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Isocyanide insertion reaction in alkylcomplexes of iron: A dihaptoiminoacyl derivative of iron (II)
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PolyhedmVol.2,No. 9.pp.%7-%8, 1983 RintcdinCkcatBritaia.
COMMUNICATIONS ISOCYAHIDE INSERTION REACTION IN ALKYLCOMPLEXES OF IRON: A DIHAPTOIMINOACYL DERIVATIVE OF IRON
Cardac?,
of Chemistry,
Gianfranco
University
of Perugia,06100
Pierfrancesco Institute
of Mineralogy,
Received
University
24 January
Bellachioma Perugia
Italy
Zanazzi
of Perugia,
1983; Accepted
16 May
06100
Perugia
Italy
1983
Abstract: The dihaptoiminoacyI complex [Fe(C0)2 (PMe3)2(q2-CMe=N-CMe3)]+ I- was obtained by reaction of [Fe(CO)z(PMes)zMeI] and tertbutylisocyanide. The structure of the complex was determined by an X-ray structure analysis. Isocyanides
are structurally
similar
and isoelectronic with carbon monoxide; therefore an understanding of isocyanide insertion'may help our understanding of CO insertion2. Moreover, isocyanide insertion is not an equilibrium reaction and can give polyinsertion3. When there is a choice within one molecuinsertion prevails le, isocyanide over CO insertion, though its calculated activation energy is higher than for CO ingertion4.This can be explained by acid catalysis'! Another reason the action may be of the metal, which acts as an acid toward the nitrogen atom to stabilize the dihaptostructure as an insertion intermediate. Two examples of dihaptoiminoacyl complexes are described in the literature 5 . We here describe the preparation of a complex of iron (II) showing this structure (Scheme 1). The reaction of [Fe(C0)2(PMe3)2MeI] (1) with tert-butylisocyanide in bensene (molar ratio l/l) quickly yields [Fe(CO)(PMe3)2(CNCMe,)(COMe)I] (2), which ionizes to the complex [Fe(CO),(PMe3)2(CNCMe3)Me]+ I- (3);(3) reaches an equi- librium with the dihaptoiminoacyl complex [Fe(CO)2(PMe3),(q2-CMe=NCMe3)]+ I- (4). With an excess of tert-butylisocyanide the reaction proceeds t: the complex [Fe(CO)(PMe3)2(CNThe complexes (3) and CMe3)2(COMe)] I- (5). equilibrium isolated because (4) cannot be between them is established in the solid staon the other hand the complex (4a) te, too; can be precipitated from a tetrahydrofurans solution of (3a) and (4a) obtained by exchange with NaBPh4in methanol; The elemental analyses of the complexes (4a) and (5) are in agreement with the proposed formulation. (4a) crystallizes in the monoclinic system with a = 29.832(4), b = 12.174(3), c = 10.650 (3) A, B= 91.45(2)', U = 3866.6 i3, D,= 1.045 g.cmm3 , Z = 4, space group P2,/n. Intensity data were measured with a Philips PW 1100 diffractometer, using MoKa radiation, p=4.7 cm-? Fig. 1
967
968
Communications The structure was solved by direct method and refined by full matrix least squares method to R = 0.075 for 1628 observed reflections and 149 parameters. 8 The molecular structure of complex (4a) is shown in Fig. 1. In addition to the Fe-PMeg and Fe-CO groups, an iminoacyl (Me-C=N-CMe3)group bonded atom is observed. Relevant internuclear distances and to the metal angles are: Fe-C8 = 1,940(13)A; Fe-N = 2.007(10)A; Cg-N = 1.211(14)i; Cg-Cl0 = 1.496(19);; CIO-Cg-N = 139.1(13); N-Cl1 = 1.523(16)A; Cg-N-C11 = 137.4(12); Cg-Fe-N = 35.7(4). The increase of the angles Clc-Cg-N and Cg-N-C,, with reference to a normal q'-iminoacyl structure5ap6 and the similar bond distances Fe-N and Fe-C8 indicate a dihaptoiminoacyl structure as found in the previously described complexes5. The structures of the complexes (3), (4) and (5) are supported by i.r. and 1 H n.m.r. spectra (Tab. 1). In particular complex (4) shows two i.r. CO stretchings, no i.r. band Comvk” vco V vcn in the range 2100-2200 cm-'(CrN stret‘GM. COW ‘COM. things) or in the range 1500-1600 cm-' at 1750 (C=N stretchings). The band cm-'is assigned to the C=N of the v2dihaptoiminoacyl structure.A compari14) mar*, ,rsso,s, 1750,flll J .,,:z.a ‘a4’t’=p. in the oson with the band observed lSW,S, I51 15oxS) 2115 ,.,, 21w., I 55,., ther two dihapto compl_elx;t (YcN' 1654 Cm-1,8band YcN= 1660 cm ’ ), indicate a: be”,.“**OIYtio”: s . ,trono,m: madl”m‘or Ihe,.r. spoc,rwn; that this band is strongly influenced by the dihapto structure. The shift is to a higher frequency with respect to the C=N stretching. This trend is opposite to that observed in the dihaptoacyl complexes7 and corresponds to the effect observed on the double bond of the cyclopropene derivatives 8 . Since the structure of cyclopropene and dihaptoiminoacyl metal are very similar, the strengthening of the double bond may be due to the partial sp hybridization on the C and N atoms, observed in cyclopropene 8 and to the quaterstructure, for which a shif'l to higher frequencies nary iminium salt :C=Nk of the C=N stretching is observed 9 . This work Acknowledgement: Fine e secondaria).
is supported
by
CNR (Progetto
finalizzato
Chimica
REFERENCES 1 A. Wojcicki, Adv. Organometal. Chem. 1974, 12, 31. 2 F. Calderazzo, Angew. Chem. Internat. Ed. 1977, 16, 299; A. Wojcicki, Adv. 30rganometal. Chem. 1973, 11, 87. Yama'moto and H. Yamasaky, J. Organometal. Chem. 1975, 90, 329. qJ. H. Berke and R. Hoffmann, J. Am. Chem. Sot. 1978, 100,7224. 5 a) R.D. Adams and D.F. Chodosh, J. Am. Chem. Sot. 1977, 99, 6544; idem, Inorg. Chem. 1978, 17, 41; idem, J. Organometal. Chem. 1976, 122,C 11; b) W.R. Roper, Chem. 1978, 157, G.E. Taylor, J.M. Waters and L.J. Wright, J. Organometal. 6C 27. Chem. 1974, K.P. Wagner, P.M. Treichel and J.C. Calabrese, J. Organometal. 299. 71, 7 G. Fachinetti, C. Floriani, F. Marchetti and S. Merlino, J. Chem. Sot. Chem. Comm. 1976, 522; W.R. Roper, G.E. Taylor, J.M. Waters and L.J. Wright, J. Or6ganometal. Chem. 1979, 182, C 46. M.K. Kemp and W.H. Flygare, J. Am. Chem. Sot. 1967, 89, 3925; W.R. Bernett, J. Chem. Ed. 1967, 44, 17. 9 R. Merenyi, "Structure Determination of iminium salts by physical methods", in "Advances in Organic Chemistry" Ed. H. Bohme and H.G. Viehe, Wiley interscience New York, 1976, Vol. 9, part 1, pp. 23-105. 5
Atomic coordinates, bond lenghts and angles and lists of F,/F, values have been deposited as supplementary material with the Editor, from whom copies are available on request. Atomic coordinates have also been deposited with theCanbridge Crystallographic Data Center.
PolyhedmVol.2,No. 9.pp.%7-%8, 1983 RintcdinCkcatBritaia.
COMMUNICATIONS ISOCYAHIDE INSERTION REACTION IN ALKYLCOMPLEXES OF IRON: A DIHAPTOIMINOACYL DERIVATIVE OF IRON
Cardac?,
of Chemistry,
Gianfranco
University
of Perugia,06100
Pierfrancesco Institute
of Mineralogy,
Received
University
24 January
Bellachioma Perugia
Italy
Zanazzi
of Perugia,
1983; Accepted
16 May
06100
Perugia
Italy
1983
Abstract: The dihaptoiminoacyI complex [Fe(C0)2 (PMe3)2(q2-CMe=N-CMe3)]+ I- was obtained by reaction of [Fe(CO)z(PMes)zMeI] and tertbutylisocyanide. The structure of the complex was determined by an X-ray structure analysis. Isocyanides
are structurally
similar
and isoelectronic with carbon monoxide; therefore an understanding of isocyanide insertion'may help our understanding of CO insertion2. Moreover, isocyanide insertion is not an equilibrium reaction and can give polyinsertion3. When there is a choice within one molecuinsertion prevails le, isocyanide over CO insertion, though its calculated activation energy is higher than for CO ingertion4.This can be explained by acid catalysis'! Another reason the action may be of the metal, which acts as an acid toward the nitrogen atom to stabilize the dihaptostructure as an insertion intermediate. Two examples of dihaptoiminoacyl complexes are described in the literature 5 . We here describe the preparation of a complex of iron (II) showing this structure (Scheme 1). The reaction of [Fe(C0)2(PMe3)2MeI] (1) with tert-butylisocyanide in bensene (molar ratio l/l) quickly yields [Fe(CO)(PMe3)2(CNCMe,)(COMe)I] (2), which ionizes to the complex [Fe(CO),(PMe3)2(CNCMe3)Me]+ I- (3);(3) reaches an equi- librium with the dihaptoiminoacyl complex [Fe(CO)2(PMe3),(q2-CMe=NCMe3)]+ I- (4). With an excess of tert-butylisocyanide the reaction proceeds t: the complex [Fe(CO)(PMe3)2(CNThe complexes (3) and CMe3)2(COMe)] I- (5). equilibrium isolated because (4) cannot be between them is established in the solid staon the other hand the complex (4a) te, too; can be precipitated from a tetrahydrofurans solution of (3a) and (4a) obtained by exchange with NaBPh4in methanol; The elemental analyses of the complexes (4a) and (5) are in agreement with the proposed formulation. (4a) crystallizes in the monoclinic system with a = 29.832(4), b = 12.174(3), c = 10.650 (3) A, B= 91.45(2)', U = 3866.6 i3, D,= 1.045 g.cmm3 , Z = 4, space group P2,/n. Intensity data were measured with a Philips PW 1100 diffractometer, using MoKa radiation, p=4.7 cm-? Fig. 1
967
968
Communications The structure was solved by direct method and refined by full matrix least squares method to R = 0.075 for 1628 observed reflections and 149 parameters. 8 The molecular structure of complex (4a) is shown in Fig. 1. In addition to the Fe-PMeg and Fe-CO groups, an iminoacyl (Me-C=N-CMe3)group bonded atom is observed. Relevant internuclear distances and to the metal angles are: Fe-C8 = 1,940(13)A; Fe-N = 2.007(10)A; Cg-N = 1.211(14)i; Cg-Cl0 = 1.496(19);; CIO-Cg-N = 139.1(13); N-Cl1 = 1.523(16)A; Cg-N-C11 = 137.4(12); Cg-Fe-N = 35.7(4). The increase of the angles Clc-Cg-N and Cg-N-C,, with reference to a normal q'-iminoacyl structure5ap6 and the similar bond distances Fe-N and Fe-C8 indicate a dihaptoiminoacyl structure as found in the previously described complexes5. The structures of the complexes (3), (4) and (5) are supported by i.r. and 1 H n.m.r. spectra (Tab. 1). In particular complex (4) shows two i.r. CO stretchings, no i.r. band Comvk” vco V vcn in the range 2100-2200 cm-'(CrN stret‘GM. COW ‘COM. things) or in the range 1500-1600 cm-' at 1750 (C=N stretchings). The band cm-'is assigned to the C=N of the v2dihaptoiminoacyl structure.A compari14) mar*, ,rsso,s, 1750,flll J .,,:z.a ‘a4’t’=p. in the oson with the band observed lSW,S, I51 15oxS) 2115 ,.,, 21w., I 55,., ther two dihapto compl_elx;t (YcN' 1654 Cm-1,8band YcN= 1660 cm ’ ), indicate a: be”,.“**OIYtio”: s . ,trono,m: madl”m‘or Ihe,.r. spoc,rwn; that this band is strongly influenced by the dihapto structure. The shift is to a higher frequency with respect to the C=N stretching. This trend is opposite to that observed in the dihaptoacyl complexes7 and corresponds to the effect observed on the double bond of the cyclopropene derivatives 8 . Since the structure of cyclopropene and dihaptoiminoacyl metal are very similar, the strengthening of the double bond may be due to the partial sp hybridization on the C and N atoms, observed in cyclopropene 8 and to the quaterstructure, for which a shif'l to higher frequencies nary iminium salt :C=Nk of the C=N stretching is observed 9 . This work Acknowledgement: Fine e secondaria).
is supported
by
CNR (Progetto
finalizzato
Chimica
REFERENCES 1 A. Wojcicki, Adv. Organometal. Chem. 1974, 12, 31. 2 F. Calderazzo, Angew. Chem. Internat. Ed. 1977, 16, 299; A. Wojcicki, Adv. 30rganometal. Chem. 1973, 11, 87. Yama'moto and H. Yamasaky, J. Organometal. Chem. 1975, 90, 329. qJ. H. Berke and R. Hoffmann, J. Am. Chem. Sot. 1978, 100,7224. 5 a) R.D. Adams and D.F. Chodosh, J. Am. Chem. Sot. 1977, 99, 6544; idem, Inorg. Chem. 1978, 17, 41; idem, J. Organometal. Chem. 1976, 122,C 11; b) W.R. Roper, Chem. 1978, 157, G.E. Taylor, J.M. Waters and L.J. Wright, J. Organometal. 6C 27. Chem. 1974, K.P. Wagner, P.M. Treichel and J.C. Calabrese, J. Organometal. 299. 71, 7 G. Fachinetti, C. Floriani, F. Marchetti and S. Merlino, J. Chem. Sot. Chem. Comm. 1976, 522; W.R. Roper, G.E. Taylor, J.M. Waters and L.J. Wright, J. Or6ganometal. Chem. 1979, 182, C 46. M.K. Kemp and W.H. Flygare, J. Am. Chem. Sot. 1967, 89, 3925; W.R. Bernett, J. Chem. Ed. 1967, 44, 17. 9 R. Merenyi, "Structure Determination of iminium salts by physical methods", in "Advances in Organic Chemistry" Ed. H. Bohme and H.G. Viehe, Wiley interscience New York, 1976, Vol. 9, part 1, pp. 23-105. 5
Atomic coordinates, bond lenghts and angles and lists of F,/F, values have been deposited as supplementary material with the Editor, from whom copies are available on request. Atomic coordinates have also been deposited with theCanbridge Crystallographic Data Center.