ether phase decanted. The precipitate was washed several times with ether and finally dried to give the deprotected product as a white powder (13 mg. 91 %). The reductive amination was carried out using a modification of a published procedure . In a typical experiment, the protected peptide la (10 pmol) was dissolved in 2 mL of a 10: 1 mixture of 0.1M phosphate buffer (pH 6.0)and CH3CN.To this peptide solution were added the carbohydrate (200pmol) dissolved in 2 mL of the Same buffer and sodium cyanoborohydride (200pmol) as a solid. The mixture was stirred at room temperature and progress of the coupling reaction monltored by analytical HPLC. The glycopeptides were purified by semipreparative HPLC and characterized by ESI-MS. Received: December 22, 1995 [286841E] German version: A n g c w Chenl. 1996,108. 1325- 1328 Keywords: glycopeptides syntheses - lipopeptides - oximes solid-phase [l]I. J. Goldstein. R. C. Hugues, M. Monsigny. T. Osawa. N. Sharon, Nature 1980,285, 66;N. Sharon, H.Lis, The Proreins. Vol. 5, Academic Press, New York, 1982,pp. 1-123. J. F. Fisher. A. W. Harrison. G. L. Bundy. K . F. Wilkinson. B. D. Rush, M. J. Ruwart, J. Med. Chem. 1991,34,3140-3143. H . Kunz, Angew. Chem. 1987,99,297;Angew. Chem. Int. E d EngI. 1987,26. 294-308,U.Sprengard, G. Kretzschmar. E. Bartnick. C. Huls. H. Kunz. ihid 1995. 107, 1104 and 1995.34. 990-993; 0.Frey, M. Hoffmann. H. Kessler, ihrd. 1995,107,2194-2195 and 1995,34, 2026-2028. M. Schnolzer. S.B. H. Kent, Screnc~1992.256.221 -225;P. E. Dawson, T. W. Muir. I. Clark-Lewis, S . B. H. Kent, ihid. 1994.266,776-779:G. Tuchscherer, Tetraheilron Lerr. 1993. 34,8419-8422.  P. E. Dawson, S. B. H. Kent, J. Arn. Cheni.So<.1993,115, 7263-7266. J. Shao. J. P. Tam, J. An?. Chern. Soc. 1995,117, 3893-3899. 1. Fisch. G Kunzi. K. Rose. R. E. Offord, Biotonjugute Chern. 1992,3,147153. 181 K. Rose, J. An?. C h m . SOC.1994,116. 30-33. B. A. Schwartz. G . R. Gray. Arch. Biochem. Biophys. 1977,181. 542-549. [lo]P. Finch. 2. Merchant. J. Chent. Soc Perkin Tran.~./,1975,16821686.Preliminary ‘ H and ”C N M R investigations on amino-oxy acetic acid u-glucose oxime demonstrate the presence in solution of a mixture of three interconvertible isomers the B-cyclic form and the acyclic Ayn ( E )and unti ( 2 )forms. [ll]P. Dumy, I. M. Eggleston, S. Cervigni, U. Sila, X. Sun, M. Mutter, Terrohedron Lrtr. 1995. 36. 1255-1258. The use of different peptides did not particularly affect the course of the reaction. R. Albert, P. Marbach. W. Bauer. U. Briner, G. Fricker, C. Bruns, J. Pless. Life Sci. 1993, 53. 517-525. was prepared following the procedure  Glucosone 2 (u-arabino-hexos-2-ulose) of D. J. Walton, T. Hvidt, W. A. Szarek. Curbolijdrate Res. 1987,167. 123  M. Mutter, R. Hersperger, Angew. Chem. 1990.102,115; Angew. Chem. Znr. Ed. Engl. 1990,29, 185-187. The pure products 18 and 19 were characterized by electrospray ionization mass spectroscopy (ESI-MS). Found: 2135.6 (calcd: 2135.2). considered whether the electrostatic activation of the electron affinity of aromatic systems could be raised to such an extent that their “antiaromatic” (LUMO-filled) reduction products would be capable of existing as thermodynamically stable compounds such that their chemical properties could be investigated. This would open up new perspectives in the chemistry even of conventional aromatic compounds. The protocol for transforming arenes into powerful oxidants by electrostatic activation is based on the fundamental conditions of Coulomb’s Law: 1 ) introduction of the maximum number of onio substituents structurally possible at the organic x-electron system (per(onio) substitution); 2) the use of onium centers of the highest possible electropositivity so as to generate high pole strengths; 3 ) choice of the shortest possible distances of the positive poles from the organic system. For a given structural type there is no freedom of choice with criterion 1). However, for criteria 2) and 3) it must be considered carefully whether the use of an element from the first period as an onium center produces a more efficient electrostatic effect than an isoelectronic element from a higher period, because the development of the positive charge of the onium center and its distance from the central system in this comparison are inversely related. Semiempirical calculations show that phosphonio substitutents are far more efficient for our purpose than triorganoammonio substituents.[’] This is consistent with the comparatively higher stability of phosphonium relative to ammonium ylides. The attempt to achieve per(onio) substitution on hexafluorobenzene (1) by the reaction with PR,/Me,SiOTf (Tf = trifluoromethanesulfonyl) under a variety of conditions led only to the formation of the 1,4-bis-phosphonio-substitutedsystem 4a,b (Scheme F I + + 2 Me,SiOTf 3 chlorobenrere. A FQ F +2L b - 2 MeaSiF F Q ‘F 20Tf- F F LC 1 4a, L = PEtpPh 4b, L = PEtPhp 2 Scheme 1. Synthesis of 1.4-bis-phosphonio-substituted benzene derivatives Charge and Potential: Arenes as Oxidants** Robert Weiss,* Robert May, and Bernd Pomrehn We have shown that the transition from neutral to cationic sets of substituents achieved for both inorganic and organic systems by using the trimethylsilyltriflate-assisted poly(onio) substitution method developed by us leads to a marked increase in their electrophilicities and electron affinities.“ This is attributed primarily to the electrostatic field effects of the cationic substituents. Recently we reported on the first per(onio) substitution of hexafluorobenzene with 4-dimethylaminopyridine (DMAP) as a preliminary highlight of this We [*] Prof. D r R. Weiss, Dr. R May, Dr. B. Pomrehn [**I Institut fur Organische Chemie der Universitlt Erlangen-Nurnberg Henkestrasse 42,D-91054 Erkangen (Germany) Fax: Int code +(9131)859132 This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. 1232 $.? VCH Verlag.~~es~~llsc/iufi m h H , D-69451 Weinherrn, 1996 Cyclic voltammetric investigations of the salts 4a,b reveal two quasi-reversible redox steps at remarkably positive potentials (Table I).[’] In spite of the relatively high electron affinity of 4a,b these salts are not activated towards further nucleophilic substitution. This in sharp contrast to the analogous substitution of hexafluorobenzene with DMAP, which under autoactivation leads to per(onio)-substituted products. In this case, in Table 1 Half-wave potentials of the poly(onio)-substituted arenes [a]. Compound  1st Reduction [V] 2nd Reduction [V] 4a 4b 6 7a 7b 9a 10 - 0.83(q) - 0.76 (q) - 1.46 (q) - 1.36(4) - 0.09 (I) - 0.19 (r) - 0.06(r) - 0.04(r) [a] r 0.04 (q) 0.03 (r) 0.14 (r) 0.60(r) 0.14(r) 0.80(r) = reversible, q = quasi-reversible. i 0570-083319613511-1232 $ 15.00+ ,2510 = irreversible Angeiv. Chem. Inr. Ed. Engl. 1996.35, No. 1 1 COMMUNICATIONS addition to steric effects. electronic effects are probably responsible for the resulting products. According to PM3 calculations the LUMO of 4a,b is predominantly localized on C atoms positioned cx to the phosphonio substitutents. so that the electronic prerequisites for further onio substitution are unfavorable. The hitherto unknown per(onio) substitution on naphthalene should. because of the larger number of cationic substituents and the inherently higher electron affinity of naphthalene, lead to a further increase of the electron affinity relative to that of the analogous benzene derivatives. By using DMAP/Me,SiOTf and octafluoronaphthalene (5)we achieved per(onio) substitution in the naphthalene system for the first time. The octacationic salt 6 could be isolated as a stable, water-soluble, pale yellow compound in almost quantitative yield (Scheme 2 ) . The replacement C8L + 8 MenSiOTf 3 Lm L+ - 8 MeaSiF L+ L' >:. / / L+ 8 OTf- 6, L = DMAP F F W F F F F 1 +4L 5 ci r41 L 4 OTf - 8 3 OTf - 9a, L = PEt3 9b, L = PPh3 10, L = PPh3 Scheme 3 Onio substitution of tetrachloropyrimido[5.4-c~pyrim1dine. RT temperature = room agents used in organic synthesis.["] As a consequence of the increasing positive charge on the phosphorus center when alkyl is replaced by ary118b1 the intially formed salt 9b, obtained when PPh, is used analogously as a nucleophile, already has such a high electron affinity that it is quantitatively reduced by excess phosphane to the new tricationic radical salt 10. The latter is a deep green isolable salt that has been fully characterized, including by a high-resolution ESR spectrum. With a strong oxidizing agent such as NO' 10 may be reconverted to 9b. The measured half-wave potential for this conversion of 0.80 V (vs. Ag/AgCl) establishes this compound as the most powerful "aromatic oxidant" known to date. Calculations show that the charge distributions in the antiaromatic red-forms of the polyphosphonio salts 4, 7, 9 are characterized by a maximum charge pairing in terms of the bis-ylidic mesomeric structures A and B/C (Fig. 1 ) . 4 OTfblwobenzene. A - 4 MenSiF 7a, L = PEt2Ph 7b, L = PEtPh2 Scheme 2. Octakic- and tetrakis(onio) substitution of octafluoronaphthalene A of DMAP with tertiary phosphanes led under otherwise identical conditions exclusively to the formation of good yields of the tetrasubstituted products 7a,b, i n which the fluoro and triorganophosphonio substituents alternated along the periphery of the naphthalene core. Investigations into the regiochemistry of the S,Ar reaction at octafluoronaphthalene indicate that substitutions at C-2/C-6 precede those at C-4/C-8.['01The interplay of steric and electronic factors evidently hinders per(onio) substitution by phosphonio substituents as for the benzene system. Electrochemical measurements on salts 6 and 7a,b confirm an unprecedented high electron affinity for benzenoid aromatic compounds (cf Table 1). Remarkably, four triorganophosphonio substituents are as effective in raising the redox potentials as eight pyridinio substituents-an expected trend (see above) in view of the higher capability of phosphonio substituents to stabilize carbanions. The tetraphosphonio-substituted salts 7a,b represent the ox-forms of a new, completely reversible two-step redox system whose oxidizing power is similar to that of chloranil.[' '1 According to PM3 model calculations, replacement of the C F groups by N in salts of the type 7a,b should lead to an even larger increase in the electron affinity.['] This could be confirmed experimentally. The reaction of tetrachloropyrimido[5,5-Lijpyrimidine[1zl(8) with four molar equivalents of PEtJ Me,SiOTf led smoothly to the formation of the corresponding tetrakis(oni0)-substituted salt 9 a (Scheme 3).[l3I The "aromatic" compound 9 a is the ox-form of a completely reversible two-step redox system (Table 1) and, with a half-wave potential of 0.60 V (vs. Ag/AgCl) for the transition oxjsem, has at least the oxidizing power of 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) one of the most powerful organic oxidizing c B Fig. I. Bis-yl~dicmesomeric structures of the red-forms. X = CF. N. The position of the pertinent redox potentials and the reversibility of the corresponding reduction steps (cf Table 1) opens up the prospect of generating such systems in a straightforward manner by chemical methods. With the synthesis of the sem-form 10 the first step in this direction has already been taken. Owing to the clear structural analogy with the corresponding quinones we designate the red-forms A-C as "quinobis-ylide~".['~IThe controlled reductive generation of suitable representatives of this class of substances is the subject of current investigations. Experimental Procedure All reactions were carried out under N, and in dried solvents. Correct C. H. N analyses were obtained for all compounds prepared. 4a,b. Compound 3 (2 mmol) and PEt,Ph or PEtPh, (2 mmol) were added to a solution of 1 ( I mmol) in chlorobenzene (20 mL) and the solution was stirred under reflux. After 24 h (4a: or 72 h for 4b) the white precipitate was filtered off. washed with Et,O ( 5 x 5 m L ) and dried for 12 h under high vacuum. 4 a : Yield: 99%: ' H NMR (400.05 MHz, CD,NO,!CF,COOD. 21 C. TMS): 6 =7.95 (m. 6H: H-2jH-4:H-6, phenyl). 7.80 (m. 4 H ; H-3;H-5. phenyl), 3.20 (m. XH: CH,). 1.38 (dt. ,J(H.P) = 22.21 Hz. 3.1(H.H) = 7 56 HI. 12H: CH,); "C NMR (100.5 MHz. CD,NO,iCF,COOD, 21 C. TMS). d = 150.27 (dm. 'J1C.F) = - 255.5 Hz. C2 C3/CS!C6. benzene). 137 54 (s: C4. phenyl). 133.61 (d. 'J(C.P) = 9.2 Hz: C2;C6. phenyl). 132.03 (d. 'J(C,P) =12.8 HI. Ci.;C5. phenyl). 121.67 (4. 'J(C.F) = - 319.8 Hz, CF,). 116.40(d. 'J(C,P) = 84.5 Hz: C1. phenyl). 109.43 (dm. '4C.P) = 84.5 Hz; CIIC4, benzene), 15.65 (d. './(C.P) = 49 7 H7. CH,). 6.09 (d. 'J(C.P) = 3.7 Hz, CH,); "P NMR (I61 7 M H r , CD,NO, CF,COOD. 21 C. ext. H,PO,): d = 35.53 (s). 4 b : Yield- 50%: ' H NMR (400.05 MHz. CD,NO,/CF,COOD. 23 C, TMS): 6 =7.99 (m. 12H. H-2:H-4.'H-6. phenyl). 7.85 (m. 8 H : H-3iH-5. phenyl). 3.54(m. COMMUNICATIONS 411. ( ' H 2 ) . 1 4 1 ((It. .'./(H.P) = 72.10 H7. './(H.H) =7.33 Hz: 6 H : CH,). "C NMR (100.5 MHI. C'D,NO, CW,COOD. 23 C. TMS). d =15O.I4 (dm. './(C'.F) = -- 265.7 HL. C?:C3,CS C6. benzene). 137.83 (d. 'J(C,P) = 3.6 Hz: C4. phenyl). 134.82 (d. 'J(C.P) = 11.1 H / : C3,C6. phenyl). 132.14 (d. ,J(C.P) = 11.9 H<: C3 C5. phcnyl). 121.71 (q. ' J ( C . F ) = - 318.0 Hr: CF,). I15.XO (d. 'J(C.P) = 88.3 H7: C l . phenyl). I10 65 (dm. './(C,P) = 88 3 Hz: C1 C4. benrenc). 19.36 (d. 'J(C.P) = 49.7 H r , CH,). 6.94 (d. 'J(C.P) = 5.5 Hz. CH,): "P NMR (161.7 MHz. CD,NOZ CF,COOD, 23 C. ext H,PO,): 0 = 26.71 (s). 6: Compound 3 (0.80 inL. 4.43 mmol) and 6 (0.605 g. 4.95 inmol) were added to a solution o f 5 (0.149 g. 0 55 mmol) i n chlorobenzene (20 mL) and the solution was stirred under reflux. After 12 h the yellow precipitate \+as filtered off. washed with CH,CI, ( 4 x 5 mL) and dried for 13 h under high vacuum. Yield: 1.34g (98%): ' H NMR (400.05 MHr. CD,CN. 24 C . TMS): 0 = 8.05 (d. 'J(H.H) =7.57 HL. XH. H-2,H-6). 7.83 (d. 'J(H.H) =7.51 Hz. XH; H-2,H-6). 6.87 (d. .'J(H,H) = 7.57H~.8H.H~3,H-5),6.86(d.'J(H.H)=757Hz.XH:H-3,H-5).3.24(s.24H: CH,). 3.20 ( s . 24H: CH,); "C NMR (100.5MHz. CD'CN. 24 C. TMS): h =157.30 ( s : C4. DMAP). 156.81 (s: C4. DMAP). 142.29 (s: C2;C6. DMAP). 14042 (s: C2C6. DMAP). 140.37 (s. C1 C4.C5 CX, naphthalene). 138.49 (5. C2: C3 C6.C7. naphthalene). 131.34 (s: C9:CIO. naphthalene). 121.88 (q. 'J(C.F) = - 319.9 HziCF,). I I ~ . ~ ~ ( S : C ~ , C S , D M1 A 1 0P. 7) 0. ( ~ ; C 3C5.DMAP).41.80(s, C H , ) . 4 1 . 6 0 ( ~ CH,): : I9F NMR (470.4 MHz. CD,CN. 20 C.C,F,): d = -77.9 ( s . CF.3). 7a,b- Compound 3 ( 2 mmol) and PEt,Ph or PEtPh, ( 2 mmol) were added to :I solution of 5 (0.5 mmol) i n chlorobenzene (20 m L ) and the solution was stirred under reflux. After 48 h the suspension was cooled to - 20 C. the precipitation was coinpleted by the addition of Et,O (20 mL). and the precipitate was filtered off. washed with E t 2 0 ( 5 x 5 mL). and dricd for 1 2 h under high vacuum. [I] R. Weiss. N. J. Salomon, G E. Miess. R. Roth. AiiLqrw.Chmi. 1986, YH. 925, Angrn. C h i f . In2 E d €fig(. 1986, 25, 9 17. 121 R . Weiss, R. Roth, J. Chciii Soc. C h i i . Con?fiiwi.1987, 317.  R. Weiss. R. Roth. .Tnithc\t.\ 1987. 870.  R. Weiss. J. Seuhert. Atlgiw. Cbcm 1994. 106. 900: A n p i t . . Cbcfi?.In/.E d Engl. 1994. 33, 891.  R. Weiss, J. Seubert, F. Hainpel, Angeii'. Cliriii. 1994, 106. 2038: Aiigew. C/icwi. lm. Ed. Eiig1. 1994, 33. 1952. [h] R. Weiss. B. Pomrehn. E Hampel. W. Bauer. A!~goic C ~ E I1995. ~ I . 107, 1446; AtIg(,ll c/iPt7I. / f i r . Ed. Etlg/ 1995. 34, 1319.  B. Pomrehn. Dissertation, Universitit Erlangen-Nurnberg. 1996. [XI The corresponding salts of the benzene parent structure have already been reported- a ) L Homer, G. Mummenthey. H. Moser, P. Beck. CIi~ni.BPI.1966. YY. 2782: b) H Bock. U. L. Knoblauch. P. Hamel. ibid 1986, 119, 3749 191 The electrochemical invcstigationa were carried out at room temperature under N 2 with ferrocenc as the internal standard in a 0.1 k NEt,BF,.'CH,CN elecrrolyte solution against a saturated Ag;AgCl electrode iinincrsed in a 0.1 ~i NEt,CI'CH,CN solution. Auxiliary and working electrodes were made of platinum. [lo] C L. Cheong. B. J. Wakefield. J, Cliivii. So<..PerXiii Truns. 1 1988. 3301. [ l I ] M. E. Peovcr. J. C/iwii. Sol,. 1962. 4540.  F. G. Fischer. J. Roch. W. P. Neumann. Liebig.5 A m . C h i ? . 1960. 631, 147. [I31 R. May. Dissertation. Universitilt Erlangen-Niirnberg, 1993. [I41 Because of the inverse polarity of the functional groups the red-forms may also be designated as "antiquinones". 7a. pale yellow powder: yield. 9 5 % : ' H NMR (400.05 MHz, CD,CN, 24 C. TMS) h=7.85(m.XH;H-2 H-6.phenyl).7.73(rn.4H.H-4.phenyI).7.67(m,SH. H-3.H-5. pheiiyl). 2.85 (m. 1 6 H ; CH,). 1.06 (dt. ,J(H.P) = 21.73 Hr, .'J(H.H) = 7.57 Hz. IZH;CH,), 1.01 (dL3J(H.P) = 22.22 Hr.'..I(H.H) =7.32 Hz.12H.CH,); "C NMR (100 5 MHz. CD,CN. 24 C. TMS). d = 167.65 (dd. 'J(C.F) = - 362.9 Hr. './(C.F) =10.1 Hz: C4 C8. naphthalene). 166.26 (din. 'J(C.F) = - 270 3 Hr: C?,C6. naphthalene). 136.82 (d. 'J(C.P) = 3 7 Hr: C4, phenyl). 135.99 (s: C4, phenyl). 133.39 (d. 'J(C.P) =11.0 Hz: C2 C6. phenyl). 132.27 (d. 'J(C.P) = 9.2 H7; C 2 C6. phenyl). 131.63 (d. 'J(C.P) = 12.8 Hr: C3 C5. phenyl). 131.46 (d. 'J(C.P) = I 2 9 Hz: C3 C5. phenyl). 119.88 (in: C9 C10. naphthalene). p3 121.92 (q, 'J(C.F) = 319.9 Hz: CF,). 120.01 (d. 'J(C.P) = 86.4 Hz: CI. phenyl). Jan Foerstner, Falk Olbrich, and Holger Butenschon* 116.31 (d. 'J(C.P) = 84.6 Hz: CI. phenyl). 106.46 (in: C 3 C7. naphthalene). 102.26 (dd. 'J(C.P) =75.3 Hz. 'J(C.F) =19.4 H r : CI C5. naphthalene). 17.78 (d. Dedicated to Prqf>ssor Ertt,in Weis., 'J(C.P) = 44.1 H7: CH,). 15.40 (d. 'J(C.P) = 47.8 HL: CH,). 6.64 (d. 'J(C,P) = 3.7 H r . CH,). 6.1 1 (d. './(C.P) = 5.5 Hz: CH,): "F NMR (470.4 MHz. CD,CN. on the occcision of' his 70ih biriliday 20 C. C,)F,,): 6 = -78.0 (5. 12F: CF,). -14.8 (in. 2 F . F-4 F-8). -67.9 (in. 2 F: F-2.F-6). "P NMR (161 7 MHz. CD,CN. 20 C. cxt. H,PO,): 6 = 42.98 (dd. "Phosphaalkynes correspond to alkynes in all aspects, to ni'./(P.F) =18 4 HI: "J(P.F) = 8.7 HI: P-3 P-7). 35.71 (d. ',/(P.F) = 6 2 H7: triles in nothing." This remark by Regitz"] is substantiated by P-I P-5). A New Mode of Reaction of tevt-Butylphosphaethyne: Trinuclear Cyclopentadienylcobalt Clusters with P, PS, and PO as Complex Ligands** ~ 7 b . pale orange powder: yield. 88%: 'H N M R (400.05 MHz. CD,CN. 21 C. TMS): h =7.85 7.62 (m. 4 0 H ; phenyl). 3.33 (m. 8 H ; CH,), 1.11 (m, 12H: CH,). " C NMR (100.5 MHz. CD,CN, 21 C. TMS): 6 =137.19 (s: C4. phenyl). 136 69 (s: C4. phenyl), 133.34 (d. 'J(C,P) = 1 I .0 Hz: C2:C6. phenyl). 132.55 (d. 'J(C.P) = 1 1 1 Hz: C2tC6. phenyl). 131.66 (d. 'J(C,P) = 14.7 Hz: C3 C5. phenyl). 130 70 (d. .'J(C.P) =12.9 Hz; C3 C5. phenyl). 129.66 (m: CY'CIO. naphthalene). 121.92 (9. ' J ( C . F ) = - 3 1 9 . 9 H z : C F 3 ) , I 1 9 . l 0 ( d . ~ J ( C , P )86.4Hr:Cl.phenyl). = ll5.57(d. 'J(C.P) = 84.6 Hz: C1. phenyl). 103.72 (m. C3:C7. naphthalene), 101.18 ( m ; C1 C5. naphthalene). 18.53 (d. 'J(C.P) = 51.5 Hz; CH,). 17.44 (d. 'J(C.P) = 53 3 Hz: CH,). 8.21 (d. 'J(C,P) = 5.5 H7: CH,). 7.09 (d. 'J(C.P) = 3.7 Hz: CH,): "FNMR(470.4 MHz.CD,CN.20 C.C,F,)-h = -78.0(s. 12F:CF,). -69.0(m. 2F. F-4 F-X), -66.6(m. 2 F ; F-2 F-6): "P NMR(161.7 MHr,CD,CN,20 C.ext H,PO,): d = 32.63 (d. 'J(P,F) = 18.2 Hz. P-3 P-7). 26.07 (d. ',/(P.F) = 4 I f l / : P-I P-S) 9a: Compound 9 ( I inmol) *as suspended in CH,CI, (30 niL) and 3 (4 inniol) nab added. Subsequently. PEt, (4 mmol) dissolved in CH,CI, (10 inL) was added to the mixture. After the mixture had been stirred for 12 h a t room temperature. the pale green precipitate was filtered off, washed with CH'CI, (3 x 5 m L ) and dried for 12 h under high vacuum. Yield. 62"h: ' H NMR (399.65 MHz. CD,3CN. 20 C. TMS): 2 85 (m, 24H: CH,) 1.29 (in, 36H; CH,). 10. Compound 9 ( I minol) was suspended i n CH,C12 (20 inL) and 3 (4 inmol) was added. Subsequently PPh, (6 mmol) dissolved in CH,CI, (20 InL) was added to the mixture. After the mixture had been stirred for 12 h at room temperature Et,O (100 mL) was added to precipitate a green solid. The solid h a s filtered off, washed with Et,O (3 x 5 mL) and dried for 12 h under vacuum Yield: 6 9 % ; UV.Vis (CH ,CN). i,,, (c) = 668 (4870). 614 ( 5 3 5 5 ) . "'072 (2920). 439 (6330). 382 (8520). 270 (370x5). 214 (91945). Receiwd: Deceinbei- 15. 1995 [ Z 8655 IE] Germail version: ,Aiigiw C h i l i . 1996. 108. 1319 1371 Keywords: arenes . heterocycles . nucleophilic aromatic substitutions phosphoniurn salts * polycations the results of our investigations of the chemistry of [w-phosphanyl(ethylcyclopentadienyl)]cobalt complexes. Herein we report on reactions of such complexes with terr-butylphosphaethyne that in addition to diphosphete complexes result in the formation of p,-phosphido clusters in good yields. The "naked" phosphorus ligand in these clusters can be oxidized with elemental sulfur or with oxygen in the air to give PS and PO ligands, respectively. The chemistry of phosphaethynes has been investigated intensely in the past few years.[2J In a few cases mononuclear transition metal complexes with a monomeric phosphaethyne ligand have been Because we were able to coordinate alkynes with the [(o-di-/cv/-butylphosphanyl)ethylcycIopentadienyl]cobalt (Cp'Co) fragment without di- or trimerization.''. we investigated reactions of Cp'Co complexes with tcrt-butylphosphaethyne. The paramagnetic chloride 1 and the [*I Prof. Dr H. ButenschBn. DiplLChem. J. Foerstner lnstitut fur Orgdnische Chemie der Universitit Schneiderberg 1 B. D-30167 Hannover (Germany) Fax: Int. code +(511)762-4616 e-mail: holger.butenschoenin mhox.oci.uni~hannover.de Dr. F. Olbrich Chemisches Institut der Universitat Magdeburg (Germany) [**I We thank the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen lndustrie for their financial support and BASF AG. Bayer AG. Chemetall GinbH, and Hiils AG for donations ofchemicals. We are indebted to ENRAF-NONIUS for their kind support in performing the X-ray crystal structure analysis. We thank Dr G Remherg. GBttingen, and Dr. A. Kornick. Hannover. for mass spectra and helpful discussions.