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Reaction between Os(SnClMe2)(κ2-S2CNMe2)(CO)(PPh3)2 and either LiSnMe3 or KSnPh3 produces the distannyl complexes, Os(SnMe2SnMe3)(κ2-S2CNMe2)(CO)(PPh3)2 (1) or Os(SnMe2SnPh3)(κ2-S2CNMe2)(CO)(PPh3)2 (3), respectively. Similarly, reaction between Os(SnClMe2)Cl(CO)2(PPh3)2 (6) and KSnPh3 produces the distannyl complex, Os(SnMe2SnPh3)Cl(CO)2(PPh3)2 (7). In the 119Sn NMR spectra of these stable osmium(II) distannyl complexes both the α-Sn and β-Sn atoms show well-resolved 119Sn–119Sn and 119Sn–117Sn coupling. Each of these three distannyl complexes can be selectively functionalised at the α-Sn atom by reaction with SnCl2Me2 giving Os(SnClMeSnMe3)(κ2-S2CNMe2)(CO)(PPh3)2 (2), Os(SnClMeSnPh3)(κ2-S2CNMe2)(CO)(PPh3)2 (4), and Os(SnClMeSnPh3)Cl(CO)2(PPh3)2 (8), respectively. Treatment of compounds 3 or 7 with iodine also cleaves one α-methyl group, selectively, to give Os(SnIMeSnPh3)(κ2-S2CNMe2)(CO)(PPh3)2 (5), or Os(SnIMeSnPh3)Cl(CO)2(PPh3)2 (9). Crystal structures for complexes 3 and 7 have been determined.

The coordinatively unsaturated 1-iridaindene, Ir[C8H5(Ph-3)]Cl(PPh3)2 has a labile chloride ligand and is easily converted to the corresponding iodide, Ir[C8H5(Ph-3)]I(PPh3)2 (1) by reaction with NaI. When Ir[C8H5(Ph-3)]I(PPh3)2 (1) is treated with methyl propiolate a reactive five-coordinate complex with both a diphenylvinyl ligand from ring-opening of the 1-iridaindene, and a 3-methoxy-3-oxoprop-1-ynyl ligand from deprotonation of methyl propiolate, is first produced. Reaction of this complex with aqueous HCl generates the 2-iridafuran, Ir[OC3H(CH CPh2-3)(OMe-5)]ClI(PPh3)2 (2) probably from initial protonation at the β-carbon of the 3-methoxy-3-oxoprop-1-ynyl ligand to form a vinylidene ligand and subsequent migration of the diphenylvinyl ligand to the α-carbon of this ligand accompanied by oxygen coordination to iridium. Similar treatment of 1 with methyl propiolate followed by aqueous HI gives the corresponding complex, Ir[OC3H(CH CPh2-3)(OMe-5)]I2(PPh3)2 (3). The X-ray crystal structures of 2 and 3 together with NMR spectroscopic data confirm the 2-metallafuran structures of these complexes.

Treatment of Os(κ 2 -S 2 CNMe 2 )H(CO)(PPh 3 ) 2 with HSiMeCl 2 or HSiCl 3 gives in high yield Os(κ 2 -S 2 CNMe 2 )(SiMeCl 2 )(CO)(PPh 3 ) 2 ( 1 ) or Os(κ 2 -S 2 CNMe 2 )(SiCl 3 )(CO)(PPh 3 ) 2 ( 2 ), respectively. The crystal structures of both compounds have been determined and the Os–Si distances are 2.3672(10) A for 1 and 2.3449(12) A for 2 . In solution, and under forcing conditions, both compounds are extraordinarily unreactive towards hydroxide ions.

Heating the five-coordinate trimethylstannyl complex, Os(SnMe3)Cl(CO)(PPh3)2, in solution with triphenylphosphine induces an ortho-stannylation of one phenyl group of a triphenylphosphine ligand and an ortho-metallation of another triphenylphosphine ligand, to produce the metallacyclic complexes, Os(κ2(Sn,P)-SnMeClC6H4PPh2)(κ2(C,P)-C6H4PPh2)(CO)(PPh3) (1) and Os(κ2(Sn,P)-SnMe2C6H4PPh2)(κ2(C,P)-C6H4PPh2)(CO)(PPh3) (2), suggesting the possible intermediacy of a complex with a coordinated stannylene ligand. Spectroscopic data indicate that only one diastereomer of 1 is formed and crystal structure determination of 1 reveals that this is the diastereomer with chloride directed towards the CO ligand. Complex 2 is converted to 1 through a redistribution reaction with SnMe2Cl2. Heating the six-coordinate trimethylstannyl complex, Os(SnMe3)Cl(CO)2(PPh3)2, in solution produces the osmium(II) methyl complex, Os(Me)(SnMe2Cl)(CO)2(PPh3)2 (3), through an exchange of methyl and chloride groups on the tin and osmium. In this rearrangement, the relative locations of the two CO ligands and the two PPh3 ligands remains unchanged. However, when the six-coordinate trimethylstannyl complex, Os(SnMe3)Cl(CO)2(PPh3)2 is heated under CO, the same exchange reaction is observed but the mono-triphenylphosphine, tricarbonyl complex, Os(Me)(SnMe2Cl)(CO)3(PPh3) (4), is produced and here the SnMe2Cl ligand is located trans to the PPh3 ligand. Crystal structure determinations for 1, 2, 3, and 4 have been obtained.

Reaction between Os(SiCl3)Cl(CO)(PPh3)2 and five equivalents of MeLi produces a colourless intermediate, tentatively formulated as the lithium salt of the six-coordinate, dimethyl, trimethylsilyl-containing complex anion, Li[Os(SiMe3)(Me)2(CO)(PPh3)2]. Reaction of this material with ethanol releases methane and gives the red, coordinatively unsaturated methyl, trimethylsilyl-containing complex, Os(SiMe3)(Me)(CO)(PPh3)2 (1). An alternative synthesis of 1 is to add one equivalent of MeLi to Os(SiMe3)Cl(CO)(PPh3)2, which in turn is obtained by adding three equivalents of MeLi to Os(SiCl3)Cl(CO)(PPh3)2. Treatment of 1 with p-tolyl lithium, again gives a colourless intermediate which may be Li[Os(SiMe3)(Me)(p-tolyl)(CO)(PPh3)2], and reaction with ethanol gives the red complex, Os(SiMe3)(p-tolyl)(CO)(PPh3)2 (3). Complexes 1 and 3 are readily carbonylated to Os(SiMe3)(Me)(CO)2(PPh3)2 (2) and Os(SiMe3)(p-tolyl)(CO)2(PPh3)2 (4), respectively. Heating Os(SiMe3)Cl(CO)(PPh3)2 in molten triphenylphosphine results only in loss of the trimethylsilyl ligand and formation of the previously known complex containing an ortho-metallated triphenylphosphine ligand, Os(κ2(C,P)-C6H4PPh2)Cl(CO)(PPh3)2. In contrast, heating the five-coordinate osmium-methyl complex, Os(SiMe3)(Me)(CO)(PPh3)2 (1), in the presence of triphenylphosphine results mainly, not in tetramethylsilane elimination, but in ortho-silylation as well as ortho-metallation of different triphenylphosphine ligands giving, Os(κ2(Si,P)-SiMe2C6H4PPh2)(κ2(C,P)-C6H4PPh2)(CO)(PPh3) (5). A byproduct of this reaction is the non-silicon containing di-ortho-metallated complex, Os(κ2(C,P)-C6H4PPh2)2(CO)(PPh3) (6). A similar reaction occurs when Os(SiMe3)(Me)(CO)(PPh3)2 (1) is heated in the presence of tri(N-pyrrolyl)phosphine producing Os(κ2(Si,P)-SiMe2C6H4PPh2)(κ2(C,P)-C6H4PPh2)(CO)[P(NC4H4)3] (7) but a better synthesis of 7 is to treat 5 directly with tri(N-pyrrolyl)phosphine. Heating the six-coordinate complex, Os(SiMe3)(Me)(CO)2(PPh3)2 (2), gives two complexes both containing ortho-metallated triphenylphosphine, one with loss of the trimethylsilyl ligand, giving the known complex, Os(κ2(C,P)-C6H4PPh2)H(CO)2(PPh3), and the other with retention of the trimethylsilyl ligand, giving Os(SiMe3)(κ2(C,P)-C6H4PPh2)(CO)2(PPh3) (8). Crystal structure determinations for 5, 6, 7 and 8 have been obtained.

The thiocarbonyl analogue of Vaska’s compound is produced in high yield by first treating IrCl(CO)(PPh3)2 with CS2 and methyl triflate to give [Ir(κ2-C[S]SMe)Cl(CO)(PPh3)2]CF3SO3 (1), secondly, reacting 1 with NaBH4 to give IrHCl(C[S]SMe)(CO)(PPh3)2 (2), and finally heating 2 to induce elimination of both MeSH and CO to produce IrCl(CS)(PPh3)2 (3). When IrCl(CS)(PPh3)2 is treated with Hg(CH CHPh)2 the novel 2-iridathiophene, Ir[SC3H(Ph-3)(CH CHPh-5)]HCl(PPh3)2 (4) is produced. The X-ray crystal structure of the iodo-derivative of 4, Ir[SC3H(Ph-3)(CH CHPh-5)]HI(PPh3)2 (5) confirms the unusual 2-metallathiophene structure. Treatment of IrCl(CS)(PPh3)2 with Hg(CH CPh2)2 produces both a coordinatively unsaturated 1-iridaindene, Ir[C8H5(Ph-3)]Cl(PPh3)2 (6) and a chelated dithiocarboxylate complex, Ir(κ2-S2CCH CPh2)Cl(CH CPh2)(PPh3)2 (7). X-ray crystal structure determinations for 6 and 7 are reported.

Crystal structure determination of RuH(κ2-S2CNMe2)(CO)(PPh3)2 (1) confirms that the triphenylphosphine ligands are arranged mutually trans. 1 reacts readily with HSiClPh2 to eliminate H2 and produce the six-coordinate silyl complex, Ru(SiClPh2)(κ2-S2CNMe2)(CO)(PPh3)2 (2). Crystal structure determination of 2 reveals the same geometrical arrangement of ligands as in 1 with the silyl ligand replacing the hydride ligand. The chloride bound to silicon in 2 is replaced through reactions with 2-hydroxypyridine, 2-aminopyridine, and thallium acetate, producing, respectively, the mono-PPh3 complexes, Ru(κ2(Si,N)-SiPh2OC5H4N)(κ2-S2CNMe2)(CO)(PPh3) (3), Ru(κ2(Si,N)-SiPh2NHC5H4N)(κ2-S2CNMe2)(CO)(PPh3) (4), and Ru(κ2(Si,O)-SiPh2OCMeO)(κ2-S2CNMe2)(CO)(PPh3) (5). Crystal structure determinations of 3, 4, and 5 confirm that in each case there is formation of a five-membered chelate ring tethering the silyl ligand to ruthenium. In the formation of 3, 4, and 5 the Si-ligand and the two S atoms of the dimethyldithiocarbamate ligand remain meridional but the remaining triphenylphosphine ligand and the carbonyl ligand are interchanged in position leaving the donor atom of the tether trans to the CO ligand. An alternative way of considering the tethered silyl ligands in 3, 4, and 5 is as tethered, base-stabilised, silylene ligands and the structural data give some support for a contribution from this bonding model.

Treatment of either RuHCl(CO)(PPh3)3 or MPhCl(CO)(PPh3)2 with HSiMeCl2 produces the five-coordinate dichloro(methyl)silyl complexes, M(SiMeCl2)Cl(CO)(PPh3)2 (1a, M = Ru; 1b, M = Os). 1a and 1b react readily with hydroxide ions and with ethanol to give M(SiMe[OH]2)Cl(CO)(PPh3)2 (2a, M = Ru; 2b, M = Os) and M(SiMe[OEt]2)Cl(CO)(PPh3)2 (3a, M = Ru; 3b, M = Os), respectively. 3b adds CO to form the six-coordinate complex, Os(SiMe[OEt]2)Cl(CO)2(PPh3)2 (4b) and crystal structure determinations of 3b and 4b reveal very different Os–Si distances in the five-coordinate complex (2.3196(11) A) and in the six-coordinate complex (2.4901(8) A). Reaction between 1a and 1b and 8-aminoquinoline results in displacement of a triphenylphosphine ligand and formation of the six-coordinate chelate complexes M(SiMeCl2)Cl(CO)(PPh3)(κ2(N,N)-NC9H6NH2-8) (5a, M = Ru; 5b, M = Os), respectively. Crystal structure determination of 5a reveals that the amino function of the chelating 8-aminoquinoline ligand is located adjacent to the reactive Si–Cl bonds of the dichloro(methyl)silyl ligand but no reaction between these functions is observed. However, 5a and 5b react readily with ethanol to give ultimately M(SiMe[OEt]2)Cl(CO)(PPh3)(κ2(N,N-NC9H6NH2-8) (6a, M = Ru; 6b, M = Os). In the case of ruthenium only, the intermediate ethanolysis product Ru(SiMeCl[OEt])Cl(CO)(PPh3)(κ2(N,N-NC9H6NH2-8) (6c) was also isolated. The crystal structure of 6c was determined. Reaction between 1b and excess 2-aminopyridine results in condensation between the Si–Cl bonds and the N–H bonds with formation of a novel tridentate “NSiN” ligand in the complex Os(κ3(Si,N,N)-SiMe[NH(2-C5H4N)]2)Cl(CO)(PPh3) (7b). Crystal structure determination of 7b shows that the “NSiN” ligand coordinates to osmium with a “facial” arrangement and with chloride trans to the silyl ligand.

Reaction between Os[B(OEt)2]Cl(CO)(PPh3)2 and 1,2-ethanediol in the presence of Me3SiCl (1 equivalent) leads to the tethered boryl complex, Cl(CO)(PPh3)2 (1), in which one ethoxy substituent on the boryl ligand is exchanged with one hydroxy group of the 1,2-ethanediol leaving the other OH group available to coordinate to osmium, so giving a six coordinate complex. This formulation is confirmed by crystal structure determination. The same reactants, but with 2 equivalents of Me3SiCl, lead to the yellow, coordinatively unsaturated complex, Os Cl(CO)(PPh3)2 (2). Complex (2) adds CO to give Os Cl(CO)2 (PPh3)2 (3). Crystal structure determinations of 2 and 3 reveal a very marked difference in the Os–B distances found in the five coordinate complex 2 (2.043(4) A) and the six coordinate complex 3 (2.179(7) A). In a reaction similar to that used for forming 2 but with 1,3-propanediol replacing 1,2-ethanediol, the product is Os Cl(CO)(PPh3)2 (4). The crystal structure for 4 is also reported.

Reaction between Os(CO)2(PPh3)3 and Me3SnH produces Os(SnMe3)H(CO)2(PPh3)2 (1). Multinuclear NMR studies of solutions of 1 reveal the presence of four geometrical isomers, the major one being that with mutually cis triphenylphosphine ligands and mutually trans CO ligands. Os(SnMe3)H(CO)2(PPh3)2 undergoes a redistribution reaction, at the trimethylstannyl ligand, when treated with Me2SnCl2 giving Os(SnMe2Cl)H(CO)2(PPh3)2 (2). Solutions of 2 again show the presence of four isomers but now the major isomer is that with mutually trans triphenylphosphine ligands and mutually cis CO ligands. The redistribution reaction of 1 with SnI4 produces Os(SnMeI2)H(CO)2(PPh3)2 (3) which exists in solution as only one isomer, that with mutually trans triphenylphosphine ligands and mutually trans CO ligands. Treatment of 3 with I2 cleaves the Os–H bond with retention of geometry giving Os(SnMeI2)I(CO)2(PPh3)2 (4). The crystal structure of 4 has been determined. No isomerization of the trans dicarbonyl complex 4 occurs when 4 is heated, instead there is a formal loss of “MeSnI” and formation of OsI2(CO)2(PPh3)2 (5).

Reaction between the dichloroboryl complex, Os(BCl2)Cl(CO)(PPh3)2, and water replaces both chloride substituents on the boryl ligand, without cleavage of the OsB bond, giving yellow Os[B(OH)2]Cl(CO)(PPh3)2 (1). Compound 1 can be regarded as an example of a ‘metalla–boronic acid’ (LnMB(OH)2) and in the solid state, X-ray crystal structure determination reveals that molecules of 1 are tetragonal pyramidal in geometry (OsB, 2.056(3) A) and are arranged in pairs, as hydrogen-bonded dimers. This same arrangement is found in the crystalline state for simple boronic acids. Reaction between the dichloroboryl complex, Os(BCl2)Cl(CO)(PPh3)2, and methanol and ethanol produces yellow Os[B(OMe)2]Cl(CO)(PPh3)2 (2a) and yellow Os[B(OEt)2]Cl(CO)(PPh3)2 (2b), respectively. The crystal structure of 2b reveals a tetragonal pyramidal geometry with the diethoxyboryl ligand in the apical site and with an OsB bond distance of 2.081(5) A. Reaction between Os(BCl2)Cl(CO)(PPh3)2, and N,N′-dimethyl-o-phenylenediamine and N,N′-dimethyl-ethylenediamine produces yellow Os [ BN ( CH 3 ) C 6 H 4 N ( CH 3 )] Cl ( CO )( PPh 3 ) 2 (5) and yellow Os [ BN ( CH 3 ) C 2 H 4 N ( CH 3 )] Cl ( CO )( PPh 3 ) 2 (6), respectively. Compounds 1, 2a, 2b, 5, and 6 all react with carbon monoxide to give the colourless, six-coordinate complexes Os[B(OH)2]Cl(CO)2(PPh3)2 (3), Os[B(OMe)2]Cl(CO)2(PPh3)2 (4a), Os[B(OEt)2]Cl(CO)2(PPh3)2 (4b), Os [ BN ( CH 3 ) C 6 H 4 N ( CH 3 )] Cl ( CO ) 2 ( PPh 3 ) 2 (7), and Os [ BN ( CH 3 ) C 2 H 4 N ( CH 3 )] Cl ( CO ) 2 ( PPh 3 ) 2 (8), respectively, but in the case of 6 only, this CO uptake is easily reversible. The crystal structure of 5 is also reported.

Reaction between OsHCl(CO)(PPh3)3 and the powerful π-accepting ligand tris(N-pyrrolyl)phosphine, P(NC4H4)3, results in replacement of the PPh3 ligand trans to hydride giving OsHCl(CO)[P(NC4H4)3](PPh3)2 (1). The analogue of 1 with Cl replaced by p-tolyl, OsH(p-tolyl)(CO)[P(NC4H4)3](PPh3)2 (3), is accessible by thermal decarboxylation of Os(p-tolyl)(η2-O2CH)(CO)(PPh3)2 (2) in the presence of P(NC4H4)3. Complex 3, despite having cis-hydride and p-tolyl ligands, is resistant to reductive elimination of toluene. Osmium(0) complexes containing P(NC4H4)3 are conveniently prepared by replacement of one PPh3 ligand from Os(CO)(CE)(PPh3)3 (E=O, S) to give Os(CO)(CE)[P(NC4H4)3](PPh3)2 (4, E=O; 5, E=S). Structure determination of 4 confirms a trigonal bipyramidal geometry with the PPh3 ligands in the axial positions and the π-accepting P(NC4H4)3 ligand in the expected equatorial site.

Treatment of Os(SiMe 2 Cl)Cl(CO)(PPh 3 ) 2 with an excess of the amino-substituted silane, HSiMe 2 NMe 2 , produces a mixture of two products, the relative proportions of which depend upon the reaction conditions. These are, Os(SiMe 2 NMe 2 S iMe 2 )Cl(CO)(PPh 3 ) 2 ( 1 ) and Os(SiMe 2 NMe 2 S iMe 2 )H(CO)(PPh 3 ) 2 ( 2 ). Similar treatment of Ru(SiMe 2 Cl)Cl(CO)(PPh 3 ) 2 with HSiMe 2 NMe 2 produces the ruthenium analogues of 1 and 2 , Ru(SiMe 2 NMe 2 S iMe 2 )Cl(CO)(PPh 3 ) 2 ( 3 ), and Ru(SiMe 2 NMe 2 S iMe 2 )H(CO)(PPh 3 ) 2 ( 4 ), together with a third compound, the novel dimethylsilylene-bridged diruthenium complex, [ Ru(SiMe 2 NMe 2 S iMe 2 )(CO)(μ-{SiMe 2 }) 2 (μ-Cl)RuH 2 (CO)(PPh 3 )] ( 5 ). A ligand exchange reaction occurs when 3 is treated with 1,2-bis(diphenylphosphino)ethane (dppe) yielding Ru(SiMe 2 NMe 2 S iMe 2 )Cl(CO)(dppe) ( 6 ), in which the bis(silylene) ligand is retained. Crystal structures of 1 , 2 , 4 , and 6 reveal that the RuSiNS i and OsSiNS i rings of the bis(silylene) ligand system are folded at the Si atoms and the RuSi and OsSi distances are short, while SiN distances are long. These structural data suggest some multiple bond character in the metal–silicon bonds and this is further supported by the down-field chemical shifts observed in the 29 Si-NMR spectra of these compounds. A crystal structure has also been determined for the diruthenium complex 5 and this reveals a RuRu distance of 2.7557(2) A, and two unsymmetrically bridging dimethylsilylene ligands each with a close approach to one of the ruthenium hydride ligands (SiH, 1.56(2) and 1.67(2) A).

Reaction between OsPhCl(CO)(PPh 3 ) 2 and HSi(OEt) 3 gives the five-coordinate complex, Os[Si(OEt) 3 ]Cl(CO)(PPh 3 ) 2 ( 1 ), the crystal structure of which reveals a square pyramidal geometry with the triethoxysilyl ligand at the apical site and the two triphenylphosphine ligands arranged mutually trans . Addition of CO gives the six-coordinate complex, Os[Si(OEt) 3 ]Cl(CO) 2 (PPh 3 ) 2 ( 2 ), but this addition is thermally reversible. The chloride ligand in 1 is replaced easily and reaction with LiR gives the stable, five-coordinate complexes, Os[Si(OEt) 3 ]R(CO)(PPh 3 ) 2 ( 3a , R=phenyl; 3b , R= o -tolyl). Crystal structure determinations for 3a and 3b reveal a coordination geometry almost unchanged from that of 1 with Cl replaced by phenyl and o -tolyl, respectively. Addition of CO to 3a and 3b gives the six-coordinate complexes, Os[Si(OEt) 3 ]R(CO) 2 (PPh 3 ) 2 ( 4a , R=phenyl) ( 4b , R= o -tolyl). Crystal structure determinations for 4a and 4b confirm octahedral geometry for each compound. Despite having adjacent aryl and silyl ligands neither 3a , 3b nor 4a , 4b show any tendency to undergo reductive elimination of RSi(OEt) 3 . IR, 1 H-, 13 C- and 29 Si-NMR data for all new complexes are presented.

Reaction between Os(CS)(CO)(PPh 3 ) 3 and propyne gives a complex mixture of products from which can be isolated the simple oxidative addition product Os(CCMe)H(CS)(CO)(PPh 3 ) 2 ( 1 ) and the osmabenzene Os(η 2 -C[S]CMeCHCHC Me)(CO)(PPh 3 ) 2 ( 2 ), where the two propyne molecules in the osmabenzene ring have linked tail-to-tail. Treatment of 1 with HCl gives, as the ultimate product, the propenylthioacyl complex, Os(η 2 -C[S]CHCHMe)Cl(CO)(PPh 3 ) 2 ( 3 ). The crystal structures of compounds 1 – 3 have been determined.

A convenient preparation of Hg[C6H4(CH2OH)-2]Cl (1) involves treatment of dilithiated benzyl alcohol with HgCl2. 1 is smoothly oxidised to Hg[C6H4(CHO)-2]Cl (2) by reaction with pyridinium chlorochromate (PCC). The crystal structure of 2 reveals a two coordinate linear arrangement at mercury supplemented by weaker interactions with the aldehyde oxygen atoms both intramolecularly and intermolecularly. Treatment of 2 with NaI effects symmetrisation with the formation of Hg[C6H4(CHO)-2]2 (3). Reaction between 3 and the Wittig reagent Ph3PCH2 results in the formation of Hg[C6H4(CHCH2)-2]2 (4). The crystal structure of 4 has been determined.

Reaction between Os(CO) 2 (PPh 3 ) 3 and the silatrane, HSi{OCH 2 CH 2 } 3 N, gives the osmium(II) silatranyl, hydride complex Os(Si{OCH 2 CH 2 } 3 N)H(CO) 2 (PPh 3 ) 2 ( 1 ), as a mixture of three isomers, the structures of which were determined by NMR spectroscopy. Reaction between OsH 4 (PPh 3 ) 3 and the silatrane, HSi{OCH 2 CH 2 } 3 N, gives the osmium(IV) silatranyl, trihydride complex Os(Si{OCH 2 CH 2 } 3 N)H 3 (PPh 3 ) 3 ( 2 ). The crystal structure of 2 has been determined and all three hydride ligands located. The three hydrides all make close approaches to the silicon atom but the distances between silicon and each of the hydrides suggests that any Si⋯H interactions must be weak. The interatomic distance between Si and N in the silatranyl ligand is large and the nitrogen atom has near planar geometry. Compound 2 can be methylated or protonated at nitrogen giving the complexes [Os(Si{OCH 2 CH 2 } 3 NMe)H 3 (PPh 3 ) 3 ]I ( 3 ), and [Os(Si{OCH 2 CH 2 } 3 NH)H 3 (PPh 3 ) 3 ]CF 3 SO 3 ( 4 ), respectively.

Reaction between MHCl(CO)(PPh3)3 (M=Ru, Os) and the o-halophenyl mercury compounds, Hg(C6H4X-2)2 (X=Cl, Br, I) gives the five co-ordinate complexes, M(C6H4X-2)Cl(CO)(PPh3)2 (1a M=Ru, X=Cl; 1b M=Ru, X=Br; 2a M=Os, X=Cl; 2b M=Os, X=Br; 2c M=Os, X=I). In these complexes there is a significant bonding interaction between the coordinatively unsaturated metal centre and the o-halo-substituent on the σ-bound phenyl group as revealed by crystal structure determinations of 2a, 2b, and 2c. Each of the five-coordinate complexes readily adds CO forming the corresponding six-coordinate dicarbonyl complexes, M(C6H4X-2)Cl(CO)2(PPh3)2 (5a M=Ru, X=Cl; 5b M=Ru, X=Br; 6a M=Os, X=Cl; 6b M=Os, X=Br; 6c M=Os, X=I). Crystal structure determination of 6a confirms regular octahedral geometry for these six-coordinate complexes with no interaction between the metal centre and the o-halo-substituent on the σ-bound phenyl group. The complexes 1a, b, 2a–c, 5a, b, 6a–c, are potentially precursors of benzyne complexes through reduction (removal of ClX) but all attempts at reduction were unsuccessful. The related thiocarbonyl complexes, Os(C6H4X-2)Cl(CS)(PPh3)2 (7a X=Cl; 7b X=Br) and Os(C6H4X-2)Cl(CO)(CS)(PPh3)2 (8a X=Cl; 8b X=Br), have been prepared similarly beginning with OsHCl(CS)(PPh3)3. The crystal structure of 8a has been determined. Both 8a and 8b undergo a slow migratory-insertion reaction upon heating to yield the corresponding η2-thioacyl complexes, Os(η2-C[S]C6H4X-2)Cl(CO)(PPh3)2 (9a X=Cl; 9b X=Br), the crystal structures of both of which have been determined. Once the o-halophenyl group is no longer directly bonded to the metal, as in 9a and 9b, normal reactivity returns to the o-halo substituent and 9b undergoes lithium–bromine exchange when treated with n-butyllithium and the resulting lithiated material, when treated with SnnBu3Cl, gives Os(η2-C[S]C6H4SnnBu3-2)Cl(CO)(PPh3)2 (10).

The reaction between [Hg(o-C6H4PPh2)2] and [MHCl(CO)(PPh3)3] gives the complexes [ MCl(o-C 6 H 4 P Ph2)(CO)(PPh3)2] [M=Ru (1), Os (2)], which contain a four-membered cyclometallated ring. A single-crystal X-ray diffraction study of 2 shows the geometry about osmium to be distorted octahedral with the phosphorus atoms in a meridional arrangement. Both complexes react with CO, which displaces one of the triphenylphosphine ligands, the product from 2 being [ OsCl(o-C 6 H 4 P Ph2)(CO)2(PPh3)]. In the case of 1, there is an accompanying migratory insertion of coordinated CO into the RuC bond to give the five-membered cyclic acyl complex [ RuCl(o-C(O)C 6 H 4 P Ph2)(CO)2(PPh3)]. Complex 2 reacts with AgSbF6 in the presence of CO to give [ Os(o-C 6 H 4 P Ph2)(CO)2(PPh3)2]SbF6.

Three nitrogen-containing aromatic heterocycles, 2-(1′-naphthyl)pyridine, 2-phenylquinoline, and 2,3-diphenylquinoxaline, have been mercurated in the naphthyl or phenyl ring 2-position and then symmetrised to form the mercury compounds Ar2Hg (Ar=Nppy (3), Phqn (1) or Dpqx (5), respectively). These reagents are suitable for trans-metallation and reaction with MHCl(CO)(PPh3)3 affords the complexes M(η2-C,NAr)Cl(CO)(PPh3)2, (6, M=Ru, Ar=Nppy; 7, M=Os, Ar=Nppy; 8, M=Ru, Ar=Phqn; 9, M=Os, Ar=Phqn; 10, M=Ru, Ar=Dpqx; 11, M=Os, Ar=Dpqx) in which each product features an aryl ligand that forms a strongly chelated five-membered ring through coordination of the heterocyclic N atom. The chloride ligand in each of the complexes 6–11 can be replaced by dimethyl dithiocarbamate to give ultimately the mono-triphenylphosphine complexes, M(η2-Ar)(η2-S2CNMe2)(CO)(PPh3) (12, M=Ru, Ar=Nppy; 13, M=Os, Ar=Nppy; 14, M=Ru, Ar=Phqn; 15, M=Os, Ar=Phqn; 16, M=Ru, Ar=Dpqx; 17, M=Os, Ar=Dpqx). Similarly, compound 10 when treated with Na(acac) gives Ru(η2-Dpqx)(η2-acac)(CO)(PPh3) (18), while treatment with trifluoroacetic acid gives Ru(η2-Dpqx)(O2CCF3)(CO)(PPh3)2 (19). Many of these complexes were found to be very robust, making them suitable for electrophilic aromatic substitution reactions under harsh conditions. In each case, the presence of the metal had both an activating and a directing effect on the aryl ring to which it was bonded. Bromination or nitration reactions, both of which are not normally possible with organometallic substrates, were carried out successfully, giving rise to monobrominated or dinitrated products, respectively. The following compounds were characterised, M(η2-Ar-4-Br)Cl(CO)(PPh3)2 (20, M=Ru, Ar=Phqn; 21, M=Os, Ar=Phqn; 22, M=Ru, Ar=Dpqx; 24, M=Os, Ar=Dpqx), M(η2-Dpqx-4-Br)(η2-S2CNMe2)(CO)(PPh3) (23, M=Ru; 25, M=Os), Os(η2-Ar)Cl(CO)(PPh3)2 (26, Ar=Nppy-6,8-(NO2)2; 27, Ar=Phqn-4,6-(NO2)2). Crystal structures of compounds 7, 12, 15, 18, 19, 21, 23 and 25 have been determined.

When treated with lithium triethylborohydride, the cationic carbyne complexes [Os(–CR)(CO)2(PPh3)2]+(R=1-naphthyl, 1; R=2-naphthyl, 2) form 3 and 4, respectively, which both have the formula Os(C11H8)(CO)2(PPh3)2. NMR studies of these two isomeric vinylidene complexes show that the product derived from the 1-naphthyl carbyne cation involves attack at the naphthyl ring in the position para to the carbyne carbon to give 3, while that derived from the 2-naphthyl carbyne cation involves attack at the naphthyl ring in the position ortho to the carbyne carbon to give 4. The structure of 4 has been confirmed by an X-ray crystal structure determination. Addition of HCl to the vinylidene complexes 3 or 4 results in the formation of the corresponding naphthylmethyl complexes, Os(CH2R)Cl(CO)2(PPh3)2 (R=1-naphthyl, 5; R=2-naphthyl, 6).

Treatment of the dichlorocarbene-containing complex, Os(CCl2)Cl2(CO)(PPh3)2 with two equivalents of 1-naphthyllithium or two equivalents of 2-naphthyllithium in the presence of N,N,N′,N′-tetramethylethylenediamine (tmeda) gives the corresponding carbyne-containing complexes Os(CR)Cl(CO)(PPh3)2 (R=1-naphthyl (1); R=2-naphthyl (2)). Similar treatment of Ru(CCl2)Cl2(CO)(PPh3)2 with two equivalents of phenyllithium or 1-naphthyllithium yields Ru(CR)Cl(CO)(PPh3)2 (R=Ph (3); R=1-naphthyl (4)). When 1, 2, 3 and 4 are carbonylated in the presence of AgClO4 the corresponding carbyne-containing cations [M(CR)(CO)2(PPh3)2]ClO4 are formed (M=Os, R=1-naphthyl (5); M=Os, R=2-naphthyl (6); M=Ru, R=Ph (7); M=Ru, R=1-naphthyl (8)). When Ru(CPh)Cl(CO)(PPh3)2 is added to an acetonitrile solution containing two equivalents of AgClO4 in the absence of CO the complex [Ru(CPh{AgOClO3})(NCMe)(CO)(PPh3)2]ClO4 (9) can be isolated. Addition of LiCl to 9 yields the complex Ru(CPh{AgCl})Cl(CO)(PPh3)2 (10). The acids HX react with the neutral carbyne complexes 1, 2, 3 or 4 to form the corresponding carbene complexes M(CHR)ClX(CO)(PPh3)2 (M=Os, R=1-naphthyl, X=Cl (11); M=Os, R=2-naphthyl, X=Cl (12); M=Ru, R=Ph, X=Cl (13); M=Ru, R=1-naphthyl, X=Cl (14); M=Os, R=1-naphthyl, X=ClO4 (15); M=Os, R=1-naphthyl, X=F (16)). Treatment of complexes 1 or 2 with PhICl2 leads to corresponding monochlorocarbene-containing complexes Os(CClR)Cl2(CO)(PPh3)2 (R=1-naphthyl (17); R=2-naphthyl (18)) which subsequently rearrange on addition of aqueous base to give the σ-naphthyl, dicarbonyl complexes OsRCl(CO)2(PPh3)2 (R=1-naphthyl (19); R=2-naphthyl (20)). The single crystal X-ray structures of [Os(C-1-naphthyl)(CO)2(PPh3)2]ClO4, Os(CH-2-naphthyl)Cl2(CO)(PPh3)2, and Os(2-naphthyl)Cl(CO)2(PPh3)2 have been determined.

Oxidative addition of the tin-hydride bond of (p-tolyl)3SnH to the formal osmium(0) nitrosyl complexes, OsCl(NO)(PPh3)3 and “OsH(NO)(PPh3)2”, affords the osmium(II) stannyl complexes, Os[Sn(p-tolyl)3]HCl(NO)(PPh3)2 (1), and Os[Sn(p-tolyl)3]H2(NO)PPh3)2 (2) respectively. “OsH(NO)(PPh3)2” was generated in situ by thermal elimination of H2 from OsH3(NO)(PPh3)2 (5). It was established from 1H and 31P NMR evidence that 1 has two cis phosphine ligands, one of which is trans to the hydride ligand and the other trans to the stannyl ligand. The high trans influence of the hydride ligands confers lability on one phosphine ligand, which can be readily replaced by reaction with sodium dimethyldithiocarbamate forming OsH[Sn(p-tolyl)3](S2CNMe2)(NO)(PPh3) (3), and reaction with carbon monoxide gives eventually, after displacement of one triphenylphosphine and loss of HCl, Os[Sn(p-tolyl)3](NO)(CO)2(PPh3) (4), a formal osmium(O) stannyl complex. The crystal structure of this five-coordinate osmium-tin complex, 4, has been determined.

The reaction of Qn 2 Hg (Qn = 8-quinolyl) with OsHCl(CO)(PPh 3 ) 3 gives Os(η 2 -Qn)Cl(CO)(PPh 3 ) 2 ( 1 ), in which the 8-quinolyl ligand binds through both N and C-8 forming a 4-membered chelate ring. Reaction of 1 with AgPF 6 to remove chloride, followed by addition of either Nal or NaS 2 CNMe 2 , gives the neutral compounds Os(η 2 -Qn)I(CO)(PPh 3 ) 2 ( 2 ) or Os(η 1 -Qn)(η 2 -S 2 CNMe 2 )(CO)(PPh 3 ) 2 ( 3 ), respectively, while reaction with AgPF 6 followed by CO gives [Os(η 2 -Qn)(CO) 2 (PPh 3 ) 2 ] + PF 6 - ( 4 ). Single crystal X-ray structures of 2 and 3 have been determined. In 2 , the 8-quinolyl ligand is chelated through C-8 and N, but in 3 it is coordinated only through C-8.

In this paper we describe the synthesis of 3-metallated pyrroles where the pyrrole ring is otherwise unsubstituted at either carbon or nitrogen.

N -Acetylpyrrole and N -phenylsulfonylpyrrole are each selectively mercurated in the 2-position on treatment with mercuric chloride. The resulting organomercuric chlorides are symmetrized to the corresponding diorganomercury derivatives (2-C 4 H 3 NC[O]CH 3 ) 2 Hg ( 2 ) and (2-C 4 H 3 NSO[O]Ph) 2 Hg ( 4 ) by the action of sodium iodide. The crystal structures of (2-C 4 H 3 NC[O]CH 3 HgCl ( 1 ) and (2-C 4 H 3 NC[O]CH 3 ) 2 Hg ( 2 ) have been determined. The acetyl oxygen atom interacts weakly with the mercury centre in both cases, but more strongly in 1 than 2 . Treatment of the hydrido complexes MHCl(CO)(PPh 3 ) 3 (M  Ru, Os) with the diorganomercurial 2 or 4 affords in good yield the 2-pyrrolyl complexes CH 3 )Cl(CO)(PPh 3 ) 2 or , respectively. In each case the pyrrolyl group is coordinated in a bidentate fashion through C-2 and an oxygen atom of the N -substituent. The chloride ion in ( 7 ) is labile, and upon treatment with AgSbF 6 and CO, the cationic complex is formed. Treatment of 7 with AgSbF 6 and sodium dimethyldithiocarbamate gives the neutral monophosphine complex ( 10 ), the crystal structure of which has been determined.

Treatment of the tetrafluoroethylene complex, IrCl(η 2 -C 2 F 4 )(PPh 3 ) 2 , ( 1 ), with HCl or Cl 2 gives IrCl 2 (CF 2 CF 2 H)(PPh 3 ) 2 ( 2 ) or IrCl 2 (CF 2 CF 2 Cl)(PPh 3 ) 2 ( 3 ), respectively. These coordinately unsaturated complexes react with various neutral ligands to give stable, six-coordinate, tetrafluoroethyl and halotetrafluoroethyl complexes. The single crystal X-ray structure of one of these compounds, the carbonyl derivative of ( 3 ), IrCl 2 (CF 2 CF 2 Cl)(CO)(PPh 3 ) 2 ( 15 ) was determined. The acetonitrile derivative of ( 2 ), IrCl 2 (CF 2 CF 2 H)(CH 3 CN)(PPh 3 ) 2 ( 17 ) undergoes a reaction with HCl that proceeds through the intermediate fluorocarbene complex, [IrCl 2 (=CFCF 2 H)(CH 3 CN) (PPh 3 )] + ( 18 ), to give, upon hydrolysis, IrCl 2 (C[O]CF 2 H)(CH 3 CN)(PPh 3 ) 2 ( 19 ). The acetonitrile ligand, by virtue of its position trans to the acyl group, can be thermally displaced from ( 19 ) to give IrCl 2 (C[O]CF 2 H)(PPh 3 ) 2 ( 20 ). The vacant coordination site in ( 20 ) can be filled by other neutral ligands. Thermal treatment of any of the acyl complexes results finally in a reverse migration process and formation of IrCl 2 (CF 2 H)(CO)(PPh 3 ) 2 ( 23 ).

The reactions of η 2 -C 2 F 4 complexes of ruthenium and osmium with halogens give rise to complexes containing a halotetrafluoroethyl ligand, e.g. , M(η 2 -C 2 F 4 (CO) 2 (PPh 3 ) 2 (M = Ru or Os) with iodine or chlorine gives MX(C 2 F 4 X)(CO) 2 (PPh 3 ) 2 (M = Ru or Os; X = I or Cl). Similarly, Os(η 2 -C 2 F 4 )CO)(CNR)PPh 3 ) 2 reacts with iodine to give OsI(C 2 F 4 I) (CO)(CNR)(PPh 3 ) 2 , and Os(η 2 -C 2 F 4 )Cl(NO)PPh 3 ) 2 gives OsCl 2 (C 2 F 4 CI)(NO)PPh 3 ) 2 upon treatment with chlorine. The ruthenium halotetrafluoroethyl compounds decompose readily to form RuX 2 (CO) 2 (PPh 3 ) 2 , but the osmium halotetrafluoroethyl complexes proved to be quite unreactive, even towards abstraction of α-fluoride. The crystal structure of OsI(C 2 F 4 I (CO) 2 (PPh 3 ) 2 has been determined.

Treatment of M(CO) 2 (PPh 3 ) 3 with HER 2 R′ (M  Os; E  Si; R  R′ Me, Et, Ph; R  Ph, R′  H; E  Ge, Sn; R  R′ p -tolyl; M  Ru; E  Sn; R  R′= p -tolyl) affords the corresponding oxidative addition products M(ER 2 R′)H(CO) 2 (PPh 3 ) 2 ( 1 – 8 ). The crystal structures of two complexes, Os(SiEt 3 )H(CO) 2 (PPh 3 ) 2 ( 2 ) and Os(Ge[ p -tolyl]) 3 H(CO) 2 (PPh 3 ) 2 ( 6 ) have been determined. Reaction between HSnMe 3 and any one of the following compounds, OsHCl(CO)(PPh 3 ) 3 , Os(Ph)X(CO)(PPh 3 ) 2 (X  I, Cl), Os(SiMe 2 Cl)Cl(CO)(PPh 3 ) 2 , yields the osmium(IV) complex Os(SnMe 3 ) 2 H 2 (CO)(PPh 3 ) 2 ( 9 ). Determinations of T 1 suggest that the hydride ligands in 9 are coordinated in the classical manner rather than as η 2 -dihydrogen.

Reaction between the iridium(III) complex IrHCl 2 (PPh 3 ) 3 and Hg( o -tolyl) 2 yields the red, coordinatively unsaturated, mercury-containing, iridium(III) complex Ir( o -tolyl){Hg(σ-tolyl)}Cl(PPh 3 ) 2 ( 1 . 31 P- 199 Hg coupling in the 31 P NMR spectrum of 1 confirms the presence of IrHg bonding. Compound 1 undergoes reversible addition of CO to give the six-coordinate complex Ir( o -tolyl){Hg( o -tolyl)}Cl(CO)(PPh 3 ) 2 ( 2 ), which, in turn, undergoes reductive-elimination of Hg( o -tolyl) 2 to give IrCl(CO)(PPh 3 ) 2 . Treatment of 1 with HCl or iodine preferentially cleaves the HgC bond to give the complexes Ir( o -tolyl)Cl(HgX)(PPh 3 ) 2 .

Substitution of a single triphenylphosphine ligand in OsHCl(CO)(PPh3)3 by PCl3, PCl2Ph, Ph PCHCMeCMeC H or Ph2(mesityl) [mesityl = 2,4,6-trimethylphenyl] gives complexes with the new ligand trans to the hydride ligand and mutually cis to the two tirphenylphosphine ligands. The PCl3 and PCl2Ph complexes undergo slow substitution reactions at phosphorus, at temperatures > 50°C, with the nucleophiles methoxide, toluidine and hydride. The hydride ligand is readily cleaved either by acetonitrile solutions of aqueous perchloric acid, to give cationic acetonitrile containing complexes or by chlorine, to give neutral dichloride complexes. In all but one instance the products are isolated as mixtures of isomeric complexes with trans triphenylphosphine ligands. An exception to this dominant stereochemistry is observed for the complex containing the bulky mesitylphosphine ligand, OsHCl(PH2mesityl) (CO)(PPh3)2 for which the product of the hydride cleavage and subsequent carbonylation reaction consists of an almost equal mixture of isomers [OsCl(PH2mesityl)(CO)2(PPh3)2]ClO4 with cis and trans triphenylphosphine ligands. The structure of one of these isomers, with a mesitylphosphine trans to triphenylphosphine, has been determined by X-ray crystallography.

The crystal structure of the complex trans -[OsCl(NO)(PPh 3 ) 2 (OSNC 6 H 4 Me-4) has been determined and confirms that the sulphur(IV) heterocumulene adopts a pseudo-olefinic mode of coordination (η 2 -NS), with the pyramidal sulphur trans to chloride.

Reaction of Ru(CF3)Br(CO)2(PPh3)2 with an excess of BBr3 produces a red salt identified as [RuBr(CO)2C(C6H4PPh2)2]BBr4. Upon standing this solid loses CO and BBr3, to form RuBr2(CO)[C(C6H4PPh2)2], A, the structure of which has been determined by X-ray diffraction. The geometry about ruthenium is approximately octahedral, with the two phosphorus atoms of the tridentate biphosphinocarbene ligand mutually trans, and one bromide trans to the carbene carbon. The other bromide and the carbonyl ligand are statistically interchanged about a crystallographic diad axis which passes through the carbene carbon, the ruthenium, and the trans bromide. The RuP distance is 2.353(2) A, the RuBr distances are 2.638(2) A (trans to carbene) and 2.537(2) A (trans to CO), and the RuC(carbene) distance is 1.941(12) A. Bromide is removed from compound A by treatment with AgSbF6 in MeCN to give [RuBr(CO)(CH3CN)C(C6H4PPh2)2]SbF6, and this when treated with CO gives [RuBr(CO)2C(C6H4PPh2)2]SbF6. The dicarbonyl cation reacts with NaBH4 to give Rubr(CO)2[CH(C6H4PPh2)2], and with HNEt2 to give RuBr(CO)2[C(NEt2)(C6H4PPh2)2].

Reaction of Os(CO)2(PPh3)2 with a two-fold excess of di-p-tolydiazomethane in benzene at reflux temperature affords the yellow OsH(CO)2[(C6H3-p-Me)(p-tolyl)CNNC(p-tolyl)2](PPh3) (A) in high yield. The structure of A has been determined by X-ray crystallography. The geometry about osmium is octahedral, with the hydride ligand trans to triphenylphosphine and the carbonyl ligands mutually cis. The ketazine ligand is bound to osmium through nitrogen and the ortho-carbon of a p-tolyl group. The OsN and OsC distances are 2.119(5) and 2.100(7) A, respectively.

Stable osmium phosphido complexes, Os(η 2 -chelate)(PH 2 )(CO)(PPh 3 ) 2 , (chelate = acetate, N , N -dimethyldithiocarbamate, acetylacetonate, or nitrite) have been prepared by treating [OsCl(PH 3 )(NCCH 3 )(CO)(PPh 3 ) 2 ]ClO 4 with sodium acetate, sodium N , N -dimethyldithiocarbamate, acetylacetone/DBU, and sodium nitrite/DBU respectively. These and the related phosphido complexes OsX(PH 2 )(CO) 2 (PPh 3 ) 2 , (X = H, Cl, OAc) undergo reactions with the electrophiles H + , R + , Fe(CO) 4 , AuI, S 8 , and Se and the products have all been characterised. An X-ray diffraction study has established the structure of Os(η 2 -OAc)(PH 2 AuI)(CO)(PPh 3 ) 2 · (CH 2 Cl 2 ) 2 . The preparation of complexes with the unusual methylphosphinite (PH 2 OMe) ligand, M(PH 2 OMe)(CO) 2 (PPh 3 ) 2 (M = Ru, Os) and [MH(PH 2 OMe)- (CO) 2 (PPh 3 ) 2 ]ClO 4 (M = Ru, Os) and the methylthiophosphinite (PH 2 SMe) ligand, [OsX(PH 2 SMe)(CO) 2 (PPh 3 ) 2 ]ClO 4 , (X = Cl, H) are also described.

A trifluoromethyl iridium(I) complex Ir(CF3)(CO)2(PPh3)2 (1 has been prepared by the reaction of Hg(CF3)2 with IrH(CO)2(PPh3)2, or by thermal decomposition of Ir(COCF3)(CO)2(PPh3)2 (3), which is produced from (CF3CO)2O and a reduced iridium(−I) species. Either the reaction of IrH(CO)(PPh3)3 with Hg(CF3)2 or the reversible thermal decarbonylation of 1 yields the coordinatively unsaturated complex Ir(CF3)(CO)(PPh3)2 (2). Derivatives Ir(CF3)L(CO)(PPh3)2 (L = C2F4 (4), L = C2H4 (5), L = O2 (6)) result from treatment of 1 with tetrafluoroethylene, or 2 with ethylene or oxygen, respectively. Both 1 and 2 undergo oxidative addition of Cl2, I2, HCl, H2 and CH3I to give trifluoromethyl iridium(III) complexes IrCl2(CF3)(CO)(PPh3)2 (7), IrI2 (CF3)(CO)(PPh3)2 (8), IrHCl(CF3)(CO)(PPh3)2 (9), cis-IrH2(CF3)(CO)(PPh3)2 (10) and IrI(CH3)(CF3)(CO)(PPh3)2 (11), respectively. The iodo ligand in 11 is labile and can be replaced by an acetonitrile ligand to yield [Ir(CH3)(CF3)(L)(CO)(PPh3)2]ClO4 (L = CH3CN (12)). This ligand can in turn be replaced by p-tolylisocyanide (L = CN-p-C6H4CH3 (13)) or Cl− to give IrCl(CH3)(CF3)(CO)(PPh3)2 (14). Complexes 1 and 9 each react with AlCl3 to give the difluoromethyl species IrCl2(CF2H)(CO)(PPh3)2 (15). A difluorocarbene iridium(I) complex, IrCl(CF2)(CO)(PPh3)2 (16), has been prepared by thermal decarbonylation of Ir(COCF2Cl)(CO)2(PPh3)2 (18), and a complex containing both CF3 and CF2 ligands, Ir(CF2)(CF3)(CO)(PPh3)2 (17), has been made by treatment of either IrCl(CO)(PPh3)2, 2 or 16 with Cd(CF3)2 · glyme. Both 16 and 17 are hydrolysed to give carbonyl species IrCl(CO)2(PPh3)2 and 1, respectively, while 16 reacts with t-butylamine to give an isocyanide complex, IrCl(CN-t-C4H9)(CO)(PPh3)2 (20). Addition of HCl to 16 or 17 produces 15 or 9, respectively. Complexes 4, 11 and 17 have been characterised by X-ray diffraction studies.

The hydrido complexes MHCl(CO)(PPh3)3 (M = Ru, Os) react with the organomercury compounds R2Hg (R = phenyl, p-tolyl, o-tolyl, trans-β-styryl) to give the five-coordinate, σ aryl and alkenyl complexes MRCl(CO)(PPh3)2 in high yield. Bromide and iodide analogues of these compounds can be prepared through reaction with silver perchlorate followed by addition of excess bromide or iodide ions. The X-ray crystal structures of two of the complexes, Ru(p-tolyl)Cl(CO)(PPh3)2 and Ru(o-tolyl)Cl(CO)(PPh3)2, have been determined.

Rh(CF3)(CO)(PPh3)2 has been made by treating RhH(CO)(PPh3)3 with Hg(CF3)2, and found to display reactivity consistent with a 16 e−, d8 complex, in that it undergoes addition of a number of small molecules, including O2, X2 (X = Cl, Br, I) and MeI. Treatment of Rh(CF3)(CO)(PPh3)2 with aqueous acids results in hydrolysis of the trifluoromethyl group to a carbonyl ligand. Confirmation that this reaction proceeds via a difluorocarbene intermediate came from the reaction with dry HCl, which gave RhCl2(CF2H)(CO)(PPh3)2. A study of this reaction, by multinuclear NMR spectroscopy and 2H-labelling experiments led to the proposal of a mechanism for the formation of RhCl2(CF2H)(CO)(PPh3)2 that involves hydride migration to a cationic difluorocarbene ligand bound to rhodium. Another difluoromethyl complex RhCl2(CF2H)(PPh3)2 is formed when RhHCl2(PPh3)3 is treated with Hg(CF3)2. The crystal structure of this complex has been determined, and displays square pyramidal geometry with the CF2H ligand occupying the apical position.

Catecholate displaces chloride from both the carbene centre and the metal in Ru[CCl(2-pyrrolyl)]Cl2(CO)L2 (L = PPh3) to give Ru[C(OC 6 H 4 O )(2-pyrrolyl)]Cl(CO)L2 (A). Cations derived from A can be deprotonated to ruthenium-substituted 1-azafulvene intermediates which undergo further reactions including methylation at nitrogen to give Ru[C(OC 6 H 4 O )(2-N-methylpyrrolyl)]I(CO)L2 (E). The crystal structure of E is reported.

Dimethyldithiocarbamate displaces chloride from both the carbene centre and the metal in Ru[CCl(2-pyrrolyl)]Cl2(CO)(PPh3)2 to give the stable ruthenium-substituted 1-azafulvene Ru(C[C 4 H 3 N]SCNMe 2 S )(η2-S2CNMe2)(CO)(PPh3) (A). Compound A can be protonated (reversibly) or methylated at the nitrogen of the 1-azafulvene to give compounds B and C respectively. The structure of B has been determined by a single crystal X-ray study.

The reaction of two equivalents of LiR (R = p-tolyl) with the dichlorocarbene complex OsCl2(CCl2)(CO)(PPh3)2 gives the carbyne complex Os(CR)Cl(CO) (PPh3)2 (I) in good yield. X-ray crystal structure determination shows that I is mononuclear with an OsC distance of 1.78(2) A. The OsC bond reacts with electrophiles rather than nucleophiles. Thus, HCl adds to give the alkylidene complex OsCl2(CHR)(CO)(PPh3)2, Cl2 forms OsCl2(CClR)(CO)(PPh3)2 and sulphur, selenium and tellurium react to yield to corresponding dihapto-chalcoacyls Os(η2-C[X]R)Cl(CO)(PPh3)2 (X = S, Se, Te). Group Ib metal halides also add to the OsC bond to form the adducts Os(C[M X]R)Cl(CO)(PPh3)2 (MX = CuI, AgCl, AuCl). The X-ray crystal structure determination of Os(C[A gCl]R)Cl(CO)(PPh3)2 (II) suggests that this complex can be considered as a dimetallacyclopropene derivative. Crystals of I are monoclinic, space group P21/n, a 17.030(2), b 12.774(1), c 18.315(3) A, β 107.96 (1)°, V 3793.2 A3, Z = 4, Dm 1.53(1), Dc 1.54. Crystals of II are monoclinic, space group P21/n, a 13.021(2), b 23.714(2), c 12.999(2) A, β 90.556(2)°, V 4013.7 A3, Z = 4, Dm 1.705(5), Dc 1.695. The structures were solved by conventional heavy-atom methods, and refined by full-matrix least-squares employing anisotropic thermal parameters for all non-hydrogen atoms except for the carbon atoms of the phenyl rings. Phenyl hydrogen atoms were included in calculated positions. Final residuals R were 0.040 and 0.037, respectively.

Purple IrCl3(CCl2)(PPh3)2 results from reaction between IrHCl2(PPh3)3 and Hg(CCl3)2. X-ray crystal structure determination reveals an octahedral complex with trans-phosphine ligands and a short IrC distance to the CCl2 ligand of 1.872(7) A, compatible with an iridiumcarbon double bond. Chloride is easily displaced from the dichlorocarbene ligand and the products which have been derived include IrCl3(CO)(PPh3)2, IrCl3(CS)(PPh3)2, IrCl3(CNMe)(PPh3)2, IrCl3(CClNMe2)(PPh3)2, IrCl3(CNHCH2CH2NH)(PPh3)2 and IrCl(CSCH2CH2S)-(PPh3)2.

Octahedral osmium complexes of the type OsRX(CS)L(PPh 3 ) 2 (R  p -tolyl; X  Cl, Br, I or O 2 CCF 3 ; L  CO or CNR), which have adjacent R and CS ligands, undergo rearrangement to dihapto -thioacyl complexes Os[η 2 -C(S)R]XL(PPh 3 ) 2 , and the X-ray structure determination of a representative example Os[η 2 -C(S)R] (η 1 -O 2 CCF 3 ) (CO) (PPh 3 ) 2 , is reported.

The structure of the maleic anhydride complex Ru(η2-C4H2O3)(CO)(CN-p-tolyl)(PPh3)2 (1) has been determined by X-ray crystallography. Crystals of 1 are monoclinic, space group P21/c, a 9.917(1), b 20.244(3), c 20.768(3) A, β 99.80(1)°. Z = 4, Dc 1.406 g cm−3. The structure was solved by conventional Patterson and Fourier techniques and refined by full matrix least squares. The refinement converged to R = 0.061, Rw = 0.063. The geometry about ruthenium is approximately trigonal bipyramidal with the maleic anhydride and the two triphenylphosphines equatorial. The maleic anhydride coordinates to ruthenium via the alkene (C(1)C(4)) bond. The elongated C(1)C(4) bond and the values of ν(CN) and ν(CO) in the infrared spectrum suggest a strong alkene π-acceptor component in the Ru-maleic anhydride interaction.

Os(η2-CH2O)(CO)2(PPh3)2 results from direct reaction of formaldehyde with the zerovalent complex, Os(CO)2(PPh3)3. The structure of Os(η2-CH2O)(CO)2(PPh3)2 was determined by X-ray crystallography. The crystals are triclinic, space group P 1 , a 18.739(2), b 11.157(1), c 9.986(1) A, α 116.70(1), β 93.20(1), γ 107.93(1)°, V 1727.69 A3, Z = 2, Dm 1.55(2), Dc 1.57 g cm−3. Refinement of atomic parameters was by full-matrix least-squares methods, employing anisotropic thermal parameters for all non-hydrogen atoms except for the carbon atoms of the phenyl rings. The formaldehyde hydrogen atoms were located from difference electron density maps, other hydrogens were included in calculated positions. Final residuals were R = 0.047 and Rw = 0.061 for 3508 unique observed reflections measured on an automatic diffractometer. The complex itself is monomeric, although interstices in the crystal lattice are occupied by hydrogen-bonded water dimers which fulfil a purely space-filling role. The osmium is bonded to two mutually trans triphenylphosphines, two carbonyls, and the η5-formaldehyde, in an arrangement which is best described as distorted octahedral. The geometry of the coordinated formaldehyde is characterised by OsO 2.039(7), OsC 2.186(8) and CO 1.584(11) A. The OsP bonds are equivalent at 2.372(2) and 2.378(2) A but the OsCO bond trans to the formaldehyde carbon 1.931(7) A is longer than that trans to the formaldehyde oxygen 1.907(7) A. Os(η2-CH2O)(CO)2(PPh3)3 has proved to be a useful synthetic precursor for stable formyl, hydroxymethyl, methoxymethyl, and halomethyl (CH2X, X  Cl, Br, I) complexes. The compounds Os(CHO)H(CO)2(PPh3)2, Os(CH2OH)H(CO)2(PPh3)2, Os(CH2OMe)Cl(CO)2(PPh3)2 and Os(CH2Cl)Cl(CO)2(PPh3)2 are illustrative of the many compounds which have been characterised. A general synthetic route to neutral formyl osmium complexes, Os(CHO)X(CO)2(PPh3)2 (X = halide or alkyl) has been developed from reaction of the cations [OsX(CO)3(PPh3)2]+ with BH4−. Acetaldehyde also reacts with Os(CO)2(PPh3)3 forming Os(η1-C[O]CH3)H(CO)2(PPh3)2. No reaction was observed with benzaldehyde, and trichloroacetaldehyde affords the cation, [OsCl(CO)2(PPh3)3]+.

The formimidoyl complex, Ru(CHNR)(O2CCH3)(CO)(PPh3)2 (R = p-tolyl) is converted to neutral, cationic, and dicationic compounds containing the coordinated secondary carbenes CHNHR and CHN(CH3)R by protonation and methylation respectively.

The synthesis and characterisation of the molecules cis -OsH(CH 3 CO)(CO) 2 - (PPh 3 ) 2 , cis -OsH(CH 3 )(CO) 2 and cis -OsH(CH 2 OH)(CO) 2 (PPh 3 ) 2 , each of which models an intermediate postulated to occur in one of several metal- catalyzed processes, are described.

Acylphosphido complexes, OsCl[PH(C[O]R)](CO)2(PPh3)2, (R = t-Bu, CH3, CO2Et, Ph, p-C6H4NO2, CF3; 2a–e, 3) are formed when OsCl(PH2)(CO)2(PPh3)2 is treated with the appropriate acid chloride or anhydride. Related complexes, MX[PH(C[O]CF3)](CO)L′(PPh3)2, (M = Ru, X = Cl, L′ = CO: 7; M = Os, X = H, L′ = CO; 8; M = Os, X = Cl, L′ = PMe3; 9) are also prepared from the related PH2 complexes and trifluoroacetic anhydride. The structure of a representative example of one of these with a pivaloylphosphido ligand, 2a, has been determined. The pale yellow crystals are triclinic, space group P 1 , a 10.691(1), b 12.565(3), c 17.291(2) A, α 97.39(1), β 103.871(9), γ 102.72(1)° with Z = 2 and V 2159 A3. When 3 is treated with sodium hydride in THF at reflux for 1.5 h, HCl is lost and a η2-phospha-alkenyl complex OS(PC[O ]CF3)(CO)2(PPh3)2 (10) is formed. The two-coordinate phosphorus atom in 10 is nucleophilic, and with Fe2(CO)9 forms the adduct Os[P(Fe(CO) 4 )C[O ]CF3](CO)2(PPh3)2 (12), and with methyl iodide gives a methyltrifluoroacylphosphido complex, OsI[PMe(C[O]CF3)](CO)2(PPh3)2 (11b). Both 10 and 12 have been structurally characterized. Bright orange of 12 crystallize in the monoclinic space group P21/c, with a 12.168(3), b 18.135(3), c 21.804(3) A and β 103.11(2)°, Z = 4, V 4686 A3. Complete details of the structure of 10 are also reported. The bonding in 10 and 12 is discussed in terms of two canonical forms, one with phospha-alkene like character, the other with phosphinidene character.