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Preparation, characterization and crystal structure of Fe((OPPh2)2N)3
ELSEVIER
InorganicaChimicaActa241 (1996) 111-115
Note
Preparation, characterization and crystal structure of Fe((OPPh2) 2N) 3 C. Scott Browning, David H. Farrar *, Daniel C. Frankel Department of Chemistry, Universityof Toronto, Toronto, Ont., MSS IA1, Canada
Received3 February1995;revised21 June 1995
Abstract White crystals of Fe((OPPhz)2N) 3 were obtained from the reaction of a solution of Fe2(CO)9 and excess (PPh2)2NH, under an air atmosphere. This product does not form if the solvents are rigorously degassed and the reaction is performed under argon. The structure of the complex, as determined by single crystal X-ray crystallography, is an octahedral tris-chelate arrangement of the oxidized anionic ligand, [ (O=PPh2)2N] - coordinated to an Fe(III) center. The asymmetric unit of the unit cell also contains a disordered THF solvent molecule. The complex crystallizes in the triclinic s~ace group Pi, with Z=2, affi13.581(3), bffi 13.886(8), cffi18.781(7) A, affi95.48(4), /3ffi98.73(2), 7=97.82(3) °, V-- 3444(2) A3, Mr = 1377, Dx-- 1.33 Mg m -3, F(000) = 1434, Tffi298 K and R---0.086 for 5959 observed reflections. The magnetic moment of the compound Fe((OPPh2)2N)3 was found to be 5.4 BM, using the Gouy method. Reaction of the oxidized ligand, (OPPh2)2NH, with Fe(III) salts, such as Fe(NO3)3, produces Fe((OPPh2)2N) 3 in high yields. Keywords: Crystalstructures;Iron complexes;Phosphinoaminecomplexes
1. Introduction We have been examining the transition-metal coordination chemistry of bis(diphenylphosphino)amine ligands. In our initial studies we compared the reactivity of bis(diphenylphosphino)amine (dppa) and bis(diphenylphosphino)methane (dppm) coordinated to platinum [ 1 ]. The dppa ligand was found tO be susceptible to P-N bond cleavage reactions. The dppm ligand is known to undergo P C bond cleavage reactions in dppm-bridged binuclear ironcarbonyl complexes. For example, reaction of dppm with Fe2(CO)9 produces the binuclear complex Fe2(CO)6(p,CO) (/x-dppm) [2]. Upon heating, the dppm ligand in this complex undergoes P--C bond cleavage to form a phosphido and P-C bridged binuclear complex Fe2 (CO) 6(/z-PPh2) (/xPPhCH2) [ 3 ]. The reactivity ofdppm-bridged binuclear iron complexes prompted us to explore the reaction of dppa with iron carbonyl. This paper describes the reaction of Fe2(CO)9 and dppa, in THF solvent under an air atmosphere, and the resulting product Fe((OPPh2) 2N) 3Reactions of related phosphinoamine ligands with Fe(CO)s and Fe2(CO)9 have been reported. King and coworkers [4] have published an extensive study on the ligand bis(difluorophosphino)methylamine, (PF2)2NMe. They have shown that reaction of the ligand with Fe(CO)5 yielded * Correspondingauthor. 0020-1693/96/$15.00 © 1996ElsevierScienceS.A. All fightsreserved SSD10020-1693 ( 95 ) 04737-T
both the chelated, square pyramidal, product Fe(r/2F2PN(Me)PF2)2(CO), and the bis-bridged iron binuclear compound, Fe2(CO)4(p-F2PN(Me)PF2)2(/z-CO). The ligand (PF2)2NMe reacts with Fe3(CO)12 to give binuclear products [ 5 ]. Reactions between diphosphitoamine ligands and iron carbonyls also have been reported. Fe(CO)5 reacts with (P(OPh)2)2NR, (R--Me, Ph) to form chelated products and a binuclear compound [ (CO)2Fe(p-CO) (p(PhO)2PN(R)P(OPh)2)2Fe(CO)2] [6]. The compound Fe2(CO)9 has been shown to react with (P(OMe)2)2NMe to yield a binuclear product [ 7 ].
2. Experimental 2.1. General procedures
All chemicals were obtained commercially and used without further purification. (PPh2)2NH [8] and (OPPh2)2NH [ 9] were prepared by literature methods. 31p NMR spectra were recorded on a Gemini 300 spectrometer operating at 121.5 MHz. P(OMe)3 in C6D6 was used as an external reference. Fast-atom bombardment mass spectroscopic (FAB MS) analyses were performed in a nitrobenzyl alcohol matrix using a Varian VG70-250S mass spectrometer with a Xe gas ionizing source at 8 kV and 1 mA.
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C S. Browning et al. / lnorganica Chiraica Acta 241 (1996) 111-115
Analytical analyses were obtained from Canadian Microanalytical Service, Ltd., Delta, B.C., Canada. The magnetic moment was determined at 23 °C, by the Gouy technique using Hg[Co(NCS)4] as a calibrant. Diamagnetic corrections were applied using literature values [10].
2.1.1. Synthesis of Fe((OPPhz)aN)3 Method a . Fe2(CO)9 (120 mg, 0.33 mmol) and (PPh2)2NH (750 mg, 1.95 mmol) were stirred in THF (50 ml) for 1 day at 23 °C and allowed to stand for 1 week at 0 °C. The white crystalline product Fe( (OPPh2)2N)3 precipitated out of solution. Yield: 230 mg, 50%. FAB MS parent ion peak at m/z = 1305 (the isotopic distribution for the product was identical to that calculated for Fe((OPPh2)zN)3). Anal. Found for Fe ((OPPh2) 2N) 3"THF, C76I~FeN3OTPt: C, 66.3; H, 5.0; N, 3.0. Calc.: C, 65.9; H, 4.9; N, 3.0%. M.p. > 300 °C. Method b. To an ethanol solution (70 ml) of Fe(NO3)3 (164 mg, 0.68 mmol) was added (OPPh2)2NH (750 rag, 1.80 retool). The resulting suspension was refluxed for 2 h to dissolve the ligand. The white crystalline product Fe( (OPPh2)2N)3 precipitated from the solution upon lowering the solvent volume under vacuum. Yield: 170 rag, 80%. 2.2. Data collection, solution and refinement for
Fe(( OPPhz)2N)~ "THF Data for the crystal structure analysis of the compound Fe( (OPPh2)2N)3 .THF are given in Table 1. Crystals were Table 1
X-rayexperimentaldataforFe((OPPhz)2N)3"THF Empirical formula
Mr
CTc,Hs~eN3OvP~ 1377
Crystal system Space group
triclinic ei (No. 2)
a (A)
13.581(3)
b (A) c (A) a (°) /3(°)
13.886(8) 18.781(7) 95.48(4) 98.73(2) 97.82(3) 3444(2)
~,(°) V (A3) C.entering reflections, Orange (°) Z D, (Mg m -3 ) F(O00) p,(Mo Ka) (cm -I) Indices 20 range (°) No. of data (R~v) No. of data used, criterion No. standards, frequency, decay (%) Final R (Rw) No. variables (observed/variables) Largest (av.) final shift/e.s.d. Fmal e - density map (e .~-3) (Maximum near) Goodness-of-fit
25, 12-15 2 1.33
1434 4.15 h - 14,14; k - 14,14; 10,20; 1-42 7372 (0.0158) 5959, I > 3or(1) 3, 2h, 0.01 0.086 (0.091) 478 (12.5) 0.17 (<0.01) - 0.65 to 0.72 (H41D) 7.50
grown by slow evaporation of a CH2C12/THF solution of product. The crystals rapidly decomposed by solvent loss upon removal from the mother liquor. A crystal was mounted on a glass fibre and quickly coated in epoxy resin to prevent solvent loss. Accurate cell dimensions and crystal orientation matrix were determined on a CAD-4 diffractometer by a least squares treatment of the setting angles of 25 reflections in the range 1 2 < 0 < 15°. o>scans of several intense low-angle reflections revealed that the crystal mosaicity was poor. Intensifies of reflections with indices h - 14 to 14, k - 14 to 14, l 0 to 20, and 1 < 0< 21°, were measured; intensities of three reflections measured every 2 h decayed by 0.01% during data collection. 7372 reflections measured were corrected for Lorentz and polarization effects. Crystal faces could not be identiffed due to the epoxy coating. 5959 reflections with I > 3o-(1) were labeled observed and used in the structure solution and refinement. Space group P1 was determined by a successful structure refinement. The structure was solved by the direct methods [ 11]. Positions for 88 non-H atoms associated with the Fe complex were determined. A subsequent difference Fourier synthesis revealed the presence of electron density associated with a disordered THF molecule. The disorder appears to arise from several orientations of the THF molecule derived by small rotations about the centroid of the THF ring, in the plane of the molecule. All attempts to refine a model for this disorder were unsuccessful. In the final cycles an O atom and four C atoms, forming a highly distorted ring, were refined with anisotropic thermal parameters. Refinement was by fullmatrix least-squares calculations with anisotropic thermal parameters for all atoms except the phenyl ring C atoms which were refined with isotropic thermal parameters. Data were corrected for absorption effects using the program DIFABS [ 12] with minimum and maximum absorption corrections of 0.954 and 1.215 respectively. In the final refinement cycles, the H atoms associated with the phenyl rings were positioned on geometric grounds and included (as riding atoms) in the structure factor calculation ( U~o= 0.08 ,~z). No corrections for secondary extinction were applied. The atomic coordinates are given in Table 2. Selected bond lengths and angles for the molecule are listed in Table 3. An ORTEP [ 13] view of the molecule is presented in Fig. 1. For clarity only the a-C atoms of the phenyl rings are shown. Neutral atom scattering factors were used [ 14]. All calculations were carried out on a MicroVaxII computer with the NRCVAX Crystal Structure System [15] and an Apollo computer using SHELX76 [ 16] and SHELX86 [ 11 ] programs.
3. Results and discussion
Reaction of Fe2(CO)9 with excess dppa, for I day at room temperature in THF solution under an air atmosphere, did not yield the expected dppa-bridged iron binuclear species. The room temperature 31p N'MR spectrum of a white product,
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CS. Browning et al. / Inorganica Chimica Acta 241 (1996) 111-115
Table2 Positionalparan~tersand equivalentisotropicdisplacementcoefficientsfor Fe((OPPba)2N)3"THF"
Table 2 (continued) Atom
x
y
z
U~/ Ul~ b
Atom
x
y
z
U~I Ut~ b
Fe O(1) 0(2) 0(3) 0(4) 0(5) 0(6) N(1) N(2) N(3) P(I) P(2) P(3) P(4) P(5) P(6) C(lll) C(112) C(113) C(114) C(ll5) C(116) C(121) C(122) C(123) C(124) C(125) C(126) C(211) C(212) C(213) C(214) C(215) C(216) C(221) C(222) C(223) C(224) C(225) C(226) C(311) C(312) C(313) C(314) C(315) C(316) C(321) C(322) C(323) C(324) C(325) C(326) C(411) C(412) C(413) C(414) C(415) C(416) C(421) C(422)
0.1810(l) 0.2393(4) 0.3123(4) 0.0570(4) 0.2373(4) 0.1209(4) 0.1246(4) 0.4328(5) 0.0713(5) 0.1036(5) 0.3475(2) 0.4183(2) 0.0155(2) 0.1831(2) 0.0994(2) 0.1086(2) 0.3686(6) 0.3029(9) 0.320(1) 0.401(1) 0.4669(9) 0.4516(7) 0.3593(6) 0.4524(8) 0.4591(9) 0.3744(9) 0.280(1) 0.2761(8) 0.4956(6) 0.4570(8) 0.5184(9) 0.6190(9) 0.659(1) 0.5980(9) 0.4701(6) 0.4583(7) 0.4995(8) 0.5530(8) 0.5681(8) 0.5247(7) -0.1139(7) -0.164(1) -0.268(1) -0.3141(1) -0.272(1) -0.166(1) 0.0118(6) 0.0498(8) 0.0468(9) 0.0021(8) -0.0348(8) -0.0302(7) 0.1813(7) 0.0940(9) 0.093(1) 0.183(1) 0.269(1) 0.2724(9) 0.2602(7) 0.2281(9)
0.6917(1) 0.6532(4) 0.7827(4) 0.5969(4) 0.5889(4) 0.7930(4) 0.7390(4) 0.6908(5) 0.4656(5) 0.9171(5) 0.6539(2) 0.7631(2) 0.4979(2) 0.5083(2) 0.8924(2) 0.8403(2) 0.7270(6) 0.7120(8) 0.772(1) 0.841(1) 0.8554(9) 0.7988(7) 0.5335(6) 0.5058(8) 0.4092(9) 0.3486(9) 0.372(1) 0A679(8) 0.8785(6) 0.9635(7) 1.0531(9) 1.0557(9) 0.9738(9) 0.8830(9) 0.7155(6) 0.7583(7) 0.7234(8) 0.6477(8) 0.6046(9) 0.6402(7) 0.4990(7) 0.431(1) 0.429(1) 0.4957(1) 0.560(1) 0.561(1) 0.4062(6) 0.3212(8) 0.251(1) 0.2669(9) 0.3484(8) 0.4191(7) 0.5475(7) 0.5651(8) 0.6003(9) 0.6126(9) 0.6011(9) 0.5688(8) 0.4119(7) 0.3302(9)
0.7254(1) 0.6368(3) 0.7656(3) 0.6860(3) 0.7801(3) 0.6720(3) 0.8126(3) 0.6954(4) 0.7794(4) 0.7817(3) 0.6263(1) 0.7624(1) 0.7064(1) 0.8160(1) 0.6976(1) 0.8396(1) 0.5542(4) 0.4907(6) 0.4334(8) 0.4451(7) 0.5059(6) 0.5611(5) 0.5921(4) 0.5924(5) 0.5598(6) 0.5319(6) 0.5317(7) 0.5651(5) 0.7648(4) 0.7627(5) 0.7607(6) 0.7611(6) 0.7640(6) 0.7653(6) 0.8425(4) 0.9094(5) 0.9726(6) 0.9662(6) 0.9022(6) 0.8390(6) 0.7148(5) 0.7485(7) 0.7528(8) 0.7233(8) 0.680(1) 0.6764(8) 0.6315(4) 0.6403(6) 0.5807(7) 0.5137(6) 0.5042(6) 0.5632(5) 0.9100(5) 0.9337(6) 1.0071(7) 1.0524(8) 1.0318(7) 0.9580(6) 0,8193(5) 0.8562(6)
0.033(1)* 0.045(2)* 0.039(2)* 0.044(2)• 0.040(2)* 0.043(2)* 0.040(2)• 0.047(3)* 0.054(3)* 0.045(3)• 0.043(1), 0.043(1)* 0.042(1)* 0.047(1), 0.040(1), 0.040(1)* 0.046(2) 0.084(3) 0.110(4) 0.105(4) 0.090(4) 0.066(3) 0.045(2) 0.076(3) 0.093(4) 0.095(4) 0.106(4) 0.077(3) 0.047(2) 0.069(3) 0.090(4) 0.086(3) 0.095(4) 0.086(3) 0.048(2) 0.069(3) 0.083(3) 0.087(3) 0.088(3) 0.073(3) 0.056(3) 0.114(4) 0.144(6) 0.126(5) 0.160(6) 0.119(5) 0.042(2) 0.080(3) 0.104(4) 0.086(3) 0.076(3) 0.061(3) 0.059(3) 0.088(3) 0.111(4) 0.109(4) 0.103(4) 0.084(3) 0.058(3) 0.093(4)
C(423) C(424) C(425) C(426) C(Sll) C(512) C(513) C(514) C(515) C(516) C(521) C(522) C(523) C(524) C(525) C(526) C(611) C(612) C(613) C(614) C(615) C(616) C(621) C(622) C(623) C(624) C(625) C(626) O C(1) C(2) C(3) C(4)
0.289(1) 0.370(1) 0.409(1) 0.3442(8) 0.1870(6) 0.2455(7) 0.3164(9) 0.3246(9) 0.2654(8) 0.1969(7) -0.0237(6) -0.0406(9) -0.141(1) -0.217(1) -0.203(1) -0.1033(9) -0.0071(6) -0.0384(9) -0.134(1) -0.194(1) -0.166(1) -0.0708(9) 0.2059(6) 0.2193(7) 0.2982(8) 0.3595(8) 0.3465(8) 0.2694(7) 0.108(1) 0.036(3) -0.009(1) 0.056(2) 0.099(3)
0.255(1) 0.2663(9) 0.338(1) 0.4185(8) 0.9815(6) 0.9523(7) 1.0207(8) 1.1184(9) 1.1482(8) 1.0797(7) 0.9042(6) 0.9650(9) 0.970(1) 0.914(1) 0.850(1) 0.8456(9) 0.8255(7) 0.9028(9) 0.890(1) 0.806(1) 0.730(1) 0.7403(9) 0.8928(6) 0.8466(7) 0.8862(8) 0.9715(8) 1.0167(8) 0.9781(7) 0.8559(9) 0.879(2) 0.833(1) 0.821(2) 0.818(2)
0.8615(7) 0.8376(6) 0.8005(8) 0.7911(6) 0.6669(4) 0.6196(5) 0.5952(6) 0.6198(6) 0.6667(5) 0.6914(5) 0.6520(4) 0.6005(6) 0.5661(8) 0.5839(7) 0.6328(7) 0.6674(6) 0.8760(5) 0.9124(6) 0.9353(7) 0.9224(7) 0.8841(8) 0.8593(7) 0.9137(4) 0.9748(5) 1.0343(6) 1.0288(6) 0.9685(5) 0.9096(5) 0.2624(8) 0.174(2) 0.099(1) 0.120(1) 0.227(1)
0.104(4) 0.095(4) 0.127(5) 0.082(3) 0.042(2) 0.060(3) 0.088(4) 0.087(3) 0.076(3) 0.063(3) 0.047(2) 0.089(4) 0.117(5) 0.110(4) 0.108(4) 0.090(4) 0.049(2) 0.089(4) 0.110(4) 0.104(4) 0.126(5) 0.098(4) 0.040(2) 0.066(3) 0.082(3) 0.072(3) 0.074(3) 0.059(3) 0.133(7)* 0.31(2)* 0.102(8)* 0.15(1)* 0.22(2),
(continued)
"E.s.d.s are given in parentheses.
b Starred atomswere refinedwith anisotropicthermalparameters. isolated by cooling the THF solution to 0 °C, was devoid of resonances. Thus a single crystal X-ray crystallographic study was undertaken. The structure solution revealed a heavy atom surrounded by three chelated ligands. The ligands refined as chelated forms of the oxidized anionic ligand, [ (O-PPh2) 2N] - . The asymmetric unit of the unit cell also contained a THF solvent molecule. The octahedral tris-chelate geometry of Fe((OPPh2) 2N) 3 is comparable to that of ferric acetylacetonate [ 17]. The low quality of the X-ray data precludes a detailed discussion of the geometry of the molecule. The three O - F e - O chelate angles are equivalent and average to 89.3(2) ° . The nonchelate O - F e - O angles range from 87.7(2) to 93.6(2) °. The Fe-O bond lengths have values from 1.987(5) to 2.036(4) A, and are well within other Fe ( I I I ) - O bond lengths reported in the literature which range from 1.960(2) to 2.085(3) ~, [181. The bond angles and lengths in the ligands do not vary greatly from expected values [ 19]. The O - P - N - P - O atoms show only slight deviation from planarity; the largest deviation from the least squares planes was 0.159(1) /k (P(3) o
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C S. Browning et aL / lnorganica Chimica Acta 241 (1996) 111-115
Table 3 Molecular geometry of Fe((OPPh2) 2N)3"TI-IF" Distances (,~) Fe-O(1) Fe-O(2) Fe--O(3) Fe--O(4) Fe-O(5) Fe,-O(6) O(1)-P(I) O(2)-P(2) O(3)-P(3)
2.006(5) 2.036(4) 1.987(5) 2.005(5) 1.995(5) 2.004(5) 1.511(6) 1.510(6) 1.520(6)
O(4)-P(4) O(5)-P(5) O(6)-P(6) N(1)-P(I) N(1)-P(2) N(2)-P(3) N(2)-P(4) N(3)-P(5) N(3)-P(6)
1.524(6) 1.499(6) 1.504(6) 1,595(6) 1,588(7) 1,597(7) 1.578(7) 1.574(7) 1.595(7)
Angles (°) O(1)-Fe--O(2) O(1 )-Fe--O(3) O(2)-Fe--O(3) O(1 )-Fe--O(4) O(2)-Fe,-O(4) O(3)-Fe-O(4) O(1)-Fe-O(5) O(2)-Fe-O(5) O(3)-Fe-O(5) O(4)-Fe-O(5) O( 1)-Fe-O(6) O(2)-Fe-O(6) O(3)-Fe-O(6) O(4)-Fe-O(6) O(5)-Fe-O(6)
89.0(2) 89.5(2) 176.9(2) 93.3(2) 87.7(2) 89.7(2) 87.9(2) 93.6(2) 89.1(2) 178.2(2) 176.4(2) 89.0(2) 92.7(2) 89.6(2) 89.2(2)
Fe-O(I)-P(1) Fe--O(2)-P(2) Fe-O(3)-P(3) Fe--O(4)-P(4) Fe-O(5)-P(5) Fe--O(6)-P(6) P(1)-N(1)-P(2) P(3)-N(2)-P(4) P(5)-N(3)-P(6) O(I)-P(1)-N(1) O(2)-P(2)-N(1) O(3)-P(3)-N(2) O(4)-P(4)-N(2) O(5)-P(5)-N(3) O(6)-P(6)-N(3)
130.7(3) 127.6(3) 132.7(3) 129.4(3) 131.7(3) 130.3(3) 123.7(4) 124.2(5) 125.6(4) 117.2(3) 116.6(3) 116.7(3) 116.4(3) 116.7(3) 116.5(3)
4. Supplementary material Tables of complete molecular geometry, anisotropic displacement coefficients, H atom coordinates ( 11 pages) and tables of structure factors (17 pages) are available from author D.H.F.
"E,s.d.s are given in parentheses.
c(311,% c,6,1,
with the known value of 5.7 BM measured for Fe(acac)3 [20]. The complex Fe ((OPPh2) 2N) 3 also has been isolated from the reaction of Fe2(CO)9 with excess dppa in CH3CN or CH2C12, arid from the reaction ofFeC13 with 3 equiv, ofdppa, in THF. This product does not form if the solvents are rigorously degassed and the reaction is performed under argon. Reaction of oxidized dppa, (OPPh2)2NH [9], or the salt Li [ (OPPh2) 2N] [ 21 ], with Fe (III) salts, such as Fe (NO3) 3, produces Fe( (OPPh2)2N)3 in high yields. In a study on metal carbonyl reactions with fl-diketones, Dunne and Cotton [20] reported the synthesis of ferric trisacetylacetonate by refluxing Fe2(CO)9 in acetylacetone. The /3-diketone oxidizes the metal centre and hydrogen gas is evolved in the process. In addition, transition metal catalysis of phosphine oxidation has been reported with several phosphine ligands [ 22]. These observations suggest that one possible pathway for the reaction of Fe2(CO)9 with dppa may be metal-assisted 02 oxidation of dppa to (OPPh2)2NI-I, and oxidation of Fe(O) to Fe(III) coupled with reduction of three dppa protons to 3/2 H2.
0,
_
Acknowledgements We thank the Natural Sciences and Engineering Research Council of Canada for research support.
utbl
I
--
P(1) References
C(511)I<~
P(2~ ~ N ( 1 ) (~ ;(211'
Fig. 1. A view of the molecule Fe((OPPh2)2N) 3 with 50% probability ellipsoids. Only the a-C atoms of the phenyl rings are shown, for clarity.
from the plane defined by P(3), P(4), N(2), 0 ( 3 ) and 0(4)). All data obtained for Fe( (OPPh2)2N)3 agree with the formulation as an Fe(III) complex with three oxidized anionic ligands, [(O--PPh2)2N]-. The final electron density map for the structure of Fe ((OPPh2) 2N) 3 showed no significant residual electron density near the N atoms. The FAB MS parent ion peak and the isotopic distribution are consistent with the product's formulation. The magnetic moment of the Fe atoms in the compound Fe((OPPh2)2N) 3 was found to be 5.4 BM, using the Gouy method. This is in good agreement
[ 1] C.S. Browning and D.H. Farrar, J. Chem. Soc. Dalton Trans., (1995) 521. [2] F.A. Cotton and J.M. Troup, J. Am. Chem. Sot., 96 (1974) 4422. [3] N.M. Doherty, G. Hogarth, S.A.R. Knox, K.A, Macpherson, F. Melchior and A.G. Orpen, J. Chem. Soc., Chem. Commun., (1986) 540. [4] (a) R.B. King and L Gimeno, Inorg. Chem., 17 (1978) 2390; (b) M.G. Newton, R.B. King, M. Chang and J. Gimeno, J. Am. Chem. Soc., 99 (1977) 2802. [5] M.G. Newton, R.B. King, M. Chang and L Gimeno, J. Am. Chem. Soc., 100 (1978) 326. [6] M.S. Balakrishna,T.K. Prakasha, S.S. Krishnamurthy,U, Siriwardane and N.S. Hosmane, J. Organomet. Chem., 390 (1990) 203. [ 7] G.M. Brown, LE. Finholt, R3. King, J.W. Bibber and J.H. Kim, lnorg. Chem., 21 (1982) 3790. [8] F.T. Wang, J. Najdzionek, K.L. Leneker, H. Wasserman and D.M. Braitsch, Synth. React. lnorg. Met.-Org. Chem,, 8 (1978) 119. [91 G. Ewart, A.P. Lane, J. McKechie and D.S. Payne, J. Chem. Soc., (1964) 1543. [ 10] P.W. Seldom, Magnetochemistry, Interscience, New York, 1956.
C.S. Browning et al. / lnorganica Chimica Acta 241 (1996) 111-115
[ 11 ] G. M. Sheldrick, SHELX86, Structure Solving Program, University of GOttingen,Germany, 1986. [ 12] N. Walker and D. Stuart, Acta Crystallogr., Sect. A, 39 (1983) 158. [13] C.K. Johnson, ORTEP I1. Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, USA, 1976. [ 14] International Table of Crystallography, Vol. 4, Kynoch, Birmingham, 1969. [ 15] A.C. Larson, F.L. Lee, Y. LePage, M. Webster, J.P. Charland and E.J. Gabe, The NRCVAX Crystal Structure System, Chemistry Division, NRC, Ottawa, Canada, 1990. [ 16] G.M. Sheldrick, SHELX76, program for crystal structure determination and refinement, University of Cambridge, UK, 1976. [ 17] J. Iball and C.H. Morgan, Acta CrystaUogr., Sect. A, 23 (1967) 239.
115
[18] (a) H.L.K. Wah, M. Postel and F. Total, lnorg. Chem,, 28 (1989) 233; (b) E. Durcanska, T. Glowiak, J. Kozisek, I. Ondrejkovicova and G. Ondrejovic, Acta Crystallogr., Sect. C, 45 (1989) 410; (c) H.L.K. Wah, M. Postel and F. Tomi, New J. Chem., 12 (1988) 289. [ 19] (a) M. O'Keeffe and N.E. Brese, J. Am. Chem. Soc., 113 ( 1991) 3226; (b) A.G. Orpen, L. Brammer, F.H. Allen, O Kennard, D.G. Watson and R. Taylor, J. Chem. Soc., Dalton Trans., (1989) S1. [20] T.G. Dunne and F.A. Cotton, lnorg. Chem., 2 (1963) 263. [21] V.H. Richter, E. Fluck, H. Riffel and H. Hess, Z. Anorg. Allg. Chem., 496 (1983) 109. [22] (a) A. Sen and J. Halpern J. Am. Chem, Soc., 99 (1977) 8337; (b) V. Vancova and I. Ondrejkovicova, Collect. Czech. Chem. Commun., 56 (1991) 2869; (c) V.J. Choy and C.J. O'Connor, Coord. Chem. Rev., 9 (1972) 145; (d) J.S. Valentine, Chem. Rev., 73 (1973) 235.
InorganicaChimicaActa241 (1996) 111-115
Note
Preparation, characterization and crystal structure of Fe((OPPh2) 2N) 3 C. Scott Browning, David H. Farrar *, Daniel C. Frankel Department of Chemistry, Universityof Toronto, Toronto, Ont., MSS IA1, Canada
Received3 February1995;revised21 June 1995
Abstract White crystals of Fe((OPPhz)2N) 3 were obtained from the reaction of a solution of Fe2(CO)9 and excess (PPh2)2NH, under an air atmosphere. This product does not form if the solvents are rigorously degassed and the reaction is performed under argon. The structure of the complex, as determined by single crystal X-ray crystallography, is an octahedral tris-chelate arrangement of the oxidized anionic ligand, [ (O=PPh2)2N] - coordinated to an Fe(III) center. The asymmetric unit of the unit cell also contains a disordered THF solvent molecule. The complex crystallizes in the triclinic s~ace group Pi, with Z=2, affi13.581(3), bffi 13.886(8), cffi18.781(7) A, affi95.48(4), /3ffi98.73(2), 7=97.82(3) °, V-- 3444(2) A3, Mr = 1377, Dx-- 1.33 Mg m -3, F(000) = 1434, Tffi298 K and R---0.086 for 5959 observed reflections. The magnetic moment of the compound Fe((OPPh2)2N)3 was found to be 5.4 BM, using the Gouy method. Reaction of the oxidized ligand, (OPPh2)2NH, with Fe(III) salts, such as Fe(NO3)3, produces Fe((OPPh2)2N) 3 in high yields. Keywords: Crystalstructures;Iron complexes;Phosphinoaminecomplexes
1. Introduction We have been examining the transition-metal coordination chemistry of bis(diphenylphosphino)amine ligands. In our initial studies we compared the reactivity of bis(diphenylphosphino)amine (dppa) and bis(diphenylphosphino)methane (dppm) coordinated to platinum [ 1 ]. The dppa ligand was found tO be susceptible to P-N bond cleavage reactions. The dppm ligand is known to undergo P C bond cleavage reactions in dppm-bridged binuclear ironcarbonyl complexes. For example, reaction of dppm with Fe2(CO)9 produces the binuclear complex Fe2(CO)6(p,CO) (/x-dppm) [2]. Upon heating, the dppm ligand in this complex undergoes P--C bond cleavage to form a phosphido and P-C bridged binuclear complex Fe2 (CO) 6(/z-PPh2) (/xPPhCH2) [ 3 ]. The reactivity ofdppm-bridged binuclear iron complexes prompted us to explore the reaction of dppa with iron carbonyl. This paper describes the reaction of Fe2(CO)9 and dppa, in THF solvent under an air atmosphere, and the resulting product Fe((OPPh2) 2N) 3Reactions of related phosphinoamine ligands with Fe(CO)s and Fe2(CO)9 have been reported. King and coworkers [4] have published an extensive study on the ligand bis(difluorophosphino)methylamine, (PF2)2NMe. They have shown that reaction of the ligand with Fe(CO)5 yielded * Correspondingauthor. 0020-1693/96/$15.00 © 1996ElsevierScienceS.A. All fightsreserved SSD10020-1693 ( 95 ) 04737-T
both the chelated, square pyramidal, product Fe(r/2F2PN(Me)PF2)2(CO), and the bis-bridged iron binuclear compound, Fe2(CO)4(p-F2PN(Me)PF2)2(/z-CO). The ligand (PF2)2NMe reacts with Fe3(CO)12 to give binuclear products [ 5 ]. Reactions between diphosphitoamine ligands and iron carbonyls also have been reported. Fe(CO)5 reacts with (P(OPh)2)2NR, (R--Me, Ph) to form chelated products and a binuclear compound [ (CO)2Fe(p-CO) (p(PhO)2PN(R)P(OPh)2)2Fe(CO)2] [6]. The compound Fe2(CO)9 has been shown to react with (P(OMe)2)2NMe to yield a binuclear product [ 7 ].
2. Experimental 2.1. General procedures
All chemicals were obtained commercially and used without further purification. (PPh2)2NH [8] and (OPPh2)2NH [ 9] were prepared by literature methods. 31p NMR spectra were recorded on a Gemini 300 spectrometer operating at 121.5 MHz. P(OMe)3 in C6D6 was used as an external reference. Fast-atom bombardment mass spectroscopic (FAB MS) analyses were performed in a nitrobenzyl alcohol matrix using a Varian VG70-250S mass spectrometer with a Xe gas ionizing source at 8 kV and 1 mA.
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Analytical analyses were obtained from Canadian Microanalytical Service, Ltd., Delta, B.C., Canada. The magnetic moment was determined at 23 °C, by the Gouy technique using Hg[Co(NCS)4] as a calibrant. Diamagnetic corrections were applied using literature values [10].
2.1.1. Synthesis of Fe((OPPhz)aN)3 Method a . Fe2(CO)9 (120 mg, 0.33 mmol) and (PPh2)2NH (750 mg, 1.95 mmol) were stirred in THF (50 ml) for 1 day at 23 °C and allowed to stand for 1 week at 0 °C. The white crystalline product Fe( (OPPh2)2N)3 precipitated out of solution. Yield: 230 mg, 50%. FAB MS parent ion peak at m/z = 1305 (the isotopic distribution for the product was identical to that calculated for Fe((OPPh2)zN)3). Anal. Found for Fe ((OPPh2) 2N) 3"THF, C76I~FeN3OTPt: C, 66.3; H, 5.0; N, 3.0. Calc.: C, 65.9; H, 4.9; N, 3.0%. M.p. > 300 °C. Method b. To an ethanol solution (70 ml) of Fe(NO3)3 (164 mg, 0.68 mmol) was added (OPPh2)2NH (750 rag, 1.80 retool). The resulting suspension was refluxed for 2 h to dissolve the ligand. The white crystalline product Fe( (OPPh2)2N)3 precipitated from the solution upon lowering the solvent volume under vacuum. Yield: 170 rag, 80%. 2.2. Data collection, solution and refinement for
Fe(( OPPhz)2N)~ "THF Data for the crystal structure analysis of the compound Fe( (OPPh2)2N)3 .THF are given in Table 1. Crystals were Table 1
X-rayexperimentaldataforFe((OPPhz)2N)3"THF Empirical formula
Mr
CTc,Hs~eN3OvP~ 1377
Crystal system Space group
triclinic ei (No. 2)
a (A)
13.581(3)
b (A) c (A) a (°) /3(°)
13.886(8) 18.781(7) 95.48(4) 98.73(2) 97.82(3) 3444(2)
~,(°) V (A3) C.entering reflections, Orange (°) Z D, (Mg m -3 ) F(O00) p,(Mo Ka) (cm -I) Indices 20 range (°) No. of data (R~v) No. of data used, criterion No. standards, frequency, decay (%) Final R (Rw) No. variables (observed/variables) Largest (av.) final shift/e.s.d. Fmal e - density map (e .~-3) (Maximum near) Goodness-of-fit
25, 12-15 2 1.33
1434 4.15 h - 14,14; k - 14,14; 10,20; 1-42 7372 (0.0158) 5959, I > 3or(1) 3, 2h, 0.01 0.086 (0.091) 478 (12.5) 0.17 (<0.01) - 0.65 to 0.72 (H41D) 7.50
grown by slow evaporation of a CH2C12/THF solution of product. The crystals rapidly decomposed by solvent loss upon removal from the mother liquor. A crystal was mounted on a glass fibre and quickly coated in epoxy resin to prevent solvent loss. Accurate cell dimensions and crystal orientation matrix were determined on a CAD-4 diffractometer by a least squares treatment of the setting angles of 25 reflections in the range 1 2 < 0 < 15°. o>scans of several intense low-angle reflections revealed that the crystal mosaicity was poor. Intensifies of reflections with indices h - 14 to 14, k - 14 to 14, l 0 to 20, and 1 < 0< 21°, were measured; intensities of three reflections measured every 2 h decayed by 0.01% during data collection. 7372 reflections measured were corrected for Lorentz and polarization effects. Crystal faces could not be identiffed due to the epoxy coating. 5959 reflections with I > 3o-(1) were labeled observed and used in the structure solution and refinement. Space group P1 was determined by a successful structure refinement. The structure was solved by the direct methods [ 11]. Positions for 88 non-H atoms associated with the Fe complex were determined. A subsequent difference Fourier synthesis revealed the presence of electron density associated with a disordered THF molecule. The disorder appears to arise from several orientations of the THF molecule derived by small rotations about the centroid of the THF ring, in the plane of the molecule. All attempts to refine a model for this disorder were unsuccessful. In the final cycles an O atom and four C atoms, forming a highly distorted ring, were refined with anisotropic thermal parameters. Refinement was by fullmatrix least-squares calculations with anisotropic thermal parameters for all atoms except the phenyl ring C atoms which were refined with isotropic thermal parameters. Data were corrected for absorption effects using the program DIFABS [ 12] with minimum and maximum absorption corrections of 0.954 and 1.215 respectively. In the final refinement cycles, the H atoms associated with the phenyl rings were positioned on geometric grounds and included (as riding atoms) in the structure factor calculation ( U~o= 0.08 ,~z). No corrections for secondary extinction were applied. The atomic coordinates are given in Table 2. Selected bond lengths and angles for the molecule are listed in Table 3. An ORTEP [ 13] view of the molecule is presented in Fig. 1. For clarity only the a-C atoms of the phenyl rings are shown. Neutral atom scattering factors were used [ 14]. All calculations were carried out on a MicroVaxII computer with the NRCVAX Crystal Structure System [15] and an Apollo computer using SHELX76 [ 16] and SHELX86 [ 11 ] programs.
3. Results and discussion
Reaction of Fe2(CO)9 with excess dppa, for I day at room temperature in THF solution under an air atmosphere, did not yield the expected dppa-bridged iron binuclear species. The room temperature 31p N'MR spectrum of a white product,
113
CS. Browning et al. / Inorganica Chimica Acta 241 (1996) 111-115
Table2 Positionalparan~tersand equivalentisotropicdisplacementcoefficientsfor Fe((OPPba)2N)3"THF"
Table 2 (continued) Atom
x
y
z
U~/ Ul~ b
Atom
x
y
z
U~I Ut~ b
Fe O(1) 0(2) 0(3) 0(4) 0(5) 0(6) N(1) N(2) N(3) P(I) P(2) P(3) P(4) P(5) P(6) C(lll) C(112) C(113) C(114) C(ll5) C(116) C(121) C(122) C(123) C(124) C(125) C(126) C(211) C(212) C(213) C(214) C(215) C(216) C(221) C(222) C(223) C(224) C(225) C(226) C(311) C(312) C(313) C(314) C(315) C(316) C(321) C(322) C(323) C(324) C(325) C(326) C(411) C(412) C(413) C(414) C(415) C(416) C(421) C(422)
0.1810(l) 0.2393(4) 0.3123(4) 0.0570(4) 0.2373(4) 0.1209(4) 0.1246(4) 0.4328(5) 0.0713(5) 0.1036(5) 0.3475(2) 0.4183(2) 0.0155(2) 0.1831(2) 0.0994(2) 0.1086(2) 0.3686(6) 0.3029(9) 0.320(1) 0.401(1) 0.4669(9) 0.4516(7) 0.3593(6) 0.4524(8) 0.4591(9) 0.3744(9) 0.280(1) 0.2761(8) 0.4956(6) 0.4570(8) 0.5184(9) 0.6190(9) 0.659(1) 0.5980(9) 0.4701(6) 0.4583(7) 0.4995(8) 0.5530(8) 0.5681(8) 0.5247(7) -0.1139(7) -0.164(1) -0.268(1) -0.3141(1) -0.272(1) -0.166(1) 0.0118(6) 0.0498(8) 0.0468(9) 0.0021(8) -0.0348(8) -0.0302(7) 0.1813(7) 0.0940(9) 0.093(1) 0.183(1) 0.269(1) 0.2724(9) 0.2602(7) 0.2281(9)
0.6917(1) 0.6532(4) 0.7827(4) 0.5969(4) 0.5889(4) 0.7930(4) 0.7390(4) 0.6908(5) 0.4656(5) 0.9171(5) 0.6539(2) 0.7631(2) 0.4979(2) 0.5083(2) 0.8924(2) 0.8403(2) 0.7270(6) 0.7120(8) 0.772(1) 0.841(1) 0.8554(9) 0.7988(7) 0.5335(6) 0.5058(8) 0.4092(9) 0.3486(9) 0.372(1) 0A679(8) 0.8785(6) 0.9635(7) 1.0531(9) 1.0557(9) 0.9738(9) 0.8830(9) 0.7155(6) 0.7583(7) 0.7234(8) 0.6477(8) 0.6046(9) 0.6402(7) 0.4990(7) 0.431(1) 0.429(1) 0.4957(1) 0.560(1) 0.561(1) 0.4062(6) 0.3212(8) 0.251(1) 0.2669(9) 0.3484(8) 0.4191(7) 0.5475(7) 0.5651(8) 0.6003(9) 0.6126(9) 0.6011(9) 0.5688(8) 0.4119(7) 0.3302(9)
0.7254(1) 0.6368(3) 0.7656(3) 0.6860(3) 0.7801(3) 0.6720(3) 0.8126(3) 0.6954(4) 0.7794(4) 0.7817(3) 0.6263(1) 0.7624(1) 0.7064(1) 0.8160(1) 0.6976(1) 0.8396(1) 0.5542(4) 0.4907(6) 0.4334(8) 0.4451(7) 0.5059(6) 0.5611(5) 0.5921(4) 0.5924(5) 0.5598(6) 0.5319(6) 0.5317(7) 0.5651(5) 0.7648(4) 0.7627(5) 0.7607(6) 0.7611(6) 0.7640(6) 0.7653(6) 0.8425(4) 0.9094(5) 0.9726(6) 0.9662(6) 0.9022(6) 0.8390(6) 0.7148(5) 0.7485(7) 0.7528(8) 0.7233(8) 0.680(1) 0.6764(8) 0.6315(4) 0.6403(6) 0.5807(7) 0.5137(6) 0.5042(6) 0.5632(5) 0.9100(5) 0.9337(6) 1.0071(7) 1.0524(8) 1.0318(7) 0.9580(6) 0,8193(5) 0.8562(6)
0.033(1)* 0.045(2)* 0.039(2)* 0.044(2)• 0.040(2)* 0.043(2)* 0.040(2)• 0.047(3)* 0.054(3)* 0.045(3)• 0.043(1), 0.043(1)* 0.042(1)* 0.047(1), 0.040(1), 0.040(1)* 0.046(2) 0.084(3) 0.110(4) 0.105(4) 0.090(4) 0.066(3) 0.045(2) 0.076(3) 0.093(4) 0.095(4) 0.106(4) 0.077(3) 0.047(2) 0.069(3) 0.090(4) 0.086(3) 0.095(4) 0.086(3) 0.048(2) 0.069(3) 0.083(3) 0.087(3) 0.088(3) 0.073(3) 0.056(3) 0.114(4) 0.144(6) 0.126(5) 0.160(6) 0.119(5) 0.042(2) 0.080(3) 0.104(4) 0.086(3) 0.076(3) 0.061(3) 0.059(3) 0.088(3) 0.111(4) 0.109(4) 0.103(4) 0.084(3) 0.058(3) 0.093(4)
C(423) C(424) C(425) C(426) C(Sll) C(512) C(513) C(514) C(515) C(516) C(521) C(522) C(523) C(524) C(525) C(526) C(611) C(612) C(613) C(614) C(615) C(616) C(621) C(622) C(623) C(624) C(625) C(626) O C(1) C(2) C(3) C(4)
0.289(1) 0.370(1) 0.409(1) 0.3442(8) 0.1870(6) 0.2455(7) 0.3164(9) 0.3246(9) 0.2654(8) 0.1969(7) -0.0237(6) -0.0406(9) -0.141(1) -0.217(1) -0.203(1) -0.1033(9) -0.0071(6) -0.0384(9) -0.134(1) -0.194(1) -0.166(1) -0.0708(9) 0.2059(6) 0.2193(7) 0.2982(8) 0.3595(8) 0.3465(8) 0.2694(7) 0.108(1) 0.036(3) -0.009(1) 0.056(2) 0.099(3)
0.255(1) 0.2663(9) 0.338(1) 0.4185(8) 0.9815(6) 0.9523(7) 1.0207(8) 1.1184(9) 1.1482(8) 1.0797(7) 0.9042(6) 0.9650(9) 0.970(1) 0.914(1) 0.850(1) 0.8456(9) 0.8255(7) 0.9028(9) 0.890(1) 0.806(1) 0.730(1) 0.7403(9) 0.8928(6) 0.8466(7) 0.8862(8) 0.9715(8) 1.0167(8) 0.9781(7) 0.8559(9) 0.879(2) 0.833(1) 0.821(2) 0.818(2)
0.8615(7) 0.8376(6) 0.8005(8) 0.7911(6) 0.6669(4) 0.6196(5) 0.5952(6) 0.6198(6) 0.6667(5) 0.6914(5) 0.6520(4) 0.6005(6) 0.5661(8) 0.5839(7) 0.6328(7) 0.6674(6) 0.8760(5) 0.9124(6) 0.9353(7) 0.9224(7) 0.8841(8) 0.8593(7) 0.9137(4) 0.9748(5) 1.0343(6) 1.0288(6) 0.9685(5) 0.9096(5) 0.2624(8) 0.174(2) 0.099(1) 0.120(1) 0.227(1)
0.104(4) 0.095(4) 0.127(5) 0.082(3) 0.042(2) 0.060(3) 0.088(4) 0.087(3) 0.076(3) 0.063(3) 0.047(2) 0.089(4) 0.117(5) 0.110(4) 0.108(4) 0.090(4) 0.049(2) 0.089(4) 0.110(4) 0.104(4) 0.126(5) 0.098(4) 0.040(2) 0.066(3) 0.082(3) 0.072(3) 0.074(3) 0.059(3) 0.133(7)* 0.31(2)* 0.102(8)* 0.15(1)* 0.22(2),
(continued)
"E.s.d.s are given in parentheses.
b Starred atomswere refinedwith anisotropicthermalparameters. isolated by cooling the THF solution to 0 °C, was devoid of resonances. Thus a single crystal X-ray crystallographic study was undertaken. The structure solution revealed a heavy atom surrounded by three chelated ligands. The ligands refined as chelated forms of the oxidized anionic ligand, [ (O-PPh2) 2N] - . The asymmetric unit of the unit cell also contained a THF solvent molecule. The octahedral tris-chelate geometry of Fe((OPPh2) 2N) 3 is comparable to that of ferric acetylacetonate [ 17]. The low quality of the X-ray data precludes a detailed discussion of the geometry of the molecule. The three O - F e - O chelate angles are equivalent and average to 89.3(2) ° . The nonchelate O - F e - O angles range from 87.7(2) to 93.6(2) °. The Fe-O bond lengths have values from 1.987(5) to 2.036(4) A, and are well within other Fe ( I I I ) - O bond lengths reported in the literature which range from 1.960(2) to 2.085(3) ~, [181. The bond angles and lengths in the ligands do not vary greatly from expected values [ 19]. The O - P - N - P - O atoms show only slight deviation from planarity; the largest deviation from the least squares planes was 0.159(1) /k (P(3) o
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C S. Browning et aL / lnorganica Chimica Acta 241 (1996) 111-115
Table 3 Molecular geometry of Fe((OPPh2) 2N)3"TI-IF" Distances (,~) Fe-O(1) Fe-O(2) Fe--O(3) Fe--O(4) Fe-O(5) Fe,-O(6) O(1)-P(I) O(2)-P(2) O(3)-P(3)
2.006(5) 2.036(4) 1.987(5) 2.005(5) 1.995(5) 2.004(5) 1.511(6) 1.510(6) 1.520(6)
O(4)-P(4) O(5)-P(5) O(6)-P(6) N(1)-P(I) N(1)-P(2) N(2)-P(3) N(2)-P(4) N(3)-P(5) N(3)-P(6)
1.524(6) 1.499(6) 1.504(6) 1,595(6) 1,588(7) 1,597(7) 1.578(7) 1.574(7) 1.595(7)
Angles (°) O(1)-Fe--O(2) O(1 )-Fe--O(3) O(2)-Fe--O(3) O(1 )-Fe--O(4) O(2)-Fe,-O(4) O(3)-Fe-O(4) O(1)-Fe-O(5) O(2)-Fe-O(5) O(3)-Fe-O(5) O(4)-Fe-O(5) O( 1)-Fe-O(6) O(2)-Fe-O(6) O(3)-Fe-O(6) O(4)-Fe-O(6) O(5)-Fe-O(6)
89.0(2) 89.5(2) 176.9(2) 93.3(2) 87.7(2) 89.7(2) 87.9(2) 93.6(2) 89.1(2) 178.2(2) 176.4(2) 89.0(2) 92.7(2) 89.6(2) 89.2(2)
Fe-O(I)-P(1) Fe--O(2)-P(2) Fe-O(3)-P(3) Fe--O(4)-P(4) Fe-O(5)-P(5) Fe--O(6)-P(6) P(1)-N(1)-P(2) P(3)-N(2)-P(4) P(5)-N(3)-P(6) O(I)-P(1)-N(1) O(2)-P(2)-N(1) O(3)-P(3)-N(2) O(4)-P(4)-N(2) O(5)-P(5)-N(3) O(6)-P(6)-N(3)
130.7(3) 127.6(3) 132.7(3) 129.4(3) 131.7(3) 130.3(3) 123.7(4) 124.2(5) 125.6(4) 117.2(3) 116.6(3) 116.7(3) 116.4(3) 116.7(3) 116.5(3)
4. Supplementary material Tables of complete molecular geometry, anisotropic displacement coefficients, H atom coordinates ( 11 pages) and tables of structure factors (17 pages) are available from author D.H.F.
"E,s.d.s are given in parentheses.
c(311,% c,6,1,
with the known value of 5.7 BM measured for Fe(acac)3 [20]. The complex Fe ((OPPh2) 2N) 3 also has been isolated from the reaction of Fe2(CO)9 with excess dppa in CH3CN or CH2C12, arid from the reaction ofFeC13 with 3 equiv, ofdppa, in THF. This product does not form if the solvents are rigorously degassed and the reaction is performed under argon. Reaction of oxidized dppa, (OPPh2)2NH [9], or the salt Li [ (OPPh2) 2N] [ 21 ], with Fe (III) salts, such as Fe (NO3) 3, produces Fe( (OPPh2)2N)3 in high yields. In a study on metal carbonyl reactions with fl-diketones, Dunne and Cotton [20] reported the synthesis of ferric trisacetylacetonate by refluxing Fe2(CO)9 in acetylacetone. The /3-diketone oxidizes the metal centre and hydrogen gas is evolved in the process. In addition, transition metal catalysis of phosphine oxidation has been reported with several phosphine ligands [ 22]. These observations suggest that one possible pathway for the reaction of Fe2(CO)9 with dppa may be metal-assisted 02 oxidation of dppa to (OPPh2)2NI-I, and oxidation of Fe(O) to Fe(III) coupled with reduction of three dppa protons to 3/2 H2.
0,
_
Acknowledgements We thank the Natural Sciences and Engineering Research Council of Canada for research support.
utbl
I
--
P(1) References
C(511)I<~
P(2~ ~ N ( 1 ) (~ ;(211'
Fig. 1. A view of the molecule Fe((OPPh2)2N) 3 with 50% probability ellipsoids. Only the a-C atoms of the phenyl rings are shown, for clarity.
from the plane defined by P(3), P(4), N(2), 0 ( 3 ) and 0(4)). All data obtained for Fe( (OPPh2)2N)3 agree with the formulation as an Fe(III) complex with three oxidized anionic ligands, [(O--PPh2)2N]-. The final electron density map for the structure of Fe ((OPPh2) 2N) 3 showed no significant residual electron density near the N atoms. The FAB MS parent ion peak and the isotopic distribution are consistent with the product's formulation. The magnetic moment of the Fe atoms in the compound Fe((OPPh2)2N) 3 was found to be 5.4 BM, using the Gouy method. This is in good agreement
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