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Article Cite This: Organometallics XXXX, XXX, XXX−XXX

Synthesis, Characterization, and Antimicrobial Activity of RhIII and IrIII β‑Diketonato Piano-Stool Compounds Christine M. DuChane, Loren C. Brown, Virginia S. Dozier, and Joseph S. Merola* Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United States S Supporting Information *

ABSTRACT: A series of RhIII and IrIII half-sandwich compounds of the type [(η5-Cp*R)M(β-diketonato)Cl] were synthesized and characterized, including 17 X-ray crystallographic structures. In general, the complexes were synthesized in short reaction times and in good yield. The antimicrobial properties of these complexes were tested against a variety of microbes, and several complexes were found to have good activity against Mycobacterium smegmatis.

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INTRODUCTION Inorganic and organometallic compounds featuring β-diketonato ligands are prevalent throughout the literature in numerous synthetic, catalytic, and biological applications. The simplest β-diketonato ligand, acetylacetonato (acac), is a classic anionic ligand that has been known to form stable complexes with nearly all transition metals via bidentate O2 chelation, yielding a six-membered ring with the metal.1 Less commonly, acac coordinates as a monodentate ligand through either one oxygen or the central carbon (Figure 1).2 These complexes are readily synthesized under basic conditions via reaction between stoichiometric amounts of the ligand and metal salt.

stronger nucleophile yields synthetically challenging complexes.6 This approach has been extensively applied in the synthesis of gold(I)7 and gold(III)6 complexes, as well as in the synthesis of elaborate sandwich complexes,8 heterobimetallic compounds,9 and multinuclear metallacycles.10 Half-sandwich acac complexes of the late transition metals are less common throughout the literature. In 1979, Rigby et al. reported the reaction of pentamethylcyclopentadienyl (Cp*) RhIII and IrIII chloride dimers with select β-diketone ligands, including CH3COCH2COCH3 (acacH) and CF3COCH2COCF3 (hfacH).11 Complexes of these ligands with (η6-hexamethylbenzene)ruthenium(II) have also been synthesized and shown to react with various neutral monodentate ligands.12 More recently reported is the C−H activation of 2-phenylpyridine by (η6-hexamethylbenzene)ruthenium(II) complexes with fluorinated β-diketone ligands.13 Organometallic complexes of the late transition metals have recently emerged as valuable contributors in medicinal chemistry.14 Chemotherapeutic potential has been demonstrated for half-sandwich ruthenium, rhodium, and iridium complexes with (C,N)-,15,16 (N,N)-,17,18 (N,O)-,19 and (O,O)chelating ligands,20 as well as for a family of [(η6-parene)Ru(pta)X2] (abbreviated RAPTA, for ruthenium arene pta (pta = 1,3,5-triaza-7-phosphaadamantane)) complexes,21 in addition to others.22 Several excellent reviews have been published detailing medicinal applications of promising organometallic half-sandwich anticancer agents.23 There have been significantly fewer reports on the antimicrobial properties of these complexes. In addition to possessing chemotherapeutic properties, several members of

Figure 1. Various coordination modes of acac.

Acac compounds have been used in a wide variety of catalytic applications. Complexes including Pd(acac)2, Co(acac)3, and Fe(acac)3 have been found to catalyze either hydrogenation or oxidation. Other oxidation catalysts include nickel, cobalt, or copper complexes of the form MCl(acac)(PPh3),3 as well as additional derivatives of this general form with more complex ligands.4 Derivatives of Rh(acac)L2 have been shown to catalyze hydroboration (L = cyclooctene) and hydroformylation (L = CO, H2CCH2).3 Additional catalytic applications include the synthesis of macromolecules and polymers.5 Transition-metal−acetylacetonato complexes are commonly used as synthetic precursors to inorganic or organometallic complexes via the “acac method”, in which protonation of a weakly coordinated acac ligand followed by replacement with a © XXXX American Chemical Society

Received: October 4, 2017

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DOI: 10.1021/acs.organomet.7b00742 Organometallics XXXX, XXX, XXX−XXX

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Organometallics

Scheme 1. General Synthetic Route to Half-Sandwich RhIII and IrIII Complexes of β-Diketonato Ligandsa

the RAPTA family of ruthenium complexes have exhibited biological activity against bacterial and fungal cells, with selectivity determined by the identity of the X ligand.24 Halfsandwich complexes [Cp*M(quinolin-8-ol)Cl] (M = Rh, Ir) have also been shown to have both moderate anticancer activity and weak antimicrobial activity. In all cases, the activity of the rhodium complex was found to be better than or equal to that of the iridium complex.25 The majority of studies on the biological activity of rhodium and iridium complexes have employed the pentamethylcyclopentadienyl anion (Cp*) as the η5 ligand, though studies with Cp*(phenyl), Cp*(biphenyl),16,18 and Cp*(alkoxy)17 have been reported. Despite this deficit in the literature, the studies that do feature derivatized Cp* ligands (Cp*R) have illustrated the importance of these modifications, particularly on cellular uptake. In earlier work, we reported the antistaphylococcal activity of [Cp*Ir(en)Cl2] (en = ethylenediamine)26 and the antimycobacterial activity of [Cp*Ir(aa)Cl] (aa = amino acid).27 The findings reported here complement previous research by presenting a series of [Cp*RM(β-diketonato)Cl] complexes that show improved values for the minimum inhibitory concentration (MIC) of Mycobacterium smegmatis, a nonpathogenic and fast-growing member of the Mycobacterium genus. Due to the relative ease of use associated with M. smegmatis, it is often employed in research laboratories as a model organism for more pathogenic members of the Mycobacterium family.28 In this article we report the synthesis, characterization (including 17 single-crystal X-ray structures), and antimicrobial activities against M. smegmatis of 16 rhodium(III) and 20 iridium(III) piano-stool complexes with β-diketonato ligands.

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a

Refer to Table 1 for complex identification.

Table 1. Complexes Discussed in This Articlea Rh complex

Ir complex

Cp*R

ligand

1-Rh

1-Ir 2-Ir 3-Ir 4-Ir 5-Ir 6-Ir 7-Ir 8-Ir 9-Ir 10-Ir 11-Ir 12-Ir 13-Ir 14-Ir 15-Ir

methyl ethyl n-propyl isopropyl n-butyl isobutyl n-pentyl n-hexyl n-heptyl n-octyl cyclohexyl phenyl benzyl phenethyl methyl phenyl methyl methyl methyl isopropyl phenyl benzyl phenethyl methyl

acac acac acac acac acac acac acac acac acac acac acac acac acac acac dppm dppm pva dpvm bza bza bza bza bza dbzm

3-Rh

7-Rh 8-Rh

12-Rh 13-Rh 14-Rh 15-Rh 16-Rh 17-Rh 18-Rh 19-Rh

RESULTS AND DISCUSSION

Synthesis and Characterization. We first attempted to synthesize these complexes via the experimental details provided in Rigby’s 1979 report;11 however, we found the reactants to have poor solubility in his chosen solvent, acetone. Fortunately this problem was overcome by changing the solvent to an acetone/methanol mixture, though dichloromethane was later found to give more consistent results in many cases. Complexes were synthesized via reaction between the Cp*R metal(III) chloride dimer and 2 equiv of sodium acetylacetonato (acacNa), benzoylacetone (bza), pivaloylacetone (pva), dibenzoylmethane (dbzm), dipivaloylmethane (dpvm), or dipropionylmethane (dppm) under basic conditions (Scheme 1 gives the general reaction; Table 1 gives the complex numbering scheme and identification). Reaction progression was frequently associated with a color change from red to orange (M = Rh) or orange to yellow (M = Ir). Following completion, the solvent was removed under vacuum and the crude mixture dissolved in minimal dichloromethane (DCM) and then filtered. The majority of complexes required no further purification following solvent removal. When purification was necessary, complexes were either triturated with hexanes or recrystallized from DCM and hexanes, n-pentane, or diethyl ether to yield red, orange, or yellow crystalline solids in moderate to excellent (48−98%) yields. Characterization included 1H NMR, 13C NMR, high-resolution mass spectroscopy (HRMS), C,H analysis, and single-crystal X-ray diffraction, when possible.

21-Rh 22-Rh 23-Rh 24-Rh a

17-Ir 18-Ir 19-Ir 20-Ir

24-Ir

Abbreviations are defined in Scheme 1.

In many cases, using a large excess of acacNa yielded a bisacac complex in which the NMR spectra showed displacement of the chloride by a second, C3-bound acac (Figure 2). Whereas Rigby reported the isolation and characterization of the bis-acac Cp* iridium complex,11 our attempts at isolation yielded only degradation products. This phenomenon was observed through NMR spectroscopy for both rhodium and iridium complexes, including those with derivatized Cp* ligands, and was particularly prevalent in methanolic solutions. Formation of the bis-acac complex was not observed in the synthesis of complexes with β-diketonato ligands other than acacNa. This could be suppressed by using only a slight excess of ligand in dichloromethane that had been dried over molecular sieves. X-ray Crystal Structures of Half-Sandwich Acac Complexes. Red, orange, or yellow single crystals used for X-ray diffraction were obtained from vapor diffusion of hexanes B


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Organometallics

Figure 2. NMR spectra illustrating the formation of the bis-acac complex for 9-Ir. The spectra have been cut from 2.0−4.6 ppm to aid in visualization of the distinguishing attributes.

minimum Ir−O distance of 1.994 Å to a maximum of 2.144 Å, with a mean of 2.056 Å. The complexes in the study fall very close to, but somewhat above, the mean, ranging from 2.0805(16) to 2.116(3) Å. The previously reported O−Ir−O angles range from 82.66 to 95.993° with a mean of 86.296°. Again, the extreme ranges of angles follow the same descriptions as given for the rhodium complexes: small angles force a crowded environment,33 and large angles correlate with the bonding of other ions to the acac.34 The iridium complexes reported herein fall from 87.02(8) to 88.45(11)°, a very narrow range that lies in the center of the range found in the literature. There appears to be no significant correlation between substituents on the acac ligand or on the cyclopentadienyl with the M−O distances or the O−M−O angles. Antimicrobial Activity. In previous work, we demonstrated that piano-stool complexes of Rh and Ir exhibit antimicrobial activity.26,27 For both Rh and Ir, various amino acid complexes had very good antimycobacterial activity, including some compounds with activity against Mycobacterium tuberculosis. In general, greater activity was found for complexes with hydrophobic groups on the amino acid as well as more hydrophobic groups on the Cp ring. On the other hand, we found that diamine complexes of Cp*R Rh and Ir complexes had no antimycobacterial activity but did have antistaphylococcal activity. Given that amino acids are (N,O)-chelators and diamines are (N,N)-chelators, it was of interest to test the activity of (O,O)-chelators such as the acetylacetonato complexes described here. The majority of these acac complexes were found to have moderate to very good antimycobacterial activity (Table 2) and little to no activity against the other microbes tested in the broad panel, including S. aureus, E. coli, and others. Two iridium complexes, 20-Ir and 24-Ir, were not tested due to solubility issues. Activity was measured using the sequential dilution technique in 96-well plates, with results recorded as the minimum inhibitory concentration (MIC), which is the highest concentration at which no cell growth was detected in a well. In all direct comparisons of Cp*RM(β-diketonato)Cl (M = Rh(III), Ir(III)) complexes, the rhodium analogue was found to have greater activity. In general, in comparison to the parental monomeric unit, addition of a chelating β-diketonato

or diethyl ether into saturated solutions of acetone or dichloromethane. Of the 17 structures, 15 crystals were found to belong to monoclinic space groups and the remaining two crystals to orthorhombic space groups. Structures crystallizing in monoclinic space groups included 1-Ir, 12-Rh, 13-Rh, 14-Rh, 14-Ir, 15-Rh, 15-Ir, 18-Rh, 18-Ir, 21-Rh (which contained one molecule of DCM in the lattice), 23-Rh, and 24-Rh in space group P21/c (No. 14), 4-Ir and 17Ir in space group P21/n (No. 14, alternate setting), and 22-Rh in space group P21 (No. 4). Compounds crystallizing in monoclinic space groups with a substituted Cp*R group crystallized so that the absolute value of the Cl−M−centroid− R dihedral angle ranged from approximately 7 to 50°, with the exception of 4-Ir, which had a dihedral angle of approximately 180°. This is likely due to a relatively low barrier to rotation of the isopropyl group, as evidenced by disorder present in the crystal structure at these atoms. Structures crystallizing in orthorhombic space groups were 19-Rh (P212121, No. 19) and 7-Ir (Pna21, No. 33). π−π stacking occurs between the phenyl of the bza ligand and the cyclopentadienyl group of 19-Rh. A search of the Cambridge Crystallographic Database (CCD)29 found 304 entries containing the Rh(acac) fragment with a wide range of substituents both on the metal and on the acac ligand. The geometry of the acac Rh fragment varies widely with those substituents. The average Rh−O bond length is 2.064 Å with a low value of 1.964 Å and an unusually high value of 2.275 Å. Many of the structures exhibiting bond lengths on the higher end of this range are not actually delocalized acetylacetonate; rather, the central C is un-ionized, as in acetylacetone.30 The O−Rh−O angle ranges from 78.7°, which places the acac ligand in a crowded environment,31 to 96.4°, in which case the oxygen atoms bond to another ion in addition to metal chelation.32 For the compounds reported here, the Rh−O bonds fall squarely into the middle of the reported values, ranging from 2.0613(10) to 2.1044(15) Å. The O−Rh−O angles range from 86.98(9) to 89.02(9)°, a narrow range that falls within the center of the range found in the CCD. Similarly, a search of the CCD for iridium acetylacetonate complexes found 211 complexes with an acac ligand, showing a C


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Organometallics Table 2. MIC Values against Mycobacterium smegmatis of Complexes Discussed in This Articlea

a

Rh complex

MIC (μM)

Ir complex

MIC (μM)

1-Rh

5.37

3-Rh

9.98

7-Rh 8-Rh

2.33 4.52

12-Rh 13-Rh 14-Rh 15-Rh 16-Rh 17-Rh 18-Rh 19-Rh

2.30 4.46 4.32 2.50 4.32 4.82 2.19 9.20

1-Ir 2-Ir 3-Ir 4-Ir 5-Ir 6-Ir 7-Ir 8-Ir 9-Ir 10-Ir 11-Ir 12-Ir 13-Ir 14-Ir 15-Ir

69.26 33.61 16.32 32.65 31.74 31.74 30.88 15.03 14.65 28.56 30.18 30.53 29.73 14.49 16.32

17-Ir 18-Ir 19-Ir 20-Ir

15.87 14.65 30.53 NA

21-Rh 22-Rh 23-Rh 24-Rh

16.10 7.83 15.24 8.05

24-Ir

NA

Diffraction Gemini E Ultra diffractometer operating with Mo Kα radiation. Data collection and data reduction were performed using Agilent’s CrysAlisPro software.36 Structure solution was performed using SHELXT-20143037 and refined using SHELXL-201431 via Olex2. The final refinement model involved anisotropic displacement parameters for non-hydrogen atoms and a riding model for all hydrogen atoms. Olex2 was used for molecular graphics generation.38 Searches of the Cambridge Crystallographic Database29 were carried out using the program Conquest,39 and the results were analyzed with the statistical functions of the program Mercury.40 Synthesis and Characterization. General Synthesis of (Cp*R)M(acac)Cl Compounds. A round-bottom flask was charged with the appropriate amounts of [Cp*RMCl2]2 (M = Rh, Ir) and acacNa in dichloromethane (5 mL). The solution was stirred magnetically for 30 min to 2 h while the color changed from red to clear orange (M = Rh) or from orange to clear yellow (M = Ir). The mixture was filtered to remove excess reagent, and then the solvent was removed via reduced pressure to give a red, orange, or yellow crystalline solid or oil. Synthesis of 1-Rh. Following the general procedure, [Cp*RhCl2]2 (0.0600 g, 0.0971 mmol) and sodium acetylacetonate (0.0279 g, 0.199 mmol) were reacted in DCM to give 1-Rh as an orange solid (0.0678 g, 94%). Characterization matched previously reported data.11 Synthesis of 1-Ir. Following the general procedure, [Cp*IrCl2]2 (0.0502 g, 0.0630 mmol) and sodium acetylacetonate (0.0180 g, 0.129 mmol) were reacted in DCM to give 1-Ir as a yellow solid (0.0542 g, 93%). Characterization matched previously reported data.11 Synthesis of 2-Ir. Following the general procedure, [(Cp*ethyl)IrCl2]2 (0.0202 g, 0.0245 mmol) and sodium acetylacetonate (0.0075 g, 0.0539 mmol) were reacted in DCM to give 2-Ir (0.0223 g, 95.6%). 1 H NMR (400 MHz, CDCl3, δ): 5.20 (s, 1H, C(O)CHC(O)), 2.08 (q, J = 7.6 Hz, 2H, CpCH2CH3), 1.92 (s, 6H, C(O)CH3), 1.601 (s, 6H, Cp*Me), 1.598 (s, 6H, Cp*Me), 1.10 (t, J = 7.7 Hz, 3H, CpCH2CH3). 13C NMR (101 MHz, CDCl3, δ): 184.8 (C(O)CH3), 100.2 (C(O)CHC(O)), 85.5 (Cp*C), 84.7 (Cp*C), 83.2 (Cp*C), 28.1 (C(O)CH3), 17.2 (CpCH2CH3), 12.5 (CpCH2CH3), 8.8 (Cp*Me), 8.5 (Cp*Me). HRMS/ESI+ (m/z): calcd for C16H24[193Ir]O2, 441.1400; found, 441.1399. Anal. Calcd for C16H24Cl[193Ir]O2: C, 40.37; H, 5.08. Found: C, 40.62; H, 4.97. Synthesis of 3-Rh. Following the general procedure, [(Cp*n‑propyl)RhCl2]2 (0.1 g, 0.1488 mmol) and sodium acetylacetonate (0.045 g, 0.3214 mmol) were reacted in DCM to give 3-Rh (0.091 g, 76.5%). 1 H NMR (400 MHz, CDCl3, δ): 5.10 (s, 1H, C(O)CHC(O)), 2.22− 2.14 (m, 2H, CpCH2CH2CH3), 1.99 (s, 6H, C(O)CH3), 1.63 (s, 6H, Cp*Me), 1.63 (s, 6H, Cp*Me), 1.48 (app sextet, J = 14.9, 7.4 Hz, 2H, CpCH2CH2CH3), 0.97 (t, J = 7.4 Hz, 3H, CpCH2CH2CH3). 13C NMR (101 MHz, CDCl3, δ): 186.5 (C(O)CH3), 98.5 (d, J = 1.4 Hz, C(O)CHC(O)), 93.4 (d, J = 9.5 Hz, Cp*C), 93.2 (d, J = 9.1 Hz, Cp*C), 92.1 (d, J = 9.4 Hz, Cp*C), 28.4 (d, J = 1.1 Hz, C(O)CH3), 25.5 (CpCH2CH2CH3), 21.3 (CpCH2CH2CH3), 14.3 (CpCH2CH2CH3), 8.7 (Cp*Me), 8.6 (Cp*Me). HRMS/ESI+ (m/ z): calcd for C17H26RhO2, 365.0982; found, 365.0991. Synthesis of 3-Ir. Following the general procedure, [(Cp*n‑propyl)IrCl2]2 (0.0650 g, 0.0762 mmol) and sodium acetylacetonate (0.0225 g, 0.1607 mmol) were reacted in DCM to give 3-Ir (0.0711 g, 95.2%). 1 H NMR (400 MHz, CDCl3, δ): 5.20 (s, 1H, C(O)CHC(O)), 2.11− 2.01 (m, 2H, CpCH2CH2CH3), 1.92 (s, 6H, C(O)CH3), 1.60 (s, 6H, Cp*Me), 1.60 (s, 6H, Cp*Me), 1.49 (app sextet, J = 15.2, 7.5 Hz, 2H, CpCH2CH2CH3), 0.96 (t, J = 7.4 Hz, 3H, CpCH2CH2CH3). 13C NMR (101 MHz, CDCl3, δ): 184.8 (C(O)CH3), 100.1 (C(O) CHC(O)), 84.8 (Cp*C), 84.4 (Cp*C), 83.2 (Cp*C), 28.1 (C(O) CH 3 ), 25.8 (CpCH 2 CH 2 CH 3 ), 21.5 (CpCH 2 CH 2 CH 3 ), 14.4 (CpCH2CH2CH3), 8.8 (Cp*Me), 8.8 (Cp*Me). HRMS/ESI+ (m/ z): calcd for C17H26O2[193Ir], 455.1557; found, 455.1559. Synthesis of 4-Ir. Following the general procedure, [(Cp*i‑propyl)IrCl2]2 (0.0668 g, 0.0970 mmol) and sodium acetylacetonate (0.0251 g, 0.0235 mmol) were reacted in DCM to give 4-Ir (0.0672 g, 89.96%). 1H NMR (400 MHz, CDCl3, δ): 5.24 (s, 1H, C(O)CHC(O)), 2.50 (hept, J = 7.2 Hz, 1H, CpCH(CH3)2 1.92 (s, 6H, C(O)CH3), 1.64 (s, 6H, Cp*Me), 1.61 (s, 6H, Cp*Me), 1.26 (d, J = 7.2 Hz, 6H, CpCH(CH3)2). 13C NMR (101 MHz, CDCl3, δ): 184.6

Abbreviations are defined in Scheme 1.

ligand improved the activity for rhodium complexes and diminished the activity for iridium complexes.

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CONCLUSION The work reported here extends two aspects of our research: the synthesis and characterization of pentasubstituted cyclopentadienyl piano-stool complexes with four methyl groups and one unique “R” substituent on the ring and the study of pianostool complexes of iridium and rhodium as antimicrobial agents. This work shows that the acetylacetonate ligand and its substituted variants provide an effective chelate ligand set that imparts antimycobacterial activity. Despite these promising results, many of these compounds seem to be somewhat unstable for long-term storage in biological media, which may reduce their therapeutic potential.

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EXPERIMENTAL SECTION

Materials. Rhodium and iridium dimers [Cp*RMCl2]2 were synthesized as reported previously.35 Reagent-grade solvents and all other materials for synthesis, purification, and characterization were purchased from commercial sources and used as received unless otherwise stated. Sodium acetylacetonato and 2,2,6,6-tetramethyl-3,5heptanedione were purchased from Alfa Aesar (Ward Hill, MA 01835), 3,5-heptanedione, 1-phenyl-1,3-butanedione, and 1,3-diphenyl-1,3-propanedione were purchased from Sigma-Aldrich (St. Louis, MO 63013), and 2,2-dimethyl-3,5-hexanedione was purchased from Strem Chemicals (Newburyport, MA 01950). Deuterated solvents for NMR spectroscopy were obtained from Cambridge Isotope Laboratories. Instrumentation. 1H NMR and 13C NMR spectra were collected on a Varian MR-400 NMR spectrometer. 13 C NMR were correspondingly recorded at 101 MHz. Elemental analyses were performed by Atlantic Microlabs (Norcross, GA, USA). HRMS were collected on an Agilent 6220 Accurate Mass TOF LC-MS. X-ray crystallographic data were collected at 100 K on a Rigaku Oxford D


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Organometallics

(m/z): calcd for C20H32O2Rh, 407.1452; found, 407.1457. Anal. Calcd for C20H32O2RhCl: C, 54.25; H, 7.28. Found: C, 54.50; H, 7.18. Synthesis of 8-Ir. Following the general procedure, [(Cp*n‑hexyl)IrCl2]2 (0.0208 g, 0.0222 mmol) and sodium acetylacetonate (0.0071 g, 0.0507 mmol) were reacted in DCM to give 8-Ir (0.0222 g, 94.1%). 1 H NMR (400 MHz, CDCl3, δ): 5.20 (s, 1H, C(O)CHC(O)), 2.10− 2.02 (m, 2H, CpCH2(CH2)4CH3), 1.92 (s, 6H, C(O)CH3), 1.60 (s, 6H, Cp*Me), 1.59 (s, 6H, Cp*Me), 1.49−1.18 (m, 8H, CpCH2(CH2)4CH3), 0.88 (t, J = 6.3 Hz, 3H, CpCH2(CH2)4CH3). 13 C NMR (101 MHz, CDCl3, δ): 184.8 (C(O)CH3), 100.2 (C(O) CHC(O)), 84.8 (Cp*C), 84.8 (Cp*C), 83.2 (Cp*C), 31.7 (C(O) CH3), 29.5 (hexyl), 28.3 (hexyl), 28.1 (hexyl), 23.9 (hexyl), 22.7 (hexyl), 14.2 (CpCH2(CH2)4CH3), 8.8 (Cp*Me), 8.7 (Cp*Me). HRMS/ESI+ (m/z): calcd for C20H32O2[193Ir], 497.2026; found, 497.2029. Anal. Calcd for C20H32O2[193Ir]Cl: C, 45.14; H, 6.06. Found: C, 45.31; H, 5.91. Synthesis of 9-Ir. Following the general procedure, [(Cp*n‑heptyl)IrCl2]2 (0.0492 g, 0.0510 mmol) and sodium acetylacetonate (0.0157 g, 0.1121 mmol) were reacted in DCM to give 9-Ir (0.0524 g, 94.08%) 1 H NMR (400 MHz, CDCl3, δ): 5.18 (s, 1H, C(O)CHC(O)), 2.07− 2.02 (m, 2H, CpCH2(CH2)5CH3), 1.90 (s, 6H, C(O)CH3), 1.581 (s, 6H, Cp*Me), 1.578 (s, 6H, Cp*Me), 1.45−1.37 (m, 2H, CpCH2(CH2)5CH3), 1.36−1.19 (m, 8H, CpCH2(CH2)5CH3), 0.89− 0.84 (m, 3H, CpCH2(CH2)5CH3). 13C NMR (101 MHz, CDCl3, δ): 184.8 (C(O)CH3), 100.2 (C(O)CHC(O)), 84.78 (Cp*C), 84.75 (Cp*C), 83.2 (Cp*C), 31.9 (heptyl), 29.9 (heptyl), 29.2 (heptyl), 28.4 (heptyl), 28.1 (C(O)CH3), 23.9 (heptyl), 22.8 (heptyl), 14.2 (CpCH2(CH2)5CH3), 8.8 (Cp*Me), 8.7 (Cp*Me). HRMS/ESI+ (m/ z): calcd for C21H34O2[193Ir], 511.2183; found, 511.2183. Anal. Calcd for C21H34O2[193Ir]Cl: C, 46.18; H, 6.27. Found: C, 46.39; H, 6.18. Synthesis of 10-Ir. Following the general procedure, [(Cp*n‑octyl)IrCl]2 (0.0522 g, 0.0526 mmol) and sodium acetylacetonate (0.0155 g, 0.1107 mmol) were reacted in DCM to give 10-Ir (0.0549 g, 86.3%) 1 H NMR (400 MHz, CDCl3, δ): 5.20 (s, 1H, C(O)CHC(O)), 2.09− 2.04 (m, 2H, CpCH2(CH2)6CH3), 1.92 (s, 6H, C(O)CH3), 1.60 (s, 6H, Cp*Me), 1.596 (s, 6H, Cp*Me), 1.47−1.20 (m, 12H, CpCH2(CH2)6CH3), 0.90−0.85 (m, 3H, CpCH2(CH2)6CH3). 13C NMR (101 MHz, CDCl3, δ): 184.8 (C(O)CH3), 100.2 (C(O) CHC(O)), 84.8 (Cp*C), 84.7 (Cp*C), 83.2 (Cp*C), 32.0 (octyl), 29.9 (octyl), 29.5 (octyl), 29.3 (octyl), 28.3 (octyl), 28.1 (C(O)CH3), 23.9 (octyl), 22.8 (octyl), 14.2 (CpCH2(CH2)6CH3), 8.8 (Cp*Me), 8.7 (Cp*Me). HRMS/ESI+ (m/z): calcd for C22H36O2[193Ir], 525.2339; found, 525.2338. Anal. Calcd for C22H36O2[193Ir]Cl: C, 47.17; H, 6.48. Found: C, 47.30; H, 6.34. Synthesis of 11-Ir. Following the general procedure, [(Cp*cyclohexyl)IrCl2]2 (0.0493 g, 0.0528 mmol) and sodium acetylacetonate (0.0172 g, 0.1229) were reacted in acetone to give 11-Ir (0.0520 g, 92.9%). 1H NMR (400 MHz, CDCl3, δ): 5.23 (s, 1H, C(O)CHC(O)), 2.11−2.01 (m, 1H, CpCH((CH2)5), 1.92 (s, 6H, C(O)CH3), 1.82−1.73 (m, 4h, CpCH(CH2)5) 1.63 (s, 6H, Cp*Me), 1.61 (s, 6H, Cp*Me), 1.49−1.09 (m, 6H, CpCH(CH2)5). 13C NMR (101 MHz, CDCl3, δ): 184.8 (C(O)CH3), 100.1 (C(O)CHC(O)), 88.3 (Cp*C), 83.1 (Cp*C), 82.1 (Cp*C), 35.7 CpCH(CH2)5) 31.1 (C(O)CH3), 30.9 (cyclohexyl), 27.9 (cyclohexyl), 27.1 (cyclohexyl), 26.0 (cyclohexyl), 22.7 (cyclohexyl), 9.3 (Cp*Me), 8.9 (Cp*Me). HRMS/ESI+ (m/z): calcd for C20H30O2[193Ir], 495.1870; found, 495.1881. Anal. Calcd for C20H30O2[193Ir]Cl: C, 45.31; H, 5.70. Found: C, 45.61; H, 5.83. Synthesis of 12-Rh. Following the general procedure, [Cp*phenylRhCl2]2 (0.0500 g, 0.0674 mmol) and sodium acetylacetonate (0.0193 g, 0.132 mmol) were reacted in acetone (12 mL) and methanol (3 mL) to give 12-Rh as an orange solid (0.0312 g, 53%). 1 H NMR (400 MHz, CDCl3, δ): 7.48 (dd, J = 7.2, 2.4 Hz, 2H, Ph), 7.42−7.35 (m, 3H, Ph), 5.16 (s, 1H, C(O)CHC(O)), 2.00 (s, 6H, C(O)CH3), 1.76 (s, 6H, Cp*Me). 1.57 (s, 6H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 186.4 (C(O)CH3), 130.1 (Ph), 129.8 (Ph), 128.7 (Ph), 128.7 (Ph), 98.6 (d, J = 1.5 Hz, C(O)CHC(O)), 98.2 (d, J = 8.8 Hz, Cp*C), 91.0 (d, J = 9.0 Hz, Cp*C), 90.2 (d, J = 9.9 Hz, Cp*C), 28.3 (d, J = 1.3 Hz, C(O)CH3), 9.1 (Cp*Me), 9.0 (Cp*Me). HRMS/ESI+ (m/z): calcd for C20H24O2Rh, 399.0826; found,

(C(O)CH3), 100.3 (C(O)CHC(O)), 88.5 (Cp*C), 84.4 (Cp*C), 82.2 (Cp*C), 28.0 (C(O)CH3), 25.4 (CpCH(CH3)2), 21.0 (CpCH(CH3)2), 9.2 (Cp*Me), 9.1 (Cp*Me). HRMS/ESI+ (m/z): calcd for C17H26O2[193Ir], 455.1557; found, 455.1552. Anal. Calcd for C17H26O2[193Ir]Cl: C, 41.67; H, 5.35. Found: C, 41.92; H, 5.27. Synthesis of 5-Ir. Following the general procedure, [(Cp*n‑butyl)IrCl2]2 (0.0444 g, 0.0504 mmol) and sodium acetylacetonate (0.0141 g, 0.1008 mmol) were reacted in DCM to give 5-Ir (0.0483 g, 90.8%). 1 H NMR (400 MHz, CDCl3, δ): 5.20 (s, 1H, C(O)CHC(O)), 2.10− 2.04 (m, 2H, CpCH2(CH2)2CH3), 1.92 (s, 6H, C(O)CH3), 1.59 (s, 12H, Cp*Me), 1.47−1.30 (m, 4H, CpCH2(CH2)2CH3), 0.95−0.88 (m, 3H, CpCH2(CH2)2CH3). 13C NMR (101 MHz, CDCl3, δ): 184.8 (C(O)CH3), 100.1 (C(O)CHC(O)), 84.74 (Cp*C), 84.7 (Cp*C), 83.2 (Cp*C), 30.5 (CpCH2(CH2)2CH3), 28.1 (C(O)CH3), 23.6 (CpCH2(CH2)2CH3), 23.0 (CpCH2(CH2)2CH3), 14.1 (CpCH2(CH2)2CH3), 8.8 (Cp*Me), 8.7 (Cp*Me). HRMS/ESI+ (m/z): calcd for C18H28O2[193Ir], 469.1713; found, 469.1717. Anal. Calcd for C18H28O2[193Ir]Cl: C, 42.89; H, 5.60. Found: C, 43.15; H, 5.63. Synthesis of 6-Ir. Following the general procedure, [(Cp*i‑butyl)IrCl2]2 (0.0408 g, 0.0463 mmol) and sodium acetylacetonate (0.0137 g, 0.0979 mmol) were reacted in DCM to give 6-Ir (0.0399 g, 85.4%). 1 H NMR (400 MHz, CDCl3, δ): 5.19 (s, 1H, C(O)CHC(O)), 2.00 (d, J = 7.4 Hz, 2H, CpCH2CH(CH3)2), 1.92 (s, 6H, 2x C(O)CH3), 1.80−1.66 (m, 1H, CpCH2CH(CH3)2), 1.604 (s, 6H, 2x Cp*Me), 1.601 (s, 6H, 2x Cp*Me), 0.93 (d, J = 6.7 Hz, 6H, CpCH2CH(CH3)2). 13C NMR (101 MHz, CDCl3, δ): 184.8 (C(O)CH3), 100.1 (C(O)CHC(O)), 84.4 (Cp*C), 84.2 (Cp*C), 83.4 (Cp*C), 32.9 (CpCH211CH(CH3)2), 28.1 (C(O)CH3), 28.07 (CpCH2CH(CH3)2), 22.8 (CpCH2CH(CH3)2), 9.2 (Cp*Me), 8.8 (Cp*Me). HRMS/ESI+ (m/z): calcd for C18H28O2[193Ir], 469.1713; found, 469.1707. Synthesis of 7-Rh. Following the general procedure, [(Cp*n‑pentyl)RhCl2]2 (0.0203 g, 0.0278 mmol) and sodium acetylacetonate (0.0088 g, 0.0629 mmol) were reacted in DCM to give 7-Rh (0.0227 g, 95.38%). 1H NMR (400 MHz, CDCl3, δ): 5.09 (s, 1H, C(O)CHC(O)), 2.23−2.14 (m, 2H, CpCH2(CH2)3CH3), 1.98 (s, 6H, C(O)CH3), 1.621 (s, 6H, Cp*Me), 1.618 (s, 6H, Cp*Me), 1.52−1.36 (m, 2H, CpCH2(CH2)3CH3), 1.37−1.25 (m, 4H, CpCH2(CH2)3CH3), 0.92−0.85 (m, 3H, CpCH2(CH2)3CH3). 13C NMR (101 MHz, CDCl3, δ): 186.5 (C(O)CH3), 98.4 (d, J = 1.2 Hz, C(O)CHC(O)), 93.6 (d, J = 9.2 Hz, Cp*C), 93.1 (d, J = 9.1 Hz, Cp*C), 92.0 (d, J = 9.2 Hz, Cp*C), 31.9 (C(O)CH3), 28.3 (pentyl), 27.7 (pentyl), 23.5 (pentyl), 22.5 (pentyl), 14.0 (CpCH2(CH2)3CH3), 8.62 (Cp*Me), 8.55 (Cp*Me). HRMS/ESI+ (m/z): calcd for C19H30O2Rh, 393.1295; found, 393.1292. Synthesis of 7-Ir. Following the general procedure, [(Cp*n‑pentyl)IrCl2]2 (0.0495 g, 0.0545 mmol) and sodium acetylacetonate (0.0167 g, 0.1193 mmol) were reacted in DCM to give 7-Ir (0.0534 g, 94.68%). 1H NMR (400 MHz, CDCl3, δ): 5.20 (s, 1H, C(O)CHC(O)), 2.10−2.04 (m, 2H, CpCH2(CH2)3CH3), 1.92 (s, 6H, C(O)CH3), 1.60 (s, 6H, Cp*Me), 1.59 (s, 6H, Cp*Me), 1.49−1.38 (m, 2H, CpCH2(CH2)3CH3), 1.37−1.28 (m, 4H, CpCH2(CH2)3CH3), 0.92− 0.85 (m, 3H, CpCH2(CH2)3CH3). 13C NMR (101 MHz, CDCl3, δ): 184.8 (C(O)CH3), 100.1 (C(O)CHC(O)), 84.7 (Cp*C), 84.2 (Cp*C), 32.0 (C(O)CH3), 28.1 (pentyl), 28.0 (pentyl), 23.8 (pentyl), 22.6 (pentyl), 14.0 (CpCH2(CH2)3CH3), 8.8 (Cp*Me), 8.7 (Cp*Me). HRMS/ESI+ (m/z): calcd for C19H30O2[193Ir], 483.1870; found, 483.1877. Synthesis of 8-Rh. Following the general procedure, [(Cp*n‑hexyl)RhCl2]2 (0.0200 g, 0.0265 mmol) and sodium acetylacetonate (0.0076 g, 0.0542 mmol) were reacted in acetone to give 8-Rh (0.0205 g, 87.6%). 1H NMR (400 MHz, CDCl3, δ): 5.10 (s, 1H, C(O)CHC(O)), 2.23−2.14 (m, 2H, CpCH2(CH2)4CH3), 1.99 (s, 6H, C(O)CH3), 1.63 (s, 6H, Cp*Me), 1.63 (s, 6H, Cp*Me), 1.48−1.22 (m, 8H, CpCH2(CH2)4CH3), 0.88 (t, J = 6.3 Hz, 3H, CpCH2(CH2)4CH3). 13 C NMR (101 MHz, CDCl3, δ): 186.5 (C(O)CH3), 98.4 (d, J = 1.3 Hz, C(O)CHC(O)), 93.6 (d, J = 9.5 Hz, Cp*C), 93.1 (d, J = 9.5 Hz, Cp*C), 92.0 (d, J = 9.5 Hz, Cp*C), 31.7 (C(O)CH3), 29.5 (hexyl), 28.3 (hexyl), 28.0 (hexyl), 23.5 (hexyl), 22.6 (hexyl), 14.2 (CpCH2(CH2)4CH3), 8.62 (Cp*Me), 8.6 (Cp*Me). HRMS/ESI+ E


Article

Organometallics

to give 15-Rh as a red-orange solid (0.126 g, 95%). 1H NMR (400 MHz, CDCl3, δ): 5.10 (s, 1H, C(O)CHC(O)), 2.24 (app qd, J = 7.5 Hz, 4H, C(O)CH2CH3), 1.62 (s, 15H, Cp*Me), 1.12 (t, J = 7.6 Hz, 6H, C(O)CH2CH3). 13C NMR (101 MHz, CDCl3, δ): 190.5 (C(O)CH2CH3), 96.1 (d, J = 1.5 Hz, C(O)CHC(O)), 91.9 (d, J = 9.4 Hz, Cp*C), 34.0 (d, J = 1.0 Hz, C(O)CH2CH3), 11.2 (C(O)CH2CH3), 8.5 (Cp*Me). HRMS/ESI+ (m/z): calcd for C 17 H 26 O 2 Rh, 365.0982; found, 365.0986. Anal. Calcd for C17H26O2RhCl: C, 50.95; H, 6.54. Found: C, 51.05; H, 6.52. Synthesis of 15-Ir. Following the general procedure, [Cp*IrCl2]2 (0.0500 g, 0.0628 mmol), 3,5-heptanedione (0.0187 mL, 0.138 mmol), and Na2CO3 (0.0171 g, 0.138 mmol) were reacted in acetone (15 mL) to give 15-Ir (0.0402 g, 65%). 1H NMR (400 MHz, CDCl3, δ): 5.19 (s, 1H, C(O)CHC(O)), 2.18 (q, J = 7.5 Hz, 4H, C(O)CH2CH3), 1.59 (s, 15H, Cp*Me), 1.11 (t, J = 7.6 Hz, 6H, C(O)CH2CH3). 13C NMR (101 MHz, CDCl3, δ): 188.7 (C(O)CH2CH3), 97.8 (C(O)CHC(O)), 83.3 (Cp*C), 33.9 (C(O)CH2CH3), 11.0 (C(O)CH2CH3), 8.7 (Cp*Me). HRMS/ESI+ (m/z): calcd for C17H26O2[193Ir], 455.1557; found, 455.1551 Anal. Calcd for C17H26O2[193Ir]Cl: C, 41.67; H, 5.35. Found: C, 41.96; H, 5.34. Synthesis of 16-Rh. Following the general procedure, [Cp*phenylRhCl2]2 (0.0323 g, 0.0435 mmol), 3,5-heptanedione (0.124 mL, 0.0915), and Na2CO3 (0.0137 g, 0.1105 mmol) were reacted in acetone (12 mL) and methanol (3 mL) to give 16-Rh as an orange solid (0.0182 g, 89.07%). 1H NMR (400 MHz, CDCl3, δ): 7.46 (dd, J = 7.4, 2.2 Hz, 2H, Ph), 7.42−7.31 (m, 3H, Ph), 5.16 (s, 1H, C(O)CHC(O)), 2.24 (qd, J = 7.5, 3.2 Hz, 4H, C(O)CH2CH3), 1.76 (s, 6H, Cp*Me), 1.56 (s, 6H, Cp*Me), 1.06 (t, J = 7.5 Hz, 6H, C(O)CH2CH3). 13C NMR (101 MHz, CDCl3, δ): 190.4 (C(O)CH2CH3), 130.2 (Ph), 129.7 (Ph), 128.7 (Ph), 128.6 (Ph), 98.2 (d, J = 8.8 Hz, Cp*C), 96.5 (d, J = 1.4 Hz, C(O)CHC(O)), 90.8 (d, J = 9.2 Hz, Cp*C), 90.1 (d, J = 9.9 Hz, Cp*C), 34.1 (C(O)CH2CH3), 11.1 (C(O)CH2CH3), 9.0 (Cp*Me), 8.9 (Cp*Me). HRMS/ESI+ (m/z): calcd for C22H28O2Rh, 427.1139; found, 427.1149. Synthesis of 17-Rh. Following the general procedure, [Cp*RhCl2]2 (0.0400 g, 0.0647 mmol), 2,2-dimethyl-3,5-hexanedione (0.0207 mL, 0.1327 mmol), and Na2CO3 (0.0177 g, 0.1424 mmol) were reacted in acetone (15 mL) to give 17-Rh (0.1322 g, 96%). 1H NMR (400 MHz, CDCl3, δ): 5.22 (s, 1H, C(O)CHC(O)), 2.01 (s, 3H, C(O)CH3), 1.61 (s, 15H, Cp*Me), 1.13 (s, 9H, C(O)C(CH3)3). 13C NMR (101 MHz, CDCl3, δ): 195.3 (C(O)C(CH3)3), 187.0 (C(O)CH3), 93.4 (d, J = 1.4 Hz, C(O)CHC(O)), 91.9 (d, J = 9.2 Hz, Cp*C), 40.4 (C(CH3)3), 28.8 (d, J = 1.1 Hz, C(O)CH3), 28.6 (C(CH3)3), 8.6 (Cp*Me). HRMS/ESI+ (m/z): calcd for C18H28O2Rh, 379.1139; found, 379.1151. Synthesis of 17-Ir. Following the general procedure, [Cp*IrCl2]2 (0.0500 g, 0.0628 mmol), 2,2-dimethyl-3,5-hexanedione (0.0215 mL, 0.138 mmol), and Na2CO3 (0.0171 g, 0.138 mmol) were reacted in acetone (15 mL) to give 17-Ir as a yellow solid (0.0623 g, 98%). 1H NMR (400 MHz, CDCl3, δ): 5.32 (s, 1H, C(O)CHC(O)), 1.95 (s, 3H, C(O)CH3), 1.59 (s, 15H, Cp*Me), 1.13 (s, 9H, C(O)C(CH3)3). 13 C NMR (101 MHz, CDCl3, δ): 193.5 (C(O)C(CH3)3), 185.3 (C(O)CH3), 95.2 (C(O)CHC(O)), 83.2 (Cp*C), 40.4 (C(CH3)3), 28.6 (C(O)CH3), 28.4 (C(CH3)3), 8.8 (Cp*Me). HRMS/ESI+ (m/ z): calcd for C18H28O2[193Ir], 469.1713; found, 469.1708. Anal. Calcd for C18H28O2[193Ir]Cl: C, 42.89; H, 5.60. Found: C, 42.69; H, 5.48. Synthesis of 18-Rh. Following the general procedure, [Cp*RhCl2]2 (0.1007 g, 0.1629 mmol), 2,2,6,6-tetramethyl-3,5-heptanedione (0.070 mL, 0.3340 mmol), and Na2CO3 (0.0485 g, 0.3911 mmol) were reacted in acetone (15 mL) to give 18-Rh as a red-orange solid (0.1520 g, 87%). 1H NMR (400 MHz, CDCl3, δ): 5.37 (s, 1H, C(O)CHC(O)), 1.60 (s, 15H, Cp*Me), 1.13 (s, 18H, C(O)C(CH3)3). 13C NMR (101 MHz, CDCl3, δ): 195.6 (C(O)), 91.6 (d, J = 9.2 Hz, Cp*C), 88.4 (d, J = 1.4 Hz, C(O)CHC(O)), 40.8 (C(CH3)3), 28.7 (C(O)CH3), 8.5 (Cp*Me). HRMS/ESI+ (m/z): calcd for C 21 H 34 O 2 Rh, 421.1608; found, 421.1611. Anal. Calcd for C21H34O2RhCl: C, 55.21; H, 7.50. Found: C, 55.50; H, 7.62. Synthesis of 18-Ir. Following the general procedure, [Cp*IrCl2]2 (0.500 g, 0.0628 mmol), 2,2,6,6-tetramethyl-3,5-heptanedione (0.0286 mL, 0.138 mmol), and Na2CO3 (0.0171 g, 0.138 mmol) were reacted

399.0805. Anal. Calcd for C20H24O2RhCl: C, 55.25; H, 5.56. Found: C, 55.50; H, 5.67. Synthesis of 13-Rh. Following the general procedure, [Cp*benzylRhCl2]2 (0.0712 g, 0.0924 mmol) and sodium acetylacetonate (0.0272 g, 0.194 mmol) were reacted in acetone (12 mL) and methanol (3 mL) to give 13-Rh as an orange solid (0.0746 g, 90%). 1 H NMR (400 MHz, CDCl3, δ): 7.25−7.22 (m, 2H, Ph), 7.25−7.22 (m, 1H, Ph), 7.13−7.09 (m, 2H, Ph), 5.14 (s, 1H, C(O)CHC(O)), 3.62 (s, 2H, CH2), 2.03 (s, 6H, C(O)CH3), 1.66 (s, 6H, Cp*Me), 1.63 (s, 6H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 186.6 (C(O)CH3), 130.8 (Ph), 129.0 (Ph), 128.3 (Ph), 127.0 (Ph), 98.6 (d, J = 1.5 Hz, C(O)CHC(O)), 93.7 (d, J = 9.1 Hz, Cp*C), 92.5 (d, J = 9.1 Hz, Cp*C), 91.4 (d, J = 9.3 Hz, Cp*C), 29.7 (CH2), 28.4 (d, J = 1.1 Hz, C(O)CH3), 8.9 (Cp*Me), 8.6 (Cp*Me). HRMS/ESI+ (m/z): calcd for C21H26O2Rh, 413.0982; found, 413.0978. Anal. Calcd for C21H26O2RhCl: C, 56.20; H, 5.84. Found: C, 56.50; H, 5.97. Synthesis of 13-Ir. Following the general procedure, [Cp*benzylIrCl2]2 (0.0204 g, 0.0215 mmol) and sodium acetylacetonate (0.0067 g, 0.0465 mmol) were reacted in DCM (10 mL) to give 13-Ir as a yellow solid (0.0208 g, 90%). 1H NMR (400 MHz, CDCl3, δ): 7.32−7.26 (m, 2H, Ph), 7.24−7.19 (m, 1H, Ph), 7.15−7.11 (m, 2H, Ph), 5.24 (s, 1H, C(O)CHC(O)), 3.48 (s, 2H, CH2), 1.96 (s, 6H, C(O)CH3), 1.63 (s, 6H, Cp*Me), 1.61 (s, 6H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 184.9 (C(O)CH3), 137.4 (Ph), 128.8 (Ph), 128.3 (Ph), 126.8 (Ph), 100.3 (C(O)CHC(O)), 85.5 (Cp*C), 83.7 (Cp*C), 82.4 (Cp*C), 30.1 (CH2), 28.1 (C(O)CH3), 9.0 (Cp*Me), 8.8 (Cp*Me). HRMS/ESI+ (m/z): calcd for C21H26O2[193Ir], 503.1557; found, 503.1549. Synthesis of 14-Rh. Following the general procedure, [Cp*phenethylRhCl2]2 (0.0750 g, 0.0939 mmol) and sodium acetylacetonate (0.0289 g, 0.207 mmol) were reacted in acetone (10 mL) and methanol (1 mL) to give 14-Rh as an orange solid (0.0798 g, 92%). 1 H NMR (400 MHz, CDCl3, δ): 7.29−7.26 (m, 1H, Ph), 7.25−7.21 (m, 2H, Ph), 7.09−7.06 (m, 2H, Ph), 5.08 (s, 1H, C(O)CHC(O)), 2.77 (t, J = 7.4 Hz, 2H, CpCH2CH2Ph), 2.51 (t, J = 7.5 Hz, 2H, CpCH2CH2Ph), 1.98 (s, 6H, C(O)CH3), 1.61 (s, 6H, Cp*Me), 1.43 (s, 6H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 186.5 (C(O)CH3), 140.2 (Ph), 128.7 (Ph), 126.6 (Ph), 98.5 (d, J = 1.2 Hz, C(O) CHC(O)), 93.9 (d, J = 9.2 Hz, Cp*C), 92.0 (d, J = 9.5 Hz, Cp*C), 91.6 (d, J = 9.9 Hz, Cp*C), 34.0 (CH2CH2Ph), 28.3 (C(O)CH3), 26.0 (CH2CH2Ph), 8.6 (Cp*Me), 8.3 (Cp*Me). HRMS/ESI+ (m/z): calcd for C22H28O2Rh, 427.1139; found, 427.1136. Anal. Calcd for C22H28O2RhCl: C, 57.09; H, 6.10. Found: C, 56.83; H, 6.09. Synthesis of 14-Ir. Following the general procedure, [Cp*phenethylIrCl2]2 (0.0750 g, 0.0768 mmol) and sodium acetylacetonate (0.0220 g, 0.157 mmol) were reacted in acetone (15 mL) to give 14-Ir as a yellow solid (0.0542 g, 93%). 1H NMR (400 MHz, CDCl3, δ): 7.30−7.26 (m, 1H, Ph), 7.26−7.19 (m, 2H, Ph), 7.12−7.07 (m, 2H, Ph), 5.19 (s, 1H, C(O)CHC(O)), 2.77 (t, J = 7.5 Hz, 2H, CpCH2CH2Ph), 2.38 (t, J = 7.6 Hz, 2H, CpCH2CH2Ph), 1.91 (s, 6H, C(O)CH3), 1.59 (s, 6H, Cp*Me), 1.43 (s, 6H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 184.8 (C(O)CH3), 140.7 (Ph), 128.7 (Ph), 128.6 (Ph), 100.2 (C(O)CHC(O)), 85.7 (Cp*C), 83.1 (Cp*C), 82.6 (Cp*C), 34.3 (CH2CH2Ph), 28.1 (C(O)CH3), 26.3 (CH2CH2Ph), 8.8 (Cp*Me), 8.4 (Cp*Me). HRMS/ESI+ (m/z): calcd for C22H28O2[193Ir], 517.1713; found, 517.1719. Anal. Calcd for C22H28O2[193Ir]Cl.C3H6O: C, 49.21; H, 5.62. Found: C, 49.44; H, 5.58. General Synthesis of (Cp*R)M(dppm, pva, dpvm)Cl Compounds. A round-bottom flask was charged with appropriate amounts of [Cp*RMCl2]2 (M = Rh, Ir), β-diketone, and Na2CO3 in acetone or dichloromethane (10 mL). The solution was stirred magnetically for 30 min to 2 h while the color changed from red to clear orange (M = Rh) or from orange to clear yellow (M = Ir). The solvent was then removed under reduced pressure and the residue taken up in minimal DCM and then filtered. The solvent was then removed via reduced pressure to give a red, orange, or yellow crystalline solid or oil. Synthesis of 15-Rh. Following the general procedure, [Cp*RhCl2]2 (0.102 g, 0.166 mmol), 3,5-heptanedione (0.0450 mL, 0.331 mmol), and Na2CO3 (0.0421 g, 0.339 mmol) were reacted in acetone (15 mL) F


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Organometallics in acetone (15 mL) to give 18-Ir as a yellow solid (0.0668 g, 97%). 1H NMR (400 MHz, CDCl3, δ): 5.37 (s, 1H, C(O)CHC(O)), 1.60 (s, 15H, Cp*Me), 1.13 (s, 18H, C(O)C(CH3)3). 13C NMR (101 MHz, CDCl3, δ): 193.9 (C(O)), 90.1 C(O)CHC(O)), 83.0 (Cp*C), 40.8 (C(CH3)3), 28.5 (C(O)CH3), 8.8 (Cp*Me). HRMS/ESI+ (m/z): calcd for C21H34O2[193Ir], 511.2183; found, 511.2173. Anal. Calcd for C21H34O2[193Ir]Cl: C, 46.18; H, 6.27. Found: C, 46.47; H, 6.24. General Synthesis of (Cp*R)M(bza, dbzm)Cl Compounds. A round-bottom flask was charged with appropriate amounts of [Cp*RMCl2]2 (M = Rh, Ir), β-diketone, and Na2CO3 in an acetone/ methanol mixture or dichloromethane (10 mL). The solution was stirred magnetically for 30 min to 2 h while the color changed from red to clear orange (M = Rh) or from orange to clear yellow (M = Ir). The solvent was then removed under reduced pressure and the residue taken up in minimal DCM and then filtered. Cold diethyl ether was added and the resulting red, orange, or yellow precipitate collected. Synthesis of 19-Rh. Following the general procedure, [Cp*RhCl2]2 (0.0600 g, 0.0971 mmol), 1-phenyl-1,3-butanedione (0.0323 g, 0.199 mmol), and Na2CO3 (0.0265 g, 0.214 mmol) were reacted in acetone (10 mL) and methanol (1 mL) to give 19-Rh as a red-orange solid (0.0480 g, 57%). 1H NMR (400 MHz, CDCl3, δ): 7.90−7.85 (m, 2H, phenyl), 7.43−7.37 (m, 1H, phenyl), 7.37−7.31 (m, 2H, phenyl), 5.77 (s, 1H, C(O)CHC(O)), 2.14 (s, 3H, C(O)CH3), 1.67 (s, 15H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 188.5 (C(O)CH3), 179.5 (C(O)Ph), 139.4 (d, J = 1.2 Hz, Ph), 130.7 (Ph), 128.1 (Ph), 127.4 (Ph), 95.6 (d, J = 1.5 Hz, C(O)CHC(O)), 92.2 (d, J = 9.3 Hz, Cp*C), 29.1 (d, J = 0.9 Hz, C(O)CH3), 8.7 (Cp*Me). HRMS/ESI+ (m/z): calcd for C20H24O2Rh, 399.0826; found, 399.0824. Synthesis of 19-Ir. Following the general procedure, [Cp*IrCl2]2 (0.0750 g, 0.0942 mmol), 1-phenyl-1,3-butanedione (0.0313 g, 0.193 mmol), and Na2CO3 (0.0257 g, 0.2073 mmol) were reacted in acetone (12 mL) and methanol (2 mL) to give 19-Ir as a yellow powder (0.0637 g, 65%). 1H NMR (400 MHz, CDCl3, δ): 7.91−7.85 (m, 2H, phenyl), 7.47−7.41 (m, 1H, phenyl), 7.38−7.31 (m, 2H, phenyl), 5.88 (s, 1H, C(O)CHC(O)), 2.07 (s, 3H, C(O)CH3), 1.65 (s, 15H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 186.6 (C(O)CH3), 177.4 (C(O)Ph), 139.0 (Ph), 130.8 (Ph), 128.3 (Ph), 127.2 (Ph), 97.3 (C(O)CHC(O)), 83.7 (Cp*C), 28.9 (C(O)CH3), 8.9 (Cp*Me). HRMS/ESI+ (m/z): calcd for C20H24O2[193Ir], 489.1406; found, 489.1414. Anal. Calcd for C20H24O2[193Ir]Cl: C, 45.82; H, 4.62. Found: C, 45.90; H, 4.54. Synthesis of 20-Ir. Following the general procedure, [(Cp*i‑propyl)IrCl2]2 (0.0506 g, 0.0593 mmol), 1-phenyl-1,3-butanedione (0.0204 g, 0.1258 mmol), and Na2CO3 (0.0202 g, 0.1629 mmol) were reacted in DCM to give 20-Ir (0.0535 g, 82.7%). 1H NMR (400 MHz, CDCl3, δ): 7.88−7.83 (m, 2H, Ph), 7.47−7.40 (m, 1H, Ph), 7.38−7.30 (m, 2H, Ph), 5.91 (s, 1H, C(O)CHC(O)), 2.56 (hept, J = 7.1 Hz, 1H, CpCH(CH3)2), 2.06 (s, 3H, C(O)CH3), 1.71 (s, 3H, Cp*Me), 1.68 (s, 6H, Cp*Me), 1.67 (s, 3H, Cp*Me), 1.30 (d, J = 7.1 Hz, 3H, CpCH(CH3)2), 1.29 (d, J = 7.1 Hz, 3H, CpCH(CH3)2). 13C NMR (101 MHz, CDCl3, δ): 186.4 (C(O)CH3), 177.3 (C(O)Ph), 139.0 (Ph), 130.8 (Ph), 128.3 (Ph), 127.2 (Ph), 97.4 (C(O)CHC(O)), 89.0 (Cp*C), 88.9 (Cp*C), 84.4 (Cp*C), 82.4 (Cp*C), 82.37 (Cp*C), 28.8 (C(O)CH3), 25.3 (CpCH(CH3)2), 21.14 (CpCH(CH3)2), 21.09 (CpCH(CH3)2), 9.4 (Cp*Me), 9.3 (Cp*Me), 9.12 (Cp*Me), 9.11 (Cp*Me). HRMS/ESI+ (m/z): calcd for C22H28O2[193Ir], 517.1713; found,517.1710. Synthesis of 21-Rh. Following the general procedure, [Cp*phenylRhCl2]2 (0.0609 g, 0.0821 mmol), 1-phenyl-1,3-butanedione (0.0273 g, 0.168 mmol), and Na2CO3 (0.0224 g, 0.181 mmol) were reacted in acetone (10 mL) and methanol (1 mL) to give 21-Rh as an orange solid (0.0497 g, 60%). 1H NMR (400 MHz, CDCl3, δ): 7.86− 7.81 (m, 2H, Ph), 7.57−7.52 (m, 2H, Ph), 7.42−7.29 (m, 6H, Ph), 5.83 (s, 1H, C(O)CHC(O)), 2.15 (s, 3H, C(O)CH3), 1.81 (s, 6H, Cp*Me), 1.67 (s, 3H, Cp*Me), 1.62 (s, 3H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 188.5 (C(O)CH3), 179.5 (C(O)Ph), 139.3 (Cp*Ph), 130.8 (Cp*Ph), 130.2 (acac Ph), 129.7 (acac Ph), 128.8 (acac Ph), 128.7 (acac Ph), 128.1 (Cp*Ph), 127.4 (Cp*Ph), 98.7 (d, J = 8.8 Hz, Cp*C), 98.2 (d, J = 8.8 Hz, Cp*C), 95.9 (d, J = 1.4 Hz, C(O)CHC(O)), 91.6 (d, J = 9.2 Hz, Cp*C), 90.69 (d, J = 9.0 Hz,

Cp*C), 90.5 (d, J = 10.3 Hz, Cp*C), 29.1 (d, J = 1.0 Hz, C(O)CH3), 9.4 (Cp*Me), 9.3 (Cp*Me), 9.1 (Cp*Me). HRMS/ESI+ (m/z): calcd for C25H26O2Rh, 461.0982; found, 461.0999. Anal. Calcd for C25H26O2RhCl: C, 60.44; H, 5.27. Found: C, 60.51; H, 5.29. Synthesis of 22-Rh. Following the general procedure, [Cp*benzylRhCl2]2 (0.0655 g, 0.0820 mmol), 1-phenyl-1,3-butanedione (0.0273 g, 0.168 mmol), and Na2CO3 (0.0224 g, 0.181 mmol) were reacted in acetone (10 mL) and methanol (1 mL) to give 22-Rh as an orange solid (0.0689 g, 79%). 1H NMR (400 MHz, CDCl3, δ): 7.92− 7.87 (m, 2H, bz), 7.45−7.34 (m, 3H, bz), 7.32−7.27 (m, 2H, Ph), 7.28−7.19 (m, 1H, Ph), 7.16−7.11 (m, 2H, Ph), 5.82 (s, 1H, C(O)CHC(O)), 3.68 (s, 2H, CH2), 2.18 (s, 3H, C(O)CH3), 1.719 (s, 3H, Cp*Me), 1.718 (s, 3H, Cp*Me), 1.70 (s, 3H, Cp*Me), 1.69 (s, 3H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 188.6 (C(O)CH3), 179.6 (C(O)Ph) 139.3 (Ph) 136.7 (bz) 130.8 (Ph), 129.0 (bz), 128.3 (bz), 128.1 (Ph), 127.4 (Ph) 127.0 (bz) 95.8 (d, J = 1.2 Hz, (C(O) CHC(O)), 98.2 (d, J = 8.8 Hz, Cp*C), 91.0 (d, J = 9.0 Hz, Cp*C), 90.2 (d, J = 9.9 Hz, Cp*C), 29.8 (CH2) 29.2 (d, J = 1.0 Hz, C(O) CH3), 9.1 (Cp*Me), 9.0 (Cp*Me), 8.8 (Cp*Me), 8.7 (Cp*Me). HRMS/ESI+ (m/z): calcd for C26H28O2Rh, 475.1139; found, 475.1130. Anal. Calcd for C26H28O2RhCl: C, 61.13; H, 5.52. Found: C, 61.20; H, 5.59. Synthesis of 23-Rh. Following the general procedure, [Cp*phenethylRhCl2]2 (0.0604 g, 0.0751 mmol), 1-phenyl-1,3-butanedione (0.0299 g, 0.1767 mmol), and Na2CO3 (0.0245 g, 0.1976 mmol) were reacted in acetone (10 mL) and methanol (1 mL) to give 23-Rh as an orange solid (0.0387 g, 48.7%). 1H NMR (400 MHz, CDCl3, δ): 7.87−7.82 (m, 2H, Cp*Ph), 7.42−7.37 (m, 1H, Cp*Ph), 7.36−7.30 (m, 2H, Cp*Ph), 7.30−7.26 (m, 1H, Ph), 7.26−7.18 (m, 2H, Ph), 7.09−7.06 (m, 2H, Ph), 5.76 (s, 1H, C(O)CHC(O)), 2.80 (t, J = 7.4 Hz, 2H, CH2CH2Ph), 2.57 (t, J = 7.4 Hz, 2H, CH2CH2Ph), 2.12 (s, 3H, C(O)CH3), 1.663 (s, 3H, Cp*Me), 1.660 (s, 3H, Cp*Me), 1.483 (s, 3H, Cp*Me), 1.480 (s, 3H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 188.5 (C(O)CH3), 179.4 (C(O)Ph) 140.2 (Ph), 139.3 (Cp*Ph), 130.67 (Cp*Ph), 128.72 (acac Ph), 128.70 (acac Ph), 128.1 (Cp*Ph), 127.4 (Cp*Ph), 126.7 (acac Ph), 95.7 (d, J = 1.2 Hz, (C(O)CHC(O)) 94.2 (d, J = 9.3 Hz, Cp*C), 94.1 (d, J = 9.1 Hz, Cp*C), 92.2 (d, J = 9.1 Hz, Cp*C), 92.1 (d, J = 9.1 Hz, Cp*C), 91.8 (d, J = 9.6 Hz, Cp*C), 34.0 (CH2CH2Ph), 29.1 (C(O)CH3), 26.1 (CH2CH2Ph), 8.73 (Cp*Me), 8.71 (Cp*Me), 8.4 (Cp*Me). HRMS/ESI+ (m/z): calcd for C27H30O2Rh, 489.1295; found, 489.1307. Anal. Calcd for C27H30O2RhCl: C, 61.78; H, 5.76. Found: C, 61.94; H, 5.83. Synthesis of 24-Rh. Following the general procedure, [Cp*RhCl2]2 (0.0420 g, 0.0680 mmol), 1,3-diphenyl-1,3-propanedione (0.0335 g, 0.150 mmol), and Na2CO3 (0.185 g 0.150 mmol) were reacted in acetone (5 mL) and methanol (5 mL) to give 24-Rh as a red solid (0.0553 g, 82%). 1H NMR (400 MHz, CDCl3, δ): 7.99−7.92 (m, 4H, phenyl), 7.46−7.33 (m, 6H, phenyl), 6.44 (s, 1H, C(O)CHC(O)), 1.71 (s, 15H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 181.5 (C(O)Ph), 139.9 (Ph), 130.9 (Ph), 128.2 (Ph), 127.5 (Ph), 93.2 (C(O)CHC(O)), 92.4 (d, J = 9.1 Hz, Cp*C), 8.8 (Cp*Me). HRMS/ ESI+ (m/z): calcd for C25H26O2Rh, 461.0982; found, 461.0992. Anal. Calcd for C25H26O2RhCl: C, 60.44; H, 5.27. Found: C, 60.15; H, 5.40. Synthesis of 24-Ir. Following the general procedure, [Cp*IrCl2]2 (0.0512 g, 0.0643 mmol), 1,3-diphenyl-1,3-propanedione (0.0313 g, 0.1396 mmol), and Na2CO3 (0.0200 g, 0.1613 mmol) were reacted in acetone (5 mL) and methanol (1 mL) to give 24-Ir as a gold colored solid (0.0538 g, 71.45%). 1H NMR (400 MHz, CDCl3, δ): 7.97−7.93 (m, 4H, phenyl), 7.49−7.43 (m, 2H, phenyl), 7.40−7.34 (m, 4H, phenyl), 6.53 (s, 1H, C(O)CHC(O)), 1.69 (s, 15H, Cp*Me). 13C NMR (101 MHz, CDCl3, δ): 179.2 (C(O)Ph), 139.5 (Ph), 131.0 (Ph), 128.4 (Ph), 127.3 (Ph), 94.7 (C(O)CHC(O)), 83.9 (Cp*C), 9.0 (Cp*Me). HRMS/ESI+ (m/z): calcd for C25H26O2[193Ir], 551.1557; found, 551.1557. Anal. Calcd for C25H26O2[193Ir]Cl: C, 51.23; H, 4.47. Found: C, 51.51; H, 4.47. Biological Testing. MICs were measured by a broth microdilution of fresh overnight cultures of Staphylococcus aureus, Mycobacterium smegmatis, Candida albicans, Aspergillus niger, Escherichia coli, and Pseudomonas aeruginosa according to the Clinical and Laboratory Standards Instutute (CCLI) guidelines with 10% brain heart infusion G


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Organometallics

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broth (BHIB) containing 0.1% dimethyl sulfoxide at an inoculum of 105 CFU mL−1.41 Samples were likewise dissolved in 10% BHIB containing 0.1% dimethyl sulfoxide and inoculated with 50 μL of a 1000-fold dilution of each mid log-phase microbial culture and then subjected to a 2-fold dilution series in 96-well microtiter plates before incubation at 30 or 37 °C. After 3 days, the MIC (μg mL−1), defined to be the lowest concentration of compound completely inhibiting the appearance of turbidity by eye, was determined and confirmed by absorbance at 540 nm. Control wells containing 50 μL of a 1000-fold dilution of each mid log-phase microbial culture were inoculated with 10% BHIB containing 0.1% dimethyl sulfoxide to confirm that 0.1% DMSO alone does not inhibit growth. For Table 2, the units of μg mL−1 were converted to μM.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.7b00742. NMR spectra are reported for all compounds listed in this paper as well as thermal ellipsoid plots for all compounds characterized by single-crystal X-ray crystallography (PDF) Accession Codes

CCDC 1577420−1577436 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*J.S.M.: e-mail, [email protected]; tel, +1 (540)231-4510. ORCID

Christine M. DuChane: 0000-0001-9575-3424 Loren C. Brown: 0000-0001-7346-7339 Joseph S. Merola: 0000-0002-1743-1777 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors thank Dr. Joseph O. Falkinham, III, and Myra Williams for testing the antimicrobial activity of the various metal complexes, Dr. Carla Slebodnick for her assistance with several crystal structures, and Emily Ressegue for assistance in synthesizing ligands. We also thank the Virginia Tech Department of Chemistry for funds and supplies and the Hamilton Company for a generous syringe grant.

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REFERENCES

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