Inorg. Chem. 1995,34, 2113-2120 2113 Reactivity of a Tetrakis(pyrazoly1)borate Oxorhenium Complex Ant6nio Paulo, Angela Domingos, Joaquim Marsalo, Ant6nio Pires de Matos, and Isabel Santos* Departamentos de Quimica e Radiois&opos, ICEN-INETI, 2686 Sacavkm Codex, Portugal Received September 7, 1994@ The rhenium(VI1) compound [Re03{ B(pz)4)] (1) is easily reduced by triphenylphosphine in tetrahydrofuran providing, in 60% yield, a very reactive oxo complex of Re that, on the basis of its reactivity, we tentatively formulate as “[ReO@-O){B(pz)4)]2” (2). This air-stable compound is insoluble in tetrahydrofuran and water and slightly soluble in chloroform and dichloromethane and is a versatile material for the synthesis of monomeric compounds of Re(V): [ReO{B(pz)4ICl21 (3), [ReOCL){B(pz)dI (L = OCHZCH~O (4), CdW2 (S)), [ReO{B(pz)d- (ORh1 (R = Me (a), Et (71, Ri (81, Ph (9)), [ReO{B(pz)4}(SPh>21 (lo), and [ReO(r2-OCONPh){B(pz)4)l (11). Compounds 3-11 were characterized by elemental analyses, IR and ‘H NMR spectroscopies, and, in the case of compounds 9 and 10, X-ray crystallography. Compound 9 crystallizes in the triclinic space group Pi with cell parameters a = 9.611(4) A, b = 11.808(3) A, c = 12.400(5) A, a = 88.69(2)’, /3 = 69.61(3)’, y = 74.01(3)’, V = 1264(1) A3, 2 = 2, and R = 0.031, R, = 0.037 for 5226 reflections (Fo > 3u(F0)); compound 10 also crystallizes in the triclinic space group Pi with cell parameters a = 10.563(3) A, b = 11.768(2) A, c = 12.149(3) A, a = 94.10(2)”, /3 = 100.50(2)’, y = 92.44(2)”, V = 1479(1) A3, Z = 2, and R = 0.043, R, = 0.051 for 4721 reflections (Fo > 30(F0)). For all the compounds the characterization includes laser desorption and electron impact Fourier transform ion cyclotron resonance mass spectrometry. For complex 2 variable-temperature ‘H NMR studies are also described. Introduction The total or partial deoxygenation of oxometal centers by Lewis bases, with the simultaneous reduction of the metal and sometimes with formation of oxo-bridged dimers, is a well- known process.’ Typical examples of dimerization are the oxorhenium(V) compound [ReO@-O)(r5-C5Mes)]2, obtained by reduction of [Re03(y5-C5Mes)] with triphenylphosphine, and the compound [Re0@-0)(tacn)]z2+ (tacn = 1,4,7-triazacy- clononane), obtained by reduction of [ReO(oCH~CH20)(tacn)]+ with zinc amalgam or by reduction of (Re03(tacn))+ with triphenylph~sphine,~-~ As part of our ongoing studies on the chemistry of Re(VII), Re(V), and Re(II1) with the ligand [ B ( ~ z ) ~ ] - , ~ v ~ we have previously described the compound [Reo{ B(pz)4}C12] (3), and one of the synthetic methods used was the reduction of [ReOs- {B(pz)4)] (1) with triphenylphosphine in the presence of trimethylsilyl ~hloride.~ For better insight regarding possible intermediates of this reaction, we studied the reduction of compound 1 in tetrahydrofuran using stoichiometric amounts of triphenylphosphine, but in the absence of trimethylsilyl chloride. This reaction leads to a very reactive compound that we tentatively formulate as ‘.‘[ReO@-O){B(pz)4}]”’ (2). Using *Abstract published in Advance ACS Abstracts, March 15, 1995. (1) Holm, R. H. Chem. Rev. 1987, 87, 1401. (a) Henmann, W. A.; Serrano, R.; Kusthardt, U.; Ziegler, M. L.; Guggolz, E.; Zahn, T. Angew. Chem., Int. Ed. Engl. 1984, 23, 515. (b) Henmann, W. A.; Serrano, R.; Kusthardt, U.; Guggolz, E Nuber, B.; Ziegler, M. L. J. Organomet. Chem. 1985,287,329. (c) Hemnann, W. A. J. Organomer. Chem. 1986, 300, 11 1. (d) Henmann, W. A.; Floel, M.; Kulpe, J.; Felixberger, J. K.; Herdtweck, E. J. Organomer. Chem. 1988, 355, 297. (a) Pomp, C.; Wieghardt, K. Polyhedron 1988, 7, 2537. (b) Bohm, G.; Wieghardt, K.; Nuber, B.; Weiss, J. Angew. Chem., In?. Ed. Engl. 1990, 29, 787. Conry R. R.; Mayer J. M. Inorg. Chem. 1990, 29, 4862. Domingos, A.; Marplo, J.; Paulo, A.; Pires de Matos, A.; Santos, I. Inorg. Chem. 1993, 32, 5114. Paulo, A.; Domingos, A,; Pires de Matos, A.; Santos, I.; Carvalho, M. F. N. N.; Pombeiro, A. J. L. Inorg. Chem. 1994, 33, 4729. this compound as starting material, we have investigated the possibility of preparing the previously described complexes [ReO{B(pz)4lC121 (3Y and [R~O(OCH~CH~O){B(P~)~}I (4): as well as other new clxorhenium compounds with the ligand [B(pz)J. We now report the synthesis and characterization of compound 2 and of the new compounds [ReO(C&02)- {B(pzk)l (S), [ReO{B@z)4I(OR>21(R = Me (a), Et (7), Ri (8), Ph (9)), [ReO{B@z)d(SPh)21(10), and [ReO(rZ-OCONPh)- {B(pz)4}] (11) prepared by reacting 2 with cathecol, alcohols, thiophenol, and phenyl isocyanate, respectively. Experimental Section General Procedures. All reactions were carried under an argon atmosphere, using freshly distilled solvents which were dried and deoxygenated by standard methods? [ReO3{B(pz)d}] (1) was prepared as previously described? PPh3 was recrystallized from ethanol and dried under vacuum at 70 “C. Me3SiC1 was dried over P205 and deoxygenated prior to use. Phenol and catechol were sublimated prior to use. Thiophenol was dried over Na2S04 and distilled under reduced pressure. All the other reactants were used as supplied. ‘H hMR spectra were recorded on a General Electric 300 MHz instrument and were referenced intemally using the residual solvent resonance relative to tetramethylsilane. The FTICR mass spectra were obtained by laser desorption (LD) and electron impact (EI), with an Extrel (Waters) FTMS 2001-DT instrument, following a published technique? IR spectra were recorded as KBr pellets on a Nicolet SDXC FT-E? spectrometer. Carbon, hydrogen, and nitrogen analyses were performed on a Perkin-Elmer automatic analyzer. Synthesis and Characterization of ‘‘[ReO~-O)(B(pz)4}]~” (2). To a suspension of [Re03{B(p~)~}] (1) (1.2 g, 2.30 “01) in THF (50 mL) was added, at room temperature, a solution of PPh3 (640 mg, 2.40 mmol) in TI-IF. The original white suspension turned immediatly to a dark brown solution. The reaction mixture was stirred overnight, and a significant amount of a dark green insoluble material was formed. The dark green solid was isolated, washed with THF and n-hexane, and dried under vacuum (680 mg, 1.36 mmol of Re, yield 60%). (7) Pemn, D. D.; Annarego, W. L. F. Purijication of Laboratory Chemicals, 3rd ed.; Pergamon Press: New York, 1988. 0020-1669/95/1334-2113$09.00/0 0 1995 American Chemical Society