J. CHEM. SOC. DALTON TRANS. 1994 3225Synthesis and Solution Multinuclear Magnetic ResonanceStudies of Homoleptic Copper([) Complexes of Sulfur,Selenium and Tellurium Donor LigandsJane R . Black and William Levason*Department of Chemistry, University of Southampton, Southampton SO9 5NH, UKThe complexes [CuL,] [O,SCF,] (L = Me$, Me,Se, Me,Te, Ph,S, Ph,Se or Ph,Te) and [Cu(L-L),]PF,[L-L = RE(CH,),ER (E = S or Se, R = Me or Ph); RE(CH,),ER (E = S, Se or Te; R = Me or Ph)] havebeen prepared and characterised by analysis, IR, and in particular multinuclear NMR spectroscopy ('H,77Se, lZ5Te and 63Cu). Variable-temperature NMR studies have been used t o probe various exchangeprocesses occurring i n solution. For a limited number of complexes 63Cu NMR resonances have beenobserved, the first examples from Group 16 donor complexes.We have recently reported' a study of various homolepticcopper(1) complexes with P-, As- or Sb-donor ligands bymultinuclear NMR spectroscopy, including in many cases theobservation of the copper-63 NMR resonances.? Here wereport a similar study involving mono- and bi-dentate sulfur,selenium and tellurium ligands. Several copper(1) complexes ofdithioethers and diphosphine disulfides or diselenides have beenreported,' but homoleptic complexes with seleno- or telluro-ethers are unknown, and no copper-63 NMR resonances appearto have been observed with any Group 16 donor ligands.ResultsSynthesis and Properties.-The complexes [Cu(L-L),]Y[Y = PF, or BF,; L-L = MeS(CH,),SMe, MeSe(CH,),SeMe,PhS(CH,),SPh or PhSe(CH,),SePh, n = 2 or 3; RTe(CH,),-TeR, R = Me or Ph; Ph,(E)PCH,P(E)Ph,, E = S or Se] wereobtained in high yield from the reaction of the appropriate L-Lwith [CU(M~CN),]PF,~ in dry methanol or CH,CI,. Several ofthe complexes of the dithioether and phosphine sulfide andselenide ligands have been reported previously, often made byreduction of copper(I1) salts with, or in the presence of, L-L.2-6*sThe use of copper(1) precursors is a cleaner route.Theditelluroether complexes are pale orange, the others white andmostly dry-air stable in the solid state, although decompositionoccurs slowly in halogenated solvents producing green or bluesolutions. Analytical data are given in Table 1 . The FAB massspectra confirmed the formulations, exhibiting features due to[Cu(L-L),] + and [Cu(L-L)] + sometimes with lower-mass ionsdue to ligand fragmentation.The 'H NMR data (Table 2) areconsistent with the formulations but otherwise unexceptional.X-Ray structural data (from complexes with different anions)have confirmed the presence of a distorted-tetrahedra1 geometrywith chelating ligands in the complexes with MeS(CH,),SMeand EtS(CH,),SEt.6.9The reaction of [Cu(MeCN),]PF, with 4 equivalents ofPh,PE (E = S or Se)$ gave the tris complexes [Cu(Ph,-PE),]PF,, previously obtained as BF,- or ClO,-The [Cu(Ph,PE),] + cations are probably trigonal planar (cf.t 63Cu, I = i, 69"/,, E = 26.528 MHz, D, = 365, quadrupole moment-0.211 x lo-'* m2; ,'Cu, I = $, 31%, Z = 28.417 MHz, D, = 201,quadrupole moment -0.195 x lo-,* m2.1 Phosphine tellurides are too unstable to be useful ligands in thesesystems.Table 1 Analytical dataAnalysis (%)'C21.3 (21.2)24.9 (25.0)52.2 (52.3)50.9 (51.3)15.1 (15.0)18.1 (18.0)37.9 (37.8)36.9 (37.2)14.0 ( I 3.9)32.4 (32.4)54.0 (54.3)46.3 (46.4)58.8 (59.4)52.9 (52.6)23.6 (23.4)16.8 (16.7)12.8 (12.8)61.6(61.5)51.2(51.4)52.9 (53.2)43.4 (43.9)44.8 (45.1 )H4.7 (5.0)4.1 (4.4)2.9 (3.2)3.1 (3.6)3.1 (3.2)2.9 (3.4)2.2 (2.8)2.7 (2.9)3.9 (4.0)3.1 (3.4)3.7 (4.2)3.2 (3.7)5.2 (5.2)3.9 (3.7)2.8 (2.9)4.1 (4.2)3.3 (3.5)2.7 (3.0)3.6 (3.7)2.8 (3.2)4.1 (4.5)4.9 (4.7)a Calculated values in parentheses.NMR spectra.CH,Cl, was present in the 'H[Cu(Me,PS),]+ 8 > and Tiethof et al.' showed by IR spectro-scopy that they are extensively dissociated in solution.The31P NMR results (below) show no evidence that tetrakiscomplexes can be formed even with a large excess of L and areconsistent with previous conclusions of rapid dissociativeligand exchange.Attempts to prepare [CuL,]Y (e.g. L = Me,S, Ph,S orMe,Se) from [Cu(MeCN),]Y and an excess of L in MeCN,MeOH or CH,CI, gave materials with variable compositionoften containing some MeCN. However the complexes[CuL,]BF, (L = Ph,Se or Ph,Te) were successfully obtainedby this route from anhydrous methanol solution. A moregeneral route to the homoleptic complexes was developedinvolving reaction of L = Me2E or Ph,E (E = S, Se or Te) with[(Cu(O,SCF,)},(C,H,)] lo in dry benzene under rigorouslyanhydrous conditions.With the exception of the pale orangePh,Te complex, the products were white powders whic3226 J. CHEM. SOC. DALTON TRANS. 1994decomposed in moist air and are extensively dissociated insolution (below). The [Cu(Me,Te),][O,SCF,] and [Cu{ MeTe-(CH,),TeMe},]PF, complexes are also light sensitive, darken-ing on prolonged exposure. The complexes analysed as [CuL,]-[O,SCF,] and the IR spectra are consistent with the presenceof 03SCF, - ions.' ' These homoleptic Group 16 complexesare much less stable than the Group 15 analogues such asCCu(PR,),I + a 'Multinuclear NMR Studies.-The 'H NMR spectra of[Cu{MeE(CH,),EMe},]+ (E = S, Se or Te, n = 3; E = S orSe, n = 2) in CD,CN showed only singlet 6(Me) resonancesdown to the freezing point of the solvent (228 K).Slowpyramidal inversion at the Group 16 atom would be expected toproduce several closely spaced resonances due to the NMR-distinguishable invertomers. These data could either indicatethat pyramidal inversion remains fast on the NMR time-scale,or that we are failing to resolve the separate resonances, sincethe quadrupolar copper nuclei cause broadening of the protonsignals. It could also result from rapid exchange processes suchas reversible intramolecular ring opening.The 31P-(1H}, 77Se-('H}, lz5Te-{ 'H} and 63Cu NMR dataare collected in Tables 3-5. The behaviour shows complexvariations with the ligand present and sometimes with temp-erature and in the presence of an excess of ligand.The spectraof the complexes will be described in turn here andrationalisations of the trends reserved for the Discussion section.Phosphine chalcogenides. The ,'P-{ 'H} NMR spectra of[Cu(Ph,PE),] + in CH2C12 show single resonances over thetemperature range 300-1 80 K (Table 3), little shifted from thoseof the free Ph,PE. Addition of an excess of Ph,PS to a solutionof [Cu(Ph,PS),]PF, in CH,Cl, resulted in only a singleresonance at any temperature > 175 K. Analogous results wereobtained for [CU(Ph,PSe),]PF6 (Tables 3 and 4). The ,lP-{ 'H} NMR spectrum of [Cu{Ph,(S)PCH,P(S)Ph,},]PF, inCH2Cl, is a singlet at 300 K, and is very little affected by coolingthe solution to 180 K. Addition of free L-L to this solutionshows separate resonances for the free and co-ordinated L-Lonly at <ca.233 K, above this temperature only a singlesharp resonance is present consistent with fast exchange.The ,lP-(lH} and 77Se-{'H} data for [Cu{Ph,(Se)P-CH,P(Se)Ph,},]PF, (Tables 3 and 4) are similar, showingrapid exchange between added L-L and the complex at>ca. 223 K. No resonances were observed for any ofthe phosphine chalcogenide complexes even in the presenceof an excess of L-L.Table 2 Proton NMR dataComplex[cu{ MeS(CH,),SMe} ,]PF,"[cu{ MeS(CH,),SMe} 2]PF,b[Cu{PhS(CH,),SPh} ,]BF,'[Cu{ PhS(CH,),SPh} ,]BF,"[cu{ MeSe(CH,),SeMe},]PF,'[Cu{MeSe(CH,),SeMe} 2]PF,b[Cu{ PhSe(CH,),SePh),]PF,'[CU(P~S~(CH,),S~P~},]PF,~[CU{M~T~(CH,),T~M~},]PF,~[Cu{ PhTe(CH,),TePh},]PF,'[Cu{ Ph(S)PCH,P( S)Ph, } ,]PF,'[Cu{ Ph,( Se)PCH,P(Se)Ph,} 2]PF,cCCu(Me,S),ICO,SCF,I "CCu(Me,Se),ICO,SCF,I a~C~(Me,Te),lCO,SCF,I '6 ( J / W2.47 (s, 6 H), 3.27 (s, 4 H)2.0 (q, 2 H), 2.24 (s, 6 H), 2.75 (t, 4 H)3.30 (s, 4 H), 7.3-7.6 (m, 10 H)2.13 (q, 2 H), 3.33 (t, 4 H), 7.2-7.6 (m, 10 H)2.0 (q, 2 H), 2.10 (s, 6 H), 2.70 (t, 4 H)3.35 [s, 4 H, 'J(Se-H) = 111, 7.2-7.6 (m, 10 H)1.83 (q, 2 H), 2.85 (t, 4 H), 7.2-7.6 (m, 10 H)1.94 (q, 2 H),d 2.01 (s, 6 H), 2.75 (t, 4 H)2.00 (q, 2 H), 3.00 (t, 4 H), 7.1-7.7 (m, 10 H)3.90 [It, 2 H, 'J(P-H) = 131, 7.2-7.8 (m, 20 H)4.10 [t, 2 H, 'J(P-H) = 131, 7.3-7.8 (m, 20 H)2.69 (s)2.45 (s)2.06 (s)2.14 [s, 6 H, 'J(S*H) = 9],3.10 [s, 4 H, 'J(S*H) = 111a In (CD,),CO.In CD,CN. ' In CD,CI,. ,J(Te-H) not clear due to overlap of Me and CH, resonances.Table 3 ,lP-{ 'H} NMR spectroscopic dataComplex " 6(31 P) 1J(31P-77Se)/Hz 6(, 'P)' 'J( 'P-77Se)'/Hz40.3 - 43.2 - [Cu(Ph 3ps) 31+ [Cu(Ph,PSe),] + 29.7 640 35.8 758[Cu { Ph, (S)PCH , P( S)Ph, ,] + 3 1 .3 - 35.2 -[Cu(Ph2(Se)PCHZP(Se)Phz},]+ 19.7 698 25.4 754" At 300 K in CH,CI,. Relative to external 85% H3P04. ' Free L or L-L.Table 4 Selenium-77 and 125Te NMR dataComplex "[Cu(Ph,PSe),] +[Cu{Ph,(Se)PCH,P(Se)Ph,},] '[Cu{MeSe(CH,),SeMe},] + '[Cu{ PhSe(CH,),SePh} ,] + [Cu{ MeSe(CH,),SeMe} ,] + '[Cu{ PhSe(CH,),SePh} ,] +'[Cu(Ph,Se),] + [Cu(Me,Se),] +[ Cu{ MeTe( CH,) ,TeMe} ,] + '[ Cu{ PhTe( CH ,),TePh} ,] +[Cu(Me,Te)] +[Cu(Ph,Te),] +6(77Se or lzsTe)b- 198-308(d) (210 K) + 56 + 256 + 58 + 286 + 395-33 (263 K) + 49+315-37 (290 K) + 5786 (free ligand)- 275 (d)- 254 (d) + 127 + 336 + 74 + 289+4160 + 104 + 4660 + 685CommentExchange at all temperatures 300-175 KAt 300 K very broad d at 6 ca.- 3006 +45 at 225 K, rapid exchange with L-L at > ca. 240 K6 + 254 at 175 K, rapid exchange with L-L at > ca. 240 K6 +51.5 at 233 K6 +280 at 233 K6 +368at 183 K-28 at 190 K+42 at 230 K6 +306at 203 K6 -14at 183K6 + 550 at 183 K, rapid exchange with Ph,Te at > 203 Ka In CH,CI,-CD2Cl2 unless indicated otherwise. Relative to external neat Me,Se or Me,Te at 300 K. In MeCN-CD,CN. In Me,CO-(CD,),COJ. CHEM. SOC. DALTON TRANS. 1994[CuL,][O,SCF,](L = Me,S or Ph,S).No copper NMRresonance was observed from solutions of [Cu(Me,S),]-[O,SCF,] in acetone over the range 300-185 K. However onadding an excess of Me,S (ca. > 10: 1 mol ratio) to the solutiona copper signal was present at all temperatures (Fig. 1). This isconsistent with extensive dissociation of the tetrakis complex insolution to low-symmetry species. The large excess of added Lshifts the equilibrium in favour of the [CuL,]' ion which isresponsible for the observed signal. The resonance shifts to highfrequency as the temperature is lowered (Table 5). Treatment of[Cu(MeCN),]PF, with a large excess of Me,S in MeCN gave aclear solution with a similar ,,Cu NMR resonance, showingthat the tetrakis cation is also formed under these conditions,although the pure solid complex was not isolated from suchsolutions.The 'H NMR spectra of mixtures of [Cu(Me,S),]+and Me,S in (CD,),CO show two resonances only at c ca. 235(a )Q500 400 300 200 100 0 -100bI I I I 1 I 1 I I I 300 200 100 0 -1 006Fig. 1 Copper-63 NMR spectra of (a) [Cu(Me,S),][O,SCF,] +a 10-fold excess of Me,S in acetone at 183 K and (b) [Cu{PhSe-(CH,),SePh},]PF, in MeCN at 300 K3227K showing rapid exchange above this temperature. No 63Curesonance was seen for [Cu(Ph,S),][O3SCF3] in CH,Cl, evenin the presence of an excess of Ph,S.[Cu(MeSCH,CH,SMe),]PF, and [Cu(PhSCH,CH,SPh),]-BF4. No 63Cu NMR resonances were found for solutions ofeither complex in CH,Cl, over the accessible temperature range(300-175 K), even in the presence of added L-L.[Cu(MeSCH,CH,CH,SMe),]PF, and [Cu(PhSCH,CH,-CH,SPh),]BF,.The former complex exhibited 6(63Cu) at + 75in MeCN solution at 300 K, which shifted to higher frequencyand broadened on cooling, reaching + 120 at 233 K. Howeverno resonance was observed from solutions of [Cu(PhSCH,-CH,CH,SPh),]BF, in Me,CO at any temperature, even in thepresence of an excess of L-L.[CuL,][O,SCF,] (L = Me,Se or Ph,Se). No "Se NMRresonance was detectable from a solution of [Cu(Me,Se),]+ inacetone at 300 K. On cooling a broad resonance (6 = -33)appeared at ca. 263 K, which sharpened quickly on cooling.Addition of varying amounts of Me,Se to this solution yieldedonly a single resonance the chemical shift of which varied withthe amount of added L, consistent with rapid exchange.Even atthe lowest temperature obtainable (185 K) only a singleresonance was present, showing that exchange remained fastwith respect to the selenium NMR time-scale. For [Cu(Ph,-Se),]+ in acetone a broad resonance was present at 300 K whichsharpened on cooling. The effect of adding free Ph,Se to thesolution mirrored that of the Me,Se system. Neither complexexhibited a ,,Cu NMR resonance in solution at anytemperature over the range 300-185 K, and no resonance wasobserved from solutions of [Cu(Ph,Se),] + containing an excessof Ph,Se over the same temperature range. In contrast,solutions of [Cu(Me,Se),] + containing a large excess ofMe,Se ( > 10: 1 mol ratio) showed a broad signal at283 K at 6 ca. -56 (W+ = 1500 Hz), which sharpens anddrifts to higher frequency on cooling reaching - 16 ( W , =800 Hz) at 185 K.[Cu(MeSeCH,CH,SMe),]PF, and [Cu(PhSeCH,CH,Se-Ph),]PF,.Both complexes exhibited single 77Se NMRresonances over the range 300-225 K, but no ,,Cu resonanceswere seen. Addition of the appropriate L-L to these solutionsresulted in single 77Se resonances at 300 K consistent with rapidexchange. However the resonances broadened on cooling, andfor both systems separate resonances for the complex and L-Lwere observed at c c a . 240 K, showing exchange slowing onlowering the temperature.[Cu{MeSe(CH,),SeMe},]PF, and [Cu(PhSe(CH,),Se-Ph),]PF,. Both complexes show relatively sharp 77Se NMRresonances with small negative co-ordination shifts (Table 4).They also exhibited 63Cu NMR resonances from MeCNsolutions over the accessible temperature range (300-233 K)(Table 5 and Fig.1). Whilst that of [Cu(PhSe(CH,),SePh},]+shows the usual ' high-frequency shift with decreasingTable 5 Copper-63 NMR dataComplex 6(63Cu) ( W,/Hz)" CommentCCu(Me,s>,l+[Cu{ MeS(CH,),SMe},]' '[Cu(Me,Se),] +[Cu{ MeSe(CH,),SeMe},] +[Cu{PhSe(CH,),SePh},] +[Cu(Me,Te),] +[Cu(Ph,Te),] +[Cu{MeTe(CH,),TeMe},] + '[Cu{ PhTe(CH ,),TePh} ,] ++ 80 (2500)+ 2 1 (1 500) (293 K) + 18 (1500)+ 75 (1000)- 56 (1 500) (283 K)- 56 (600) (290 K)- 153 (3400)+21 (1500)- 36 (6000) (at 273 K)At 183 K, 6 + 126, W, = 1000 Hz (only seen in presence of excess of Me,S)At 233 K, 6 + 120, W, = 2000 HZAt 185 K, 6 - 16, W, = 800 Hz (only seen in presence of excess of Me,Se)At 233 K, 6 + 18, W, = 3500 HZAt 233 K, 6 +42, W, = 2500 HZAt 193 K, 6 -39, W, = 750 Hz (resonances quoted in presence of a large excess ofMe,Te, see text)At 233 K, 6 - 116, W, = 4500 Hz, signal disappears at c 220 K (only seen in thepresence of an excess of Ph,Te)At 230 K, 6 + 13, W, = 3000 HZNo resonance at 300 or < ca.220 Ka At 300 K relative to [Cu(MeCN),]+ in MeCN-CD,CN. In Me,CO-(CD,),CO. ' In MeCN-CD,CN. In CH,Cl,-CD,Cl,3228 J. CHEM. SOC. DALTON TRANS. 1994temperature, curiously the resonance position of[Cu(MeSe(CH,),SeMe} ,] + was essentially unchanged withtemperature.[CuL,][O,SCF,] (L = Me,Te or Ph,Te). The lz5Te NMRspectrum of [Cu(Me,Te),]+ in acetone at 300 K was a sharpsinglet, which broadened and shifted to high frequency on cool-ing.Rapid exchange occurred with added Me,Te down to thefreezing point of the solvent. In contrast to other [CuL,]'complexes, a solution of [Cu(Me,Te),] + in acetone exhibiteda very broad 63Cu resonance at 6 -126 (Wi = 3500 Hz),which broadened rapidly on cooling and was not observed atc c a . 250 K. However, in the presence of a large excess(> 10-fold) of Me,Te, a sharp 63Cu resonance is present at6 - 56 (W+ = 600 Hz) at 290 K, which shifts on cooling tohigher frequency but is still sharp at 193 K (6 -39, W, =750 Hz) (Fig. 2). Solutions containing smaller excesses of Me,Tegave broader 63Cu resonances at intermediate chemical shifts.The sharp 63Cu resonance observed in the presence of a largeexcess of Me,Te must correspond to that of the tetrakis complexfor which slow quadrupolar relaxation of the copper would beexpected.In the absence of added Me,Te, or with only smallquantities of it, dissociative equilibria [Cu(Me,Te),] +[Cu(Me,Te),] + + Me,Te {e [Cu(Me,Te),] + + Me,Te ?}are probably present and exchange with the (unobserved)lower-symmetry complexes would account for these effects. 'In the case of [Cu(Ph,Te),]+ in acetone a single 125Teresonance was present at room temperature, and this remainedover the accessible temperature range, showing a small low-frequency shift with decreasing temperature. Addition of anexcess of Ph,Te to the solution gave only a singlet at ambienttemperatures, but this broadened on cooling below ca.220 K,and below ca. 210 K separate resonances for free Ph,Te and[Cu(Ph,Te),]+ were resolved (Fig. 3). No 63Cu resonance wasobserved from solutions of [Cu(Ph,Te),] + in acetone, but withadded Ph,Te a broad resonance at 6 - 153 ( W+ = 3400 Hz)was present at 300 K. On cooling this broadened anddisappeared altogether at < 220 K.[Cu{ MeTe(CH ,) ,TeMe} JPF, and [Cu { PhTe(CH ,) ,Te-Ph},]PF6. The former complex exhibited a sharp singlet lz5TeNMR resonance in MeCN solution which varied little withtemperature. A relatively broad 63Cu resonance was present at300 K, 6 + 21 ( W, = 1500 Hz) which broadened on cooling,but the chemical shift of which was insensitive to temperature.In contrast, although the [Cu(PhTe(CH,),TePh},]PF, com-plex in CH,Cl, exhibited a relatively sharp lZ5Te resonanceover the range 300-185 K, no 63Cu signal was evident at roomtemperature. On cooling to 273 K a broad resonance at 6 - 36(W+ = 6000 Hz) appeared, but on further cooling thisbroadened rapidly and merged into the baseline at c ca.220 K.DiscussionThe homoleptic copper(1) complexes formed with monodentateGroup 16 ligands R,E, which have not been reportedpreviously, ' are tetrakis(1igand) species on the basis of theanalytical data. However they are highly unstable, decomposingreadily in air, and extensively dissociated in solution on thebasis of the NMR studies described above. The rapid exchangein solution with added ligand observed for all the complexesover a wide temperature range demonstrates the extremesubstitution lability of these systems.The observation of 63CuNMR resonances from solutions of [CuL,]' (L = Me,$Me,Se, Me,Te or Ph,Te) in the presence of a large excess of theof the tetrakis complexes, since the copper resonance will beseen only in an environment approaching cubic symmetry. TheI I I I I appropriate L shows that the equilibria can be shifted in favourI 1i4 44 -56 -1 56(b )1 I I I I174 74 -26 -126 -226 -326 680 640 600 560Copper-63 NMR spectra of (a) [Cu(Me,Te),][O,SCF,] + a6 6Fig. 210-fold excess of Me,Te in acetone at 300 K and (b) [Cu- Fig. 3 The IZ5Te-{'H) NMR spectrum of a mixture of [Cu(Ph,-(Me,Te),][O,SCF,] in acetone at 300 K Te),][O,SCF,] + Ph,Te in acetone at 210 J .CHEM. SOC. DALTON TRANS. 1994 3229corresponding failure to observe 63Cu resonances fromsolutions of Ph,S or Ph,Se complexes, even in the presenceof an excess of L, is taken as evidence for extensive dissociationunder these conditions. Comparison with previous studiesof copper(1)-Group 15 ligand complexes ',15 shows that thepresent Group 16 complexes are much more substitution labileand more extensively dissociated. Even the complexes of thechelating bidentate ligands are remarkably labile in solution,with exchange with added L-L rapid on the NMR time-scaledown to quite low temperatures. This must largely reflectelectronic differences between the donor types, since stericeffects are relatively unimportant in Group 16 ligandchemistry.', Neutral Group 16 donor ligands are weaker CJdonors than are their Group 15 analogue^,^^,'^ and whenbound to the electron-rich d lo copper(x) centre the second lonepair on the donor atom may produce significant 71 repulsion.Although studies of Group 16-transition metal bonds haveattracted much less discussion than M-P bonding, it has beensuggested that in bonds to electron-rich metal centres (whichwould include Cu') the lability decreases and the bond strengthincreases as Group 16 is descended.' Our data are consistentwith this.Multinuclear NMR Studies.-Apart from the evidence forextensive dissociation and rapid exchange in solution discussedabove, the main features of interest in the 77Se and 12'Te NMRspectra are the co-ordination shifts.In most transition-metalsystems, co-ordination of mono- or bi-dentate seleno- ortelluro-ethers results in high-frequency shifts in the selenium ortellurium resonance. ' Particularly large high-frequency shiftsare observed with five-membered chelate rings, with smallershifts in six-membered chelate rings and with monodentateligands. These effects parallel those familiar in ,'P NMR studiesof the corresponding phosphine systems. l8 Rare exceptions tothese generalisations have been reported in some [PtMe,X-(L-L)] systems (L-L = diseleno- or ditelluro-ether)." In allthe copper(1) systems co-ordination of the ligand results in ashift of the selenium or tellurium NMR resonance to lowfrequency of the free L-L resonance (Table 4). Moreover for theselenium ligands where data are available for comparable five-and six-membered rings, the largest low-frequency shifts arepresent for the smaller-ring complexes.The origin of the'chelate ring effect' is disputed even in the much studieddiphosphine systems. ' * The low-frequency co-ordination shiftsin the Group 16 systems presumably result from the effect of theelectron-rich d lo metal centre.The co-ordinated bidentate ligands are chiral and thepresence of invertomers is usually evident in the 'H, 77Se or125Te NMR spectra.,' In these copper systems we have noevidence for such invertomers; either pyramidal inversionremains fast on the NMR time-scale over the temperature rangestudied, or the relatively broad lines preclude observation ofthe small differences in chemical shifts expected between theinvertomers.A major interest in the present work was to study the 63CuNMR spectra, since no examples from Group 16 donor com-plexes have been reported previously.' ' 63Cu resonances wereobserved only from a limited range of complexes (Table 5) anddisappointingly no examples of ' J couplings to 77Se or 12'Tewere resolved. The factors which affect the observation of 63CuNMR resonances are the rate of quadrupolar relaxation ofthe 63Cu nuclei and the nature and rate of dynamic processesoccurring in solution. These will in turn be influenced by thetemperature, distortions from regular symmetry and theelectronic properties of the ligands. It is also clear that thereis considerable interrelation between these various factorsand hence the observed behaviour is complex.In fact, 63Curesonances were observed only with some monodentate ligandsand in some six-membered chelate-ring complexes, presumablybecause these ligands are better able to approach the tetrahedralgeometry required at the copper centre, whereas the five-membered rings deviate further from Td geometry. The factthat [Cu{PhS(CH,),SPh},] + fails to exhibit a ,,Cu resonanceand that [Cu{ PhTe(CH,),TePh} ,] + does so only over a limitedrange of conditions shows how sensitive the relaxation rates areto small changes in metal environment.Comparison of the 63Cu chemical shifts reported show that asin Group 15' the chemical shifts move to low frequency as thedonor atom becomes heavier, and that the typical shifts withdonor lie in the order (for a limited range of examples)P > S > Se z Te w As > Sb > halide.ExperimentalPhysical measurements were made as described previously.2 'The 'H NMR spectra were recorded from solutions in CD,Cl,,CD,CN or (CD,),CO on JEOL FX90Q or Bruker AC300 orAM360 spectrometers, 31P-{1H} spectra from 5% CD,Cl,-CH,Cl, solutions on a Bruker AM360 at 145.8 MHz, 77Se-(1H)spectra at 68.68 MHz, '25Te-{1H} spectra at 113.6 MHz, and,,Cu spectra similarly at 95.5 MHz.Phosphorus chemical shiftsare reported relative to external 85% H,PO,, selenium shiftsrelative to neat external Me,Se, tellurium shifts relative to neatexternal Me,Te, and copper shifts relative to a solution of[Cu(MeCN),]BF, in MeCN at 300 K.The FAB mass spectrawere recorded on a VG Analytical 70-250-SE normal-geometrydouble-focusing spectrometer using 3-nitrobenzyl alcohol asthe matrix.The complexes [Cu(MeCN),]Y (Y = PF, or BF4)7 and[{CU(~~SCF~)},(C,H,)]~~ were made by literature methods.Complexes were made in dried solvents under a dry nitrogenatmosphere. The [CuL4][0,SCF3] complexes were stored andhandled in a dry-box.[CuL,][O,SCF,] (L = Me,S, Me,Se, Me,Te, Ph,S orPh,Se).-The compound L (3.4 mmol) was added to [{Cu-(O,SCF,)},(C,H,)] (0.4 mmol) in freshly distilled benzene (10cm3). The solvent was removed in uacuo, and dry diethyl ether(10 cm3) was added to the resulting oil, while cooling the flask inan ice-bath. The white solid was filtered off using a Schlenkstick, washed with anhydrous diethyl ether (2 x 10 cm3), anddried in uacuo.The complex [Cu(Ph,Te),][O,SCF,] was madesimilarly, except that the oil was triturated with pentane, andthe pale orange solid washed with pentane (2 x 10 cm3) anddried in uacuo. Yields typically 50%.[Cu(Ph,PE),]PF,.-A solution of Ph,PE (4 mmol) and[Cu(MeCN),]PF, (0.37 g, 1.0 mmol) were refluxed in dryCH,Cl, (1 5 cm3) under nitrogen for 30 min. The solution wascooled, dry diethyl ether added producing a white precipitate,and the mixture refrigerated. The product was filtered off,washed with diethyl ether (2 x 10 cm3), and dried in uacuo.Complexes of the diphosphine disulfide and diselenide ligandswere made similarly using a 2: 1 ligand: Cu ratio.YieldsThe complexes of the bidentate ligands were made by similar60-75%.routes, typical examples being described.[Cu(MeS(CH,),SMe},]PF,.-A solution of MeS(CH,),-SMe (0.3 g, 3.5 mmol) and [Cu(MeCN),]PF, (0.56 g, 1.5mmol) in anhydrous methanol (20 cm3) was refluxed for 20min. On cooling a white crystalline solid separated, which wasfiltered off, washed with diethyl ether (2 x 10 cm3) and dried inuacuo. Yield 0.46 g, 68%.[Cu(PhS(CH,),SPh},]BF,.-A solution of PhS(CH,),SPh(0.49 g, 1.88 mmol) and [Cu(MeCN),]BF, (0.28 g, 0.89 mmol)in CH,Cl, (10 cm3) was warmed and stirred for 20 min. Thereaction mixture was evaporated to an oil which was trituratedwith pentane (10 cm3) and then ethanol (2 x 10 cm'). Thewhite product was washed with diethyl ether (10 cm3) and driedin uacuo.Yield 0.30 g, 50%3230 J. CHEM. SOC. DALTON TRANS. 1994[Cu{MeSe(CH,),SeMe),]PF,.-A solution of MeSe-(CH,),SeMe (0.55 g, 2.4 mmol) and [Cu(MeCN),]PF, (0.41 g,1 . 1 mmol) in CH,Cl, (15 cm3) was refluxed for 30 min andfiltered on cooling. Addition of pentane (20 cm3) to the filtrateyielded a white solid, which was filtered off, washed withpentane (3 x 10 cm3), and dried in uacuo. Yield 0.52 g , 70%.[Cu{PhSe(CH,),SePh),]PF,.-A solution of PhSe(CH,),-SePh (1.38 g, 4.05 mmol) in CH,Cl, (10 cm3) was added to asuspension of [Cu(MeCN),]PF, (0.75 g, 2.0 mmol) in CH,CI,(10 cm3). The mixture was refluxed for 1 h, cooled and filtered,and the filtrate concentrated to yield an oily material. This wasredissolved in CH,Cl, (10 cm3) and pentane added until thesolution became cloudy. Removal of the solvent in uacuo left awhite solid which was washed with pentane (3 x 10 cm3) anddried in uacuo.Yield 1.24 g, 69%.[Cu{MeTe(CH,),TeMe),]PF,.-A solution of MeTe-(CH,),TeMe (1.04 g, 3.2 mmol) and [Cu(MeCN),]PF,(0.57 g, 1.53 mmol) in dry CH,Cl, (15 cm3) was refluxed for30 min and filtered on cooling. Anhydrous diethyl ether (25 cm3)was added to the filtrate, which became cloudy and an oily solidseparated. The solvent was removed in uacuo, and the paleyellow solid washed with dry diethyl ether (2 x 10 cm3) anddried in vacuo. Yield 0.98 g, 74%.References1 J. R. Black, W. Levason, M. D. Spicer and M. Webster, J. Chem. Soc.,2 J . A. Tiethof, A.T. Hetey and D. W. Meek, Inorg. Chem., 1974,13,3 E. W. Ainscough, H. A. Bergen, A. M. Brodie and K. L. Brown,4 E. W. Ainscough, A. M. Brodie and K. L. Brown, J. Chem. Soc.,Dalton Trans., 1993, 3129.2505.J. Chem. Soc., Dalton Trans., 1976, 1649.Dalton Trans., 1980, 1042.5 E. W. Ainscough, A. M. Brodie and K. C. Palmer, J. Chem. SOC.,6 M. M. Olmstead, W. K. Musker and R. M. Kessler, Inorg. Chem.,7 G. J . Kubas, Znorg. Synth., 1979, 19, 90.8 P. G. Eller and P. W. R. Corfield, Chem. Commun., 1971, 105.9 E. N. Baker and G. E. Norris, J. Chem. SOC., Dalton Trans., 1977,877.10 R. G. Saloman and J. K. Kochi, J. Am. Chem. SOC., 1973,95,3300;M. B. Dines and P. H. Bird, J. Chem. SOC., Chem. Commun., 1973,12.1 1 M. G. Miles, G. Doyle, R. P. Cooney and R. S. Tobias, Spectrochim.Acta, Part A, 1969, 25, 1515; R. J. Batchelor, J. N. R. Ruddick,J. R. Sams and F. Aubke, Znorg. Chem., 1977,16, 1414.12 S. Kitagawa, M. Munakata and M. Sasaki, Inorg. Chim. Acta, 1986,120, 77.13 W. Levason and E. G. Hope, Coord. Chem. Rev., 1993,122, 109.14 S. G. Murray and F. R. Hartley, Chem. Rev., 1981,81,365.15 P. Granger, in Transition Metal NMR, ed. P . S . Pregosin, Elsevier,Amsterdam, 199 1, p. 265.16 H.-B. Kraatz, H. Jacobsen, T. Zeigler and P. M. Boorman,Organometallics, 1993, 12,76.17 H. Schumann, A. M. Arif, A. L. Rheingold, C. Janiak, R. Hoffmannand N. Kuhn, Znorg. Chem., 199 1,30, 161 8.18 P. E. Garrou, Chem. Rev., 1981, 81, 229; A. L. Crumbliss andR. J. Topping, in Phosphorus-31 NMR Spectroscopy in Stereo-chemical Analysis, eds. J. G. Verkade and L. D. Quin, VCH, DeerfieldBeach, FL, 1987, p. 53 1.19 E. W. Abel, K. G. Orrell and A. W. G. Platt, J. Chem. Soc., DaltonTrans., 1983, 2345; E. W. Abel, K. G. Orrell, S. P. Scanlan,D. Stevenson, T. Kemmitt and W. Levason, J. Chem. Soc., DaltonTrans., 1991, 591.20 E. W. Abel, S. K. Bhargava and K. G. Orrell, Prog. Inorg. Chem.,1984,32, 1.21 R. A. Cipriano, W. Levason, R. A. S. Mould, D. Pletcher andM. Webster, J. Chem. Soc., Dalton Trans., 1990,2609.Dalton Trans., 1976, 2375.1981,20, 151.Received 6th June 1994; Paper 4103346