Design and synthesis of potent and selective pyridazin-4(1H)-one-based PDE10A inhibitors interacting with Tyr683 in the PDE10A selectivity pocket

Utilizing structure-based drug design techniques, we designed and synthesized phosphodiesterase 10A (PDE10A) inhibitors based on pyridazin-4(1H)-one. These compounds can interact with Tyr683 in the PDE10A selectivity pocket. Pyridazin-4(1H)-one derivative 1 was linked with a benzimidazole group through an alkyl spacer to interact with the OH of Tyr683 and fill the PDE10A selectivity pocket. After optimizing the linker length, we identified 1-(cyclopropylmethyl)-5-[3-(1-methyl-1H-benzimidazol-2-yl)propoxy]-3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one (16f) as having highly potent PDE10A inhibitory activity (IC₅₀ = 0.76 nM) and perfect selectivity against other PDEs (>13,000-fold, IC₅₀ = >10,000 nM). The crystal structure of 16f bound to PDE10A revealed that the benzimidazole moiety was located deep within the PDE10A selectivity pocket and interacted with Tyr683. Additionally, a bidentate interaction existed between the 5-alkoxypyridazin-4(1H)-one moiety and the conserved Gln716 present in all PDEs.     

Coumarin-thiazole and -oxadiazole derivatives: Synthesis,bioactivity and docking studies for aldose/aldehyde reductase inhibitors

In continuation of our previous efforts directed towards the development of potent and selective inhibitors of aldose reductase (ALR2), and to control the diabetes mellitus (DM), a chronic metabolic disease, we synthesized novel coumarin-thiazole 6(a–o) and coumarin-oxadiazole 11(a–h) hybrids and screened for their inhibitory activity against aldose reductase (ALR2), for the selectivity against aldehyde reductase (ALR1). Compounds were also screened against ALR1. Among the newly designed compounds, 6c, 11d, and 11g were selective inhibitors of ALR2. Whereas, (E)-3-(2-(2-(2-bromobenzylidene)hydrazinyl)thiazol-4-yl)-2H-chromen-2-one 6c yielded the lowest IC₅₀ value of 0.16 ± 0.06 μM for ALR2. Moreover, compounds (E)-3-(2-(2-benzylidenehydrazinyl)thiazol-4-yl)-2H-chromen-2-one (6a; IC₅₀ = 2.94 ± 1.23 μM for ARL1 and 0.12 ± 0.05 μM for ARL2) and (E)-3-(2-(2-(1-(4-bromophenyl)ethylidene)hydrazinyl)thiazol-4-yl)-2H-chromen-2-one (6e; IC₅₀ = 1.71 ± 0.01 μM for ARL1 and 0.11 ± 0.001 μM for ARL2) were confirmed as dual inhibitors. Furthermore, compounds 6i, 6k, 6m, and 11b were found to be selective inhibitors for ALR1, among which (E)-3-(2-(2-((2-amino-4-chlorophenyl)(phenyl)methylene)hydrazinyl)thiazol-4-yl)-2H-chromen-2-one (6m) was most potent (IC₅₀ = 0.459 ± 0.001 μM). Docking studies performed using X-ray structures of ALR1 and ALR2 with the given synthesized inhibitors showed that coumarinyl thiazole series lacks the carboxylate function that could interact with the anionic binding site being a common ALR1/ALR2 inhibitors trait. Molecular docking study with dual inhibitor 6e also suggested plausible binding modes for the ALR1 and ALR2 enzymes. Hence, the results of this study revealed that coumarinyl thiazole and oxadiazole derivatives could act as potential ALR1/ALR2 inhibitors.     

Identification of novel quinazolin-4(3H)-ones as inhibitors of thermolysin,the prototype of the M4 family of proteinases

A combinatorial series of novel quinazolin-4(3H)-ones were synthesised and their structures were established based on spectroscopic data (IR, NMR, EI-MS, and FAB-MS). The compounds were tested for inhibition of the zinc metalloproteinase thermolysin (TLN) utilizing a chemical array-based approach. Some of the compounds were found to inhibit TLN, with IC₅₀ values ranging from 0.0115 μM (compound 3) to 122,637 μM (compound 29). Compound 3 [3-phenyl-2-(trifluoromethyl) quinazolin-4(3H)-one] (IC₅₀ = 0.0115 μM) and compound 35 [3-(isopropylideneamino)-2,2-dimethyl-2,3-dihydroquinazolin-4 (1H)-one] (IC₅₀ = 0.2477 μM) were found to be the most potent inhibitors.     

Synthesis and evaluation of pharmacological properties of some new xanthone derivatives with piperazine moiety

A series of new xanthone derivatives with piperazine moiety [1–7] was synthesized and evaluated for their pharmacological properties. They were subject to binding assays for α₁ and β₁ adrenergic as well as 5-HT_1A, 5-HT₆ and 5-HT_7b serotoninergic receptors. Five of the tested compounds were also evaluated for their anticonvulsant properties. The compound 3a 3-methoxy-5-{[4-(2-methoxyphenyl)piperazin-1-yl]methyl}-9H-xanthen-9-one hydrochloride exhibited significantly higher affinity for serotoninergic 5-HT_1A receptors (K_i = 24 nM) than other substances. In terms of anticonvulsant activity, 6-methoxy-2-{[4-(benzyl)piperazin-1-yl]methyl}-9H-xanthen-9-one (5) proved best properties. Its ED₅₀ determined in maximal electroshock (MES) seizure assay was 105 mg/kg b.w. (rats, p.o.). Combining of xanthone with piperazine moiety resulted in obtaining of compounds with increased bioavailability after oral administration.     

Construction and functionalization of pyranone ring fused with pyran moiety: Design and synthesis of novel pyrano[4,3-b]pyran-5(4H)-ones as potential inhibitors of sirtuins

Novel pyrano[4,3-b]pyran-5(4H)-one based small molecules were designed as potential inhibitors of sirtuins (i.e., yeast sir2, a homolog of human SIRT1). Elegant synthesis of these compounds was performed via a multi-step sequence consisting of MCR, Sandmeyer type iodination, Sonogashira type coupling followed by iodocyclization and then Pd-mediated various C–C bond forming reactions. The overall strategy involved the construction of a pyran ring followed by the fused pyranone moiety and subsequent functionalization at C-8 position of the resultant core pyrano[4,3-b]pyran-5(4H)-one framework. The crystal structure analysis of a representative iodolactonized product (6d) is presented. Some of the synthesized compounds showed promising inhibitory activities when tested against yeast sir2 in vitro. The compound 6g showed dose dependent inhibition (IC₅₀ = 78.05 μM) of yeast sir2 and good interactions with this protein in silico.     

Synthesis and evaluation of tricyclic derivatives containing a non-aromatic amide as inhibitors of poly(ADP-ribose)polymerase-1 (PARP-1)

Highly potent poly(ADP-ribose)polymerase-1 (PARP-1) inhibitors, including 9-hydroxy-1,2-dihydro-4H-thiopyrano[3,4-c]quinolin-5(6H)-one derivatives with a non-aromatic A-ring, were synthesized. Among the derivatives, 12a showed low nanomolar enzyme and cellular activity (IC₅₀ = 42 nM, ED₅₀ = 220 nM) with good water solubility. Further, 12a exhibited microsomal stability in vitro and brain permeability in vivo.     

Discovery of (1R,6S)-5-[4-(1-cyclobutyl-piperidin-4-yloxy)-phenyl]-3,4-diaza-bicyclo[4.1.0]hept-4-en-2-one (R,S-4a): Histamine H3 receptor inverse agonist demonstrating potent cognitive enhancing and wake promoting activity

A series of fused cyclopropyl-4,5-dihydropyridazin-3-one (3,4-diaza-bicyclo[4.1.0]hept-4-en-2-one) phenoxypiperidine analogs was designed and synthesized, leading to the identification of (1R,6S)-5-[4-(1-cyclobutyl-piperidin-4-yloxy)-phenyl]-3,4-diaza-bicyclo[4.1.0]hept-4-en-2-one (R,S-4a) as a second-generation pyridazin-3-one H₃R antagonist. Compound R,S-4a was a potent H₃R functional antagonist in vivo in the rat dipsogenia model, demonstrated potent wake activity in the rat EEG/EMG model, and enhanced short-term memory in the rat social recognition memory model at doses as low as 0.03–0.3 mg/kg po.     

New monoterpenes from stalks and infructescence of Sibiraea leavigata

Chemical investigation of the ethanol extract of the stalks and infructescence of Sibiraea leavigata led to the isolation of two new monoterpenes named (4R)-2-(2-hydroxy-4-methyl-3-pentenyl)furan-2(5H)-one (1) and (2R,4R)-2-(2-hydroxyethyl)-4-(2-methyl-1-propenyl)furan-5H-2-one (2) along with eight known phenylpropanoids (3–10). Their structures were established on the basis of the interpretation of spectroscopic data and electronic circular dichroism (ECD) calculations. In addition, all of these isolates were evaluated for their cytotoxic activity. The results showed that compound 3 displayed moderate cytotoxicity with IC₅₀ values ranging from 10.8 to 49.2 μg mL⁻¹ against five cell lines. While 1 showed selective promotion effects on proliferation of gastric cancer MGC803 and RSC96 cell lines.     

Design and synthesis of novel chromenone derivatives as interleukin-5 inhibitors

A novel series of chromenone analogs were synthesized and evaluated for their inhibitory activity against interleukin-5. Among them 5-(cyclohexylmethoxy)-3-[3-hydroxy-3-(4-hydroxyphenyl)propyl]-4H-chromen-4-one (9b, 94% inhibition at 30 μM, IC₅₀ = 4.0 μM) and 5-(cyclohexylmethoxy)-3-[3-hydroxy-3-(4-methoxyphenyl)propyl]-4H-chromen-4-one (9c, 94% inhibition at 30 μM, IC₅₀ = 6.5 μM) showed the most potent activity. According to the SAR studies introduction of propanone unit in between chromenone and ring B as in 5-(cyclohexylmethoxy)-3-[3-(4-phenyl)-3-oxopropyl]-4H-chromen-4-ones (8) moderately increased the activity. However, the reduction of these propanones 8 to propanols 9 remarkably enhanced the activity. A small substituent at position 4 of ring B in 9, especially with hydrogen bonding capability, provides favorable contribution. Disappearance of IL-5 inhibitory activity upon saturation of chroman-4-one of 9 to chroman-4-ones 10 proves the critical importance of planar chromen-4-one unit of this scaffold in the IL-5 inhibition.     

New pentafluorophenyl complexes with phosphine-amide ligands

A series of nickel(II) and palladium(II) complexes containing one or two pentafluorophenyl ligands and the phosphino-amides o-Ph₂PC₆H₄CONHR [R = ⁱPr (a), Ph (b)] displaying different coordination modes have been synthesised. The chelating ability of these ligands and the influence of both coligands and the metal centre in their potential hemilabile behaviour have been explored. The crystal structure of (b) has been determined and reveals N–H⋯O intermolecular hydrogen bonding. Bis-pentafluorophenyl derivatives [M(C₆F₅)₂(o-Ph₂PC₆H₄CO-NHR)] [M = Ni; R = ⁱPr (1a); R = Ph (1b); M = Pd; R = ⁱPr (2a); R = Ph (2b)] in which (a) and (b) act as rigid P, O-chelating ligands were readily prepared from the labile precursors cis-[M(C₆F₅)₂(PhCN)₂]. X-ray structures of (1a), (1b) and (2a) have been established, allowing an interesting comparative structural discussion. Dinuclear [{Pd(C₆F₅)(tht)(μ-Cl)}₂] reacted with (a) and (b) yielding the monopentafluorophenyl complexes [Pd(C₆F₅)Cl{PPh₂(C₆H₄–CONH–R)}] (R = ⁱPr (3a), Ph (3b)) that showed a P, O-chelating behaviour of the ligands, confirmed by the crystal structure determination of (3a). New cationic palladium(II) complexes in which (a) and (b) behave as P-monodentate ligands have been synthesised by reacting them with [{Pd(C₆F₅)(tht)(μ-Cl)}₂], stoichiometric Ag(O₃SCF₃) and external chelating reagents such as cod [Pd(C₆F₅)(cod){PPh₂(C₆H₄-CONH-R)}](O₃SCF₃)(R = ⁱPr (4a), Ph (4b)) and 2,2′-bipy [Pd(C₆F₅)(bipy){PPh₂(C₆H₄-CONH-R)}](O₃SCF₃) (R = ⁱPr (5a), Ph (5b)). When chloride abstraction in [{Pd(C₆F₅)(tht)(μ-Cl)}₂] is promoted by means of a dithioanionic salt as dimethyl dithiophospate in the presence of (a) or (b), the corresponding neutral complexes [Pd(C₆F₅){S(S)P(OMe)₂}{PPh₂(C₆H₄-CONH-R)}] (R = ⁱPr (6a), Ph (6b)) were obtained.     

The scope of thallium nitrate oxidative cyclization of chalcones; synthesis and evaluation of isoflavone and aurone analogs for their inhibitory activity against interleukin-5

The oxidative cyclization of 2′-hydroxy-6′-cyclohexylmethoxychalcones 5 using thallium (III) nitrate (TTN) in alcoholic solvents produced isoflavones 2 and (or) aurones 3 depending on the electronic nature of p-substituents on ring B. Chalcones with strong electron donating substituents (OH, OCH₃) were exclusively converted to isoflavones 2. Chalcone with weak electron donating substituents (CH₂CH₃) was transformed into isoflavone 2 and the aurone 3 in approximate ratio 1:1. Chalcones with hydrogen or electron withdrawing substituents (Cl, CHO, COOCH₃, and NO₂) formed aurones 3. Synthesized isoflavones 2 and aurones 3 were evaluated for their inhibitory activity against interleukin-5. Among them, 5-(cyclohexylmethoxy)-3-(3,4,5-trimethoxyphenyl)-4H-chromen-4-one (2h, >100% inhibition at 50 μM, IC₅₀ = 6.1 μM) gave most potent activity. All the aurones 3 were inactive.     

Investigation of 4-amino-5-alkynylpyrimidine-2(1H)-ones as anti-mycobacterial agents

In vitro anti-mycobacterial activities of novel 4-amino-5-alkynylpyrimidine-2(1H)-ones were investigated. 4-Amino-5-heptynylpyrimidine-2(1H)-one (3) and 4-amino-5-(2-phenylethynyl)pyrimidine-2(1H)-one (7) displayed potent in vitro activity against Mycobacterium bovis and Mycobacterium tuberculosis. Compounds 3 and 7 were also assessed for their in vivo activity in BALB/c mice infected with M. tuberculosis (H37Ra). Both compounds showed promising in vivo efficacy at a dose of 25 mg/kg for 2 weeks. Importantly, compounds 3 and 7 interacted synergistically with the front-line anti-tuberculosis drug isoniazid in vitro and in vivo. These results suggest that this class of compounds has strong anti-mycobacterial potential.     

Exploration of the 5-bromopyrimidin-4(3H)-ones as potent inhibitors of PDE5

The substituents both at the 6-position of the 5-bromopyrimidinone ring and at the 5′-position of the phenyl ring of 5-bromopyrimidin-4(3H)-ones were explored. 5-Bromo-6-isopropyl-2-(2-propoxy-phenyl)pyrimidin-4(3H)-one was identified as a new scaffold for potent PDE5 inhibitors. The crystal structures of PDE5/2e and PDE5/10a complexes provided a structural basis for the inhibition of 5-bromopyrimidinones to PDE5. In addition, it was also found that there is a great tolerance for the substitution at the 5′-position of the phenyl ring of 5-bormopyrimidinones and the resulted compound 13a has the highest inhibition activity to PDE5 (IC₅₀, 1.7 nM).     

Expanding the 4,4′-bipyridine ligand: Structural variation in {M(pytpy)2}2+ complexes (pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine,M = Fe,Ni, Ru) and assembly of the hydrogen-bonded,one-dimensional polymer {[Ru(pytpy)(Hpytpy)]}n3n+

The solid state structures of [Ni(1)₂][NO₃]₂ · 2MeOH · 2H₂O, [Fe(1)₂][ClO₄]₂ · 2MeOH · 0.5H₂O, [Ru(1)₂][PF₆]₂ and [Ru(1)₂][PF₆][NO₃] (1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine) are presented and the structural variation observed for the {M(1)₂}²⁺ unit is discussed. Protonation of the pendant pyridine group in [Ru(1)₂]²⁺ leads to the formation of a hydrogen-bonded, one-dimensional polymer [{Ru(1)(H1)}_n]³ⁿ⁺ exemplifed by the solid-state structure of [{Ru(1)(H1)}{Fe(NCS)₆} · 1.25H₂O]_n.     

Synthesis and biological evaluation of novel 2-(substituted phenylaminocarbonylmethylthio)-6-(2,6-dichlorobenzyl)-pyrimidin-4(3H)-ones as potent HIV-1 NNRTIs

A series of novel 2-(phenylaminocarbonylmethylthio)-6-(2,6-dichlorobenzyl)-pyrimidin-4(3H)-ones have been designed and synthesized. All of the new compounds were evaluated for their anti-HIV activities in MT-4 cells. Most of these new compounds showed moderate to potent activities against wild-type HIV-1 with an EC₅₀ ranging from 4.48 μM to 0.18 μM. Among them, 2-[(4-bromophenylamino)carbonylmethylthio]-6-(2,6-dichlorobenzyl)-5-methylpyrimidin-4(3H)-one 4b3 was identified as the most promising compound (EC₅₀ = 0.18 ± 0.06 μM, CC₅₀ >243.56 μM, SI >1326). The structure–activity relationship (SAR) of these new congeners is discussed.     

Development of 2-aryl substituted quinazolin-4(3H)-one,pyrido[4,3-d]pyrimidin-4(3H)-one and pyrido[2,3-d]pyrimidin-4(3H)-one derivatives as microsomal prostaglandin E2 synthase-1 inhibitors

mPGES-1 is inducible terminal synthase acting downstream of COX enzymes in arachidonic acid pathway, regulates the biosynthesis of pro-inflammatory prostaglandin PGE₂. Cardiovascular side effect of coxibs and NSAIDs, selective for COX-2 inhibition, stimulated interest in mPGES-1, a therapeutic target with potential to deliver safe and effective anti-inflammatory drugs. The synthesis and structure activity relationship of a series of compounds from 2-aryl substituted quinazolin-4(3H)-one, pyrido[4,3-d]pyrimidin-4(3H)-one and pyrido[2,3-d]pyrimidin-4(3H)-one scaffolds as mPGES-1 inhibitor are discussed. A set of analogs (28, 48, 49) were identified with <10 nM potencies in the recombinant human mPGES-1 enzyme and in the A549 cellular assays. These analogs were also found to be potent in the human whole blood assay (<400 nM). Furthermore, the representative compound 48 was shown to be selective with other prostanoid synthases and was able to effectively regulate PGE₂ biosynthesis in clinically relevant inflammatory settings, in comparison with celecoxib.     

Mononuclear arene ruthenium complexes containing 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine as chelating ligand: Synthesis and molecular structure

The mononuclear cations of the general formula [(η⁶-arene)RuCl(pdpt)]⁺ (pdpt = 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine; arene = C₆H₆ (1); C₆H₅Me (2); p-PrⁱC₆H₄Me (3); C₆Me₆ (4)) have been synthesised from 5,6-diphenyl-3-(pyridine-2-yl)-1,2,4-triazine (pdpt) and the corresponding chloro complexes [(η⁶-C₆H₆)Ru(μ-Cl)Cl]₂, [(η⁶-C₆H₅Me)Ru(μ-Cl)Cl]₂, [(η⁶p-PrⁱC₆H₄Me)Ru(μ-Cl)Cl]₂ and [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂, respectively. The X-ray crystal structure analyses of [1][PF₆] · (C₆H₆)_2.5 and [2][PF₆] · (CH₃CN)₂ reveal a typical piano-stool geometry around the metal centre and in the crystal packing a complexed networks of intermolecular interactions.     

Novel 3-arylfuran-2(5H)-one-fluoroquinolone hybrid: Design,synthesis and evaluation as antibacterial agent

3-Arylfuran-2(5H)-one, a novel antibacterial pharmacophore targeting tyrosyl-tRNA synthetase (TyrRS), was hybridized with the clinically used fluoroquinolones to give a series of novel multi-target antimicrobial agents. Thus, twenty seven 3-arylfuran-2(5H)-one-fluoroquinolone hybrids were synthesized and evaluated for their antimicrobial activities. Some of the hybrids exhibited merits from both parents, displaying a broad spectrum of activity against resistant strains including both Gram-negative and Gram-positive bacteria. The most potent compound (11) in antibacterial assay shows MIC₅₀ of 0.11 μg/mL against Multiple drug resistant Escherichia coli, being about 51-fold more potent than ciprofloxacin. The enzyme assays reveal that 11 is a potent multi-target inhibitor with IC₅₀ of 1.15 ± 0.07 μM against DNA gyrase and 0.12 ± 0.04 μM against TyrRS, respectively. Its excellent inhibitory activities against isolated enzymes and intact cells strongly suggest that 11 deserves to further research as a novel antibiotic.     

Synthesis and preliminary evaluation of pharmacological properties of some piperazine derivatives of xanthone

A series of 9 piperazine derivatives of xanthone were synthesized and evaluated for cardiovascular activity. The following pharmacological experiments were conducted: the binding affinity for adrenoceptors, the influence on the normal electrocardiogram, the effect on the arterial blood pressure and prophylactic antiarrhythmic activity in adrenaline induced model of arrhythmia (rats, iv). Three compounds revealed nanomolar affinity for α₁-adrenoceptor which was correlated with the strongest cardiovascular (antiarrhythmic and hypotensive) activity in animals’ models. The most promising compound was 4-(3-(4-(2-methoxyphenyl)piperazine-1-yl)propoxy)-9H-xanthen-9-one hydrochloride (12) which revealed antiarrhythmic activity with ED₅₀ value of 0.69 mg/kg in adrenaline induced arrhythmia (rats, iv). Other synthesized xanthone derivatives, that is, (R,S)-4-(2-hydroxy-3-(4-(2-methoxyphenyl)piperazine-1-yl)propoxy)-9H-xanthen-9-one hydrochloride (10) and (R,S)-4-(2-acetoxy-3-(4-(2-methoxyphenyl)piperazine-1-yl)propoxy)-9H-xanthen-9-one hydrochloride (11) also acted as potential antiarrhythmics in adrenaline induced model of arrhythmia in rats after intravenous injection (ED₅₀ = 0.88 mg/kg and 0.89 mg/kg, respectively). These values were lower than values obtained for reference drugs such as propranolol and urapidil, but not carvedilol.Results were quite promising and suggested that in the group of xanthone derivatives new potential antiarrhythmics and hypotensives might be found.     

Metal-assisted preparation of the alkenyl ketone and carbonyl complexes from 1-alkyne and H2O: C–C triple bond cleavage of terminal alkyne

Reactions of Cp*RhCl₂(PPh₃) (1) with 1-alkyne and H₂O in the presence of KPF₆ generated alkenyl ketone complexes [Cp*Rh(CRCHCOCH₂R)(PPh₃)](PF₆) (2) (R = Ph (a), C₆H₄−p-Me (b), C₆H₄-p-COOMe (c), C₆H₄-p-NO₂ (d)). A similar complex [Cp*Rh(CPhCHCOCH₂Ph)(PMePh₂)](PF₆) (2e) was obtained by use of Cp*RhCl₂(PMePh₂). It was revealed by X-ray analyses of 2b, 2c and 2e that the complexes 2 consist of the five-membered ring structures bound by the carbon and oxygen atoms of the alkenyl ketone group. Similar reactions of Cp*IrCl₂(PPh₃) (6) or (C₆Me₆)RuCl₂(PPh₃) (7) proceeded with a cleavage of C–C triple bond of 1-alkyne without formation of an alkenyl ketone complex, affording the corresponding carbonyl complexes, [Cp*IrCl(PPh₃)(CO)](PF₆) (8) or [(C₆Me₆)RuCl(PPh₃)(CO)](PF₆) (9). The diphosphine complexes [(Cp*MCl₂)₂{μ-diphos}] (4: M = Rh, diphos = dppm,; 12a: M = Ir, diphos = dppm; 12b: M = Ir, diphos = dppb) gave a Cl-bridged rhodium complex [{Cp*Rh(μ-Cl)}₂{μ-dppm}](PF₆)₂ (5), mono-carbonyl or dicarbonyl iridium complexes,[(Cp*IrCl₂){μ-dppm}{Cp*IrCl(CO)}](PF₆)(13a) or [{Cp*IrCl(CO)}₂{μ-dppb}](PF₆)₂ (14b), respectively.