The five-coordinate silyl complexes Ru(SiR 3 )Cl(CO)(PPh 3 ) 2 (R 3 ) Me 3 (1a), Et 3 (1b), Ph 3 (1c), Me 2 Cl (1f)) are conveniently prepared through reaction of Ru(Ph)Cl(CO)(PPh 3 ) 2 with the appropriate silane, HSiR 3 . Reaction of the Si-Cl bond in 1f with ethanol or hydroxide gives the corresponding ethoxysilyl or hydroxysilyl products Ru(SiMe 2 X)Cl(CO)(PPh 3 ) 2 (X ) OEt (1d), OH (1e)). Ethyne readily inserts into the Ru-Si bond of 1a-d, and the corresponding five-coordinate, silylalkenyl complexes Ru(CHdCHSiR 3 )Cl(CO)(PPh 3 ) 2 (R 3 ) Me 3 (2a), Et 3 (2b), Ph 3 (2c), Me 2 OEt (2d)) can be isolated in good yield. The complexes Ru(CHdCHSiR 3 )Cl(CO) 2 (PPh 3 ) 2 (SiR 3 ) SiMe 3 (3a), SiEt 3 (3b), SiMe 2 OEt (3d)) result from carbonylation of 2a,b,d. An X-ray crystal structure determination of Ru(CHdCHSiMe 2 -OEt)Cl(CO) 2 (PPh 3 ) 2 (3d) has been obtained. Reaction of Ru(CHdCHSiMe 3 )Cl(CO)(PPh 3 ) 2 (2a) with CN-p-tolyl or sodium acetate gives Ru(CHdCHSiMe 3 )Cl(CO)(CN-p-tolyl)(PPh 3 ) 2 (4a) or Ru(CHdCHSiMe 3 )(η 2 -O 2 CCH 3 )(CO)(PPh 3 ) 2 (5a), respectively. Insertion of ethyne into the Ru-Si bond of 1e results in the formation of the metallacyclic ring-containing complex, Ru(CHdCHSiMe 2 OH)Cl(CO)(PPh 3 ) 2 (6e), in which the hydroxysilyl oxygen atom is coordinated to ruthenium. Reaction of 6e with AgClO 4 gives [Ru(CHdCHSiMe 2 OH)(CO)-(NCMe)(PPh 3 ) 2 ]ClO 4 (7e) and substitution of the labile acetonitrile in this compound with CO or CN-p-tolyl generates [Ru(CHdCHSiMe 2 OH)(CO) 2 (PPh 3 ) 2 ]ClO 4 (8e) or [Ru(CHdCHSiMe 2 OH)(CO)(CN-p-tolyl)(PPh 3 ) 2 ]ClO 4 (9e), respectively. The crystal structure of 9e has been determined. Deprotonation of 8e or 9e with KOH gives the neutral complexes Ru-(CHdCHSiMe 2 O)(CO) 2 (PPh 3 ) 2 (10e) or Ru(CHdCHSiMe 2 O)(CO)(CN-p-tolyl)(PPh 3 ) 2 (11e), respectively. Complex 1b has been shown to catalyze the hydrosilylation of both ethyne and phenylethyne by HSiEt 3 .

The molybdenum(II) and tungsten(II) complexes [MCp(2)L] (Cp = eta(5)-cyclopentadienyl; L = C(2)H(4), CO) react with perfluoroalkyl iodides to give a variety of products. The Mo(II) complex [MoCp(2)(C(2)H(4))] reacts with perfluoro-n-butyl iodide or perfluorobenzyl iodide with loss of ethylene to give the first examples of fluoroalkyl complexes of Mo(IV), MoCp(2)(CF(2)CF(2)CF(2)CF(3))I (8) and MoCp(2)(CF(2)C(6)F(5))I (9), one of which (8) has been crystallographically characterized. In contrast, the CO analogue [MoCp(2)(CO)] reacts with perfluorobenzyl iodide without loss of CO to give the crystallographically characterized salt, [MoCp(2)(CF(2)C(6)F(5))(CO)](+)I(-) (10), and the W(II) ethylene precursor [WCp(2)(C(2)H(4))] reacts with perfluorobenzyl iodide without loss of ethylene to afford the salt [WCp(2)(CF(2)C(6)F(5))(C(2)H(4))](+)I(-) (11). These observations demonstrate that the metal-carbon bond is formed first. In further contrast the tungsten precursor [WCp(2)(C(2)H(4))] reacts with perfluoro-n-butyl iodide, perfluoro-iso-propyl iodide, and pentafluorophenyl iodide to give fluoroalkyl- and fluorophenyl-substituted cyclopentadienyl complexes WCp(eta(5)-C(5)H(4)R(F))(H)I (12, R(F) = CF(2)CF(2)CF(2)CF(3); 15, R(F) = CF(CF(3))(2); 16, R(F) = C(6)F(5)); the Mo analogue MoCp(eta(5)-C(5)H(4)R(F))(H)I (14, R(F) = CF(CF(3))(2)) is obtained in similar fashion. The tungsten(IV) hydrido compounds react with iodoform to afford the corresponding diiodides WCp(eta(5)-C(5)H(4)R(F))I(2) (13, R(F) = CF(2)CF(2)CF(2)CF(3); 18, R(F) = CF(CF(3))(2); 19, R(F) = C(6)F(5)), two of which (13 and 19) have been crystallographically characterized. The carbonyl precursors [MCp(2)(CO)] each react with perfluoro-iso-propyl iodide without loss of CO, to afford the exo-fluoroalkylated cyclopentadiene M(II) complexes MCp(eta(4)-C(5)H(5)R(F))(CO)I (21, M = Mo; 22, M = W); the exo-stereochemistry for the fluoroalkyl group is confirmed by an X-ray structural study of 22. The ethylene analogues [MCp(2)(C(2)H(4))] react with perfluoro-tert-butyl iodide to yield the products MCp(2)[(CH(2)CH(2)C(CF(3))(3)]I (25, M = Mo; 26, M = W) resulting from fluoroalkylation at the ethylene ligand. Attempts to provide positive evidence for fluoroalkyl radicals as intermediates in reactions of primary and benzylic substrates were unsuccessful, but trapping experiments with CH(3)OD (to give R(F)D, not R(F)H) indicate that fluoroalkyl anions are the intermediates responsible for ring and ethylene fluoroalkylation in the reactions of secondary and tertiary fluoroalkyl substrates.

Os(SiCl3)Cl(CO)(PPh3)2 is prepared by treatment of OsPhCl(CO)(PPh3)2 with excess HSiCl3 and serves in turn as the starting material for the syntheses of three more five-coordinate silyl complexes Os(SiR3)Cl(CO)(PPh3)2 (R = F, OH, Me) via substitution of the chloride groups on silicon. All four compounds were fully characterized, including a single-crystal solid-state structure of each derivative. Carbonyl stretching frequencies decrease and Os−Si bond lengths increase as R changes in the order from F to Cl to OH to Me. Ab initio calculations were performed on the model complexes Os(SiR3)Cl(CO)(PH3)2 (R = F, Cl, OH, Me) to explain the trends observed in the IR and X-ray studies, and the importance of the π-acceptor capacities of the silyl groups are discussed.

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