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 .

Reaction between (PyPh)2Hg (PyPh = 2-(2‘-pyridyl)phenyl) and MHCl(CO)(PPh3)3 proceeds smoothly to form M(η2-PyPh)Cl(CO)(PPh3)2 (M = Ru (1a); M = Os (1b)). In both complexes the PyPh ligand is bound as a stable five-membered chelate ring. The chloride ligand in these complexes can be removed through reaction with a silver salt and other ligands then introduced. In this way the compounds M(η2-PyPh)I(CO)(PPh3)2 (M = Ru (2a); M = Os (2b)), [M(η2-PyPh)(CO)2(PPh3)2]SbF6 (M = Ru (3a); M = Os (3b)), and M(η2-PyPh)(η2-S2CNMe2)(CO)(PPh3) (M = Ru (4a); M = Os (4b)) have been prepared. The coordinated PyPh ligand in 1a and 1b is activated by the metal toward electrophilic substitution at the phenyl ring. Nitration occurs in both the phenyl 4- and 6-positions of 1a or 1b, i.e., ortho and para to the metal, to give M(η2-PyPh-4,6-(NO2)2)Cl(CO)(PPh3)2 (M = Ru (5a); M = Os (5b)). Under appropriate conditions the mono-nitrated derivative, Os(η2-PyPh-4-NO2)Cl(CO)(PPh3)2 (5c), can also be isolated. Bromination of 1a or 1b occurs in the phenyl 4-position, i.e., para to the metal, to give M(η2-PyPh-4-Br)Cl(CO)(PPh3)2 (M = Ru (6a); M = Os (6b)). With excess brominating agent ([PyrH][Br3]) and a longer reaction time the unusual mixed triphenylphosphine/pyridine complex, Os(η2-PyPh-4-Br)Cl(CO)(Pyr)(PPh3) (6c) (Pyr = pyridine), is formed. The brominated osmium substrate (6b) can be lithiated through reaction with BuLi. Although this intermediate has not been isolated, further treatment with the electrophiles CO2/H+ or Bu3SnCl forms Os(η2-PyPh-4-CO2H)Cl(CO)(PPh3)2 (7a) or Os(η2-PyPh-4-SnBu3)Cl(CO)(PPh3)2 (7b), respectively. The functionalized pyridylphenyl ligand in 6a can be removed by heating with acid, to give 2‘-(3-bromophenyl)pyridine, in modest isolated yield. The structures of [Os(η2-PyPh)(CO)2(PPh3)2]SbF6 (3b), Os(η2-PyPh)(η2-S2CNMe2)(CO)(PPh3) (4b), Os(η2-PyPh-4-NO2)Cl(CO)(PPh3)2 (5c), Os(η2-PyPh-4-Br)Cl(CO)(PPh3)2 (6b), and Os(η2-PyPh-4-Br)Cl(CO)(Pyr)(PPh3) (6c) have all been determined by X-ray crystal structure analyses.

Treatment of IrCl(CS)(PPh3)2 with an excess of KI gives orange IrI(CS)(PPh3)2 (1). IrI(CS)(PPh3)2 (1) reacts reversibly with dioxygen to form the brown dioxygen complex Ir(O2)I(CS)(PPh3)2 (2). Reaction between IrI(CS)(PPh3)2 (1) and 2 equiv of ethyne produces the green-brown tethered iridacyclobutadiene complex Ir[C3H2(CHCHS-1)]I(PPh3)2 (3), one ethyne combining in a cycloaddition reaction with the IrC multiple bond to the CS ligand to form the four-membered IrC3 ring and the second ethyne alkylating the sulfur atom to give the vinylthio substituent at the 1-position of the metallacyclic ring, which is tethered to the iridium through an Ir−C bond. In reactions related to those with ethyne, phenylacetylene reacts with IrCl(CS)(PPh3)2 to give as the major product the tethered iridacyclobutadiene Ir[C3H(CHC{Ph}S-1)(Ph-3)]Cl(PPh3)2 (4), with the phenyl substituent adjacent to the iridium, and as the minor product the isomeric tethered iridacyclobutadiene Ir[C3H(CHC{Ph}S-1)(Ph-2)]Cl(PPh3)2 (5). A thermal reaction of Ir[C3H(CHC{Ph}S-1)(Ph-3)]Cl(PPh3)2 (4) with further phenylacetylene produces the tethered, substituted cyclopentadienyliridium complex Ir[η5-C5H2(SCPhCH-1)(Ph-3)(Ph-5)]Cl(PPh3) (6), which retains the iridium−carbon bond to the vinylthio substituent. Methyl propiolate reacts with IrI(CS)(PPh3)2 (1) to form exclusively the tethered iridacyclobutadiene Ir[C3H(CHC{CO2Me}S-1)(CO2Me-2)]I(PPh3)2 (7). Treatment of this iridacyclobutadiene, 7, with silver triflate allows introduction of a third methyl propiolate, which brings about ring expansion of the iridacyclobutadiene to form the stable tethered iridabenzene Ir[C5H2(CHC{CO2Me}S-1)(CO2Me-2)(CO2Me-4)]Cl(PPh3)2 (8). Complex 8 retains the same vinylthio tethering group as found in 7. The structures of 2−8 have been confirmed by X-ray crystal structure determinations. Both NMR spectroscopic and structural data for 8 support the formulation of this compound as a tethered metallaaromatic molecule.

The five-coordinate ruthenium boryl complexes, Ru(BR2)Cl(CE)(PPh3)2 (E = O, BR2 = BO2C6H4 (1a); E = O, BR2 = BO2C10H6 (1b); E = O, BR2= B(NH)2C6H4 (1d); E = O, BR2 = B(NH)SC6H4 (1e); E = S, BR2 = BO2C6H4 (2a); E = S, BR2 = B(NH)SC6H4 (2e); E = N-p-tolyl, BR2 = BO2C6H4 (3a)), result from the reactions of RuHCl(CE)(PPh3)3 with the appropriate borane. Related osmium compounds, Os(BR2)Cl(CE)(PPh3)2 (E = O, BR2 = BO2C6H4 (4a); E = O, BR2 = BO2C6H3CH3 (4c); E = O, BR2 = B(NH)2C6H4 (4d); E = O, BR2 = B(NH)SC6H4 (4e); E = S, BR2 = BO2C6H4 (5a)), cannot be prepared from the hydrides but are formed from reactions between Os(Ph)Cl(CE)(PPh3)2 and the appropriate borane. A boryl complex of ruthenium of formula Ru(BO2C6H4)Cl(PPh3)2·H2O (6) results from reaction of RuHCl(PPh3)3 with HBO2C6H4 (catecholborane). IR, 1H NMR, and 13C NMR data for the new boryl complexes are reported.

Ethyne inserts readily into the Ru−B bond of the five-coordinate boryl complex Ru(BO2C6H4)Cl(CO)(PPh3)2 (1) to form the borylalkenyl (2). Complex 2 has been characterized by IR and multinuclear NMR spectroscopy and by an X-ray crystal structure determination. In the solid state, the Ru atom in 2 is six coordinate through weak attachment of a catechol oxygen to ruthenium. Two further (4), which result from transesterification of 2 with HOCH2CH2OH and 3 with CH3CH2OH, respectively, are also described. The relevance of the observed ethyne insertion for metal-catalyzed hydroboration is discussed.