The [diethylphosphoniumbis(methylido)]gold(I) dimer 4 reacts with one equivalent of chlorine, bromine, or iodine to give a series of compounds 5a-e, for which a bicyclic structure with a remarkably short transannular gold-gold hond (229.7 pm) is demonstrated hy means of analytical and s p i r a l data as wcll as by an X-ray analysis of 5a. The two metals of formal oxidation state + I1 are separated by a very short distance.Im Verlauf ausgedehnter Arbeiten uber Ylid-Komplexe des Golds *. waren durch partielle bzw. erschopfende Halogenierung des Gold(1)-[dimethylphosphonium-bis-(methylid)]-Dimeren 3a*c) 1 Verbindungen erhalten worden, denen aufgrund analytischer Daten versuchsweise die Strukturformeln 2 und 3 zugeschrieben wurden 3d).
Lithiiertes Bis(dipheny1phosphino)methan bildet mit Chloro(trialkylphosphan)gold(I)-Komplexen ein Gold(1)-bis(diphenylphosphino)methanid, 5a, dessen '97Au-MC)Rbauerspektrum eine oligomere Struktur mit aquivalenten Goldatomen nachweist. Gleiches gilt fur ein Trimethylsilylderivat 5 b. Aus 5a werden mit Dimethyl-, Diethyl-und Di-fert-butyl-methylphosphonium-methylid R2(CH3)P = CH2 zweikernige Gold(1)-Komplexe erhalten, in denen die Metallatome durch einen Bis(dipheny1phosphino)methanid-und einen Dialkylphosphonium-bis-methylid-Liganden verbriickt sind (6a -c). Die Rontgenbeugungsanalyse von 6c zeigt einen achtgliedrigen Metallocyclus, in dem zwei fast lineare C -Au -P-Einheiten iiber ein Phosphonium-und ein Carbanionzentrum verkniipft sind. Die P -C -P-Gruppe ist mit einem gemittelten d(PC) = 174 pm und 3: PCP = 123.5(15)O noch eindeutig ylidisch und unterscheidet sich damit prinzipiell von der PCH2P-Einheit in den zahlreichen Diphosphinornethan-Komplexen vom ,,A-Frame-Typ".
Synthesis and Crystal Structure of Binuclear Gold(1) Complexeswith Bs(phosphin0)methanide and Phosphonium Bis(mcthylide) Ligand Bridges Lithiated bis(dipheny1phosphino)methane reacts with chloro(trialkylphosphane)gold(I) complexes to yield a gold(1) bis(diphenylphosphino)methanide, 5a, which is assigned an oligomeric structure with equivalent gold atoms by IgAu M6Rbauer spectroscopy. Similar results are obtained for a trimethylsilyl derivative 5 b. From 5a and dimerhyl-, diethyl-, and di-ferf-butyl-methylphosphonium methylide R2(CH3)P = CH2, binuclear gold(1) complexes are generated, in which the metal atoms are bridged by a bis(dipheny1phosphino)methanide and a dialkylphosphonium bis-methylide ligand (6a -c). X-ray diffraction analysis of 6c shows an eight-membered metallocycle, where two almost linear C -Au -P moieties are linked via a phosphonium and a carbanion center. The P -C -P group with a mean d(PC) = 174 pm and 3: PCP = 123.5(15)' is clearly ylidic, and is thus inherently different from the numerous diphosphinornethane units of ,,A-frame" type complexes.Bis(phosphino)methane R2PCH2PR2 bilden mit zahlreichen Metden cyclische Zweikernkomplexe, in denen die beiden Metallatome auf so engem transannularem Abstand gehalten werden, dal3 leicht intermetdische Wechselwirkungen induzierbar sind (1). Dieser Koordinationstyp ist inzwischen wegen seiner ungewtlhnlichen Mtlglichkeiten zur Substratbindung als ,,A-Frame"-Komplex von groBem aktuellen Interessel).
From bis(dipheny1phosphino)methanide complexes of the type /[(C,H5),Pl2CHJ2M (M = Ni, Pd, Pt), and an equivalent amount of an ylide R,(CH,)P = CH2 (R = CH,, C,H5), the three title, is the by-product of the reaction. An X-ray diffraction study of the platinum compound 5c revealed a mixed chelate structure with a planar bis@hosphino)methanide and a folded ylide ring. The central carbon of the bis(phosphin0)methanide is not in close contact with the metal. Its distances to the phosphorus atoms indicate significant double bond character, some of which is also retained in the phosphonium bis(methy1ide) group. It is more than ten years since Issleib and coworkers first showed that the bis(dipheny1phosphino)methanide anion 1 with its carbanionic centre between two phosphane donors is a very strong ligand to transition metals. Such complexes, however, were difficult to characterize due to their low solubility'), and with very few exceptions, this important result has not been exploited any further2*,). It was only in the case of the copper(1) derivative that the solid state structure could be determined by X-ray diffraction2). The ligands in this complex, shown to be a trimer, were found to be bridging two-and three-coordinate copper atoms such that both phosphorus atoms and the central carbanion were involved in coordinative bonding.
4 +R-,FCHz 0 R3P=CH-SiHzCH3 -[R~P-CHZ-S~HZ-CH~] C1' -[R~PCH,ICIThe [(methylsilyl)methyl]phosphonium salt thus formed is transformed by transylidation with further ~l i d e '~' into the [(methylsilyl)methylene]phosphorane end product. Since this reaction with H3SiCH2Cl can take place twice (until complete silylation of the ylide function), Me3P-CH2 and Et3P-CH2 respectively afford the bis(sily1)methylenephosphoranes ( I ) and (2) in almost quantitative yields. With Et3P=CHCH3 the reaction must terminate at the stage of the monosilyl compound (3).3 RsP=CHz + 2 H3SiCH2C1 --+ 2 Et3P=CHCH3 + H3SiCHzC1 --+
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