]}1/2.

the dicarbonyl monophosphine complex Ru(κ2-S2CNEt2)(Ge[p-tolyl]3)(CO)2(PPh3) (3) is formed (Scheme 1). The two ν(CO) bands in the IR spectrum of 3 at 1945 and 2004 cm−1 indicate that these ligands are mutually cis. In the 1H NMR spectrum the two equivalent ethyl substituents of the dithiocarbamate ligand are observed as an apparent triplet at 0.62 ppm (CH3) and as two multiplet signals centered at 2.82 ppm for the diastereotopic methylene (CH2) protons. The three methyl groups of the tri-p-tolylgermyl ligand appear as a singlet at 2.28 ppm. In the 13C{1H} NMR spectrum the two equivalent carbon atoms of the CO ligands are observed at 201.35 ppm as a doublet signal through coupling to the single phosphorus atom. The crystal structure of 3 has been determined, and the molecular structure is shown in Figure 3. As expected, the geometry about ruthenium is approximately octahedral, with the germyl and phosphine ligands arranged mutually trans. The Ru−Ge distance is 2.5183(2) Å, which is similar to that observed in 2a. There is a slight asymmetry in the way the dithiocarbonate ligand is bound to ruthenium with the Ru− S(1) distance of 2.4257(4) Å and the Ru−S(2) distance of 2.4560(4) Å, but this is most probably due to crystal-packing effects. Treatment of 2b with 2 equiv of sodium dimethyldithiocarbamate gives the product 4 (Scheme 1). In this product the ruthenium-bound germanium forms bonds to two p-tolyl groups and one sulfur atom of a dithiocarbamate ligand. The second sulfur of this ligand coordinates to the ruthenium center, thereby forming a bridge across the Ru−Ge bond. The

Figure 2. ORTEP diagram of 2a showing 50% probability displacement ellipsoids. Hydrogen atoms have been removed for clarity.

corresponding distance in 1 (2.4591(3) Å) but is still unexceptional. The Ru−S(2) distance (2.4875(15) Å; S(2) trans to Ge) is significantly longer than the Ru−S(1) distance (2.4549(15) Å; S(1) trans to CO), reflecting the large trans influence of the germyl ligand. Although a crystal structure determination of the analogue 2b has not been obtained, the spectral data of this compound are closely similar to those of 2a, indicating that the structure of 2b mirrors that of 2a. The labile character of one of the PPh3 ligands in 2a is illustrated by the rapid substitution reaction observed on exposure to CO. Thus, on treatment of a solution of 2a with CO the color instantly changes from orange to pale yellow and 2916


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Chart 1. Valence Bond Structures for the Metallacyclic Ring in 4

longer than the RuGe distance of 2.2821(6) Å in the germylene complex Cp*Ru(GeH[trip])H(iPr2Me) (trip = 2,4,6-iPr3C6H2).5 However, it should be noted that the shorter Ru−Ge distance in 4 may in part be caused by the bridging dithiocarbamate bringing the Ru and Ge centers closer together. The difference between the two C−S distances of the bridging dithiocarbamate ligand (C5−S3, 1.719(4) Å; C5− S4, 1.743(4) Å) is barely significant, and the Ru−S3 length (2.4441(9) Å) is normal for dithiocarbamate ligands bonded to ruthenium.47 The Ge−S4 distance (2.3325(10) Å) is slightly longer than for other reported Ge−S(dithiocarbamate) distances (average 2.27 Å).48−50 The sum of the angles Ru− Ge−C15 (115.00°), Ru−Ge−C8 (124.55°), and C8−Ge−C15 (107.34°) is 346.94°, which is midway between the ideal 329° expected for sp3-hybridized germanium and the 360° expected for a germylene complex. The metallacyclic ring in 4 is related to the corresponding rings in Ru(κ2(Si,O)-SiPh2OC[Me]O)(κ2-S2CNMe2)(CO)(PPh3)47 (where an acetate group bridges the Ru−Si bond) and Os(κ2(Sn,O)-SnMe2OC[Me]O)Me(CO)(PPh3)239 (where an acetate group bridges the Os−Sn bond). In both these cases some contributions from “basestabilized silylene or stannylene” valence bond structures were proposed. Complex 4 can also be conveniently obtained through treatment of 1 with 4 equiv of sodium dimethyldithiocarbamate in the absence of excess triphenylphosphine. It seems likely that in this case the reaction proceeds via 2b as an intermediate. We have no evidence regarding the mechanism by which 4 is formed from 2b. However, given the demonstrated lability of one PPh3 ligand in 2b, one possibility is that PPh3 dissociates from 2b and this is followed by migration of a p-tolyl group from germanium to ruthenium to form a transient germylene ligand. Subsequent addition of a dithiocarbamate sulfur to the electrophilic germylene center followed by proton-assisted cleavage of the p-tolyl group from the resulting anionic complex and coordination of the second dithiocarbamate sulfur to ruthenium would give the observed product. The feasibility of transient germylene formation during the synthesis of 4 is supported by reports in which the migration of hydride or organo groups from silyl, germyl, and stannyl ligands to the adjacent transition metal was either observed directly or was strongly implicated by the nature of the products formed.5,25−27,35,40,51−56 It is noteworthy that we have only observed p-tolyl group substitution in tri-p-tolylgermyl complexes that are either coordinatively unsaturated (see below) or can become coordinatively unsaturated through the dissociation of a labile ligand. An alternative possibility for the mechanism of formation of 4 could involve dissociation of PPh3 from 2b followed by coordination of the sulfur of an incoming dithiocarbamate ligand to ruthenium and addition of the second sulfur to germanium with subsequent loss of a p-tolyl


coordination sphere of ruthenium is completed by the ligands CO, PPh3, and bidentate dithiocarbamate. In the 1H NMR spectrum of 4 the two inequivalent p-tolyl methyl groups are observed at 2.24 and 2.27 ppm. The four inequivalent dithiocarbamate methyl groups are observed at 3.14, 3.19, 3.33, and 3.47 ppm, with the first two resonances being associated with the bridging ligand. In the 13C{1H} NMR spectrum the resonance of the carbonyl ligand appears as a doublet at 201.7 ppm through coupling to the single phosphorus atom. The crystal structure of 4 has been determined, and the molecular structure is shown in Figure 4. The geometry about


ruthenium is conveniently described as distorted octahedral, with the CO and PPh3 ligands arranged mutually cis. The geometric parameters associated with the five-membered metallacyclic ring are consistent with a bonding description for the Ru−Ge interaction that includes contributions from both of the two valence bond representations A (a tethered germyl ligand) and B (a base-stabilized germylene ligand) depicted in Chart 1. Thus, the Ru−Ge distance of 2.4187(5) Å in 4 is significantly shorter than the corresponding distances in 1 (2.4591(3) Å), 2b (2.5244(7) Å), and 3 (2.5183(2) Å) but 2917


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in good yield. In the IR spectrum of 7 a weak band at 3571 cm−1 is assigned to ν(OH). In the 1H NMR spectrum in CDCl3 the OH resonance overlaps with the signal for the residual water in the solvent. However, in C6D6 (where the residual water signal appears at 0.55 ppm) the OH resonance is observed at 1.77 ppm. Aside from the ethoxy group resonances, the other spectral properties of 7 are very similar to those of 5. Although hydroxysilyl complexes are well-known,31,33 hydroxy−germyl complexes are very rare. One example that has been reported recently is Cp*Ru(GeH[OH]trip)H2(iPr2Me) (trip = 2,4,6-iPr3C6H2), which was synthesized by the addition of water across the RuGe bond of the germylene precursor complex.5 We have no direct evidence regarding the mechanisms of these substitution reactions that occur for the coordinatively unsaturated germyl complexes 1 and 5−7. For the reactions that produce 5 or 6 from 1, migration of a p-tolyl group to ruthenium to form a transient germylene (or pyridine adduct of germylene57) intermediate could be involved in the key step. The facile exchange of the germyl alkoxy substituents observed for 5−7 could also conceivably proceed through a germylene intermediate that is formed by migration of the alkoxy group to ruthenium in the first step. However, other mechanisms are also possible for these alkoxy group exchange reactions, including one that involves addition of the incoming alcohol or water to the coordinatively unsaturated metal center as a prelude to alkoxy group exchange accompanied by proton transfer between the OR groups. These germyl alkoxy/hydroxyl exchange reactions bear some relationship to the simple substitution reactions that the triflate group on germanium undergoes in (η5-C5H5)Re(NO)(PPh3)(GePh2OTf).58 In this rhenium complex it was proposed that the germyl ligand has some germylene character and it is possible that a similar description is valid for the germyl ligands in 5−7.

substituent from the anionic intermediate, perhaps aided by proton transfer from the solvent mixture. The possibility that a transient germylene complex may be a key intermediate in the formation of 4 prompted us to investigate more fully the reactivity of the coordinatively unsaturated germyl complex 1 in solution. It has been noted previously that the tri-p-tolylstannyl complex RuCl(Sn[ptolyl]3)(CO)(PPh3)2 is unstable in solution and rearranges to the p-tolyl complex RuCl(p-tolyl)(CO)(PPh3)2, formally through migration of a p-tolyl group to ruthenium with the loss of “Sn[p-tolyl]2”.36 Although the trimethylstannyl analogues MCl(SnMe3)(CO)(PPh3)2 (M = Ru, Os) are stable in solution and do not rearrange in this way under normal conditions,36,38,40 treatment of Os(SnMe3)Cl(CO)(PPh3)2 with pyridine causes one of the methyl groups on tin to exchange places with the chloride on osmium.39 The resulting saturated osmium methyl complex, Os(SnMe2Cl)(Me)(py)(CO)(PPh3)2, can be recrystallized from dichloromethane/ ethanol without change.39 Cognizant of these results, the reaction between 1 and pyridine was investigated to determine whether a p-tolyl group on the germyl ligand might be induced to migrate to ruthenium and form a related product. However, this was found not to be the case and, on addition of pyridine and ethanol to 1, the orange five-coordinate ethoxy-substituted germyl complex RuCl(Ge[OEt][p-tolyl]2)(CO)(PPh3)2 (5) was obtained in good yield (Scheme 1). It is noteworthy that under the same conditions 1 does not undergo any reaction with ethanol in the absence of pyridine. Furthermore, we have only ever observed the monosubstituted product 5 even after treatment of solutions of 1 with pyridine and ethanol for extended periods of time. In the IR spectrum of 5 ν(CO) appears at 1931 cm−1. This is considerably higher than the ν(CO) (1913 cm−1) observed for 1 but is entirely consistent with the replacement of a tolyl group on germanium with a more electronegative ethoxy substituent.35 The two p-tolyl methyl groups in 5 are observed in the 1H NMR spectrum at 2.34 ppm, and the ethoxy group protons are observed as triplet and quartet signals at 0.57 and 3.05 ppm, respectively. In the 13 C{1H} NMR spectrum the chemical shifts of each of the ring carbon atoms of the two equivalent p-tolyl groups in 5 are very similar to the corresponding signals observed for 1. In the 31 1 P{ H} NMR spectrum of 5 the singlet resonance for the two equivalent phosphorus atoms appears at 34.58 ppm and this is also very similar to the corresponding resonance observed for 1 (33.04 ppm). The substitution of a p-tolyl group in 1 with an oxygen nucleophile is not limited to reaction with ethanol. The npropoxygermyl analogue of 5, RuCl(Ge[OnPr][p-tolyl]2)(CO)(PPh3)2 (6), can be isolated in low yield if 1 is treated with pyridine and n-propanol. The spectral properties of 6 are essentially the same as those of 5, with the exception of the resonances associated with the nPrO group, which are observed in the 1H NMR spectrum at 0.46 (t, −CH3), 0.98 (m, CH2− CH2−CH3) and 2.93 (t, O−CH2−) ppm. Interestingly, the npropoxy group in 6 is labile and, on recrystallization of 6 from dichloromethane/ethanol, the majority of the sample is converted to the ethoxygermyl analogue 5. The reaction is reversible, and on recrystallization of pure 5 from dichloromethane and n-propanol, conversion to 6 is observed. The ethoxy group in 5 can also undergo exchange with hydroxide. Thus, on treatment of a THF solution of 5 with water at ambient temperature for 1 h, the hydroxy−germyl complex RuCl(Ge[OH][p-tolyl]2)(CO)(PPh3)2 (7) is formed

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CONCLUDING REMARKS The reaction between HGe(p-tolyl)3 and RuCl(Ph)(CO)(PPh3)2 provides a convenient route to the coordinatively unsaturated tri-p-tolylgermyl complex RuCl(Ge[p-tolyl]3)(CO)(PPh3)2 (1). Selective substitution of one of the germanium p-tolyl groups occurs on treatment of 1 with excess dimethyldithiocarbamate anion to give Ru(κ2(Ge,S)Ge[p-tolyl]2S2CNMe2)(κ2-S2CNMe2)(CO)(PPh3) (4). In this product a dithiocarbamate ligand bridges the Ru−Ge bond. The structural parameters of the resulting metallacyclic ring suggest that the Ru−Ge interaction can be described in terms of contributions from both “tethered germyl” and “basestabilized germylene” valence bond structures. Treatment of 1 with pyridine and ethanol also results in selective substitution of one of the germanium p-tolyl groups. The product in this case is the coordinatively unsaturated ethoxygermyl complex RuCl(Ge[OEt][p-tolyl]2)(CO)(PPh3)2 (5). The ethoxy group in 5 is labile and undergoes reversible substitution on treatment with excess nPrOH to give RuCl(Ge[OnPr][p-tolyl]2)(CO)(PPh3)2 (6) or with water to give a rare example of a hydroxyl germyl complex, RuCl(Ge[OH][p-tolyl]2)(CO)(PPh3)2 (7). We have no direct evidence relating to the mechanisms of these substitution reactions, but it is possible that they could proceed via transient ruthenium germylene intermediates.

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EXPERIMENTAL SECTION

General Comments. Preparation of all compounds was carried out under a N2 atmosphere using standard vacuum-line and Schlenk

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techniques.59 All reactions where carried at ambient temperature and pressure unless otherwise stated. Where necessary, solvents were degassed using the standard freeze−pump−thaw method. The drying and distillation of solvents was conducted according to standard literature methods. Ru(Ph)Cl(CO)(PPh3)260 and HGe(p-Tolyl)361 were prepared using literature methods. Infrared spectra (4000−400 cm−1) of solid samples were recorded on a Perkin-Elmer Spectrum 400 FT-IR instrument using a Universal ATR Sampling Attachment with a diamond/KRS-5 crystal. 1H, 13C, and 31P NMR spectra were recorded on Bruker AVANCE 300 MHz and DRX 400 MHz instruments at 25 °C. Chemical shifts are reported in ppm. 1H NMR spectra were referenced to tetramethylsilane (0.00 ppm) or the proteo impurity in the solvents d6-benzene (7.16 ppm) and CDCl3 (7.25 ppm). 13C NMR spectra (proton decoupled) were referenced to CDCl3 (77.00 ppm) and 31P NMR spectra (proton decoupled) to 85% orthophosphoric acid (0.00 ppm), as an external standard. The 13C NMR spectrum assignments for the meta, ortho, para, and ipso carbons of the p-tolyl groups on the germyl ligands were made on the basis of literature values of related compounds.62 The 1H NMR spectrum assignments of the meta and ortho protons were subsequently made by inspection of the HSQC and HMBC twodimensional 1H−13C correlation NMR spectra. High-resolution mass spectra were recorded using electrospray ionization with a Bruker Daltronics MicrOTOF instrument. X-ray intensities were recorded on a Bruker SMART diffractometer with an APEX II CCD area detector using graphite-monochromated Mo Kα radiation (λ = 0.710 73 Å) at 87 K. Structures were solved using direct methods (SHELXS-97); non-hydrogen atoms were refined anisotropically (SHELXL-97), and H atoms were refined using a riding model. A summary of the X-ray crystal structure data is provided in Table 1. In structure 1 there was evidence of disorder (ca. 5−10%) of the Cl and CO ligands; however, it was not possible to construct a satisfactory model. In structure 2a three dichloromethane solvent molecules were present. Two of these could be refined (one with partial occupancy); however, this was not possible for the third solvent molecule. The final structure was refined following an application of the Squeeze procedure of Spek. Elemental analyses were obtained from the Microanalytical Laboratory, University of Otago. RuCl(Ge[p-tolyl] 3 )(CO)(PPh 3 ) 2 (1). RuCl(Ph)(CO)(PPh 3 ) 2 (0.200 g, 0.261 mmol) and HGe(p-tolyl)3 (0.136 g, 0.392 mmol) were dissolved in deoxygenated benzene (50 mL). The solution was heated under reflux for 2.5 h, during which time the solution changed color from orange to red. The solution was then cooled to room temperature, and the benzene was evaporated under reduced pressure to give a red-orange solid. Recrystallization of this material from dichloromethane/ethanol gave pure 1 as red-orange crystals which were recovered from solution by filtration, washed with ethanol, and dried under vacuum (yield, 0.21 g, 75%). The 1H NMR spectrum of the analytical sample showed the presence of ca. 0.5 equiv of CH2Cl2 (the single crystal used for X-ray structure determination contained 1 equiv of CH2Cl2). Anal. Calcd for C58H51ClGeOP2Ru·1/2CH2Cl2: C, 65.20; H, 4.86. Found: C, 65.06; H, 4.96. IR (cm−1): 1913 ν(CO); 799 δ(p-tolyl). 1H NMR (CDCl3, δ): 2.21 (s, 9H, CH3), 6.67 (d, 3JHH = 7.6 Hz, 6H, p-tolyl meta), 7.17 (partially obscured by phenyl, p-tolyl ortho), 7.07−7.40 (m, 30H, PPh3). 13C{1H} NMR (CDCl3, δ): 21.32 (s, CH3), 127.64 (s, p-tolyl meta), 135.97 (s, p-tolyl ortho), 136.68 (s, p-tolyl para), 140.09 (s, p-tolyl ipso),127.76 (t′,63 2,4JCP = 9.1 Hz, oPPh3), 129.57 (s, p-PPh3), 132.22 (t′, 1,3JCP = 42.3 Hz, i-PPh3), 134.77 (t′, 3,5JCP = 11.1 Hz m-PPh3), 200.94 (t, 2JCP = 14.1 Hz, CO). 31P{1H} NMR (CDCl3, δ): 33.04. Ru(κ2-S2CNEt2)(Ge[p-tolyl]3)(CO)(PPh3)2 (2a). 1 (0.200 g, 0.193 mmol) and PPh3 (0.250 g, 0.953 mmol) were dissolved in deoxygenated dichloromethane (50 mL). To this solution was added dropwise sodium diethyldithiocarbamate (0.066 g, 0.385 mmol) dissolved in ethanol (4 mL). The solution quickly changed color from orange to bright yellow. The solution was stirred for a further 15 min before the solvent was evaporated under reduced pressure to give a yellow solid. Recrystallization from dichloromethane/ethanol produced pure 2a as pale yellow crystals, which were recovered by filtration, washed with a very small volume of ethanol, and dried under

vacuum (yield, 0.19 g, 85%). All NMR data were collected in the presence of excess PPh3 to suppress phosphine dissociation. The 1H NMR spectrum of the analytical sample showed the presence of ca. 0.25 equiv of CH2Cl2 (the single crystal used for X-ray structure determination contained CH2Cl2 of solvation, but the exact amount could not be determined). Anal. Calcd for C63H61GeNOPRuS2·1/4CH2Cl2: C, 64.97; H, 5.30; N, 1.20. Found: C, 64.87; H, 5.39; N, 1.19. IR (cm−1): 1894 ν(CO); 798 δ(p-tolyl). 1H NMR (CDCl3, δ): 0.64 (t, 3JHH = 7.2 Hz, 3H, S2CN(CH2CH3)2), 0.73 (t, 3JHH = 7.2 Hz, 3H, S2CN(CH2CH3)2), 2.77 (q, 3JHH = 7.2 Hz, 2H, S2CN(CH2CH3)2), 2.92 (q, 3JHH = 7.2 Hz, 2H, S2CN(CH2CH3)2), 2.23 (s, 9H, CH3), 6.82 (d, 3JHH = 7.6 Hz, 6H, p-tolyl meta), 7.20 (partially obscured by phenyl, p-tolyl ortho), 6.96−7.52 (m, 30H, PPh3). 13C{1H} NMR (CDCl3, δ): 12.17 (s, S2CN(CH2CH3)2), 12.74 (s, S2CN(CH2CH3)2), 42.95 (s, S2CN(CH2CH3)2), 43.97 (s, S2CN(CH2CH3)2), 206.09 (s, S2CN(CH2CH3)2), 21.23 (s, CH3), 126.95 (bs, p-tolyl meta), 134.55 (bs, p-tolyl para), 136.42 (bs, p-tolyl ortho), 144.70 (s, p-tolyl ipso), 127.11 (bm o-PPh3), 129.17 (bs p-PPh3), 131.99 (bm i-PPh3), 134.72 (bm m-PPh3), 209.33 (t, 2JCP = 17.1 Hz, CO). 31P{1H} NMR (CDCl3, δ): 40.18. Ru(κ2-S2CNMe2)(Ge[p-tolyl]3)(CO)(PPh3)2 (2b). The same procedure that was adopted for 2a was followed, except that sodium dimethyldithiocarbamate (0.055 g, 0.384 mmol) was used in place of sodium diethyldithiocarbamate. Pure 2b was recovered as pale yellow crystals (yield 0.19 g, 85%). All NMR data were collected in the presence of excess PPh3 to suppress phosphine dissociation. The 1H NMR spectrum of the analytical sample showed the presence of ca. 1.25 equiv of CH2Cl2. Anal. Calcd for C61H57GeNOP2RuS2·11/4CH2Cl2: C, 60.98; H, 4.89; N, 1.14. Found: C, 60.62; H, 5.00; N, 1.08. IR (cm−1): 1895 ν(CO); 800 δ(p-tolyl). 1H NMR (CDCl3, δ): 2.26 (s, 3H, S2CN(CH3)2), 2.45 (s, 3H, S2CN(CH3)2), 2.24 (s, 9H, CH3), 6.72 (d, 3JHH = 7.2 Hz, 6H, ptolyl meta), p-tolyl ortho signals obscured by PPh3, 7.04−7.71 (m, 30H, PPh3). 13C{1H} NMR (CDCl3, δ): 37.33 (s, S2CN(CH3)2), 38.07 (s, S2CN(CH3)2), 207.28 (s, S2CN(CH3)2), 21.42 (s, CH3), 127.15 (s, p-tolyl meta), 134.58 (s, p-tolyl para), 136.40 (s, p-tolyl ortho), 126.80 (o-PPh3), 129.72 (p-PPh3), 132.05 (i-PPh3), 134.73 (mPPh3), CO not observed. 31P{1H} NMR (CDCl3, δ): 40.40. Ru(κ2-S2CNEt2)(Ge[p-tolyl]3)(CO)2(PPh3) (3). 2a (0.100 g, 0.087 mmol) in deoxygenated dichloromethane (20 mL) was placed in a Fischer−Porter bottle. While the solution was stirred, the bottle was placed under a CO atmosphere (40 kPa). The solution changed color from orange to pale yellow almost immediately. Stirring was continued for 30 min, the pressure was released, and the solvent was evaporated under reduced pressure to give a yellow solid. Recrystallization from dichloromethane/ethanol produced pure 3 as pale yellow crystals which were recovered by filtration, washed with ethanol and n-hexane, and dried over P2O5 (yield 0.052 g, 65%). The 1H NMR spectrum of the analytical sample showed the presence of ca. 0.25 equiv of CH2Cl2 (the single crystal used for X-ray structure determination did not contain any solvent of crystallization). Anal. Calcd for C46H46GeNO2PRuS2·1/4CH2Cl2: C, 59.42; H, 5.01; N, 1.50. Found: C, 59.53; H, 5.08; N, 1.49. IR (cm−1): 2004, 1945 ν(CO); 794 δ(ptolyl). 1H NMR (CDCl3, δ): 0.62 (apparent t, 3JHH = 7.2 Hz, 6H, S2CN(CH2CH3)2), 2.79 (m, 2H, S2CN(CH2CH3)2), 2.90 (m, 2H, S2CN(CH2CH3)2), 2.28 (s, 9H, CH3), 7.02 (d, 3JHH = 7.5 Hz, 6H, ptolyl meta), 7.47 (partially obscured by phenyl, p-tolyl ortho), 7.32− 7.49 (m, 15H, PPh3). 13C{1H} NMR (CDCl3, δ): 11.86 (s, S2CN(CH2CH3)2), 43.11 (s, S2CN(CH2CH3)2), 202.70 (d, 3JCP = 3.1 Hz, S2CN(CH2CH3)2), 21.32 (s, CH3), 127.55 (s, p-tolyl meta), 135.87 (s, p-tolyl para), 136.16 (s, p-tolyl ortho), 141.64 (d, 3JCP = 6.3 Hz, p-tolyl ipso), 127.85 (d, 2JCP = 9.1 Hz, o-PPh3), 129.59 (s, p-PPh3), 132.42 (d, 1JCP = 33.6 Hz, i-PPh3), 134.12 (d, 3JCP = 10.6 Hz, m-PPh3), 201.35 (d, 2JCP = 6.3 Hz, CO). 31P{1H} NMR (CDCl3, δ): 24.24. Ru(κ2 (Ge,S)-Ge[p-tolyl] 2 S 2CNMe 2)(κ2 -S 2 CNMe 2)(CO)(PPh 3) (4). Method A. To a solution of 2b (0.100 g, 0.089 mmol) dissolved in dichloromethane (20 mL) was added a solution of sodium dimethyldithiocarbamate (0.026 g, 0.182 mmol) dissolved in ethanol (10 mL). The mixture was stirred for 2 h, during which time the solution developed a pale yellow color. 2919


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The solvent was evaporated under reduced pressure to give a pale yellow solid. Recrystallization of this from dichloromethane/ethanol produced pure 4 as pale yellow crystals, which were recovered by filtration, washed with ethanol and hexane, and dried over P2O5 (yield 0.040 g, 51%). The 1H NMR spectrum of the analytical sample showed the presence of ca. 0.25 equiv of CH2Cl2 (the single crystal used for X-ray structure determination contained 1 equiv of CH2Cl2). Method B. 1 (0.100 g, 0.097 mmol) dissolved in dichloromethane (20 mL) was treated with sodium dimethyldithiocarbamate (0.052 g, 0.363 mmol) dissolved in ethanol (10 mL). The solution was then treated a s desc ribed in M ethod A . Anal. Calcd for C39H41GeN2OPRuS4·1/4CH2Cl2: C, 51.92; H, 4.61; N, 3.09. Found: C, 51.82; H, 4.75; N, 3.02. IR (cm−1): 1922 ν(CO); 807, 799 δ(ptolyl). 1H NMR (CDCl3, δ): 2.24 (s, 3H, CH3), 2.27 (s, 3H, CH3), 3.14 (s, 3H, S(CN(CH3)2)S), 3.19 (s, 3H, S(CN(CH3)2)S), 3.33 (s, 3H, S2CN(CH3)2), 3.47 (s, 3H, S2CN(CH3)2), 6.80 (d, 3JHH = 7.6 Hz, 2H, p-tolyl meta), 7.03 (d, 3JHH = 7.6 Hz, 2H, p-tolyl meta), 7.15 (partially obscured by phenyl, p-tolyl ortho), 7.42 (partially obscured by phenyl, p-tolyl ortho), 7.13 − 7.43 (m, 15H, PPh3). 13C{1H} NMR (CDCl3, δ): 38.10 (s, S2CN(CH3)2), 38.63 (s, S2CN(CH3)2), 212.57 (s, S2CN(CH3)2), 45.40 (s, S(CN(CH3)2)S), 48.64 (s, S(CN(CH3)2)S), 207.95 (s, S(CN(CH3)2)S), 21.35 (s, CH3), 128.13 (s, p-tolyl meta), 128.14 (s, p-tolyl meta), 136.43 (s, p-tolyl para), 136.62 (s, ptolyl para), 142.97 (s, p-tolyl ipso), 143.63 (s, p-tolyl ipso), p-tolyl ortho obscured by PPh3, 127.38 (d, 2JCP = 9.7 Hz, o-PPh3), 128.93 (s, p-PPh3), 133.86 (d, 3JCP = 9.8 Hz, m-PPh3), 135.10 (d, 1JCP = 42.1 Hz, i-PPh3), 201.74 (d, 2JCP = 13.1 Hz, CO). 31P{1H} NMR (CDCl3, δ): 49.00. RuCl(Ge[OEt][p-tolyl]2)(CO)(PPh3)2 (5). Pyridine (0.040 mL, 0.483 mmol) was added dropwise to a solution of 1 (0.100 g, 0.097 mmol) dissolved in dichloromethane (20 mL) and the solution stirred for 30 min. Ethanol (10 mL) was added and the solution stirred for a further 1.5 h. The solvent was evaporated under reduced pressure to give an orange solid. Recrystallization from dichloromethane/ethanol produced pure 6 as bright orange crystals, which were recovered by filtration, washed with ethanol and hexane, and dried over P2O5 (yield 0.054 g, 57%). The 1H NMR spectrum of the analytical sample showed the presence of ca. 1.0 equiv of CH2Cl2. Anal. Calcd for C53H49ClGeO2P2Ru·CH2Cl2: C, 60.39; H, 4.79. Found: C, 60.47; H, 5.03. IR (cm−1): 1931 ν(CO); 801 δ(p-tolyl). 1H NMR (CDCl3, δ): 0.57 (t, 3JHH = 6.8 Hz, 3H, OCH2CH3), 3.05 (q, 3JHH = 6.8 Hz, 2H, OCH2CH3), 2.34 (s, 6H, CH3), 6.95 (d, 3JHH = 7.2 Hz, 4H, p-tolyl meta), 7.23 (partially obscured by phenyl, p-tolyl ortho), 7.15−7.56 (m, 30H, PPh3). 13C{1H} NMR (CDCl3, δ): 18.36 (s, OCH2CH3), 21.63 (s, CH3), 61.11 (s, OCH2CH3), 128.16 (s, p-tolyl meta), 135.07 (s, p-tolyl ortho), 137.86 (s, p-tolyl para), 138.22 (s, p-tolyl ipso), 127.97 (t′, 2,4JCP = 9.6 Hz, o-PPh3), 129.89 (s, p-PPh3), 132.65 (t′, 1,3JCP = 43.8 Hz, i-PPh3), 134.92 (t′, 3,5JCP = 11.2 Hz, m-PPh3), 200.12 (t, 2 JCP = 13.9 Hz, CO).31P{1H} NMR (CDCl3, δ): 34.58. RuCl(Ge[OnPr][p-tolyl]2)(CO)(PPh3)2 (6). Pyridine (0.040 mL, 0.483 mmol) was added dropwise to a solution of 1 (0.100 g, 0.097 mmol) dissolved in dichloromethane (20 mL) and the solution stirred for 30 min. n-Propanol (10 mL) was added and the solution stirred for a further 1.5 h. The solvent was evaporated under reduced pressure to give an orange solid. Recrystallization of this material from dichloromethane/n-propanol produced 7 as a pale orange powder, which was recovered by filtration, washed with n-propanol and hexane, and dried over P2O5 (0.019 g, 20%). An analytical sample of sufficient purity for elemental analysis was not obtained. MS (m/z, ESI, DCM): calcd for m/z C51H44ClGeOP2102Ru [M − OPr]+, 945.0806, found 945.0793. IR (cm−1): 1926 ν(CO); 799 δ(p-tolyl). 1H NMR (CDCl3, δ): 0.46 (t, 3JHH = 7.6 Hz, 3H, CH3), 0.98 (m, 2H, CH2CH3), 2.34 (s, 6H, CH3), 2.93 (t, 3JHH = 6.8 Hz, 2H, OCH2), 6.95 (d, 3JHH = 7.6 Hz, 4H, p-tolyl meta), 7.23 (partially obscured by phenyl, p-tolyl ortho), 7.15−7.55 (m, 30H, PPh3). 31P{1H} NMR (CDCl3, δ): 34.67. RuCl(Ge[OH][p-tolyl]2)(CO)(PPh3)2 (7). Water (5 mL) was added to a stirred solution of 5 (0.100 g, 0.101 mmol) in distilled tetrahydrofuran (20 mL). The solution slowly turned yellow. The mixture was stirred for 2 h before the tetrahydrofuran and water were

evaporated under reduced pressure to give a yellow solid. Recrystallization of this material from dichloromethane/n-hexane produced 7 as a pale orange powder which was recovered by filtration, washed with hexane, and dried over P2O5 (yield 0.068 g, 70%). An analytical sample of sufficient purity for elemental analysis was not obtained. MS (m/z, ESI, DCM): calcd for m/z C51H45ClGeO2P2102RuNa [M + Na]+, 985.0736, found 985.0719. IR (cm−1): 3571 w ν(OH); 1926 ν(CO); 799 δ(p-tolyl). 1H NMR (C6D6, δ): 1.77 (s, 1H, OH) (signal disappears on addition of D2O). 1 H NMR (CDCl3, δ): 2.24 (s, 6H, CH3), 6.82 (d, 3JHH = 7.6 Hz, 4H, p-tolyl meta), 7.23 (partially obscured by phenyl, p-tolyl ortho), 7.20− 7.38 (m, 30H, PPh3). 13C{1H} NMR (CDCl3, δ): 20.57 (s, CH3), 127.29 (s, p-tolyl meta), 132.46 (s, p-tolyl ortho), 136.67 (s, p-tolyl para), 140.99 (s, p-tolyl ipso),127.32 (t′, 2,4JCP = 9.4 Hz, o-PPh3), 129.21 (s, p-PPh3), 130.97 (t′, 1,3JCP = 43.6 Hz, i-PPh3), 133.67 (t′, 3,5 JCP = 11.0 Hz, m-PPh3) (CO not observed because of the limited solubility of 7). 31P{1H} NMR (CDCl3, δ): 33.52.

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ASSOCIATED CONTENT

* Supporting Information S

CIF files giving crystal data and refinement details for complexes for 1, 2a, 3, and 4. This material is available free of charge via the Internet at http://pubs.acs.org. The crystallographic data for 1, 2a, 3, and 4 are also available from the Cambridge Crystallographic Data Centre (fax, +441223-336-033; e-mail, [email protected]; web, http:// www.ccdc.cam.ac.uk) as supplementary publication nos. CCDC 857680−857683, respectively.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank The University of Auckland for partial support of this work through grants-in-aid.

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DEDICATION This contribution is dedicated to the memory of Gordon Stone, good friend and outstanding chemist.

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REFERENCES

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