Organometallics 1996, 14,3101-3103
3101
Synthesis and Characterization of a Phosphaalkyne-Bridged Pentairon Carbonyl Cluster. Crystal and Molecular Structure of [{FesSedCO)s}Or-PCBut){Fe2Se(CO)s)l Pradeep Mathur" and Md. Munkir Hossain Department of Chemistry, Indian Institute of Technology, Powai, Bombay 400 076,India
Peter B. Hitchcock and John F. Nixon* School of Chemistry and Molecular Sciences, University of Sussex, Brighton B N l 9QJ, U.K. Received December 14, 1994@ Summary: The new cluster [{Fe3Sez(CO)s}(p-PCutl(FezSe(CO),}l has been isolated in moderate yield from the photolytic reaction of [FedCO)dp-Sed and the phosphaalkyne *CBut. Its structure has been established by single crystal X-ray diffraction methods: monoclinic, P21Ic (No. 14), a = 9.378(1) A, b = 17.605(3) A, c = 18.631(2) A, /3 = 93.00(1)",V = 3071.7 A3, Z = 4, R = 7.6%, R = 6.5%. The structure consists of a [FesSedCO)s/ unit and a [FezSe(CO)dPCButll unit linked by the phosphorus lone pair electrons of the phosphaalkyne.
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Introduction Transition metal clusters containing single atom ligands derived from several main group elements of the Periodic Table have been studied in detail.l-' Of the group 16 elements, sulfur has been the most extensively used for the purpose of cluster growth and cluster framework s t a b i l i z a t i ~ n .Recent ~ ~ ~ studies on seleniumand tellurium-bridged cluster compounds have shown that the nature of the main group element can significantly influence both the structure and reactivity of the c l ~ s t e r . ' ~ - 'We ~ have previously investigated the activation of CzC triple bonds of acetylenes by the Se-Sebonded "butterfly" compound [Fez(CO)s@-Sez)land demonstrated the stepwise C s C bond reduction.14J5 These complexes can also be used for the synthesis of the new Se-bridged mixed-metal cluster [M02FezCpzSe3(CO)sl.'~,~' Abstract published in Advance ACS Abstracts, April 15, 1995. (1)Whitmire, K.H. J . Coord. Chem. 1988,17, 95. (2)Roof, L. C.; Kolis, J. W. Chem. Reu. 1993,1037. (3)ComDton, N. A.: ErrinE.ton, R. J.: Norman, N. C. Adu. Organomet Chem. IS!%, 31, 91. (4)Ansari, M. A,; Ibers, J. A. Coord. Chem. Rev. 1990,100, 223. (5) Laver. Lewis. J.: Martin. A,: Raithbv. ~ , . ~T. , M.: ~~, " , P. R.: Wong. W. T. J . Chem. Soc., Dalton Trans. 1992,3411. (WAdams, R. D. I n The Chemistry of Metal Cluster Complexes; Shriver, D. F., Kaesz, H. D., Adams, R. D., Eds.; VCH: New York, 1990;Chapter 3. (7)Vahrenkamp, H. Phil. Trans. R. SOC.Lond. 1982,A308, 17. ( 8 ) Adams, R. D. Polyhedron 1985,4 , 2003. (9)Adams, R. D.;Li, J.-C.; Wu, W. J . Cluster Sci. 1993,4,423 and references therein. (10)Mathur, P.;Charkrabarty, D.; Mavunkal, I. J . J . Cluster Sci. 1993,4 , 351. (11)Mathur, P.;Mavunkal, I. J.; Rheingold, A. L. J . Chem. Soc., Chem. Commun. 1989,382. (12)Mathur, P.;Mavunkal, I. J.; Rugmini, V. Inorg. Chem. 1989, 28, 3616. (13)Lesch, D. A,; Rauchfuss, T. B. Organometallics 1982,1 , 499. (14)Mathur, P.;Hossain, Md. M. Organometallics 1993,12, 2398. (15)Mathur, P.;Hossain, Md. M.; Das, K.; Sinha, U. C. J. Chem. Soc., Chem. Commun. 1993,46. (16)Mathur, P.;Hossain, Md. M.; Rheingold, A. L. Organometallics 1993,12, 5029. @
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In view of the known similarity in ligating behavior of alkynes and phosphaalkynes, RC=P,18 we have now extended our studies to the activation of the CEP triple bond of the phosphaalkyne ButCEP by the [Fea(CO)s@-Sez)] framework. Here we report the synthesis and characterization of the unusual cluster [{FesSez(CO)e}@PCBut){FezSe(C0)6}1.
Results and Discussion When a mixture of [Fes(CO)s@-Sedland ButC=P in hexane was photolyzed with ultraviolet light for 0.5 h, and the mixture was subjected to chromatographic workup, the new cluster [{FesSez(CO)s}@-PCBut){FezSe(CO)s}I was isolated (Scheme 1)and characterized by IR and 'H NMR spectroscopy. The IR spectrum revealed the existence of only terminally-bonded carbonyl ligands, and the 'H NMR spectrum showed a single peak for the But protons. Single crystals suitable for X-ray analysis were obtained from hexane at -4 "C. Its molecular structure is shown in Figure 1, and some important bond length and bond angle parameters are listed in Table 1. The structure of [{Fe3Sez(CO)s)@-PCBut){FezSe(CO)6}]can be described as consisting of both a Fe3Se2 square pyramidal core and a FezSe triangular unit linked by a ButCP group which is +bonded t o one of the basal Fe atoms of the FesSe2 unit and to both Fe atoms of the FezSe unit. The C atom of the bridging phosphaalkyne is bonded to one Fe atom and the Se (17)Mathur, P.;Hossain, Md. M.; Rheingold, A. L. Organometallics 1994,13, 3909. (18) Nixon, J. F. Chem. Rev. 1988,88,1327;Chem. Ind. 1993,404.
0276-7333/95/2314-3101$09.00/00 1995 American Chemical Society
Notes
3102 Organometallics, Vol. 14, No. 6, 1995
Table 2. Crystallographic Data for the Complex formula fw space group a,A b, A
07
C,
A
A deg
C19HgFe5014PSe3 1008.4 P21lc 9.378(1) 17.605(3) 18.631(2) 93.00(1)
V, A3 2 Deale,gem-' p(Mo Ka),cm-l T,"C A, cm-l R
3071.7 4 2.18 59.4 25 0.7107 0.076
six-coordinate Fe atom of the Fe2Se unit forms a shorter bond to the P atom (Fe(1)-P, 2.319(5) A) than does the seven-coordinate Fe atom (Fe(2)-P, 2.3386) A). An opposite trend is observed between the bonding of these two Fe atoms and the Se atom; thus the six-coordinate Fe atom (Fe(1)-Se(l), 2.379(4) A) forms a slightly longer bond than the seven-coordinate Fe atom (Fe(B)-Se(l), 2.350(3)
A).
When a hexane of [Fe2(CO)6@-Sez)l is photolyzed for 0.5 h in the absence of the phosphaalkyne, formation 02 of insoluble black material is observed, and after extraction and chromatographic workup, small quantities of [Fez(C0)6@-Sedl and [Fe3(CO)g@-Sez)l were obtained. The presence of phosphaalkyne in the reaction medium thus serves to bridge these two species leading to the formation of [{Fe3Se2(CO)s}Cu-PCBut){FaSe(CO)6}]. Similar ligating behavior of other novel cluster carbonyls derived from phosphaalkynes has been previously re01 ported by us in the synthesis of the polymetallic Figure 1. Molecular structure of [ { F ~ ~ S ~ Z ( C O ) ~ } ( U - P Ccomplexes [MO~(C~)~(~;~~-C~H~( )M~,L(,P=C B U ~ ) M ~ But)(FezSe(C0)6)1, showing the atom-numbering scheme. [ 0 ~ 3 ( C O ) i i[R~3(CO)ii1,2~ I~~ [PtC1a(PR3)1,21 [PdC12(PR3)1,21 [Fe(C0)41,22and [W(C0)5la2). Table 1. Intramolecular Distances (A)and Angles (deg) with Estimated Standard Deviations in Parentheses Experimental Section Se(1)-Fe(1) Se(l)-C(15) Se(2)-Fe(3) Se(2)-Fe(5) Se(3)-Fe(4) Fe(l)-Fe(2) Fe( l)-C( 1) Fe(l)-C(6) Fe(2)-C(3) Fe(2)-C(14) Fe(3)-Fe(4) Fe(3)-C(5) Fe(4)-Fe(5) Fe(4)-C(8) Fe(5)-C(10) Fe(5)-C(13) Fe(l)-Se(l)-Fe(2) Fe(2)-Se(l)-C(15) Se(3)-Se(2)-Fe(4) Fe(3)-Se(2)-Fe(4) Fe(4)-Se(2)-Fe(5) Se(2)-Se(3)-Fe(4) Fe(3)-Se(3)-Fe(4) Fe(4)-Se(3)-Fe(5) Se(1)-Fe(1)-P Se(l)-Fe(l)-C(2) Fe(B)-Fe(l)-P Fe(2)-Fe(l)-C(2)
(a) Bonds 2.379(4) Se(l)-Fe(2) 1.93(2) Se(2)-Se(3) 2.353(3) Se(2)-Fe(4) 2.358(3) Se(3)-Fe(3) 2.370(3) Se(3)-Fe95) 2.690(4) Fe(1)-P 1.783(14) Fe(l)-C(2) 1.69(2) Fe(2)-P 1.80(2) Fe(2)-C(4) 1.83(2) Fe(2)-C(15) 2.646(3) Fe(3)-P 1.78(2) Fe(3)-C(12) 2.636(3) Fe(4)-C(7) 1.80(2) Fe(4)-C(9) 1.78(2) Fe(5)-C( 11) 1.82(2) P-C(l5) (b) Angles 69.3(1) Fe(l)-Se(l)-C(15) 58.8(6) Se(3)-Se(2)-Fe(3) 49.56(6) Se(3)-Se(2)-Fe(5) 67.91(8) Fe(3)-Se(2)-Fe(5) 67.54(9) Se(2)-Se(3)-Fe(3) 49.96(7) Se(2)-Se(3)-Fe(5) 68.09(8) Fe(3)-Se(3)-Fe(5) 67.93(8) Se(l)-Fe(l)-Fe(2) 74.2(1) Se(l)-Fe(l)-C(l) 164.0(6) Se(l)-Fe(l)-C(6) 55.1(1) Fe(a)-Fe(l)-C(l) 109.5(6) Fe(L)-Fe(l)-C(G)
2.350(3) 3.072(2) 2.385(3) 2.356(3) 2.349(3) 2.319(5) 1.78(2) 2.338(5) 1.76(2) 2.13(2) 2.195(5) 1.736(15) 1.80(2) 1.79(2) 1.76(2) 1.73(2) 88.5(6)
49.34(6) 49.13(7) 98.07(9) 49.25(6) 49.40(6) 98.25(9) 54.82(9) 97.9(5) 101.5(8) 109.2(6) 148.0(7)
atom of the FeaSe unit. In the Fe3Se2 unit, the Fe atom which is bonded to the P atom has two terminal carbonyl groups bonded to it, and the remaining four Fe atoms of the whole structure each have three terminal carbonyl ligands bonded t o them. The bond parameters of the Fe3Sez core are quite similar to the corresponding p a r a m e t e r s in [Fe3Sez(C0)gl.19 The
General Procedures. All reactions and other manipulations were performed using Schlenk techniques under an inert atmosphere of argon. Solvents were deoxygenated immediately prior to use. Infrared spectra were recorded on a Nicolet 5DXB or Impact 400 FT spectrometer as hexane solutions in 0.1-mm pathlength NaCl cells. 'H NMR spectra were carried out using a Carlo Erba automatic analyzer. [Fez(CO)&Sez)]23.24and B u ~ C E Pwere ~ ~ prepared as reported in the literature. Preparation of [{Fe&e2(CO)&-PCBut){Fe2Se(COe)]. A mixture of freshly prepared [Fez(CO)&-Sez)l (77 mg, 0.18 mmol) and 20 p L of ButC=P in hexane solvent (150 mL) was photolyzed for 0.5 h. The color of the solution changed from orange t o black. The solvent was removed in vacuo,and the residue was subjected to chromatographic workup using silica gel TLC plates. Using hexane as eluent, the following compounds were obtained, in order of elution: violet [Fe3(C0)9b3-Se)zl (trace amount), orange [Fez(CO)&-Sez)l (trace amount), and dark green [ { F ~ ~ S ~ Z ( C O ) & - P C B U ~ ) { F ~ Z(29 S ~ (mg, CO~}] 17% based on Se). IR (v(CO), cm-l): 2082 (m), 2064 (s), 2045 (vs), 2034 (s), 2010 (SI, 2001 (m). lH NMR 6 1.29 (s). Mp: 101-3 "C. Anal. Calcd for C19HgFe5014PSe3: C, 22.6; H, 0.89. Found: C, 22.7; H, 0.93. X-ray Structure Determination. A summary of the crystal data is given in Table 2. A crystal (0.2 x 0.14 x 0.08 mm) was mounted on an Enraf-Nonius CAD 4 diffractometer. (19)Dahl, L. F.; Sutton, P. W. Inorg. Chem. 1963,2,1067. (20)Bartsch, R.; Hitchcock, P. B.; Meidine, M. F.; Nixon, J. F. J . Organomet. Chem. 1984,266,C41. (21) Meidine, M. F.; Meir, C. J.; Morton, S.; Nixon, J. F. J . Orgunomet. Chem. 1985,297,255. (22) Hitchcock, P. B.; Meidine, M. F.; Nixon, J. F. J . Orgunomet. Chem. 1987,333,337. (23)Mathur, P.; Hossain, Md. M. Organometallics 1993,12,2398. (24) Mathur, P.; Chakrabarty, D.; Hossain, Md. M. R, Rashid, R. S.; Rugmini, V.; Rheingold, A. L. Inorg. Chem. 1992, 31, 1106. (25)Becker, G.; Gresser, G.; Uhl, W. Z.Nuturforsch. 1981,36b,16.
Organometallics, Vol. 14, No. 6, 1995 3103
Notes Intensities were collected with monochromated Mo K a radiation (p = 59.4 cm-l) in a 8-20 mode. A total of 7643 unique F1 > 2 4 F ) were reflections were collected, and 2906 with I used in the refinement. Structure analysis was by direct methods using SHEIXS-86. Full matrix least squares refinement proceeded using Enraf-Nonius MolEN programs with non-H atoms isotropic. The FezSe moiety is disordered with 0.73 occupancy as shown in Figure 1 and 0.27 occupancy related by reflection through the PlFe(2) and Se(1) plane. The final R value was 0.076 (R’ = 0.0651, and the ORTEP drawing shows the non-H atoms as 20% thermal vibrational ellipsoids.
Acknowledgment. Financial assistance by the Royal Society of Chemistry to P.M. is gratefully acknowledged. J.F.N.thanks IPSERC for their continuing support of phosphaalkyne chemistry. SupplementaryMaterial Available: Tables listing crystallographic structural details, complete fractional atomic coordinates and thermal parameters, bond distances and bond angles, and anisotropic thermal parameters (9 pages). Ordering information is given on any current masthead page. OM9409550
