shows that the strength of the arsenic-chlorine bond increases [2.04+2.59 mdyne/A] in the transition AsCl3+AsOCI3, exactly as in the system PCI3+POCl3 [2.34-+2.98 mdyne/A]. The compounds are therefore also related in the details of their bonding. AsOCI3 slowly decomposes at -25"C, and much more rapidly at ca. O'C, with formation of As2O3Cl4. 3 AsOC1, + C12 + As20,C14 + AsC1, This compound is stable up to 150°C. Its vibrational spectrum reveals disappearance of the As=O double bond, thus ruling out the structure P2O3CI,[Cl2P(O)-O-(0)PCl2]. It is also not volatile, but decomposes above 200°C with loss of AsCI3+Cl2 to give "AszOS"-a process which can be readily monitored in the mass spectrum. As203CI4 is obviously a polymer. I t can be isolated in analytically pure form, but is X-ray amorphous. No crystallization takes place even after 50 hours' annealing at 120°C. In this compounds arsenic is doubtless pentacoordinated, or hexacoordinated by way of chlorine bridges. Recrystallization of (3) from ether gives (COD)2CoLi(THF)2( 3 a ) and on addition of dimethoxyethane (DME), yellow crystals of (COD)2CoLi(DME)3( 3 h ) are obtained. The new cobalt complexes ( 3 ) were characterized by metal analyses and by their reaction with CO, in which four C O per LiCo were consumed with displacement of COD. The IR spectrum (THF) shows all four double bonds are complexed both in (3) and in the isoelectronic compound ( I ) . The 'H-NMR spectrum ([D,]THF, RT) of (36) displays two broad signals at ~ = 7 . 5 7(--CH2) and ~ = 7 . 9(CH=CH), intensity ratio 2 : 1, for the cyclooctadiene. Received: September 14, 1976 [Z 559 IE] German version: Angew. Chem. 88, 806 (1976) CAS Registry numbers: AsOCIJ. 60646-36-8: ASCIS,7784-34-1 : 0 s . 10028- 15-6: A s ~ O ~ C I60646-37-9 J. [ I ] W Dr/iiiicke and J . Weidlriri. Z. Anorg. Allg. Chem. 342. 225 (1966).  K . Seppelt. Angew. Chem. X8. 410 (1976): Angew. Chem. Int. Ed. Engl. 15. 377 ( I 976).  Calculation according to the method ofJ. Becher and R . Motre.+,Spectrochim. Acta, Part A, 23, 2449 (1967). Bis(q-l,5cyclooctadiene)cobaltlithium By Klaus Jonas, Richard Mynott, Carl Kriiger, Janine C . Sekutowski, and Yi-Hung Tsay[*l Nickel(o)-olefin complexes which d o not contain pronounced acceptors as ligands form defined dilithium-nickel-olefin complexes with lithiom[']. We now wish to report a further example of this class of compounds. Reaction ofmetallocene complexes (C5H&M with an alkali metal leads to release of the two C5H5 rings and formation of alkali metal-CsHS and elemental transition metal[21. In the case of cobaltocene and nickelocene we have now found that the deposition of transition metal is suppressed on addition of cyclooctadiene (COD). The new cobalt complex (3) and the known nickel complexes (1)[31 and (2)"' can then be isolated in high yield [ e . g . (3): 85 %]['I. (CsH5)zCo LI. COD C ~ H ~ C O C O+D L I C ~ H , THF. 0°C THF. 0°C 1 2 LI. COD (COD)ZCoLi(THE'), 1 3 ) 2 LI.2 COD (C,H5)2Ni THF. 0°C (C0D)zNi + + L1C5H5 2 LiC5H, (1) THF.0-C 1 2 LI (COD)2K~Li2(THF)4 (2) [*I Dr. K. Jonas ['I, Dr. R. Mynott [**I, Dr. C. Kruger [***I, Dr. J. C. Sekutowski [***I [****I,and Dr. Y.-H. Tsay [***I Max-Planck-Institut fur Kohlenforschung Lembkestrasse 5. D-4330 Mulheim (Germany) ['I T o whom correspondence should be addressed. [**] '-'C-NMR spectra. [***I X-Ray structure analysis. [****] J . C S. thanks the Deutsche Forschungsgemeinschaft for a study grant. A i i g w . Climni. I i i r Ed. Engl. 1 Vol. 15 ( 1 9 7 6 ) No. 12 Fig. 1. Crystal structure of (COD)ICoLi(THF), (30) Figure 1 shows the result of an X-ray structure analysis of ( 3 a ) [a=14.094(1), b= 18.799(3), c = 17.500(3)& /?=97.74(1)", space group C2/c, 3219 reflections, 1485 unobserved, R =0.064]. The bond angles at the cobalt atoms diverge 'pairwise so markedly from an ideal tetrahedron (such as occurs in the isoelectronic complex Ni(COD)2141)that the molecule is better described as a trigonal bipyramid. Its equatorial positions are occupied by Li and by one double bond each of the two olefinic ligands [ C l - C S : 1.413(7)A; C 1 1 4 1 8 : 1.419(7)A]. Owing to bridging with the axial positions of the Co [C4-C5: 1.391(8)A; C 1 4 4 1 5 : 1.401(8)A] the COD ligands assume a highly distorted boat conformation. Short L i - C distances ( L i - C I ; L i - C l 1) indicate strong ion-pair interaction['] between the Li atom in a tetrahedral environment and C atoms of the double bonds in equatorial positions. The L i - C o distance [2.654(8)A] is significantly longer than the sum of the respective covalent radii. The 13C-NMR spectrum[61of ( 3 a ) at room temperature shows only two signals for the C O D at 69.1 and 34.7ppm ([D,]THF) or at 69.5 and 33.7 ppm ([D,]toluene). On cooling a solution in [DJTHF the C O D signals become much broader only below -60°C. In [D,]toluene, on the other hand, broadening begins at O'C, and at -77°C eight signals of approximately equal intensity are observed. Four of the signals lie at 79.6, 74.3, 71.5, and 50.7 ppm (all d, average chemical shift 69.0ppm), and the other four at 38.3, 38.0, 30.2, and 29.0ppm (all t, average chemical shift 33.9 pprn). These temperature effects are reversible. The 13C-NMR spectrum of ( 3 a ) in [D8]toluene at -77°C is compatible with the structure of the crystalline complex: owing to the equatorial position of the Li atom on the cobalt, four distinct pairs of olefinic and aliphatic C atoms are expected. On raising the temperature in [D8]toluene, the Li atom is found to undergo a shift in 767 the (COD)2Co group. The strongly solvating [Ds]THF accelerates this exchange. Table I . Physical properties of complexes ( 3 ) Color Received: September 20. 1976 [Z 560 IE] German version: Angew. Chem. 88. 808 (1976) CAS Registry numbers: O, I3C, 14762-74-4 (COD)zCoLi(THF)z,60718-95-8; ( C S H ~ ) ~ C1277-43-6; - .. (3h) (31.)  131   161  K . Jorras. Angew. Chem. 87, 809 (1975): Angew. Chem. lnt. Ed. Engl. 14, 752 (1975): K . R. Porschkt., Dissertation, UniversitPt Bochum 1975. D . S. Trfart and L . N I ~ I I O I NJ.F . Am. Chem. Soc. 79, 2746 (1957): H . D . Frirz and L . Scltu/er. Chem. Ber. 97, 1829 (1964); C. E . Wrrr and L . J . Baye, J. Inorg. Nucl. Chem. 26, 2099 (1964); A . B. B ~ o i n tand H . R e i d . J . Org. Chem. 35, I191 (1970). B. Bogdartovii. M . K r i j w r . and G. Wilkr. Justus Liebigs Ann. Chem. 699, 1 (1966); K . fischer, K . Jonas, and G . Wilke, Angew. Chem. 85,620 (1973); Angew. Chem. Int. Ed. Engl. 12, 565 (1973). H . Dierks and H . Dietrich, 2. Kristallogr.. Kristallgeom.. Kristallphys., Kristallchem. 122. 1 (1965). D . J . Brairer. C. Kriigrr. P . J . Roherrs, and Y - H . Tsa?., Angew. Chem. XX, 52 (1976); Angew. Chem. Int. Ed. Engl. IS, 48 (1976); R. Zergrr, W Rhirir, and C. Strick?., J . Am. Chem. Soc. Y6. 6048 (1974). The "C-NMR spectra were recorded at 25.2 MHz. Chemical shifts relative to TMS. multiplicities characterized by off-resonance procedure as d =doublet and t=triplet. We have also prepared isoelectronic complexes of iron by the same method, and are investigating further compounds of this type formed by other transition metals. -. I R (KBr) [cm-'1 vC=S ~. .. .- . . 198-202 [a] 206-209 [b] 153-156 [c] orange red rust red (3N) ~~ [I] M.p. (dec.) ["CI .. ~~~~~ -~ ~ - ~~ ~~ I IM) vs. br 1087 vs. br 1092 vs. br ~ . . . ~~~~~ ~~ ~ [a] Dissolved in dibromomethane and precipitated with ether [b] From benzene. [c] From dibromomethaneiacetone. Proof of the structure was afforded by an X-ray structure analysis of (3b), which on the basis of 2121 significant reflections was solved by usual methods and refined to an R value 0.072. (36) crystallizes in the triclinic space group P i witha=1073.9, b=1124.5, c=1448.3pm; rw=90.58, p=91.12, y = 1 16.94"; Z = 2. The nickel atom forms an inversion center and is bonded in a planar array to two trans P and S atoms (see Fig. 1). Bis(diorganylphosphinodithioformato-S,P)nickel(lI) Complexes-Novel Four-Membered Ring Chelates[**] By Jiirgen KopJ RudolfLenck, Sigurjon N . Olafsson, and Reinhard Kramo/owsky[*] Substituted dithioformate ions of type (1) react with many elements to give well known['] four-membered ring chelates in which they coordinate via the two S atoms. A chelate formation with the donor atom of the residue Y and an S atom has been discussed but not proven[']. S /IY-C<? S (1) Fig. I . Molecular structure of the bis(chelateJ ( 3 h ) with important bond lengths (righthand side) and important bond angles (lefthand side); standard deviations in parentheses. Y = N R z , O K , SR As novel ligands of type ( I ) , we prepared the phosphinodithioformates (2) by reaction of secondaryphosphanes and carbon disulfide in the presence of aqueous potassium hydroxide13.41, The exocyclic C-S bond is significantly longer than in thioformaldehyde (rcZs = 161.I pm)I7l, and the endocyclic C - S distance is shorter than the value ( 1 . ~ - ~ = 1 7 to 6 178 pm)['] calculated for C ( s p z ) - Ssingle bonds. Together, these findings are consistent with a marked contribution of the resonance structure (3'). The Ni-S and Ni-P bond lengths are notably (31 The salts (2) react with nickel(l1) salts to give apolar, diamagnetic bis(che1ates) (3) having the composition [Ni(S,CPR,),][4~51. We have now found that the anions of (2) occur as P,S-bonded chelates in these complexes, for, in contrast to (2), they do not react in organic solvents at room temperature with sulfur[61.The high-frequency position of a band attributable to an approximate C=S stretching vibration in the IR spectra (cf. Table 1) also provides evidence for this structure. [*] Dr. J. Kopf, Dr. R Lenck. Dr. S . N. 0lafsson.and Dr. R. Kramolowsky [ '1 Institut fur Anorgdnische und Angewandte Chemie der Universitiit Martin-Luther-King-Platz 6. D-2000 Hamburg I3 (Germany) ['I Author to whom correspondence should be addressed. [**I We thank Professor Weiss and the Deutsche Forschungsgemeinschaft for supplying the diffrdctometer. 768 /3')' shorter than in all previously investigated four-membered ring chelates containing a NiS4 skeleton ( r ~= 21 i 8~ to 224 pm)['bl or planar nickel(l1)complexes with trans-NiP,X2 coordination (rNi--p=225 to 238 pm; X = CI, Br)I9I. Exper-imental Potassium diorganylphosphinodithioformates (2): All operations must be carried out under nitrogen. A solution of the secondary phosphane (30 mmol) and carbon disulfide (30mmol) in tetrahydrofuran (25 ml) is treated with a saturated aqueous solution of potassium hydroxide and the mixture stirred vigorously for 15 h at room temperature. After concentration of the THF solution and addition of ether [or of n-hexane in the case of (2c)] (2) separates out as fine, brightpink to red crystals. Yield 80 to 85 %.