J. CHEM. SOC. DALTON TRANS. 1990 301 3Spectroscopic and Electrical Properties of [Cu(C,Se,),12- and [Ni(C,Se,),12-Anion Complexes and X-Ray Crystal Structures of [NMe4],[Cu(C,Se,),]*2MeCNand [NBu",][Ni(C,Se,),]tGen-etsu Matsubayashi and Akito YokozawaDepartment of Applied Chemistry, Faculty of Engineering, Osaka University, Yamadaoka, Suita, Osaka 565,JapanThe complexes [epy],[Cu(C,Se,),]-MeCN (1) [epy = N-ethylpyridinium; C3Se:- = 4,5-di (h ydroseleno) - 1,3-diselenole- 2 -set onate] [ N Me,] [ Cu (C,Se,),] -2 M eCN (2) , [ N Me,] [ Cu (C,Se5) 2](3) and [ttf],.,[Cu(C,Se,),] (4) [ttf'' = radical cation of tetrathiafulvalene, 2 - ( I ',3'-dithiol-2'-ylidene)-I ,3-dithiole] have been prepared. Complexes [NBu",],[Ni(C,Se,),] (5) and [NMe,],[Ni-(C3Se,),]-0.5MeCN (6) have been oxidized electrochemically under a controlled current in acetonitrileor acetone to afford [NBu",] [Ni(C,Se,),] [ 7 ) r [NBu",],.,[Ni(C,Se,)~] (8), and [NMe,],.,,-[Ni(C,Se,),] (9).All the complexes behave as semiconductors. Although complexes (1 )-(3), (5),and (6) exhibit electrical conductivities of 1 x 1 O-'-I x 1 O* S cm-l for compacted pellets at25 "C, conductivities of 1.4 x 1 O-, for (4) (compacted pellet), 2.0 x 1 O4 for (7) (crystal), 0.21 for(8), and 0.056 S cm-' for (9) (compacted pellets) were observed. A single-crystal X-ray structureanalysis of (2) reveals that the CuSe, geometry around the copper(ti) ion is substantially distortedfrom square planar, with a dihedral angle of 53.7" between the two diselenolate ligand planes.Additionally the anionic moieties form a two-dimensional molecular sheet through some interligandselenium-selenium contacts in the crystal phase.The orthorhombic crystal, space group lbam, hascell dimensions a = 10.289(3), b = 23.367(6), c = 15.51 9(7) A, and Z = 4. Block-diagonal least-squares refinement, based on 704 reflections [lFol > 3o(F)], converged at R = 0.065. An X-raystructure analysis of (7) reveals an almost square-planar geometry of the [Ni(C,Se,),] - anion,which forms a one-dimensional arrangement through several selenium-selenium contacts. Thecrystals are monoclinic, space group P2,/c, with a = 21.088(3), b = 13.494(1), c = 12.381 8(9) A,p = 106.1 7(1) ", and Z = 4. The refinement, based on 3 127 reflections [IFol > 3o(F)], convergedat R = 0.067.Electronic absorption, i.r., e.s.r., and X-ray photoelectron spectra of these complexesare described.Recently metal complexes with the 4,5-dimercapto- 1,3-dithiole-2-thionate ligand (C3SS2-) have attracted much attention owingto their metallic behaviour through sulphur-sulphur molecularinteractions,'*2 of which [ttf][Ni(C,S,),], [ttf" = radicalcation of tetrathiafulvalene, 2-( 1',3'-dithiol-2'-ylidene)-1,3-dithiole],, [NMe4][Ni(C3S5)2]2,3 and [ttf][Pd(C3S,),],4were reported to be superconductors. Since selenium has morespatially extended and diffuse orbitals than sulphur, metalcomplexes of the selenium analogue of the C3SS2- ligand,C3SeS 2- [4,5-di( hydrose1eno)- 1,3-diselenole-2-selonate], mayalso become good electrical conductors through more effectiveselenium-selenium molecular interactions.However, very fewstudies of C,SeS2--metal complexes have beenThis paper reports the crystal structures of [NMe,],[Cu-(C3Se,),]-2MeCN and [NBu",][Ni(C,Se,),] and their elec-tronic absorption, i.r., e.s.r., and X-ray photoelectron spectra aswell as electrical conductivites. A preliminary report of thecrystal structure of the former complex has a~peared.~ExperimentalPreparation.-[epy],[Cu(C3Se5),]~MeCN (1) [epy = N-Ethylpyridiniurn) and "Me,] [ Cu(C3Se 5)2] (3).4,5-Bis-(benzoylseleno)-1,3-diselenole-2-selone ' (1 50 mg, 230 pmol),prepared from [PPh4]2[Zn(C,Ses)2],8 was dissolved in a meth-anol solution (10 cm3) containing sodium metal (12 mg, 520pmol) and the solution was stirred for 30 min at room temper-ature.To the resulting solution of Na,[C,Se,] was added amethanol solution (2 cm3) of an excess of [epy][C104], followedby a methanol solution (2 cm3) of CuC1, (16 mg, 120 pmol).Black solids precipitated immediately, which were collected bycentrifugation, washed with methanol and water, and dried inuacuo. They were recrystallized from acetonitrile to afford blackmicrocrystals of [epy],[Cu(C,Se,),]-MeCN (1) (yield, 65%)(Found: C, 22.45; H, 2.2; N, 3.35. Calc. for C,,H23CuN3Selo: C,22.35; H, 1.95; N, 3.35%).A similar reaction, but using [NMe,]Br instead of[epy][ClO,], afforded black microcrystals of [NMe,][Cu-(C3Se,),] (3) (yield, 97%) (Found: C, 12.65; H, 1.35; N, 1.4.Calc. for CloH12CuNSe,,: C, 12.0; H, 1.2; N, 1.4%). Thesolids were recrystallized from acetonitrile to afford blackplates of [NMe,],[Cu(C3Se,),]~2MeCN (2).The formula of(2) was confirmed by an X-ray structure analysis.Preparation of [ttf]0.4[Cu(C3Se,),] (4).-An acetonitrilesolution (10 cm3) of (3) (21 mg, 21 pmol) was added with stirringto an acetonitrile solution (15 cm3) of [ttfl3[BF4I2" (31 mg,40t Bis(tetramethy1ammonium) bis[4,5-di(hydroseleno)- 1,3-diselenole-2-selonato-Se4Se5]cuprate(~~)-acetonitrile( 1/2) and tetrabutylam-monium bis[4,5-di(hydroseleno)- 1 ,3-diselenole-2-selonato-Se4Ses]-nickelate(ni).Supplementary data available: see Instructions for Authors, J. Chem.Soc., Dalton Trans., 1990, Issue 1, pp. xix-xxii.Non-S.Z. unit employed: eV x 1.6 x J3014 J.CHEM. SOC. DALTON TRANS. 1990Table 1. Experimental data and structure refinement details" forcomplexes (2) and (7)Complex (2) (7)Formula C 8H ,,CuN,Se C,,H ,,NNiSe, ,M 1 150.6 1 162.8Crystal size/mmCrystal system Ort horhombic MonoclinicSpace group Ibam &lcalA 10.289(3) 21.088(3)23.367(6) 13.494( 1)15.5 19(7) 12.381 8(9)blA90c/A90 106.17( 1)90 90P/"Yl"u/A3 3 731(2) 3 383.8(6)z 4 4D,/g ~ m - ~ 2.057( 1) 2.283( 1) F(owRadiationIAplcm-' 110.8 149.6Scan intervalr min-' 8 8Collected octants h, k , - 1 +h, k, 1No. of data collected atroom temperature 1 865 5 336No. of independent datawith IFoI > 30(Q 704 3 127Absorption correctionrange * 1.00-0.33 1.00--0.38R 0.065 0.067R" 0.105 0.084" Rigaku-AFC diffractometers; scan ranges 3 < 20 < 50" for (2) and4 < 20 < 120" for (7).b A . C. T. North, D. C. Phillips, and F. C.Matheus, Acta Crystallogr., Sect. A , 1968, 4, 351. ' [Cw((Fol -IFc1)2/ZwlF,,12]f, where w-' = 02(Fo) + O.0015Fo2 for (2) and w-I =oZ(~,) + 0.001F02 for (7).0.10 x 0.16 x 0.42 0.05 x 0.05 x 0.55a/" 902 120.0 2 172.0Mo-K, (A = 0.710 69) CU-K, (h = 1.5418)Table 2. Fractional atomic co-ordinates for [NMe,],[Cu(C,Se,),].2MeCN (2) with estimated standard deviations (e.s.d.s) in parenthesesAtom X Y Z00.152 4(4)0.133 2(3)00.193(5)0.1 60( 7)0.052(3)00.2 5 8 (6)0.204(9)0.053(7)0.126(9)0.07( 1)00.068 l(1)0.205 8(1)0.327 O(2)0.108(2)0.3 79( 3)0.133( 1)0.246(2)0.123(2)0.052(3)0.123(3)0.3 18(3)0.261(4)0.250.199 6(3)0.204 4(3)0.250.50.50.233(2)0.250.42 1 (3)0.50.50.50.5pmol). Black solids of [ttf]0.4[C~(C3Se5)2] immediatelyprecipitated, which were collected by centrifugation, washedwith acetonitrile, and dried in vacuo (yield, 77%) (Found: C, 9.7;presence of the ttf'+ radical cation was confirmed by e.s.r.spectroscopy .H, 0.5.Cak. for C7.6H1.6CuS1.6Se10: c, 10.0; H, 0.2%). ThePreparation of [NBu",],[Ni(C,Se,),] (5) and [NMe4I2-[Ni(C,Se,),].OSMeCN (6)-4,5-Bis(benzoylseleno)-1,3-di-selenole-2-selone (150 mg, 230 pmol) was dissolved in amethanol solution (10 cm3) containing sodium metal (12mg, 520 pmol). To this was added [NMe,]Br (38 mg, 250pmol), followed by a methanol solution (3 cm3) of bis(acety1-acetonato)nickel, (30 mg, 120 pmol).Brown solids precipitatedimmediately, which were collected by filtration and dried invacua They were recrystallized from acetonitrile to affordbrown microcrystals of [NMe4],[Ni(C3Se,),]~O.5MeCN (6)(50% yield) (Found: C, 16.95; H, 2.25; N, 3.45. Calc. forCISH,,~,N,~,NiSelo: C, 16.55; H, 2.35; N, 3.2%). Similarly,[NBu",]~[N~(C~S~,),] (5) was prepared by using [NBu"J-[ClO,] instead of [NMe,]Br and recrystallized from aceto-nitrile (72% yield) (Found: C, 32.3; H, 5.2; N, 1.85. Calc.for C38H72N2NiSe10: C, 32.45; H, 5.15; N, 2.0%).Preparation of Oxidized [Ni(C3Se,),]"- (n < 1) Com-plexes.-An acetonitrile solution (50 cm3) containing complex(5) (22 mg, 16 pmol) and [NBun4][C1O4] (1.28 g, 3.7 mmol) wassubjected to a controlled-current (1 pA) electrolysis for 16 dunder a nitrogen atmosphere in an H-cell consisting of platinumwire (for both the anode and cathode).Dark red needles of[NBu",][Ni(C,Se,),] (7) were collected from the anode anddried in uucuo (20% yield). The composition of the crystals wasdetermined by an X-ray structure analysis. A similar controlled-current electrolysis of (5) dissolved in acetone afforded blackmicrocrystals of [NBU"~]~.~,[N~(C,S~~)~] (8) on the anode,which were collected and dried in vacuu (1 5% yield) (Found: C,12.0; H, 1.0; N, 0.6. Calc. for Clo~oH,~oNo~,,NiSe,o: C, 12.2; H,0.9; N, 0.4%).A controlled-current electrolysis of (6) in acetonitrile,containing an excess of [NMe,][ClO,] as electrolyte, by asimilar procedure to that described for the tetrabutylammoniumcomplexes yielded black microcrystals of [NMe,],.,,-[Ni(C,Se,),] (9) (23% yield) (Found: C, 9.15; H, 0.45; N, 0.6.Calc.for C,~,H4~,N,~,,NiSelo: C, 9.3; H, 0.4; N, 0.5%).Complex (7) was also prepared by aerial oxidation of (5) (280mg, 200 pmol) dissolved in 1,2-dichloroethane (100 cm3). Thesolution was stirred for 24 h at room temperature, concentratedto one third of its volume, and hexane (50 cm3) added to afforddark red solids. These were collected by filtration and dried inuacuo (65% yield) (Found: C, 23.1; H, 3.35; N, 1.3. Calc. forC,2H,6~NiSel,: C, 22.7; H, 3.1; N, 1.2%).X-Ray Crystal Structure Determinations of "Me,] ,[Cu(C,-Se5),]*2MeCN (2) and [NBu",][Ni(C,Se,),] (7).-Crystaldata and details of the measurements are listed in Table 1.Theunit-cell parameters were determined from 25 independentreflections having 23 < 20 -= 26" (Mo-K, radiation) and35 < 20 < 54" (Cu-K, radiation) for (2) and (7), respectively.For (2), systematic absences (hkl, with h + k + 1 odd; h01, with 1odd; hkO, with h + k odd; and Okl, with k odd) indicated twopossible space groups, Iba2 or Ibam; the latter was confirmedfrom the successful analysis. For (7), systematic absences (h01,with 1 odd; OkO, with k odd; and 00l, with l odd) enabledassignment of space group P2 /c.The structures of both complexes were solved according tothe direct (MULTAN) method.', Subsequent Fourier mapsrevealed the positions of all the non-hydrogen atoms whichwere refined anisotropically by the block-diagonal least-squaresprocedure.Atomic scattering factors used in the refinementwere taken from ref. 13. Atomic positional parameters forcomplexes (2) and (7) are shown in Tables 2 and 3, respectively.Crystallographic calculations were performed using the pro-grams of Professor K. Nakatsu, Kwansei Gakuin University, onan ACOS 900s computer at the Research Centre for ProteinEngineering, Institute for Protein Research, Osaka University.Figures 1-5 were drawn by the local version of the ORTEP ITprogram.Additional material available from the Cambridge Crystal-lographic Data Centre comprises thermal parameters andremaining bond lengths and angles.Physical Measurements.-Electronic absorption, i.r.,' e.s.r.J.CHEM. SOC. DALTON TRANS. 1990 301 5Table 3. Fractional atomic co-ordinates for [NBu",][Ni(C,Se,),] (7) with e.s.d.s in parenthesesAtom XNi 0.258 5(1)Se( 1) 0.309 73(8)Se(2) 0.464 81(9)Se(3) 0.619 56(9)Sd4) 0.508 78(8)Se(5) 0.355 71(8)Se(6) 0.207 76(8)Se(7) 0.053 06(8)Se(8) -0.102 13(9)Se(9) 0.007 88(8)Se( 10) 0.161 18(8)N 0.758 6(6)C(1) 0.397 7(7)C(2) 0.534 5(8)C(3) 0.417 2(7)C(4) 0.119 4(6)C(5) -0.017 8(6)Y0.241 8(2)0.335 O(2)0.381 l(2)0.364 9(2)0.243 3(2)0.188 7(2)0.156 3(2)0.1 17 9(2)0.150 8(2)0.245 9(2)0.289 8( 1)0.462 9(9)0.313 7(11)0.329 2(14)0.254 2(12)0.175 9(12)0.171 7(12)Z0.519 5(2)0.416 4(2)0.444 2(2)0.576 l(2)0.653 3(2)0.639 l(2)0.629 7(2)0.610 5(2)0.498 6(2)0.393 9(2)0.397 l(2)0.270 2( 10)0.492 2( 12)0.557 3( 15)0.580 5( 13)0.554 9( 13)0.500 4( 13)X0.100 3(6)0.750 8(7)0.742 3(11)0.720 O(9)0.650 O( 1 1)0.695 8(7)0.634 4(7)0.573 3(9)0.556 O(10)0.770 7(7)0.783 3(8)0.795 7(9)0.807 8( 10)0.812 4(7)0.882 9(7)0.931 7(8)1.005 7(9)Y0.229 2( 1 1)0.400 4( 10)0.468 l(13)0.403 7( 14)0.372 l(19)0.525 4(12)0.460 2( 13)0.526 6( 15)0.583 4( 17)0.388 8(11)0.437 2(12)0.360 8( 12)0.408 2( 16)0.541 7(11)0.495 l(13)0.582 3(13)0.546 4( 15)70.461 7( 12)0.1622(11)0.058 7( 15)-0.045 4(17)-0.078 l(20)0.265 7( 14)0.249 6( 16)0.241 l(17)0.133 7(19)0.368 6( 1 1)0.483 7(13)0.576 l(14)0.693 9( 15)0.284 5( 13)0.299 6(14)0.333 2(17)0.344 5( 19)Figure 1.Molecular geometry of the [Cu(C,Se,),12- anion of (2),together with the atom-labelling schemem = 3.469, n = 3.915 A( b )Figure 2. Stereoscopic packing diagram for [NMe,],[Cu(C,Se,),]~2MeCN (a) and selenium-selenium contacts among the [Cu(C,Se,)J2-anion moieties projected along the c axis (b). .Se(7) Se(6) Se(5) Se(4)Figure 3. Molecular geometry of the anion moiety of [NBu",][Ni-(C,Se,),] (7), together with the atom-labelling scheme0 0 0 0 0 Cb b bFigure 4. Stereoview of the packing of the anionic moieties of[NBu",][Ni(C,Se,),] (7) along the b axis; dashed lines represent non-bonded Se - e - Se contacts less than 4.0 AbFigure 5. Stereoview of the packing of the anionic moieties of[NBu",][Ni(C,Se,),] (7) along the c axis; dashed lines represent non-bonded Se - e Se contacts less than 4.0 Aand X-ray photoelectron spectra were measured as describedelsewhere.Electrical resistivities of the complexes weremeasured for compacted pellets [(1)-(6), (8), and (9)] and for acrystal [(7)] by the conventional two-probe method.' Cycli3016 J. CHEM. SOC. DALTON TRANS. 1990Table 4. Selected bond distances (A) and angles (") with e.s.d.s inparentheses for [NM~,],[CU(C,S~,)~]-~M~CN (2)Cu-Se( 1 ) 2.366(3) Se( 1)-C( 1) 1.90( 3)Se(a--C( 1) 1.95(3) Se(2>-C(2) 1.8 1 (2)Se(3)-C(2) 1.89(4) C( 1tC( 1') 1.21(4)Se( 1 )-Cu-Se( 1 ') 95.6( 1) Cu-Se( 1 )-C( 1) 94.9(9)Se(2)-C( l)-C( 1') 119(2) C( 1 )-Se(a-C(2) 93U)Se(l)-C(l)-Se(2) 114(2) Se( 1 )-C( 1)-C( 1 ') 127(2)Se(2)-C( 2)-Se( 3) 12 1 (1 ) Se(2)-C(2)-Se(2') 117(2)Table 5.Selected bond distances (A) and angles (") with e.s.d.s inparentheses for [NBu",][Ni(C,Se,),] (7)Se( 1)-Ni-Se( 5 )Se( 1 )-Ni-Se( 10)Se( 5)-Ni-Se( 6)Se(6)-Ni-Se( 10)C( 1 )-Se(2)-C( 2)C(2)-Se(4)-C( 3)Ni-Se(S)-C(3)Ni-Se(6)-C(4)C(4)-Se(7)-C(5)C(5)-Se(9)-C(6)2.269(3)2.284( 3)2.270( 3)2.279( 3)1.853(13)1.9 12( 16)1.862( 16)1.808( 17)1.848(20)1.896( 13)93.2( 1)87.1(1)86.5( 1)93.2( 1)94.9(7)95.1(7)101.2(4)101.7(5)95.5(6)95.1(6)1.874( 16)1.8 5 5( 12)1.892( 16)1.867( 13)1.794( 14)1.8 53( 1 7)1.909( 12)1.877( 15)1.326( 2 1)1.323(21)100.9(4)123.3( 12)1 17.2( 10)114.1(9)12 1 .O( 10)122.1 (12)117.8(10)113.3(7)118.2(11)122.0( 10)voltammograms were measured in acetonitrile as describedpreviously.'Results and DiscussionCrystal Structure of [NMe4],[Cu(C3Se,),]~2MeCN (2).-Figure 1 illustrates the geometry of the [CU(C,S~,)~]~- anionof complex (2), together with the atom-labelling scheme.Selected bond distances and angles are summarized in Table 4.The copper atom, as well as C(2) and Se(3), is located on the C2axis, and is ligated with four equivalent selenium atoms.Thec,s~, moiety is almost planar (*O.OIO A), similar to[PPh,],[Zn(C,Se,),] reported previously.8 Since the C(2)-Se(2) and C(2)-Se(3) bonds are appreciably shorter thanC(1)-Se(1) and C(l)-Se(2), electron delocalization seems to bemore effective in the terminal CSe, group than in the C2Se4moiety; in accordance with this the C(1)-C(1') bond is short.This behaviour resembles that for [PPh,],[Zn(C,Se,),] inwhich electron delocalization within the CSe, moiety wassupported from both X-ray crystallography and 77Se n.m.r.spectroscopy.8 On the other hand, in [epy],[Cu(C,S,),] l 7the terminal C-S bond (1.654 A) is considerably shortercompared with the other C-S bonds (av.1.733 A), and[NBu",][Ni(C,S,),] also showed the same tendency (terminalC-S bond, av. 1.63 A; other C-S bonds, 1.74 A).'' The electrondelocalization occurs through the central C2S4 part of theC,SS2- ligand, which is in a direct contrast to the C,SeS2-ligand.Although no comparative Cu-Se bond lengths for [diseleno-lato(2 - )]copper(r~) complexes are available, the Cu-Se bondlengths of complex (2) are somewhat shorter than those ofbis[N,N-diethyldiselenocarbamato]copper(r~) (av.2.430which arises from the difference in charges of the ligands.Moreover, the Cu-Se bond of complex (2) is longer than theCu-S bond [av. 2.272(3) A] of the [Cu(C3S,),12- anion.17 Thisdifference arises mainly from a larger atomic covalent radius forselenium (1.17 A) than for sulphur (1.04 A).2o However, thedifference (0.09 A) between the Cu-Se and Cu-S distances isappreciably smaller than that (0.17 A) between Se( 1)-C( 1)[1.90(3) A] and the corresponding S-C bond [av. 1.779(9) A] ofthe [CU(C,S,),]~- anion, indicating that the Cu-Se bond is ofhigher order than Cu-S.The [CU(C~S~,),]~- anion shown in Figure 1 exhibits anon-planar geometry with a dihedral angle of 53.7" betweenthe least-squares planes of the two ligands.This is veryuncommon since bis(dithio1ato)- and bis(diseleno1ato)-metalcomplexes usually assume planar geometries,2 althoughvery few bis[diselenolato(2 -)]metal complexes have beendetermined ~rystallographically.~~*~~ The present finding isvery similar to the unusual non-planar geometry observedin [ ~ ~ ~ ] , [ C U ( C ~ S , ) ~ ] , ' ~ where a dihedral angle of 57.3" be-tween the two dithiolato ligand planes is observed. The com-plex [mb]2[C~(C4N2S2)2]*(CH3)2C0 [mb = methylene bluecation, 3,7-bis(dimethylamino)phenothiazin-5-ium; C4N2S22-= 1,2-dicyanoethylene- 1,2-dithiolate] also has a dihedral angleof 47.3" between the two ligand~.~' Thus, two dithiolato(2 -) ordiselenolato(2 - ) ligands may form a non-planar geometryaround copper(I1) to reduce repulsion between the negativelycharged sulphur or selenium atoms of the ligands.Figure 2 shows the crystal structure of complex (2) andselenium-selenium contacts among the anion moieties.Thecopper atoms which are located on the special positions (0, 0, $)and (i 3, $) interact with each other through interligandselenium-selenium contacts (3.47-3.92 A) within the sum ofvan der Waals radius of selenium (4.0 A),,' so forming a two-dimensional sheet of interacting anions parallel to the ab plane.The spacing between the sheets is 7.760 A. The tetramethyl-ammonium cations and acetonitrile molecules are alternativelyarranged along the b axis strictly midway between the sheets.The sheet formation can be compared with the one-dimensionalmolecular interaction through sulphur-sulphur contacts ob-served for [epy],[Cu(C,S,),].' Noting the extension from aone- to two-dimensional molecular interaction, selenium withdiffuse extended p and d orbitals seems indeed to be moreeffective than sulphur in such interactions.Crystal Structure of [NBu",][Ni(C,Se,),] (7).-The mole-cular structure of the anion moiety is illustrated in Figure 3 withthe atom-labelling scheme.Selected bond lengths and angles arelisted in Table 5. The nickel atom is co-ordinated by fourselenium atoms. The C,SeS moieties are also almost lanar(+O.OlO A).The terminal C-Se bonds (av. 1.801 8; areconsiderably shorter compared with the other C-Se bonds (av.1.875 A). Electron delocalization occurs through the centralC,Se, skeleton of the C,SeS2- ligands, as for "Bun,]-[Ni(C,S,),].' The geometry around the nickel atom is slightlydistorted from planarity with a dihedral angle of 6.0" betweenthe two ligand planes. This closely resembles [NBun4]-[Ni(C,S,),] for which the dihedral angle between the twoligand planes is 6.1".18 These structures however do show somedeviation from the essentially planar geometry observed aroundthe metal atom in other four-co-ordinate NiS4 and NiSe,c~mplexes.~ p 2 2 , 2 6 , 2Comparing the structure of (7) with that of "Bun4]-[Ni(C,S,),], the difference (0.12 A) between the Ni-Se andNi-S distances is similar to that (0.14 A) between the averagevalue (1.855 A) of Se( 1)-C( l), Se(5)-C(3), Se(6)-C(4), andSe(lO)-C(6) distances and the corresponding S-C average bondlength (1.725 A) of the [Ni(C,S,),]- anion.Thus, nJ. CHEM. SOC. DALTON TRANS. 1990 30172.0 r1.6aa g 1.22 0.8 a0.4300 400 500 600 700Wavelength / nmFigure 6. Electronic absorption spectra of [epy],[Cu(C,Se,),]=MeCN(1) (1.5 x mol drn-j) in acetonitrileFigure 7. E.s.r. spectra of [epy],[Cu(C,Se,),]-MeCN (1) in the solidstate (a) and in acetonitrile at room temperature (b), together with thatof [ttfl,.,[Cu(C,Se,),] (4) in the solid state (c)I I I 1 1 1 1 1 I l l-1 .o -0.5 0E l V vs. s.c.e.Figure 8. Cyclic voltammogram of the [CU(C,S~,),]~- species(5.5 x lC4 mol drn-,) in acetonitrile: 0.1 mol dm-3 [NBu",][ClO,],scan rate, 0.1 V s-'appreciable high-bond order is deduced in the Ni-Se bondscompared with the Se-C bonds, in contrast to the[Cu(C3Se5),12 - anion.The Ni-Se distances [av.2.275(4) A] are similar tothose of [NBu",],[Ni(bds),] [bds = o-benzenediselenolate-(2-)] (2.259 A)26 and [trntsf],[Ni(tds),] {tmtsf'+ = theradical cation of tetramethyltetraselenafulvalene, 2-(4',5'-dimethyl- 1 ',3'-diselenol-2'-ylidene)-4,5-dimethyl- 1,3-diselenole;tds = [2,2-bis(trifluoromethyl)ethylene]-l, 1-diselenolate(2 - )}(av. 2.255 A),27 the only other structurally characterizedbis(diseleno1ene)nickel complexes.Figure 4 shows the molecular packing diagram of the anionmoieties of the complex projected along the b axis.Among theanions, several selenium-selenium contacts (3.603-3.95 1 A)within the sum of the van der Waals radius of selenium areobserved. The almost planar [Ni(C3Se5),] - moieties arelocated in a zigzag arrangement with a dihedral angle of 74.1'between them to form a one-dimensional anionic chain alongthe c axis. These chains interact with each other throughselenium atoms CSe(2) Se(2'), 3.643(3); Se(2) Se(3'),3.838(3); Se(3) Se(2'), 3.837(3) A] to form another molecularinteraction along the c axis (see Figure 5). Another closestselenium-selenium contact between the anionic moieties is4.101(3) A.Spectroscopic and Oxidation Properties of the [Cu(C,Se5),I2 -and [Ni(C3Se5),12 - Complexes.-The electronic absorptionspectrum of (1) dissolved in acetonitrile is illustrated in Figure 6.The intense bands at 367 and 563 nm are ascribed to the ligandn-x* transitions, which occur at longer wavelengths than thecorresponding bands (310 and 540 nm) of the sulphur analogue,[CU(C,S,),]~-.'~ This finding is also the same as that observedfor the corresponding zinc@) complexes.' Since the band at 400nm observed for the [Cu(C3S,),12 - anion is reasonablyassigned to a Cu - S charge transfer (c.t.) transition based onthe c.t.bands of some copper(@-thiolate c o m p l e x e ~ , ~ ~ - ~ ~ theband at 429 nm of the [CU(C,S~?),]~- species is reasonablyascribed to a Cu +-- Se c.t. transition. This band also occurs ata longer wavelength than the Cu +- S c.t.band, in accordancewith the higher bond order of Cu-Se over Cu-S as describedabove.Figure 7 shows the e.s.r. spectra of (1) both in the solidstate and in acetonitrile solution at room temperature, to-gether with the powder spectrum of (4) in the solid state.Complex (1) exhibits an apparently isotropic spectrum(g = 2.074) in the solid state, which can be compared withthe anisotropic spectrum found for [epy],[Cu(C3S5),]( g , , = 2.092 and g, = 2.026).17 In the solution spectrum theisotropic 63/65Cu hyperfine structure [IAo(63/6sCu)I = 73.0 x10-4 cm-'1 together with 77Se coupling [IAo(77Se)l =51.7 x 10" cm-'1 is observed. A drastic decrease inA0(63/65C~) values was proposed for CuS4 complexes uponsome distortion from a square-planar to a tetrahedral geometryaround the copper atom.3 The [CU(C~S~),]~- anion exhibitsa low A0(63/65C~) (66.5 x 10-4 cm-') in acetonitrile, indicatinga distorted CuS, geometry in solution.However, the valueof A ~ ( ~ ~ / ~ ~ c u ) for [Cu(C3Se,),l2 - in acetonitrile is close tothat of a square-planar CuSe, species, bis[N,N-diethyl-diselenocarbamato]copper(~~) (74.7 x 10" ~ r n - ' ) . ~ ~ This find-ing suggests that the [Cu(C3Se,),12 - anion assumes a planargeometry around the copper(l1) ion in solution.Complex (3) shows no e.s.r. signal in the solid state,suggesting that metal-centred oxidation occurs to give acopper(Ir1) centre and non-oxidized ligand moieties. Inaccordance with this, the v(C=C) i.r. band of the ligand occurs at1 400 cm-' which is close to that of the [Cu(C3Se,),12- species(1 410 cm-').Complex (4) shows a sharp e.s.r.signal (g = 2.008) (Figure 7)3018 J. CHEM. SOC. DALTON TRANS. 19901.0, R _ b0.2 cU I300 400 500 600 700Wavelength I nmFigure 9. Electronic absorption spectra of [NBu",],[Ni(C,Se,),] (5)(8.2 x mol drn-j) in 1,2-dichloroethane in air. Time (h):(a), 0;(b), 1; (492; (493; w,4; 0 9 5 ; (8),20which is ascribed to the ttf'+ radical cation.,, However, nosignal due to the CU(C,S~,)~ anion is observed.A cyclic voltammogram of the [Cu(C,Se,),]* - anion inacetonitrile is shown in Figure 8. Oxidation peak potentials at-0.8 and -0.15 V [us. saturated calomel electrode (s.c.e.)]correspond to the oxidation processes of [CU(C~S~,)~'J' - and[Cu(C,Se,),]'- species, respectively.Although the [Cu(C,-Se,),]' --[Cu(C,S,),] - redox process is irreversible, theoxidation peak potential is 0.17 V lower than that of the[Cu(C3S,),12 --[Cu(C,S,),] - pro~ess.'~ This behaviour issimilar to the observation that oxidation potentials of[M( C,Se,),]" - -[ M(C3Se,),](" - ' ) - are 0.06-0.39 V lowerthan those of [M(C,S,),]"--[M(C3S,),1'" - ')- (M = Ni" orPd", n = 2; Au"', n = l).,,Although complex (3) appears to be a copper(m) complex,exhibiting no e.s.r. signal in the solid state, an acetonitrilesolution of this complex gave appreciable signals in the e.s.r.spectrum, essentially the same as those of (l), indicating theformation of the copper(I1) species in solution (see Figure 8).Interestingly recrystallisation of complex (3) from acetonitrileafforded crystals of (2) which were scarcely soluble in organicsolvents.Although oxidation of the [Cu(C3Se5),] - species byiodine in solution resulted in decomposition of the Cu(C,Se,),skeleton, oxidation of the [Cu(C3SeS),l2 - species with ttf'+(the redox potential of ttfO/ttf*+, 0.33 V us. s.c.e.,') afforded afurther oxidized species, (4), as a black solid.As illustrated in Figure 9, the absorption spectrum of thenickel(I1) complex, (5), changes with time in 1,2-dichloroethanesolution in air owing to aerial oxidation of [Ni(C,Se,),]'- to[Ni(C,Se,),] - with the final spectrum being identical with thatof [NBu",][Ni(C,Se,),] (7) obtained by electrochemicaloxidation of the [Ni(C,Se,),12- species in acetonitrile. Thestable oxidation process of this anion is reflected in thereversible redox potential at 0.1 1 V us.s.c.e. which was observedin a cyclic voltammogram of complex (5) in acet~nitrile.~Although complex (7) is formally in the Ni'I'state, the bindingenergy (854.4 eV) of the Ni 2p+ electrons of this complex asdetermined by X-ray photoelectron spectroscopy is very closeto that (854.2 eV) of complex (5). This suggests a ligand-centredoxidation, as observed for [NBu",][M(C,S,),] (M = Ni, Pd,or Pt).36 Furthermore, the v(C=C) band in the i.r. spectrum of[NBu",]~[N~(C,S~,),] at 1430 cm-' is shifted to 1 380 cm-'upon the one-electron oxidation, which is similar to the low-frequency shift of v ( W ) bands of C,S,-metal complexes upon~xidation.,~ However, the i.r.spectra of the further oxidizedspecies, (8) and (9), were too broad to observe the bands.The e.s.r. spectrum of (7) measured in acetonitrile at roomtemperature shows an isotropic signal at g = 2.095, which canbe compared with that of [NBu",][Ni(C,S,),] (g = 2.04).36However, e.s.r. signals of the further oxidized species, (8) and (9),were too broad to be interpreted. This may be related toelectron delocalization through the more effective conductingpathways of these complexes, which leads to much higherconductivities, as described later. Extreme broadening of signalswas also observed for [dep~),.~~[Ni(C,S,),] [depz = 1,4-diethylpyrazinium(2 + )] which also shows a high electricalcond~ctivity.~~Electrical Conductivities.-The complexes in this studybehave as semiconductors in the temperature range measured(- 30 to + 30 "C).Electrical conductivities measured forcompacted pellets at 25 OC are 1.2 x lC7 S cm-* (activationenergy, E, = 0.37 eV) for (1), 7.1 x lC7 S cm-' (E, = 0.25 eV)for (2), and 6.9 x lC7 S cm-' (E, = 0.22 eV) for (3).Conductivities of these complexes may arise from conductionpathways constructed with selenium-selenium contacts asdescribed in the crystal structure of (2). These values can becompared with a conductivity of 7.1 x 10-" S cm-' for[epy]2[Cu(C3S,),] in which there is a one-dimensional chainarrangement through weak sulphur-sulphur contacts.' Thettf" radical cation complex (4) exhibits a somewhat higherconductivity C1.4 x S cm-' (E, = 0.76 ev)], which ispossibly due to electrical conduction through a ttf' + radicalcation column.Although the nickel complex (5) has a small conductivity(5.0 x 1C8 S cm-') for a compacted pellet at 25 "C, complex (7)exhibits a conductivity of 2.0 x 10-4 S cm-' (measured for asingle crystal along the c axis) at 25 OC.This arises from anelectrical conduction pathway constructed with molecularinteractions among the ligands through selenium-seleniumcontacts as shown in the crystal structure (Figures 4 and 5). Thefurther oxidized complexes (8) and (9) exhibit higherconductivities of 0.21 (E, = 0.075 eV) and 0.056 S cm-' (E, =0.10 eV), respectively, for compacted pellets at 25 "C. 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Soc., 1971,93,2258.1986,113,137.Received 26th April 1990; Paper OlOl872