DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1999, 1537–1538 1537 Syntheses and single-crystal structures of novel soluble phosphonato- and phosphinato-bridged titanium oxo alkoxides Gilles Guerrero,a Michael Mehring,a P. Hubert Mutin,*a Françoise Dahan b and André Vioux a a UMR CNRS 5637, Chimie Moléculaire et Organisation du Solide, Université de Montpellier II, cc 007, 34095 Montpellier cedex 5, France. E-mail: mutin@crit.univ-montp2.fr b UPR CNRS 8241, Laboratoire de Chimie de Coordination du CNRS, 205 Route de Narbonne, 31077 Toulouse cedex 4, France Received 25th March 1999, Accepted 9th April 1999 The reactions of PhP(O)(OH)2 or Ph2P(O)OH with Ti(OPri)4 in DMSO give the soluble tetranuclear complexes [Ti4(Ï3-O)(OPri)5(Ï-OPri)3(PhPO3)3]?DMSO 1 or [Ti(Ï3-O)- (OPri)(Ph2PO2)]4?0.5DMSO 2, the first examples of phosphonato- and phosphinato-bridged titanium oxo alkoxides, which have been characterised by single-crystal X-ray diffraction.Metal oxo alkoxides are not only models of the molecular species present at the initial stages of the sol–gel processing of metal alkoxides, but they also serve as molecular building blocks for the design of oxide materials by sol–gel processing and metal–organic chemical vapour deposition (MOCVD).1–3 The reactivity towards hydrolysis and condensation of metal oxo alkoxides is lower than in the parent alkoxides, and may be further decreased via replacement of some of the alkoxide ligands by carboxylate, b-diketonate or sulfonate ligands.Furthermore, the use of such ligands allows the introduction of organic functionalities for organic–inorganic hybrid materials applications.4,5 Recently, we proposed the use of organophosphorus acids as coupling molecules to prepare organic–inorganic hybrids by a sol–gel route, as the P–C bond is stable towards hydrolysis and P–OH groups readily condense with M–OR groups. A twostep synthesis was used, involving first the condensation between the organophosphorus acid and a metal alkoxide, followed by hydrolysis–condensation of the remaining alkoxy groups.6 When titanium isopropoxide and phenylphosphonic acid were used as precursors 31P NMR investigations pointed to the formation of a soluble intermediate.In the present work, we report the structural characterization of this intermediate and of another compound obtained starting from titanium isopropoxide and diphenylphosphinic acid (Scheme 1).To our knowledge, compounds 1 and 2 are the first examples of titanium oxo alkoxides modified by tridentate phosphonate (RPO3 22) or bidentate phosphinate (R2PO2 2) ligands, whereas modification by bidentate carboxylate groups has been extensively studied.7,8 Layered titanium phosphates and phosphonates are well known,9 and polymeric titanium alkoxo-phosphinates have been reported;10 however, very few molecular structures of titanium complexes with phosphato, 11,12 phosphonato 13,14 or phosphinato 15 ligands have been reported to date, whereas these ligands have been widely used to synthesise hybrid polynuclear oxo anions such as vanadates 16 and molybdates.17 The Ti–O–P bonds in 1 and 2 result from the condensation of P–OH and Ti–OPri groups.11 Most likely, the Ti–O–Ti bonds are formed by partial hydrolysis of Ti–OPri groups as nonhydrolytic condensation with elimination of an ether would require temperatures above 150 8C.In the case of 1, the sources of water could be DMSO and/or phenylphosphonic acid even after careful drying,15 although condensation of P–OH groups in the presence of Ti(OPri)4 cannot be completely ruled out.Nevertheless, in order to obtain 2 in a good yield, water had to be added to the reaction mixture.† The molecular structures of 1 and 2 and selected bond distances and angles are given in Figs. 1 and 2.‡ Compound 1 is made up of discrete clusters that consist of four titanium atoms, three tridentate phosphonato groups, three m-isopropxy groups and one m3-oxygen atom.The Ti–O–P core is best described as being based on a six-membered Ti3(m-OPri)3 ring adopting a chair conformation with alternating isopropoxy groups and six-coordinated Ti atoms; these Ti atoms are linked via a m3-O atom [Ti–m3-O–Ti 104.49(8)–106.08(8)8] leading to a Ti3O4 fragment. The markedly distorted octahedral geometry at Ti(1), Ti(2), and Ti(3) is built up by two bridging m-OPri groups [Ti–O 2.014(2)–2.044(2) Å], one terminal OPri group [Ti–O 1.770(2)–1.781(2) Å], two phosphonato-oxygen atoms [Ti–O 1.947(2)–1.984(2) Å] and the m3-oxygen atom which is trans to the terminal OPri groups [Ti–O 1.949(2)–1.976(2) Å].The trans O–Ti–O angles are in the range 162.27(8)–175.49(8)8. Each phosphonato group bridges two Ti atoms of the six membered ring and Ti(4) [Ti(4)–O 1.955(2)–2.095(2) Å]. In addition to these three phosphonato-oxygen atoms, the distorted octahedral geometry at Ti(4) [O–Ti–O trans angles 171.24(8)– 172.56(8)8] involves two terminal OPri groups [Ti(4)–O(18)/ O(19) 1.833(2)/1.786(2) Å] and a coordinated DMSO molecule [Ti(4)–O(4) 2.059(2) Å].The molecular structure of 2 is best described as a distorted cube consisting of a Ti4O4 core with the titanium and oxygen atoms occupying alternating corners. The Ti atoms show a distorted octahedral geometry [trans O–Ti–O angles 161.61(7)– 177.29(7)8] built up by one terminal OPri group [Ti–O 1.759(2)– 1.790(2) Å], two phosphinato oxygen atoms [Ti–O 2.002(2)– 2.040(2) Å] and three unsymmetrically bonded m3-oxygen atoms.The Ti–m3-O bonds trans to the isopropxy groups are Scheme 11538 J. Chem. Soc., Dalton Trans., 1999, 1537–1538 slighlty longer [Ti–m3-O 2.107(2)–2.163(2) Å] than those trans to the phosphinato oxygen atoms [Ti–m3-O 1.888(2)–1.938(2) Å]. Four sides of the Ti4O4 cube are capped by four phosphinato groups, each bridging two Ti atoms. This type of structure has been proposed for oxotitanium compounds modified by phosphonato 12 or carboxylato ligands.18 The basic structural arrangement of 1 and 2 is retained in solution, as demonstrated by the 31P NMR data in solution and Fig. 1 Molecular structure of 1. Thermal ellipsoids are shown at 60% probability. For clarity, hydrogens atoms are omitted and carbon atoms are represented by open circles. Selected interatomic distances (Å) and bond angles (8) are: Ti(1)–O(1) 1.953(2), Ti(1)–O(5) 1.976(2), Ti(1)– O(6) 2.014(2), Ti(1)–O(8) 1.781(2), Ti(4)–O(3) 1.955(2), Ti(4)–O(16) 2.095(2), Ti(4)–O(17) 2.040(2); O(1)–Ti(1)–O(7) 162.33(8), O(2)–Ti(1)– O(6) 165.22(8), O(5)–Ti(1)–O(8) 175.37(8), O(3)–Ti(4)–O(4) 172.56(8), O(16)–Ti(4)–O(18) 171.24(8), O(17)–Ti(4)–O(19) 171.83(8). Fig. 2 Molecular structure of 2. Thermal ellipsoids are shown at 60% probability. For clarity, hydrogens atoms are omitted and carbon atoms are represented by open circles. Selected interatomic distances (Å) and bond angles (8) are: Ti(1)–O(1) 1.903(2), Ti(1)–O(2) 2.160(2), Ti(1)– O(3) 1.938(2), Ti(1)–O(5) 2.004(2), Ti(1)–O(7) 2.014(2), Ti(1)–O(13) 1.765(2); O(1)–Ti(1)–O(7) 164.32(7), O(2)–Ti(1)–O(13) 177.29(7), O(3)–Ti(1)–O(5) 162.03(7).in the solid-state.† In the field of organic–inorganic hybrids, these clusters present two main interests: first, as intermediates in the sol–gel route to hybrids that we are developing, secondly, as novel building blocks for the preparation of nanostructured hybrid materials.Notes and references † Syntheses: [Ti4(m3-O)(OPri)5(m-OPri)3(PhPO3)3]?DMSO 1. Ti(OPri)4 (3.56 g, 12.52 mmol) was added to a solution of PhP(O)(OH)2 (1.00 g, 6.33 mmol) in 5 mL of dried DMSO, resulting in a cloudy mixture. After several hours a clear solution was obtained. Colourless crystals of 1 were obtained from this solution after several days. These crystals were filtered oV, washed with two 5 mL portions of Et2O and dried in vacuo giving 1.02 g [40% yield based on PhP(O)(OH)2].Colourless needles suitable for single-crystal X-Ray diVraction were recrystallised from a concentrated DMSO solution and mounted in inert oil. Calc. for C44H77O19P3STi4: C, 43.08; H, 6.78; P, 7.57; S, 2.61; Ti, 15.61. Found: C, 48.85; H, 6.52; P, 8.20; S, 3.22; Ti, 15.80. 31P NMR: d 8.45, 8.65 (CH2Cl2, 200 MHz), 8.0, 7.0 (solid-state, 400 MHz). [Ti(m3-O)(OPri)- (Ph2PO2)]4?0.5DMSO 2. To a solution of Ti(OPri)4 (1.00 g, 3.52 mmol) in 15 mL of dried DMSO was added dropwise a solution of Ph2P(O)OH (767 mg, 3.52 mmol) and H2O (34 mL, 1.88 mmol) in 15 mL of DMSO.After stirring at room temperature for 12 h, the resulting cloudy mixture was heated to 80 8C until a clear solution was obtained, which was then allowed to cool slowly to ambient temperature. The crystallised colourless needles were filtered oV, washed with 3 mL dried DMSO and dried in vacuo giving 720 mg (58% yield) of 2. X-Ray quality crystals were obtained from a dilute DMSO solution and mounted in inert oil.Calc. for C61H71O16.5P4S0.5Ti4: C, 52.35; H, 5.48; P, 8.85; S, 1.15; Ti, 13.68. Found: C, 51.98; H, 6.30; P, 10.10; S, 1.37; Ti, 15.10. 31P NMR: d 33.0 (CH2Cl2, 200 MHz), 33.3 (solid-state, 400 MHz). ‡ Data for both structures were collected on a STOE-IPDS with Mo-Ka radiation (l = 0.71073 Å). Crystal data for 1 : C44H77O19P3STi4 at 160 K, M = 1226.63, monoclinic, P21/n (no. 14), a = 11.6668(13), b = 13.9198(12), c = 35.885(3) Å, b = 90.533(15)8, V = 5827.5(10) Å3, Dc = 1.398 g cm23, Z = 4, m = 0.712 mm21.Of the 27893 reflections, 5980 unique reflections were used in the final least-squares refinement on Fo 2 for 640 variable parameters to yield wR(all) = 0.0549 and R(obs) = 0.0249 for 4478 observed reflections >4s(Fo). For 2 C61H71O16.5P4S0.5Ti4 at 180 K, M = 1399.69, monoclinic, P21/c (no. 14), a = 12.4983(10), b = 16.1317(14), c = 33.706(3) Å, b = 97.141(10)8, V = 6743.1(10) Å3, Dc = 1.379 g cm23, Z = 4, m = 0.630 mm21.Of the 52425 reflections, 10165 unique reflections were used in the final leastsquares refinement on Fo 2 for 793 variable parameters to yield wR(all) = 0.0607 and R(obs) = 0.0240 for 6923 observed reflections >4s(Fo). CCDC reference number 186/1420. See http://www.rsc.org/ suppdata/dt/1999/1537/ for crystallographic files in .cif format. 1 L. G. Hubert-Pfalzgraf, Polyhedron, 1994, 13, 1181. 2 R. C. Mehrotra and A. Singh, Chem.Soc. Rev., 1996, 25, 1. 3 V. W. Day, T. A. Eberspacher, W. G. Klemperer and C. W. Park, J. Am. Chem. Soc., 1993, 115, 8469. 4 P. Judeinstein and C. Sanchez, J. Mater. Chem., 1996, 6, 511. 5 U. Schubert, N. Hüsing and A. Lorenz, Chem. Mater., 1995, 7, 2010. 6 P. H. Mutin, C. Delenne, D. Medoukali, R. Corriu and A. Vioux, in Mater. Res. Soc. Symp. 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