3332 Inorg. Chem. zyxwvu 1989, zyxwvut 28, 3332-3334 Contribution from the Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 021 39, and Department of Radiology, Harvard Medical School and Brigham and Women's Hospital, Boston, Massachusetts 021 15 Preparation and Characterization of TcC~~(PP~~)~(M~CN) and Its Reactions with Small r-Accepting Ligands Ronald M. Pearlstein,Ia William M. Davis,la Alun G. Jones,lb and Alan Davison*'la Received January 10, zyxwvutsrqp 1989 The preparation and characterization of zyxwvuts (acetonitrile)trichlorobis(triphenylphosphine)technetium(III) from (n-Bu4N)[TcOCI,] with triphenylphosphine in acetonitrile solvent is described. The potentially rich reaction chemistry of this complex is discussed in relation to ReCl,(PPh),(MeCN). Reactions of TcCI,(PPh,),(MeCN) with C O and N O are described. Characterization of the products, carbonyltrichlorobis(triphenylphosphine)technetium( 111) and trichloronitrosylbis(triphenylphosphine)technetium(II), is also described. The carbonyl complex, C37H30C130P2Tc, which crystallizes in space group C2/c with zyxw a zyxw = 24.649 (9) A, b = 9.530 (3) A, c = 15.870 A, /3 = 116.40 (3)O, zyxwvutsrqp V= 3339 (4) A), and zyxwvut Z = 4, was structurally characterized. The Tc-C bond distance of 1.985 (9) 8, as well as the C=O stretching frequency of 2054 cm-' is indicative of the absence of significant r-back-bonding in this complex. Introduction There has been a great deal of study of technetium complexes with tertiary phosphine ligands that was due, in part, to the prospects2 of a 99mTc-phosphine myocardial imaging agent. A limitation in this research was imposed by the lack of suitable technetium phosphine starting materials that could readily be prepared in good yields. The most notable starting material^,^ TcC1,P2 (P = PPh,, PMe2Ph) and TcCI,(PM~~P~)~ have some drawbacks. The former is a complex of technetium(1V) that often undergoes unpredictable redox changes in addition to ligand substitution. The latter complex cannot be prepared with tri- phenylphosphine, presumably due to the large steric requirement of this ligand, which inhibits cis-octahedral coordination. Trop4 noted that the oxotetrachlorotechnetate ion reacted with triphenylphosphine in acetonitrile to give an unidentified orange material. We now report an improved preparation of this material and its identification as TcCI,(PP~~)~(M~CN). Since the analogous rhenium ~ o m p l e x , ~ ReC13(PPh3)2(MeCN), has been shown to be a useful synthetic reagent, some reactions of the technetium complex were performed to explore its utility. Experimental Section Instrumentation. Fourier transform IR spectra were measured from 4800 to 400 cm-' on an IBM IR/30S spectrometer with a DTGS detector and a 2-cm-l bandwidth. 'H NMR spectra were recorded at 300 MHz on a Varian XL-300 spectrometer. X-Band ESR spectra were recorded on a Varian E-line spectrometer or on a Bruker ESP 300 spectrometer equipped with a variable-temperature accessory. Fast atom bombardment mass spectra were measured on samples dissolved in a 3-nitrobenzyl alcohol matrix by using a MAT 731 mass spectrometer operating at an accelerating voltage of 8 kV. The source was equipped with an Ion Tech B11N FAB gun producing a beam with 6-8-keV xenon neutrals. Ultraviolet and visible absorption spectra were recorded on a Hewlett Packard 845 1 A photodiode array spectrophotometer. Elemental analyses were performed by Atlantic Microlab Inc., Norcross, GA. emitter (t1l2 = 2.1 X los years). All manipulations of solutions and solids were performed in a laboratory approved for the handling of radioisotopes with precautions outlined elsewhere.6 All solvents were of at least reagent grade and were used as received, except for toluene, which was distilled under N, from sodium. The complex (n-Bu,N) [TcOCI,] was prepared' by literature methods. Syntheses. Caution! %Tc is a (a) Massachusetts Institute of Technology. (b) Harvard Medical School. Deutsch, E.; Libson, K.; Vanderheyden, J. L. In Technerium in Chem- istry and Nuclear Medicine; Nicolini, M., Bandoli, G.; Mazzi, U., Eds.; Raven: New York, 1986; Vol. 2, p 161. Mazzi, U.; De Paoli, G.; Di Bernardo, P.; Magon, L. J. Inorg. Nucl. Chem. 1976, 38, 721. Trop, H. S. Ph.D. Thesis, Massachusetts Institute of Technology, 1979. Rouschias, G.; Wilkinson, G. J. Chem. Sot. A 1967, 993. (a) Davison, A.; Orvig, C.; Trop, H. S.; Sohn, M.; DePamphilis, B. V.; Jones, A. G. Inorg. Chem. 1980, 19, 1988. (b) Cotton, F. A,; Davison, A.; Day, V. W.; Gage, L. D.; Trop, H. S. Inorg. Chem. 1979, 18, 3024. Davison, A.; Trop, H. S.; DePamphilis, B. V.; Jones, A. G. Inorg. Synth. 1982, 21, 160. Preparation of TcCI,(PPh,),(MeCN). To 103.97 mg of (n-Bu4N)- [TcOCI4] (0.208 mmol) in a disposable vial was added with stirring 256 mg of triphenylphosphine dissolved in 12 mL of MeCN. The solution rapidly became very dark, but within 1 min it was bright orange. Pre- cipitation was then induced by adding a glass bead, which was agitated by the magnetic stirbar. The solution was stirred for an additional 10 min while the bright orange solid precipitated. The precipitate was collected on a medium-porosity fritted glass funnel and rinsed with 10 mL of MeCN followed by 2 mL of hexane. After drying in vacuo overnight, the product weighed 98.75 mg (62% yield). This material is slightly soluble with slow decomposition in MeCN, acetone, and toluene. It decomposes more rapidly in CH2C12. Anal. Calcd for C38H,,C1,NP2Tc: C, 59.21; H, 4.31; CI, 13.79; N, 1.82. Found: C, 58.99; H, 4.43; CI, 13.17; N, 1.89. IR (KBr): 3055 (w), 2928 (w), 2917 (w), 1481 (m), 1433 (s), 1400 (w), 1385 (w), 1367 (w), 1316 (w), 1189 (w), 1163 (w), 1120 (w), 1091 (m), 1072 (w), 1027 (w), 998 (w), 753 (w), 747 (m), 742 (m), 696 (s), 521 (s), 51 1 (s), 496 (m), 479 (w), 454 (w) cm-I. FABMS(+), m/z [ion, abundance]: 769 [M', 19%], 728 [(M - MeCN)', 91%], 693 [(M - MeCN - CI)', loo%]. Preparation of TCCI,(PP~~)~(NO). To 35.24 mg of TcCI,(PPh,),- (MeCN) (0.046 mmol) in a nitrogen-purged 50-mL round-bottomed flask with a sidearm was added 15 mL of toluene. Nitric oxide (Math- eson) was then bubbled through the resulting suspension warmed with a water bath. The acetonitrile starting material dissolved as it reacted, forming a green solution. The reaction was allowed to proceed for a total of 35 min. An aliquot of the reaction mixture gave an electron spin resonance spectrum consisting of a three-line pattern ((g) - 2.0, (a) - 12 G) due to N O superimposed on a ten-line pattern ((g) - 2.0, (a) - 130 G) due to the technetium(I1) complex. The remaining green solution was filtered, and the solvent was evaporated under reduced pressure. The residue was recyrstallized from CH,CI,/MeOH, yielding a dark green microcrystalline solid. IR (KBr): v(N0) 1805 cm-' (vs). FABMS(+), m/z [ion, abun- dance]: 723 [(M - CI)', 89%], 688 [(M - 2C1)', loo%]. Preparation of TcCI,(PP~,)~(CO). To 28.38 mg of TcC13(PPh,),- (MeCN) (0.037 mmol) in a nitrogen-purged 100-mL round-bottomed flask was added 20 mL of toluene. Carbon monoxide (Matheson) was then bubbled through the resulting suspension, which was warmed to 65 OC. The acetonitrile starting material dissolved as it reacted, forming a clear wine red solution within 10 min. The bubbling of CO continued for an additional 5 min to ensure complete reaction. The reaction mix- ture was filtered through paper, and the solvent was evaporated under reduced pressure. The residue was recrystallized from CH,Cl,/heptane, yielding 17.27 mg (62%) of small red prisms. Anal. Calcd for C37H30C130P2T~: C, 58.64; H, 3.99; CI, 14.03. Found: C, 57.58; H, 3.98; C1, 14.19. A separate preparation gives the following: C, 57.51; H, 3.94. IR (KBr): v(C0) 2054 cm-' (vs). 'H NMR (CDCI,): 8 9.9 (broad, 12 H), 7.5 (broad with shoulder, 18 H). Visible (CH,CI,), A , (a): 562 nm (770 I.mol-'an-'). FABMS(+), m/z [ion, abundance]: 693 [(M X-ray Structure Determination of TcCI,(PPh,),(CO). A small red prism grown by heptane diffusion into a CH2CI2 solution of TcC1,- (PPh3)2(CO) having approximate dimensions 0.1 X 0.1 X 0.3 mm was mounted on a glass fiber. Crystal density was determined by suspension in an aqueous CsCl solution. All measurements were made on an En- raf-Nonius CAD-4 diffractometer with graphite-monochromated Mo Ka radiation. On the basis of systematic absences (hkl, h + k # 2n , and hOI, I # 2n), a statistical analysis of intensity distribution, and the - C1 - CO)', loo%], 686 [(M - 2CI)', 95751. 0020-1669/89/1328-3332$01.50/0 0 1989 American Chemical Society