A Reactive Ru–Binaphtholate Building Block with Self-Tuning Hapticity

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  A Reactive Ru–Binaphtholate Building Block with Self-Tuning Hapticity
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  Published:  August 15, 2011 r 2011 American Chemical Society  14054  dx.doi.org/10.1021/ja204767a |  J. Am. Chem. Soc.  2011, 133, 14054 – 14062 ARTICLEpubs.acs.org/JACS A Reactive Ru  Binaphtholate Building Block withSelf-Tuning Hapticity  Johanna M. Blacquiere, Carolyn S. Higman, Robert McDonald, † and Deryn E. Fogg* Center for Catalysis Research & Innovation and Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N6N5, Canada b S  Supporting Information ’ INTRODUCTION The deployment of asymmetric catalysis in pharmaceutical andagrochemicals manufacturing 1,2  will undoubtedly see further ex-pansion with massive projected increases in the global consumerpopulation,coupledwithincreasingpressureonfeedstocks.Amongthe  “ privileged ”  chiral auxiliaries 3 central to current asymmetriccatalytic processes, the atropisomeric 1,1 0 -binaphthyl moiety standsout for its ubiquity and importance as a stereogenic element within both binaphtholates and their neutral derivatives (e.g.,BINAP, the phosphoramidites, and MOP ligands). The parent1,1 0 -binaphtholate (BINO) ligand and its 3,3 0 -functionalizedderivatives have themselves been exploited in transformationsranging from conjugate addition, vinylation, and alkynylation of C d Efunctionalities(E=O,N)toFriedel  Craftsalkylationandhydroaminoalkylation, hydroamination/cyclization, and C  Ccouplingofole fi ns,including cycloadditionandole fi n metathesisreactions. 4  6 Prominent in much of this chemistry is the hard Lewis acidcharacter of the catalysts, a re fl ection of the dominance of early and mid-transition elements, the lanthanides, and main groupmetals. Soft Lewis acids based on BINO complexes of the latetransition metals have the potential to further expand this richarea of opportunity. Advances in group 10-BINO chemistry,particularly by the Gagn  e group, are notable in this context. 7,8 Despite the enormous scope of ruthenium catalysis, 9,10 however,Ru derivatives are very recent. The  fi rst example, 18-electronRu(( R  )-BINO)(  p -cymene)  1  , was reported by Yao, Li, and co- workers in 2008, 11  while our group recently described Ru  BINOcatalystsrelevanttoasymmetricole fi nmetathesis( 2  , 3 ;Chart1). 12 Both 1 and 2 exhibitmultidentatechelationoftheBINOligand,inpreferencetothe O  , O 0 -bindingprevalentinharder,moreoxophilicmetals (see also  4  ,  5 ; Chart 1).The present work began with the search for a Ru  BINO building block that might retain the versatility of the importantprecursorcomplexRuCl 2 (PPh 3 ) 3 6a (oneofthemostwidelyusedstarting materials in ruthenium chemistry) 13  within atropisomericRu   binaphtholate complexes. One aspect of this versatility arisesfrom the capacity of   6a  to undergo  partial  functionalization orligand exchange, with retention of a stabilizing phosphine groupas required. An open question at the outset was whether reactionof   6a  with BINO would terminate at a very stable piano-stoolcomplex, as found on treating RuHCl(PPh 3 ) 3  6b  with the BINOderivative BINOP (see 5  ,Chart1), 14,15 or whetherreactive, coordi-natively unsaturated structures might be attainable. Here, wereport the successful synthesis of Ru(( S )-BINO)(PPh 3 ) 2  7  , as amixture of isomers in which the BINO ligand is bound via oxygenand an  η 3 - CCO  enolate moiety, or via a bis  enolate interaction; we describe the sensitive response of the BINO binding mode tothe coordination environment at the metal, and the resultingcapacity of   7 to support both exchange of the ancillary ligands andinstallationofadditionalreactivefunctionalitiesatthemetalcenter. ’ RESULTS AND DISCUSSION InstallationoftheBINO ligand ontherutheniumframeworkof  6a  proceeds in high yield at ambient temperature. Thus, additionofTl 2 (( S )-BINO) 16 toapurplesuspensionof  6a in THFat24  Ccaused an immediate color change to pink and deposition of TlCl. Formation of Ru(( S )-BINO)(PPh 3 ) 2  7  (Scheme 1a) was Received:  May 24, 2011  ABSTRACT:  A versatile Ru  BINO building block is reported, which o ff  ers a straightforward entry pointinto the chemistry of atropisomeric binaphtholate complexes of ruthenium. Reaction of RuCl 2 (PPh 3 ) 3  6a  with Tl 2 (( S )-BINO) a ff  ords Ru(( S )-BINO)(PPh 3 ) 2  7  as a mixture of isomers: in  7 0  , the BINO ligand is bound via  η 3 - CCO  , η 1 - O 0 donors, and in symmetrical  7 00  , via  η 3 - CCO  , η 3 - O 0 C  0 C  0 interactions. The bis(enolate) BINO bonding mode in the latter, not previously observed for any metal, underscores theremarkable geometric and electronic  fl exibility of the binaphtholate moiety. The BINO ligand proves able to stabilize complexescontainingas fewas two,and asmany asfour, additional ligands in 7 andits derivatives, enabling asynthetic versatility thatcontrasts with that of the super fi cially similar  o -catecholate complex Ru( o -cat)(PPh 3 ) 3 . As with the important achiral Ru precursor  6a  ,complex   7  undergoes facile transformation into a range of products under mild conditions, including acetonitrile, pyridine, and vinylidene derivatives. Single-crystal X-ray structures are reported for three of these complexes: Ru( η 3  , η 3 -( S )-BINO)(PPh 3 ) 2  7 00  ,Ru( η 3  , η 1 -( S )-BINO)(PPh 3 ) 2 (MeCN)  9  , and Ru( η 3  , η 1 -( S )-BINO)(PPh 3 )(py) 2  11 .  13 C { 1 H }  NMR signatures are proposed fornew and known BINO coordination modes ( η 1 - O  , η 1 - O 0 ;  η 1 - C1  , η 1 - O 0 ;  η 3 - CCO  , η 3 - O 0 C  0 C  0 ;  η 3 - CCO  , η 1 - O 0 ;  η 6 - C  6   , η 1 - O 0 ), as apotential aid to further developments in late-metal BINO chemistry.  14055  dx.doi.org/10.1021/ja204767a |  J. Am. Chem. Soc.  2011, 133,  14054–14062 Journal of the American Chemical Society ARTICLE quantitative within 1 h: this product was isolated in 82% yield by  fi ltration and reprecipitation from THF/hexanes. Charge-trans-fer MALDI-TOF MS 17 (Figure 1) and combustion analysis of  7  are consistent with the proposed formulation. In comparison,the corresponding reaction of   6a  with catecholate 18 terminatesin tris-phosphine complex   8  (Scheme 1b). The di ff  erence incoordination mode and number is an early indicator of thestructural and electronic versatility that proves a hallmark of theBINO ligand in this chemistry. 31 P { 1 H }  NMR analysisof   7 reveals a 1:4 mixture of isomers inCD 2 Cl 2  at room temperature ( 7 0  , 43.5 ppm;  7 00  , 56.9 ppm; bothsinglets). Neither complex exhibits the extremes of BINOcoordination seen in Chart 1: that is, binding through solely the oxygen sites (see  3 ) or via an  η 6 -arene, η 1 - O 0 interactionanalogous to the binding mode present in  5 . 19 Instead, we assignthe minor, higher- fi eld signal to isomer  7 0  , containing anunsymmetrically   η 3  , η 1 -bound BINO ligand, on the basis of itsresolution into an AB pattern at slightly lower temperatures(15   C: 43.7, 43.3 ppm;  2  J  PP  = 19 Hz), as well as detailed 13 C { 1 H }  NMR analysis. NMR signatures associated with thisand other BINO coordination modes are discussed in a subse-quent section. The down fi eld singlet in the  31 P { 1 H }  NMR spectrum (the sole peak observed at 60   C) 20 is due to complex  7 00  , containing a novel,  η 3  , η 3 -BINO binding mode: the nature of this interaction was con fi rmed by X-ray crystallographic(Figure 2a) and  13 C { 1 H }  NMR analysis. At 40   C in C 6 D 6  ,interconversion occurs on the 2.2 s time-scale of the  T  1  for  7 0  , asindicatedbyspinsaturationtransferexperiments( k  exchange =0.29s  1 ),althougharigorouslyquantitativeinterpretationoftherateofchemicalexchange is hampered by the potential for NOE e ff  ects. 21 The parent systems  6  are classic ruthenium precursors for which phosphine dissociation gives entry to a rich catalytic andcoordination chemistry, 13 including high-yield routes to cataly-tically important 9a,c, 10 alkylidene, allenylidene, and vinylidenederivatives. The utility of the catecholate analogue Ru( η 1  , η 1 - O,O 0 -O 2 C 6 H 4 )(PPh 3 ) 3  8  (Scheme 1b) is limited in comparison,this complex resisting, for example, transformation into vinyli-dene or benzylidene derivatives. 18 To examine the in fl uence of the BINO ligand on reactivity, we undertook treatment of   7  withacetonitrile and pyridine, as well as with  tert  -butylacetylene: thecorresponding reactions of   6a  a ff  ord RuCl 2 (PPh 3 ) 2 (L) n  deriva-tives (L = py, MeCN), 22 and vinylidene complex RuCl 2 (PPh 3 ) 2 -( d C d CH t  Bu), 23 respectively. AcetonitrileDerivatives.  AdditionofneatMeCNtosolidpink  7  resulted in immediate formation of an orange suspension, from which Ru( η 3  , η 1 -( S )-BINO)(PPh 3 ) 2 (MeCN)  9  (Scheme 2a) wasisolated as a dark pink solid in ca. 70% yield. Multinuclear NMR analysis in CD 2 Cl 2  confirmed the presence of two, cis-disposedphosphine ligands ( δ P  49.1, 48.3 ppm;  2  J  PP  = 22 Hz), and a singlenitrileligand( δ C 120.3ppm, δ H 1.37ppm).WhileX-rayanalysisof crystals grown from THF  Et 2 O suggests an  η 2 -interaction be-tween the Ru center and the C2  O1 bond (Figure 2b), the 15 HzmagnitudeoftheC1  Pcouplingconstant,aswellasthe 13 CNMR chemical shift data (vide infra), provide convincing evidence for an η 3  , η 1 -BINOstructureinsolution.Thedifferencemayreflectcrystalpacking effects. Addition of CD 3 CN to benzene solutions of   7  improves thesolubility of the products and triggers coordination of a secondacetonitrileligandviaslippagefrom η 3  , η 1 -to η 1  , η 1 -BINObinding.The equivalence of the PPh 3  ligands, which give rise to a well-resolved  31 P { 1 H }  NMR singlet at 45.5 ppm (1:2 CD 3 CN  C 6 D 6 ), is consistent with symmetrical Ru( η 1  , η 1 -( S )-BINO)-(PPh 3 ) 2 (MeCN) 2  10 . This is assigned as the sterically favored trans -PPh 3  isomer, given the absence of   3  J  P  C2  coupling. At-tempts to precipitate  10  yield only   9  , indicating facile exchange between these  fi  ve- and six-coordinate species. Pyridine Derivatives.  Reaction of   7  with pyridine, in contrast,gives bis- and tris-pyridine derivatives Ru( η 3  , η 1 -( S )-BINO)(PPh 3 )-(py) 2  11  and Ru( η 1  , η 1 -( S )-BINO)(PPh 3 )(py) 3  12  , a reflection of the higher donor ability of this ligand, relative to acetonitrile(Gutmann donor number 33.1, vs 14.1 kcal mol  1 ). 24 In neatpyridine- d  5  ,  7  is rapidly and completely converted into orange  12 (Scheme 2b), the  31 P { 1 H }  NMR singlet for the latter (56.0 ppm)integrating 1:1 versus free PPh 3 . Only minor amounts of   12  wereisolated,however,whenthepyridinesolutionwasstrippedofsolvent,subjected to azeotropic removal of free pyridine with hexanes, and Chart 1. Established Coordination Modes for Complexes of BINO and (See 5) BINOP a a BINOP = 1-diphenylphosphino-1,1 0 -binaphthyl-1 0 -olate; IMes =  N   ,  N  0 -bis(mesityl)imidazol-2-ylidene; py=pyridine.Numberingshownforone naphtholate ring; corresponding nuclei on the second bear a primelabel. For simplicity, BINO binding is described in the text using thelabels depicted. Thus,  2  is referred to as an η 3  , η 1 -BINO complex, ratherthan an  η 3 - C   , C   , O -BINO- k O  structure. The asterisk in the label  η 1* indicates the  η 1 - C1  coordination mode in  4 . 7j Scheme 1. Reactions of 6a with (a) Binaphtholate and (b) o -Catecholate Ion Figure1.  Charge-transfer MALDI mass spectrum of  7 (pyrene matrix).Inset: Simulated (top) and observed (bottom) isotope patterns.  14056  dx.doi.org/10.1021/ja204767a |  J. Am. Chem. Soc.  2011, 133,  14054–14062 Journal of the American Chemical Society ARTICLE treated with pentane to precipitate the product. The resultingfine orange suspension consisted principally of   11  (ca. 20%  12 present; 76% total yield). The proportion of  12 decreases furtheron washing the filtrand with pentane.Solutions of the initially obtained crude product in CD 2 Cl 2 exhibitabroad  31 P { 1 H } NMRsingletdueto 11  ,accompaniedby a sharp singlet for  12  (58.3 and 56.1 ppm, respectively; 20%  12 ).The breadth of the signal for  11  we attribute to dynamicaveraging between  η 3 -enolate and  η 1 - O  sites at room tempera-ture, a process observed previously with  1  , 11 and proposed for 4 . 7j  At  20   C, the peak sharpens ( ω 1/2  diminishes from 45 to5 Hz), and the corresponding  13 C { 1 H }  NMR spectrum suggestsan  η 3  , η 1 -BINO structure, in which the PPh 3  ligand lies trans toC1, as judged from the large P  C coupling constant of 19 Hz.Such a bonding mode is indeed evident on X-ray analysis of crystals of   11  that deposited from THF  Et 2 O (Figure 2c). Oncooling the NMR sample further, to   40   C, a new   31 P { 1 H } NMR singlet emerges at 48.3 ppm (ca. 20% of total integration):this may plausibly be due to the reduced-hapticity isomer Ru-( η 1  , η 1 -( S )-BINO)(PPh 3 )(py) 2  , but  13 C { 1 H }  NMR con fi rmationis precluded by the relatively low abundance of this species. Vinylidene Derivative.  A final experiment was directed atexamining the ease of converting  7  into a vinylidene complex.Reaction of   6a  with  tert  -butylacetylene affords RuCl 2 (PPh 3 ) 2 -( d C d CH t  Bu), 23 as noted above, while catecholate complex   8 proved inert to such treatment. 18 Complex   7  , in comparison,underwent an immediate color change from red to dark purple, with quantitative conversion to Ru( η 3  , η 1 -( S )-BINO)(PPh 3 ) 2 -( d C d CH t  Bu) ( 13 ; Scheme 2c). The product was isolated by precipitation from THF  hexanes, albeit in only 40% yield, dueto its high solubility. The structure depicted in Scheme 2c issupported by NMR, IR, and combustion analysis. Retention of two inequivalent phosphine ligands is evident from the AB patternin the  31 P { 1 H }  NMR spectrum (64.4, 38.3 ppm;  2  J  PP  = 27 Hz), while the vinylidene ligand gives rise to a strong, diagnostic infrared ν (C d C) band at 1633 cm  1  , as well as the expected NMR corre-lations between the C H   multiplet at 3.08 ppm and the Ru d C   andC(C H  3 ) 3  signals at 347.2 and 0.72 ppm, respectively ( 1 H  13 CHMBC;  1 H  1 H COSY). A dynamic process operative at roomtemperature obscures the  13 C NMR signals above 135 ppm, andhence unequivocal assignment of the coordination mode, as this istheregionoccupiedbythecriticalC2/C2 0 signals.Low-temperatureanalysis is consistent with an  η 3  , η 1 -BINO coordination mode (seenext section), albeit with significant electronic perturbation at C1,relative to other such complexes. 25 Complex   13  differs from theother examples studied in containing a strongly  π  -acidic vinylideneligand, as discussed below. NMRSignaturesforBINOCoordinationModes. BINO, likeits important derivative BINAP and related ligands, 26 is evidently characterized by great flexibility and variety in its coordination tolate-metal centers. To facilitate future development, we sought toestablish NMR markers for the different BINO coordinationmodes. As the NMR values for the key   13 C nuclei have not beenroutinelyreported,thechemicalshiftrangesproposedbelowmust be regarded as preliminary: whether they indeed correlate directly  with coordination mode will become clearer as the number of crystallographically and spectroscopically characterized examplesexpands, but such a correlation would greatly aid in structuralassignment where X-ray analysis is inconvenient or infeasible. Ingeneral most sensitive to changes in naphtholate binding are thechemical shifts of C2/C2 0 and C1/C1 0 (Figure 3a). 27 The formerappear generally more diagnostic, as discussed below.  13 C { 1 H } NMR signals for these ipso carbons were most readily located via 1 H-detected HMBC experiments; a  “ road map ”  for assignment of these and the remaining BINO carbons is given in the SupportingInformation.For  η 1 - O  , η 1 -O 0 -BINO complexes (e.g.,  3a  ,  3b  ,  10  ,  12 ; Table 1),thearyloxycarbonsC2andC2 0 appearatca.168ppm,andC1/C1 0 atca. 126 ppm. These locations appear relatively insensitive to changesin the NMR solvent (Table 2). For the  η 3 - CCO  ,  η 1 -O 0 - BINOcomplexes (e.g.,  1  ,  2  ,  7 0  ,  9  ,  11 ), the chemical shift for C2 0 in the Figure 2.  Perspective views of (a) Ru( η 3  , η 3 -( S )-BINO)(PPh 3 ) 2  7 00  , (b) Ru( η 3  , η 1 -( S )-BINO)(PPh 3 ) 2 (MeCN)  9  , and (c) Ru( η 3  , η 1 -( S )-BINO)-(PPh 3 )(py) 2  11  , showing the labeling scheme for key atoms. Non-hydrogen atoms are represented by Gaussian ellipsoids at the 50% probability level.Forclarity,hydrogenatomsarenotshown,solvatemoleculespresentfor 9 3 THFand 11 3 Et 2 O 3 0.25THFareomitted,andphosphinephenylgroupsaretruncated to the ipso-carbons. Scheme 2. Reactions of 7 with (a) Acetonitrile, (b) Pyridine,and (c)  tert  -Butylacetylene a a For clarity, exchange reactions between η 3 and η 1 sites in  11  (see text)are omitted.  14057  dx.doi.org/10.1021/ja204767a |  J. Am. Chem. Soc.  2011, 133,  14054–14062 Journal of the American Chemical Society ARTICLE η 1 -bound ring shows minimal change, appearing at ca. 172 ppm.That for C1 0 moves 10 ppm up fi eld, however (to ca. 115 ppm),a re fl ection of the sensitivity of C1 0 to the enolate environmentat the immediately adjacent C1 nucleus. The  η 3 - CCO  carbonsthemselves can exhibit moredramatic up fi eldshifts, dependingontheextentofshieldingbytheelectronscirculatingintheenolate π  -system:anaveragevalueof148ppmisseenforC2and97ppmforC1.Variableback-donationresultsinaratherbroadrangeofvaluesforC2( ( 6ppm)and,especially,C1( ( 12ppm),asshowninblueand red, respectively, in Figure 3a. Omitted from these ranges arethe values for  13  , which is anomalous within this series incontaining a highly   π  -acidic vinylidene ligand (a  π  -acceptorcomparable to CO). 28 This is expected to limit shielding of the η 3 -enolatenuclei:indeedthesignalforC1appearsatca.126ppm,alocationtypicalfor η 1 -boundBINO, althoughC2islessa ff  ected. Within the ranges indicated for the more typical  η 3 -enolatesappear the corresponding signals for both naphtholate rings of the  η 3  , η 3 -BINO complex   7 00 (C2/C2 0  , 145 ppm; C1/C1 0  , 93ppm). 29 For phosphine derivatives,  3  J  CP  splitting of the C1/C1 0 signal(s) is valuable in con fi rming the presence of a directRu  C1 interaction, although the dependence on the dihedralangle means that negative evidence is less reliable.The rarer  η 1 - C1  , η 1 - O 0 coordination mode exhibits a diagnos-ticketonesignalforC2(196ppmforcomplex  4 ), 7g,j althoughthe82 ppm location for C1 is not far from the lower end of the rangefor  η 3  , η 1 -BINO complexes. Finally (and in contrast to theexamples above, all of which can be assigned from the combinedC1/C1 0 and C2/C2 0 chemical shifts), the η 6  , η 1 -binding mode incomplex  5 isdistinguishablefrom η 3  , η 1 -BINObindingonlyoncea ca. 30 ppm up fi eld shift 14 for both C3 and C4 is also taken intoconsideration, as illustrated in Figure 3b. ’ CONCLUSION The BINO ligand o ff  ers a powerful source of chirality that has been exploited with great success in asymmetric catalysis by hardLewis acid   base complexes. Its incorporation into soft late-metalcomplexes, a challenge of sustained interest, is here expanded to a versatile ruthenium   binaphtholate building block. The remark-ablegeometricandelectronic fl exibilityofthebinaphtholateligandis demonstrated by its capacity to coordinate in modes rangingfrom η 1 - O  , η 1 - O 0 to η 1 - O  , η 3 - C  0 C  0 O 0 and, in the extreme, η 3 - CCO  , η 3 - C  0 C  0 O 0  binding, in addition to others previously established. 13 C { 1 H } NMRsignaturesforeachbindingmodearesuggestedonthe basis of current data, as an aid to structural assignment;the small sample sets, however (particularly for the singular  η 3  , η 3 -BINO complex   7 00 ), means that the proposed correlations of BINO coordination modes with chemical shift ranges should be Table 1.  13 C { 1 H }  NMR Ranges Associated with Di ff  erent BINO or (for 5) BINOP Coordination Modes (See Also Figure 3) a , 27 entry coord. mode compd C1 C2 C1 0 C2 0 ref 1  η 1  , η 1 3a  ,  3b  ,  10  ,  12  126  (  2 168  (  4 126  (  2 169  (  1 Table 22  η 3  , η 1 1  ,  2  ,  7 0  ,  9  ,  11  97  (  12 148  (  6 115  (  2 172  (  2 Table 23  η 3  , η 3 7 00 93.2 (t,  2  J  CP  = 4 Hz) 144.7 93.2 (t,  2  J  CP  = 4 Hz) 144.7 this work 4  η 6  , η 1 5 b 83.0 155.6   c  c 145  η 1  , η 1* 4  82.4 195.5 (d, 6 Hz)   c  c 7g,7j a  Valuesatambienttemperature,except 11  12 (20% 12 ;253K,CD 2 Cl 2 ); 13 (213K); 1 (210K).Valuesfor 7 00  , 5  , 4 inCD 2 Cl 2 ;forothers,seeTable2.Valuesfor vinylidene complex   13  are anomalous (see text) and are omitted. Peaks are singlet multiplicity, unless otherwise speci fi ed. (*) indicates the  η 1 - C1 coordination mode in  4 .  b Ranges for C3/C4: 95  97 ppm, versus 124  135 for these resonances in  η 3  , η 1 -BINO complexes.  c  Assignment not reported. Figure 3.  13 C NMR signatures for di ff  erent BINO coordination modes.(a) Chemical shift ranges for C2/C2 0 (blue) and of C1/C1 0 (red), as inTable1;dashedlinescorrespondtothe “ prime ” nuclei. 27 Theasteriskinthelabel η 1 *indicatesthe η 1 - C1 coordinationmodein 4 . 7g,j (b)Supplementary chemical shifts of C3/C4 (black), where assignment on the basis of (a) alone is ambiguous. Table 2.  13 C { 1 H }  NMR Data for Individual Compounds Grouped into Entries 1 and 2 of Table 1 a coord. mode compd solvent C1 C2 C1 0 C2 0 ref  η 1  , η 1 3a  CD 2 Cl 2  124.2 164.0 123.9 170.1 12 3b  CD 2 Cl 2  123.9 164.0 123.9 170.3 12 10  CD 3 CN  C 6 D 6  (1:2) 127.4 168.9 127.4 168.9  b 12  C 5 D 5 N 128.1 171.0 127.8 169.7  b 12  CD 2 Cl 2  not located 169.8 not located 168.7  b η 3  , η 1 1  CD 2 Cl 2  85.0 141.5 114.0 170.9 11 2  CD 2 Cl 2  95.6 (d,  2  J  CP  = 11 Hz) 154.1 (d,  2  J  CP  = 3 Hz) 116.8 174.1 (d,  3  J  CP  = 5 Hz) 12 7 0 CD 2 Cl 2  109.1 (d,  2  J  CP  = 16 Hz) 143.1 114.2 (d,  3  J  CP  = 2 Hz) 170.4 (d,  3  J  CP  = 5 Hz)  b 9  CD 2 Cl 2  106.4 (d,  2  J  CP  = 15 Hz) 143.3 (d,  2  J  CP  = 2 Hz) 115.2 (d,  3  J  CP  = 1 Hz) 172.1 (d,  3  J  CP  = 5 Hz)  b 11  CD 2 Cl 2  97.6 (d,  2  J  CP  = 19 Hz) 143.5 113.8 174.4 (d,  3  J  CP  = 5 Hz)  b 13  CD 2 Cl 2  125.6 (t,  2  J  CP  = 4 Hz) 148.0 (t,  2  J  CP  = 4 Hz) 116.0 162.0  b a For conditions, see footnote to Table 1.  b This work.  14058  dx.doi.org/10.1021/ja204767a |  J. Am. Chem. Soc.  2011, 133,  14054–14062 Journal of the American Chemical Society ARTICLE regarded as preliminary. Importantly, these BINO enolates arelabile; η 3 -coordination provides a source of coordinative stabiliza-tion where required, but does not impede binding of additionalligands at the metal center. Complexes containing as few as two,and as many as four, additional ligands are thus accessible. Thechemistry of Ru(BINO)(PPh 3 ) 2  7  described above aligns well with that of the important, achiral ruthenium precursor RuCl 2 -(PPh 3 ) 3  6a  , and compares favorably with the more circumscribedscopeofitscloserelativeRu( o -cat)(PPh 3 ) 3 .Complex  7 thuso ff  ersapotentiallypowerfulandconveniententrypointintothechemistry of atropisomeric binaphtholate complexes of ruthenium. ’ EXPERIMENTAL SECTION General.  Reactions were carried out at room temperature (24   C)under N 2  using standard Schlenk or glovebox techniques. Dry, oxygen-free solvents were obtained using a Glass Contour solvent purificationsystem and were stored over Linde 4 Å molecular sieves. Pyridine wasdistilled over sodium benzophenone ketyl and was stored over activatedsieves (Linde 4 Å) in an amber bottle in the glovebox. CDCl 3  wasdistilled over CaH 2  and stored over activated sieves (Linde 4 Å). 1,1 0 -Binaphthol (( S )-BINOL; 99% optical purity; Strem) and pyrene,anhydrous CD 2 Cl 2  , and pyridine- d  5  (all Aldrich) were used as received.RuCl 2 (PPh 3 ) 330  wasprepared byliterature methods.NMRspectrawererecordedonBrukerAvance300andAvance500spectrometers,at296K unless otherwise specified. Chemical shifts are reported relative to TMS( 13 C, 1 H)or85%externalH 3 PO 4 ( 31 P)at0ppmandwerereferencedtothe carbon or residual proton signal of the deuterated solvent. Micro-analyses were carried out by Guelph Chemical Laboratories (Guelph,ON) and X-ray analyses by Dr. Robert McDonald of the University of Alberta X-ray Crystallography Laboratory. Charge-transfer (CT)MALDI-TOF mass spectra were collected using a Bruker DaltonicsOmniflex MALDI-TOF mass spectrometer coupled to an MBraunglovebox, as previously described. 17 Synthesis of Tl 2 (( S )-BINO).  Addition of ( S )-BINOL (862 mg,3.01mmol)toastirredsolutionofTlOEt(1.652g,6.628mmol)inEt 2 O(10mL)affordedapaleyellowprecipitate.Thesuspensionwasstirredatroomtemperaturefor15h,afterwhichthesolidwasisolatedbyfiltrationand washing with Et 2 O (2 mL). Yield 87%. Caution: Tl salts are toxic 31 and must be handled using appropriate protection and secondary containment; wastes and contaminated material must be disposed of in accordance with federal regulations. Synthesis of Ru(( S )-BINO)(PPh 3 ) 2  7.  A suspension of Tl 2 (( S )-BINO) (326 mg, 0.470 mmol) and RuCl 2 (PPh 3 ) 3  6a  (450 mg,0.470 mmol) in 12 mL of THF was stirred for 1 h at 24   C, over which time it turned from purple to pink.  31 P { 1 H }  NMR analysisindicated complete reaction. As the suspension was too fine to filteroff, the solvent was stripped off under vacuum. The residue wastaken up in benzene, filtered through Celite, then glass-fiber filterpaper, and the Ru product was washed through with benzene. Thefiltrate was stripped to dryness to give a dark residue, which wasredissolved in THF (ca. 0.5 mL), treated with hexanes (6 mL), andchilled to   35   C. The air-sensitive red-pink product was filteredoff, washed with cold hexanes (3 mL) and cold 3:1 hexanes  Et 2 O(3  1 mL), and then dried. Yield: 351 mg (82%). CT-MALDI MS(pyrene matrix),  m /  z : [ 7 ] + • 910.2 (simulated: 910.2). Anal. Calcdfor C 56 H 42 O 2 P 2 Ru: C, 73.92; H, 4.65. Found: C, 74.23; H, 4.38.The product contained a mixture of   7 00 and  7 0 (ratio 4:1 in CD 2 Cl 2 ),the spectroscopic data for which are separated for convenience below. X-ray quality crystals of   7 00 deposited from THF by vapordiffusion of hexanes at 24   C. NMR signatures for the novel  η 3  , η 3 -BINO coordination mode in  7 00  were established from  1 H  13 CHMBC spectra measured at 60   C, to suppress signals for  7 0 . (Bothisomers are generally present, including at  80  C in C 7 D 8 ; solely   7 00 isobserved in CDCl 3  , but decomposition over the time-scale required for2D NMR analysis prevents characterization in this solvent.) Signals for  7 0  were assigned by spectral subtraction of resonances for  7 00 from the room-temperature spectrum of the two isomers in CD 2 Cl 2 . For the BINOnumberingscheme,seeChart1.ThemajorityoftheBINOsignalsinthese,as well as the other new complexes, could be assigned using the roadmapprovided in the Supporting Information. 32 Ru( η 3 , η 3 -( S )-BINO)(PPh 3 ) 2  7 00 .  31 P { 1 H }  NMR (121.4 MHz,CD 2 Cl 2 ):  δ  56.9 (s), 56.5 ppm in CDCl 3 .  1 H NMR (CD 2 Cl 2  , 500.1MHz):  δ  7.38 (m, 4H,  H5  and  H6  ), 7.34 (d,  3  J  H4H3  = 9.3 Hz, 2H,  H4 ),7.26 (m, 2H,  H7  ), 7.22  7.06 (m, 10H,  Ar  ), 6.91 (overlap; 28H,  Ar  ;includes H8 of  7 00 and H3 0  , H6  0 of  7 0 ),6.44(d, 3  J  H3H4  =9.3Hz,2H, H3 ). 13 C NMR (CD 2 Cl 2  , 125.6 MHz): δ 144.7 (s, C2), 137.8 (s,  C8a ), 137.4(s, C4 ),134.6 (d,  J  CP =10Hz,  Ph ),134.1 (br,  Ph ),133.8(d,  J  CP  =10Hz,  Ph ),132.3(d,  J  CP =10Hz,  Ph ),132.2(d,  J  CP =4Hz,  Ph ),130.9(s, C4a ),130.2 (d,  J  CP  = 1 Hz,  Ph ), 129.4 (s,  C5 ), 129.2 (br,  Ph ), 128.1 (d,  J  CP  =6 Hz,  Ph ), 128.0 (d,  J  CP  = 6 Hz,  Ph ), 127.4 (s,  C7  ), 127.3 (m,  Ph ), 124.9(s,  C8 ), 124.5 (s,  C6  ), 124.3 (s,  C3 ), 93.2 (t,  2  J  C1P  = 4 Hz,  C1 ). Ru( η 3 , η 1 -( S )-BINO)(PPh 3 ) 2  7 0 (20%).  Chemical shifts are givenfor key peaks only; extraction of most multiplicities and integration values was hampered by overlap with the signals due to the majorproduct  7 00 .  31 P { 1 H }  NMR (121.4 MHz, CD 2 Cl 2 ): 43.5 (s). At 288 K:43.7 (d,  2  J  PP  = 19.4 Hz), 43.3 (d,  2  J  PP  = 19.4 Hz).  1 H NMR (CD 2 Cl 2  ,500.1 MHz): δ 8.17(d, 3  J  H4H3  =9Hz, H4 ),7.89(d, 3  J  H5H6 =8Hz, H5 ),7.55 ( H5 0 ), 7.29 ( H3 ), 7.45 ( H4 0 ), 7.27 ( H6  ), 6.88 ( H3 0 ), 6.86 ( H6  0 ),6.70 ( H7   and  H7  0 ), 6.57 ( H8 ), 5.96 (d,  3  J  H8 0 H7 0  = 9 Hz,  H8 0 ).  13 C NMR (CD 2 Cl 2  ,125.6MHz):170.4(d, 3  J  CP =5Hz, C2 0 ),143.1(s,C2),141.3(d, 3  J  CP  = 3 Hz,  C8a ), 135.1 (s,  C4 ), 133.4 (s,  C8a 0 ), 129.6 (s,  C8 ), 128.9(s,  C4 0 ), 128.8 (s,  C4a ), 128.6 (s,  C5 ), 128.2 (s,  C5 0 ), 127.4 (s,  C7  ), 127.2(s, C4a 0 ),124.9(s, C7  0 ),124.6(s, C6  ),124.4(s, C3 ),124.2(s, C8 0 ),123.9(s, C3 0 ),119.8(s, C6  0 ),114.2(d, 3  J  CP =2Hz, C1 0 ),109.1(d, 3  J  CP =16Hz, C1 ). Synthesis of Ru( η 3 , η 1 -( S )-BINO)(PPh 3 ) 2 (MeCN) 9.  Additionof acetonitrile (0.5 mL) to solid  7  (151 mg, 0.166 mmol) resulted in animmediate color change from pink to orange, and complete conversionto  9  ( 31 P { 1 H }  NMR analysis). The suspension was stirred for 5 min,thenstrippedofsolvent,treatedwithcoldhexanes(2mL),andchilledto  35   C. The fine solid was isolated by pipetting off the supernatantand was dried under vacuum. Yield: 120.5 mg (76%). Anal. Calcd forC 58 H 45 NO 2 P 2 Ru: C, 73.25; H, 4.77; N, 1.47. Found: C, 72.97; H, 4.61;N,1.20. Singlecrystals of  9 3 THF depositedfromTHF byvapor diffusionof diethyl ether (Et 2 O) at 24   C. NMR analysis in CD 2 Cl 2  revealed only signals for  9 .  31 P { 1 H }  NMR (CD 2 Cl 2  , 121.4 MHz):  δ  49.1 (d,  2  J  PP  =22 Hz), 48.3 (d,  2  J  PP  = 22 Hz).  1 H NMR (CD 2 Cl 2  , 500.1 MHz):  δ  8.00(d,  3  J  H4H3  = 9.5 Hz, 1H,  H4 ), 7.81 (d,  3  J  H5H6  = 7.5 Hz, 1H,  H5 ),7.57  7.51 (m, 8H,  H5 0 and  Ph ), 7.40 (d,  3  J  H4 0 H3 0  = 8.5 Hz, 1H,  H4 0 ),7.28  7.25 (m, 3H,  Ar  ), 7.19 (d,  3  J  H3H4  = 9.0 Hz, 1H,  H3 ), 7.17 (m, 1H, H6  ), 7.14  7.11 (m, 10H,  Ph ), 6.92  6.89 (m, 7H,  H3 0 and  Ph ), 6.80(m, 1H, H6  0 ), 6.66 (m, 1H, H7  0 ), 6.62 (m, 1H, H7  ), 6.58 (d,  3  J  H8H7 = 5.0Hz,1H, H8 ),6.55  6.51(m,6H,  Ph ),5.91(d, 3  J  H8 0 H7 0  =8.5Hz,1H, H8 0 ),1.37(s,3H,C H  3 CN). 13 CNMR(CD 2 Cl 2  ,125.6MHz): δ 172.1(d,  J  CP =5 Hz,  C2 0 ), 143.3 (d,  J  CP  = 2 Hz,  C2 ), 142.3 (d,  J  CP  = 2 Hz,  C8a ), 134.8(s, C8a 0 ),134.65(d,  J  CP =8.8Hz,  Ph ),133.8(d,  J  CP =10.0Hz,  Ph ),133.1(s,  C4 ), 129.9 (s,  C3 ), 129.4 (s,  C8 ), 128.8 (s,  C4a ), 128.7 (s,  C4 0 ), 128.3(s,  C5 ), 127.9 (m,  C5 0 and  Ph ), 126.9 (s,  C7  ), 126.8 (s,  C4a 0 ), 124.6(s,  C7  0 ), 124.5 (s,  C3 0 ), 123.9 (s,  C8 0 ), 123.3 (s,  C6  ), 120.3 (s, CH 3 C  N),118.9 (s,  C6  0 ), 115.2 (d,  2  J  CP  = 1 Hz,  C1 0 ), 106.4 (d,  2  J  CP  = 15 Hz,  C1 ),3.41 (s,  C  H 3 CN). IR (Nujol):  ν (C t N) 2263 cm  1 (w).In probe reactions,  7  (ca. 10 mg) was dissolved in 1:2 CD 3 CN:C 6 D 6 and analyzed ( 31 P { 1 H }  NMR). Solely bis-nitrile,  η 1  , η 1 -BINO complex  10  wasobserved;atlowerproportionsofCD 3 CN,signalsfor 9 emerged.Poor solubility precluded analysis in neat CD 3 CN. Ru( η 1 , η 1 -( S )-BINO)(PPh 3 ) 2 (MeCN) 2  10.  31 P { 1 H }  NMR (1:2CD 3 CN:C 6 D 6  , 121.4 MHz):  δ  45.5 (s).  1 H NMR (1:2 CD 3 CN:C 6 D 6  ,500.1 MHz): 7.56 (d,  3  J  H5H6  = 8 Hz, 2H,  H5 ), 7.45  7.35 (m, 13H,  Ph ),
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