Inorg. Chem. 1996, 35, 3235-3241
3235
Dinuclear and Tetranuclear Cages of Oxodiphenylantimony Phosphinates: Synthesis and Structures Musa A. Said,† K. C. Kumara Swamy,*,† Damodara M. Poojary,‡ Abraham Clearfield,‡ M. Veith,§ and V. Huch§ School of Chemistry, University of Hyderabad, Hyderabad, 500046, A.P., India, Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, and Anorganische Chemie, Universita¨t des Saarlandes, 66041 Saarbru¨cken, Germany ReceiVed June 7, 1995X
The novel dimeric compounds [Ph2Sb(O2PR2)O]2‚2CH2Cl2 [R ) cycl-C6H11 (2) and cycl-C8H15 (3)] have been synthesized by reacting diphenylantimony trichloride (1) with 3 mol equiv of silver acetate followed by 1 mol equiv of the phosphinic acid. By the same route under more stringent conditions to exclude moisture, the mixed phosphinate-acetate [Ph2Sb(O2P(C6H11)2)(O2CMe)]2O (4) was isolated and characterized. Treatment of 2 with acetic acid/water affords the tetranuclear cage Ph8Sb4O4(OH)2(O2P(C6H11)2)2‚CH3COOH‚CH2Cl2 (5); it is possible to convert 5 to 2 by heating it with an excess of the phosphinic acid. Compounds 2, 3, and 5 have been characterized by X-ray structural analysis. All of them possess four membered Sb2O2 rings with hexacoordinated antimony. In 5 the antimony atoms in the two Sb2O2 rings are connected by oxo bridges on two sides to give an Sb4O6 cage. These structures are correlated with those of known tin cages.
Introduction Recently, we have reported the synthesis and structures of two oxo-bridged antimony(V) compounds [Ph2SbCl(O2P(C6H11)2)]2O (I) and [Ph2Sb(O2CPh)2]2O (II) in which the
of +4 and +5 can be expected to achieve coordination numbers of 6 and 7 readily, structural analogies and related chemistry can be envisioned for them. Thus we report herein the synthesis and X-ray structures of three oxoantimony(V) phosphinate compounds, [Ph2Sb(O2PR2)O]2 [R ) cycl-C6H11 (2), cycl-C8H15 (3)] and Ph8Sb4O4(OH)2(O2P(C6H11)2)2‚CH3COOH‚CH2Cl2 (5); the structures of these derivatives have been correlated with those of the analogous tin compounds. The structural interconversion between the dinuclear and the tetranuclear cages 2 and 5 is also described. Experimental Section
antimony exhibits coordination numbers of 6 and 7, respectively.1 In the course of the reactions leading to I or its dicyclooctyl phosphinate analogue [Ph2SbCl(O2P(C8H15)2)]2O, 31P NMR analysis showed the formation of other products. Coupled with this observation, the possibility of replacement of the carboxylates in II and in the corresponding acetate [Ph2Sb(O2CMe)2]2O2 by phosphinates to generate new cages prompted us to probe these reactions further. Analogous replacement reactions on the prismane [MeSnO‚O2CMe]6 in tin chemistry led to the novel “mixed prismane” [MeSnO‚1/2O2CMe‚1/2O2P(t-bu)2]63 and “crown” [(MeSn(O)O2P(t-bu)2)(MeSn(OH)(OMe)(O2P(t-bu)2)]2[H][O2P(t-bu)2]‚4MeOH‚2H2O.4 As both tin and antimony in their respective higher oxidation states †
University of Hyderabad. Texas A&M University. § Universita ¨ t des Saarlandes. X Abstract published in AdVance ACS Abstracts, April 1, 1996. (1) Said, M. A.; Kumara Swamy, K. C.; Babu, Kamlesh; Aparna, K.; Nethaji, M. J. Chem. Soc., Dalton Trans. 1995, 2151. (2) Sowerby, D. B.; Begley, M. J.; Millington, P. L. J. Chem. Soc., Chem. Commun. 1984, 896. (3) Day, R. O.; Chandrasekar, V.; Kumara Swamy, K. C.; Holmes, J. M.; Burton, S. D.; Holmes, R. R. Inorg. Chem. 1987, 26, 1050. (4) Kumara Swamy, K. C.; Schmid, C. G.; Day, R. O.; Holmes, R. R. J. Am. Chem. Soc. 1988, 110, 1067. ‡
S0020-1669(95)00713-0 CCC: $12.00
Chemicals were produced from Aldrich/Fluka or from local manufacturers; they were purified when required. Diphenylantimony trichloride was prepared according to a literature procedure.5 Solvents were purified according to standard procedures.6 Silver salts of phosphinic acids were prepared by treating the acid with a stoichiometry quantity of aqueous sodium hydroxide followed by aqueous silver nitrate, washing the precipitate with methanol, and drying in Vacuo. All reactions, unless stated otherwise, were performed under dry nitrogen atmosphere. 1H, 13C, and 31P{1H} NMR spectra were recorded on a Bruker 200 MHz spectrometer in CDCl3 solutions with shifts referenced to SiMe4 (δ ) 0) or 85% H3PO4 (δ ) 0) IR spectra were recorded on a JASCO FT/IR-5300 spectrophotometer. Elemental analyses were carried out on a Perkin-Elmer 240C CHN analyzer. CAUTION! Toxicity of the antimony compounds reported here is unknown, and hence all of them should be handled with care. Dimeric Oxodiphenylantimony Dicyclohexylphosphinate, [Ph2Sb(O2P(C6H11)2)O]2‚2CH2Cl2 (2). Route (A). A mixture of diphenylantimony trichloride (1) (1.01 g, 2.66 mmol) and silver acetate (1.77 g, 0.63 mmol) was heated in dry toluene (50 mL) for 3 h under reflux and then filtered. The precipitate was washed with 10 mL of dry toluene, and the washings were added to the filtrate. To this filtrate dicyclohexylphosphinic acid7 (1.2 g, 2.66 mmol) was added and the mixture heated overnight under reflux. The 31P NMR spectrum of the (5) Nunn, M.; Sowerby, D. B.; Wosolek, D. M. J. Organomet. Chem. 1983, 251, C45. (6) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of Laboratory Chemicals; Pergamon: Oxford, U.K., 1986. (7) Peppard, D. F.; Mason, G. W.; Andrejasich, C. M. J. Inorg. Nucl. Chem. 1965, 27, 697.
© 1996 American Chemical Society
3236 Inorganic Chemistry, Vol. 35, No. 11, 1996
Said et al.
Table 1. Crystal Data for 2, 3, and 5 2 empirical formula fw cryst syst space group Z a/Å b/Å c/Å R/deg β/deg γ/deg V/Å3 Dc/(g cm-3) cryst size/mm F(000) µ(Mo KR)/cm-1 T/°C scan method 2θ range/deg total reflcns unique reflcns obsd reflcns diffractom used final R indices largest diff.: peak; hole a
C50H68Cl4O6P2Sb2 1212.28 triclinic P1h 1 10.520(12) 11.609(10) 13.35(2) 64.65(8) 71.86(9) 68.70(8) 1350(3) 1.492 0.2 × 0.2 × 0.4 616 13.03 20 ω-θ 3.44-34.88 1713 1713 1673 (I > 2σ(I)) Siemens stoe AED2 R1 ) 0.0335 (I > 2σ(I)) WR2 ) 0.0836 0.474; -0.434
3
5
C29H42Cl2O3PSb 662.28 monoclinic P21/a 4 12.119(2) 19.739(3) 13.155(2)
C75H92Cl2O12P2Sb4 1805.43 monoclinic P21/n 4 15.111(2) 27.860(5) 18.669(2)
112.21(1)
101.10(1)
2913.4(8) 1.510 0.4 × 0.2 × 2 1360 12.19 -110 ω - 2θ 50.1 (max) 5615 5349 4372 (I > 3σ(I)) Rigaku AFC5R Ra ) 0.028 (I > 3σ(I)) Rwa ) 0.037 0.94; -0.68
7712(1) 1.555 0.3 × 0.2 × 0.1 3624 15.52 23 ω - 2θ 50.1 (max) 14492 13936 4637 (I > 3σ(I)) Rigaku AFC5R Ra ) 0.061 RWa ) 0.053 1.26; -0.73
R ) ∑||Fo| - |Fc||/∑|Fo| and Rw ) {∑w(|Fo| - |Fc|2/∑wFo2}1/2.
reaction mixture showed a major peak at 64.3 ppm (>70%) and two minor peaks at 61.1 and 54.2 ppm. The solvent was completely removed from the mixture and the residue crystallized from dichloromethane-hexane (1:3). Yield: 1.5 g, 54% (mp 284 °C). IR (major bands): 1043 (ν(PdO)) and 962 cm-1. 1H-NMR (after powdering and drying in vacuum): δ 0.70-2.20 (br m, 44H, C6H11), 7.20-8.00 (m, 20H, H(Ar)). [If no evacuation is done, a peak at 5.3 ppm for dichloromethane solvate is observed.] 31P NMR: δ 64.3. Anal. Calcd for C49H66Cl2O2P2Sb2: C, 52.20; H, 5.86. Found: C, 51.34; H, 5.81. Route (B). A mixture of 1 (0.39 g, 1.06 mmol) and AgO2P(C6H11)2 (2.65 g, 7.87 mmol) was heated under reflux in dry toluene (60 mL) for 24 h and filtered. The solvent was removed from the filtrate and the residue crystallized from dichloromethane-hexane in air to obtain 2. Yield: 0.44 g, 40%. Mp, IR, and 31P NMR of the crystalline product were identical to that obtained by route A. Dimeric Oxodiphenylantimony Dicyclohexylphosphinate, [Ph2Sb(O2P(C8H15)2O]2‚2CH2Cl2 (3). The procedure was similar to that for 2 (routes A or B). Route (A): The following quantites were used: 1, 1.97 g, 5.17 mmol; silver acetate, 2.5 g, 15.50 mmol; dicyclooctylphosphinic acid (mp 118 °C; 31P NMR, 66.7 ppm; procedure for preparation similar to that for dicyclohexylphosphinic acid7) 2.96 g, 10.33 mmol. The 31P NMR spectrum of the reaction mixture shows a major peak at 69.6 ppm (>70%) and two minor peaks at 66.1 and 60.5 ppm. The product was crystallized from dichloromethane-hexane. Yield: 2.3 g, 38.6% (mp 255 °C). IR (major bands): 1039 (ν(PdO)) and 960 cm-1. 1H NMR (after drying): δ 0.90-2.30 (br m, 60H, C8H15), 7.08-7.95 (m, 20H, H(Ar)). [A peak for dichloromethane solvent is observed at 5.3 ppm if the sample is not dried.] 31P NMR 69.6. Anal. Calcd for C56H80O6P2Sb2 (after drying): C, 58.26; H, 6.94. Found: C, 57.75; H, 7.08. The same compound could be obtained from route B in 40% yield. (µ-Oxo)bis[diphenylantimony dicyclohexylphosphinate acetate], [Ph2Sb(O2P(C6H11)2)(O2CMe)]2O (4). A mixture of 1 (0.50 g, 1.31 mmol) and silver acetate (0.875 g, 5.25 mmol) was heated in dry toluene (20 mL) for 3 h under reflux and filtered. To the filtrate, dicyclohexylphosphinic acid (0.30 g, 1.31 mmol) was added and the mixture heated under reflux for 5 h. Then the solvent was removed and the residue crystallized from dichloromethane-heptane (1:7) with stringent precautious against the ingress of moisture. Yield: 0.40 g, 27% (mp 218 °C). IR (major bands only): 1680 (ν(CdO)), 1278, 1091 (ν(PdO)), 1014, and 981 cm-1. 1H NMR (after drying): δ 0.702.00 (br m, 44H, C6H11), 2.05 (s, 6H, CH3), 7.23-8.15 (m, 20H, H(Ar)). 31P NMR: δ 53.3 Anal. Calcd for C H O P Sb : C, 54.60; H, 6.12. 52 70 9 2 2 Found: C, 54.10; H, 6.23.
Compound 4 is moisture sensitive and gives either 2 or 5 upon hydrolysis; thus crystals of 5 suitable for X-ray were grown while an attempt was made to crystallized 4 from dichloromethane-hexane mixture. Tetrameric cage Ph8Sb4O4(OH)2(O2P(C6H11)2)2‚HO2CMe‚CH2Cl2 (5). A mixture of dimer 2 (0.50 g, 0.48 mmol), acetic acid (3 mL), and water (0.2 mL) was heated under reflux for 2 h. Acetic acid was removed, and the compound was crystallized from dichloromethanehexane (1:5). Yield: 0.60 g, 69% (mp 248 °C). IR (major bands only): 1761, 1705 (ν(CdO)) and 1072 (ν(PdO)) cm-1. 1H NMR (after evacuation and removal of solvate): δ 0.63-2.15 (br m, 44H + 3H, C6H11 + CH3), 3.50-3.90 (br, 2H, OH), 6.97-8.00 (m, 40H, H(Ar)). One solvent molecule (CH2Cl2; δ(1H) 5.2 ppm) per tetrameric cage is observed if no evacuation is performed. 31P NMR: δ 57.7. Anal. Calcd for C74H90O12P2Sb4: C, 51.69; H, 5.28. Found: C, 51.45; H, 5.05. Conversion of the Tetrameric Cage (5) to the Dimer (2). A mixture of 5 (0.05 g) and dicyclohexylphosphinic acid (0.02 g) was heated under reflux in toluene (7 mL) with azeotropic removal of water for 12 h. The solvent was completely removed and 31P NMR recorded for the mixture; it showed compound 2 [δ(31P): 64.2 ppm (>85%)]. Two other minor products [δ(31P): 53.8 (
