摘要:

CHEMICAL COMMUNICATIONS, 1968 61 1 Ditertiary Phosphine Derivatives of Tetracarbonyldi- n-cyclopentadienyldi-iron By R. J. HAINES* (Research Department, South African Iron and Steel Industrial Corporation Limited, P.O. Box 450, Pretoria, Republic of South Africa) and A. L. DU PREEZ and G. T. W. WITTMANN (Department of Inorganic and A nalytical Chemistry, University of Pretoria, Pretoria) PREVIOUS studies on the substitution reactions of [C,H,Fe(CO),], have shown that under extreme conditions triphenylphosphine,f 1,2-bis (diphenyl- phosphino)ethane (diphos), and 2,2,2”-terpyridyl (terpy)2 replace the cyclopentadienyl group to yield the derivatives, Fe(C0) ,(PPh,),, Fe(C0) I)- diphos, and Fe(C0) ,terpy, respectively. Further- more the ligands L, = Me,S,,S Me4P4, Ph,P,, Me,As,4 and (CF,),As,5 react with [C,H,Fe(CO) ,Ir under milder conditions to afford bridged products of the type [C,H,Fe(CO)L],, which contain terminal carbonyl groups only.We have now found that the ditertiary phos- phines PhlPICH,],PPh, (n = 1-3) react with tetracarbonyldi-rr-cyclopentadienyldi-iron to yield novel derivatives [C,H,Fe(CO)],Ph,P[CH,],PPh, (I), in which the ligand, as well as the two carbonyl groups, bridges the iron atoms. These compounds are neutral, diamagnetic, and isomorphous. Infrared and n.m.r. data suggest that they have the structure as shown in the Figure; the bulkiness of the phenyl groups would force the cyclopentadienyl rings into the “cis” positions.612 CHEMICAL COMMUNICATIONS, 1968 TABLE .. .. .. .. * . .. .. V5H5Fe 12 iI;n = 1) (11; n = 1) [ (C,H,Fe (CO) },*~**Ph,P:dH,.PPh,]BPh, [C,H5Fe(C0)2Ph2P-C2H4-PPh2]Is .. (C,H,Fe(CO)I },Ph,PC,H,.PPh, . . [C,H,Fe(CO)P~PC,H,-PPhJ [BF J . . FIGURE. Proposed structure for [C,H,Fe(CO) ,Ph,P- [CH,],,PPh, (n = 1-3) showing the stereochemistry of the iron atoms only. The Table shows that substitution of the terminal carbonyl groups in [C,H,Fe(CO),], by the diphosphine ligands lowers the frequency of the bridging carbonyl stretching modes consider- ably. This effect may be attributed to the latter type carbonyls being able to participate in v-bond- ing. Similar effects are known for terminal and ketonic type carbonyl g r o ~ p s . ~ , ~ The reaction of [C,H,Fe(C0),], with various monodentate tertiary phosphines and phosphites has yielded mono-substituted derivatives of formula (C,H,),Fe2(CO),L (L = ligand) in which one terminal carbonyl has been substituted.These derivatives exist as mixtures of isomers and will be the subject of a future publication. The compounds (I; n = 1-3) are readily oxidised by various agents including halogens and pseudo-halogens, stannic chloride, and mercuric chloride. Treatment of a benzene solution of (I; n = 1-3) with an equimolar amount of iodine at room temperature does not afford the expected neutral iodo-complex, [C,H,Fe(CO) 11,- Ph,P[CH,],PPh2, but an ionic compound (1 : 1 .. .. .. .. .. .. .. Y (CO) (cm.-l) measured in a C,H,,, b CH,Cl, 2006ms, 1961s, 1793sa 1734vw, 1690(s)S 1826 (ms) , 1 7 72 (s,b) b 1983b 2055 (s) , 201 3 (s) b 1948b 1980b C,H, proton resonance T (CDCI,) 5.2 1 5.73 very broad 6.77 4-74 5.66 5-19 electrolyte in acetone) which precipitates from solution as the iodide.The analytical data for the tetraphenylboron derivative is consistent with the presence of the cation { [C,H,Fe(CO)],Ph,P- [CH,] ,PPh2)+ (n = 1-3). As shown by the i.r. spectra in the C-0 stretching region, the carbonyl groups in these ionic compounds are bridging. These bands are unusually broad, for example the half-band width for { [C,H,Fe(CO)],Ph,P.C,H,.P- Ph,])BPh, (in CH,Cl,) is ca. 190cm.-l. Its magnetic moment corresponds to that for one unpaired electron. This suggests that iodine oxidation of (I; n = 1-3) occurs with loss of one electron, affording a product with an effective “one-electron metal-metal bond”. The complexes { [C,H,Fe(CO)],Ph,P[CH,] n- PPh,}BPh, (11; n = 1-3) are very sensitive to oxidative or reductive attack, as expected for compounds with the above type of metal-metal bond.Hydrazine reduction of (11; n = 2) is extremely rapid, the parent compound (I; n = 2) being obtained in quantitative yield. Alcohol reduces similarly although the reaction proceeds much slower. Oxidation of (11; n = 2 or 3) with excess of iodine yields predominantIy a product {C,H,Fe(CO) ,Ph,P [CH,] ,PPh,)BPh, in which only one phosphorus atom of the diphosphine ligand is bonded to the iron. This represents an example of asymmetric cleavage, but does not occur for (11; n = 1). The iodine is inserted across the two iron atoms to afford an ionic compound ( [C,H,Fe (CO) ] ,-I*Ph,PCH,PPh,)BPh, in which the carbonyl groups are now terminal but the iodine bridging.Similar type insertion reactions have been found for [C,H,Fe(CO),],.* The iodo-compound [C,H,Fe(CO)I],Ph,P- [CH,],PPh, (TZ = 1-3) may be obtained by slowly adding an equimolar amount of iodine to a refluxing benzene solution of (I; n = 1-3), the ease of formation being reduced as n alters from 3 to 1. However, excess of iodine reacts with neutral (I; n = 1-3) in CH,Cl, to yield the same product as the corresponding reaction between (11; n = 1-3) and iodine. This,CHEMICAL COMMUNICATIONS, 1968 613 together with the observation that ([C,H,Fe(CO)],- [C5H5Fe(CO)I],Ph2P[CH2],Ph2 (n = 1, 2 or 3) Ph,P[CH,] ,PPh,}I, (n = 1-3) decomposes from the corresponding neutral (I). slowly in CH,Cl, to yield as one of the products Bromine behaves similarly to iodine in the above [C,H,Fe (CO) I J2Ph,P [CH,] ,PPh2, suggests that reactions except that the neutral bromo-deri- the paramagnetic complex [(I) (Anion)] is formed vative is more readily obtained at lower as an intermediate in the direct formation of temperatures, [ (C,H,Fe(CO) },.I-Ph2PCH,PPh2] [Anion], [C,H,- Fe(CO),Ph,P[CH,] nPPh2] [Anion] (n = 2 or 3) or (Received, March 25th, 1968; Corn. 367.) 1 B. F. Hallam and P. L. Pauson, J . Chem. SOC., 1956, 3030. 2 H. Behrens and W. Aquila, 2. Naturforsch., 1967,22b, 454. 3 R. B. King, P. M. Treichel, and F. G. A. Stone, J . Amer. Chem. SOC., 1961, 83, 3600; R. B. King and M. B. Bis- 4 R. G. Hayter, J . Amer. Chem. SOC., 1963, 85, 3120. 6E. W. Abel, Quart. Rev., 1963, 17, 133. 7 J. P. Bibler and A. Wojcicki, Inorg. CJzem., 1966, 5, 889. 8 R. J. Haines and A. L. du Preez, to be published. nette, Inorg. Chem., 1965,4, 482. W. R. Cullen and R. G. Hayter, J . Amer. Chem. SOC., 1964,86, 1030.

ISSN:0009-241X    

DOI:10.1039/C19680000611

出版商:RSC    

年代:1968

数据来源: RSC