Evert J. Ditzel

Substituted osmium clusters containing labile ligands. The preparation, characterisation, and some reactions of [Os3H(OR)(CO)9(MeCN)](R = H, Me, Et, or Ph) and the isomers of [Os3H(SR)(CO)9(MeCN)](R = Me, Et, or Ph); the crystal and molecular structure of [Os3H(SPh)(CO)9(PEt3)]

The compounds [Os3H(ER)(CO)10](E = O, R = H, Me, Et, or Ph; E = S, R = Me, Et, or Ph) react with Me3NO in MeCN to produce the acetonitrile derivatives [Os3H(ER)(CO)9(MeCN)]. For ER = OR there is only one such compound formed which has the acetonitrile ligand attached to one of the bridgehead osmium atoms. These clusters react with P(OMe)3 to form two isomers of the compounds [Os3H(OR)(CO)9{P(OMe)3}], both of which have the phosphite ligands co-ordinated to one of the bridgehead osmium atoms. For the case ER = SR three isomers of the acetonitrile derivative are formed, two with the acetonitrile ligand attached to the unique osmium atom and one as in the alkoxy case. These isomers react with phosphorus donor ligands to produce isomers of the compounds [Os3H(SR)(CO)9(PR′3)], where the phosphorus donor ligand is bound to the same osmium atom as the acetonitrile in the starting material. The compounds [Os3H(OR)(CO)8-{P(OMe)3}2] were prepared from reaction of [Os3H(OR)(CO)10] with 2.2 equivalents of Me3NO followed by P(OMe)3. All the products have been characterised by i.r. and 1H n.m.r. spectroscopy and structural assignments made. The structure of [Os3H(SPh)(CO)9(PEt3)] was confirmed by X-ray analysis and shown to consist of a riangle of Os atoms with one edge bridged by both a hydride and a phenylthiolato ligand. The triethylphosphine ligand occupies a ‘pseudo’ axial site on one of the Os atoms involved in bridge bonds. The nine carbonyl groups all occupy terminal co-ordination sites.

The [Os3(µ-H)(CO)10(MeCN)2]+ cation: synthesis and X-ray crystal structure of [Os3(µ-H)(CO)10(MeCN)2][Os(CO)3Cl3]

The clusters [Os3(CO)11(MeCN)] and [Os3(CO)10(MeCN)2] react with acids HX (X = BF4 or PF6) to form the cationic derivatives [Os3(µ-H)(CO)11(MeCN)]X and [Os3(µ-H)(CO)10(MeCN)2]X, respectively. The cluster [Os3(CO)10(MeCN)2] also reacts with dry HCl to form the salt [Os3(µ-H)-(CO)10(MeCN)2][Os(CO)3Cl3]. X-Ray analysis of this salt shows that the Os atoms in the cation lie at the vertices of an isosceles triangle. A hydride bridges the long Os–Os edge, and the two acetonitrile ligands occupy trans axial sites. Reaction of [Os3(µ-H)(µ-OH)(CO)10] with HBF4 in MeCN also produces [Os3(µ-H)(CO)10(MeCN)2]+. In this reaction direct attack of H+ on the co-ordinated OH– ligand is considered to occur with the resultant liberation of H2O. Treatment of [Os3(µ-H)(CO)10–(MeCN)2]+ with [Os(CO)4]–2 leads to the formation of the neutral complex [Os4H2(CO)14(MeCN)]. The bridging hydride of the cation may also be replaced by a bridging nitrosyl ligand by reaction with NO+.

Substitution reactions on triosmium clusters of the type [Os3(µ-H)(µ-X)-(CO)10][X = NHMe, O2CR, C5H4N, or OC(NHMe); R = H, Me, or Ph]

The reaction of [Os3H(NHMe)(CO)10] with Me3NO in solvents containing acetonitrile produces three isomers of the acetonitrile derivative [Os3H(NHMe)(CO)9(MeCN)], (2a)–(2c), together with a trace of [Os3H(NHMe)(CO)9(NMe3)]. The acetonitrile derivatives all react with P(OMe)3 to give isomers of [Os3H(NHMe)(CO)9{P(OMe)3}]. Prolonged reaction of (2c) with P(OMe)3 results in two isomers of the disubstituted complex [Os3H(NHMe)(CO)8{(P(OMe)3)}2]. Reaction of Me3NO with compounds of the type [Os3H(µ-X)(CO)10], where X is one of the bidentate ligands O2CR (R = H, Me, or Ph), C5H4N, or O C(NHMe), results in the formation of the trimethylamine derivatives [Os3H(X)(CO)9(NMe3)]. These compounds react with P(OMe)3 to form [Os3H(X)(CO)9{P(OMe)3}]. All the products were characterised by i.r., 1H n.m.r., and mass spectroscopy and structural assignments made.

Rational synthesis of dinuclear complexes of platinum(I) and platinum(II) containing bridging ortho-metallated triphenylphosphine ligands from the monomeric bis(chelate) platinum(II) complex Pt(o-C6H4PPh2)2

Comproportionation of Pt(PPh3)3 and the bis(chelate) complex Pt(o-C6H4PPh2)2 gives a dinuclear complex Pt2(µ-o-C6H4PPh2)2(PPh 3)2 which is shown by X-ray crystallography to contain two ortho-metallated triphenylphosphine ligands bridging a PtI–PtI bond [Pt–Pt 2.630(1)A]; addition of iodine gives a salt [Pt2(µ-l)(µ-o-C6H4PPh2)2(PPh3)2]l, the cation of which has an A-frame structure [Pt–Pt 2.931(2)A].

Systematic synthesis of tetranuclear osmium clusters by the reaction of trinuclear clusters with [OsH2(CO)4]; crystal structure of [Os4H3Br(CO)13]

The complex [OsH2(CO)4] reacts with the clusters [Os3(CO)12–n(MeCN)n](n= 1 or 2) to afford the tetranuclear species [Os4H2(CO)15](1) and [Os4H2(CO)14(MeCN)](2), respectively. The pyrolysis of [Os4H2(CO)14(MeCN)](2) leads to the formation of [Os4H2(CO)13]via the intermediate [Os4H2(CO)14]. The acetonitrile ligand of complex (2) is readily displaced by P(OMe)3 to give [Os4H2(CO)14{P(OMe)3}](3) along with small quantities of [Os3(CO)14{P(OMe)3}2] and [Os3(CO)9{P(OMe)3}3]. With PPh3 the reaction is so slow that fragmentation occurs and the only product isolated is [Os3(CO)10(PPh3)2]. The hydride-coupling reaction also occurs between [OsH2(CO)4] and [Os3H(X)(CO)9(NMe3)](X = Cl, Br, or I) and the complexes obtained [(4)–(6) respectively] have been fully characterised. These complexes decompose in solution via loss of HX to afford [Os4H2(CO)13]. The reaction between [Os3H(OR)(CO)9(MeCN)] and [OsH2(CO)4] proceeds smoothly for R = Me (7) or Ph (8) but for R = H the major product isolated is [Os3H(OH)(CO)10]. All the products were characterised by i.r., 1H and 13C n.m.r. spectroscopy and structural assignments made. The structure of the cluster [Os4H3Br(CO)13](5) was confirmed by an X-ray analysis and shown to consist of an OS3 triangle with a pendant OsH(CO)4 unit co-ordinated to it. One edge of the triangle is bridged by both a hydride and a bromide ligand while another edge is bridged by a hydride.

Systematic cluster build up by the reaction of [Os3H(X)(CO)9(MeCN)] (X=SR or NHMe;R=Me, Et, or Ph) with [OsH2(CO)4]

[OsH2(CO)4] reacts with the acetonitrile derivatives [Os3H(SR)(CO)9(MeCN)](R = Me, Et, or Ph) and [Os3H(NHMe)(CO)9(MeCN)] to form the tetranuclear clusters [Os4H3(SR)(CO)13] and [Os4H3(NHMe)(CO)13] respectively. The cluster [Os4H3(OPh)(CO)12(MeCN)] can be formed by treatment of [Os3H(OPh)(CO)10] with 2.2 equivalents of Me3NO followed by [OsH2(CO)4]. This cluster reacts with P(OMe)3 to form [Os4H3(OPh)(CO)12{P(OMe)3}]. All compounds were characterised by i.r., 1H n.m.r., and mass spectroscopy.

The preparation, characterisation, and some reactions of [Os3H(X)(CO)9(NMe3)](X = Cl, Br, or I)

The clusters [Os3H(X)(CO)10](X = Cl, Br, or I) react with trimethylamine oxide to produce the complexes [Os3H(X)(CO)9(NMe3)]. The trimethylamine ligand of these compounds is readily displaced by P(OMe)3 to give [Os3H(X)(CO)9{P(OMe)3}]. The compound [Os3H(Cl)(CO)9(NMe3)] also reacts with thylene, phenylacetylene, and PPh3 to give [Os3H (Cl)(CO)9( C2H4)], [Os3Cl(CO)10(CHCHPh)], or [Os3H(Cl)(CO)9(PPh3)] respectively. The compound [Os3H(Cl)(CO)8(PPh3)2] can also be prepared by the reaction of [Os3H (Cl)(CO)10] with 2.5 equivalents of Me3NO followed by PPh3. All the products were characterised by i.r. and 1H n.m.r. spectroscopy, and structural assignments made.