Roland K. Pomeroy

Group IV derivatives of Os3(μ-H)2(CO)10. Structures of HOs3(μ-H)2(CO)10(SiHPh2) and Os3(μ-H)2(CO)10(SnMe3)2

The structures of HOs3(μ-H)2(CO)10(SiHPh2) (1) and Os3(μ-H)2(CO)10(SnMe3)2 ((2) have been determined by X-ray methods. Crystals of 1 are triclinic, space group P1 with a 9.221(1), b 11.927(1), c 13.580(1) A, α 110.94(1), β 101.28(1), γ 97.39(1)°, V 1335.3(4) A3 and Z = 2. The structure was solved by heavy-atom methods and the structure refined to R 2.2% and Rw 2.3%. It consists of an Os3 triangle, two edges of which are bridged by hydrogen ligands (OsOs lengths of 3.0369(4) and 3.0847(5) A vs. 2.9383(6) A for the unbridged OsOs bond). The terminal hydride and SiHPh2 groups ligate different osmium atoms on the same edge of the Os3 cluster (the OsSi bond length is 2.455(2) A); both are in the equatorial plane. This is first case where a terminal hydride ligand has been structurally characterized in an equatorial site for an Os3 cluster. Crystals of 2 are monoclinic space group P21/n with a 9.456(2), b 22.575(4), c 13.124(4) A, β 95.40(2)°, V 2789(2) A3 and Z = 4. The structure was also solved by standard heavy-atom techniques and the structure refined to R 5.3% and Rw 6.5% with only the Os and Sn atoms permitted to have anisotropic thermal parameters. The structure of 2 is similar to 1 except that the SnMe3 ligands are bound on opposite edges of the Os3 triangle. The OsOs vector are 2.896(3) (unbridged), 3.021(3), 3.070(2) A (Os(μ-H)Os); the OsSn lengths are 2.726(5) and 2.696(4) A.

18-Electron complexes as ligands. Synthesis, structure, and stereochemical nonrigidity of (trimethylphosphine)tetracarbonylosmium-pentacarbonyltungsten complex ((Me3P)(OC)4OsW(CO)5)

Preparation et structure de (Me 3 P)(OC) 4 OsW(CO) 5 contenant une liaison donneur-accepteur non pontee entre differents atomes metalliques de transition; ce compose presente aussi une stereochimie non rigide en solution

Steric and Electronic Influences in Os~3(CO)~1~1(PR~3) Structures

The structures of Os3(CO)11(PR3) with R=F, OPh, Et, p-C6H4Me, o-C6H4Me, p-C6H4(CF3) and C6H11, and with PR3=P(OCH2)3CMe have been determined. The Os–Os bond lengths in these compounds are compared to the Os–Os lengths for the other structures of Os3(CO)11(PR3) clusters reported in the literature. In most cases, the Os–Os bond length remote from the P ligand [range, 2.8666(4)–2.9044(4) Å] and that in the pseudo-trans position [range, 2.8712(5)–2.900(1) Å] show little variation as the steric and electronic properties of the P ligand are varied. The Os–Os length cis to PR3 shows more variation [range, 2.879(1)–2.9429(4) Å] and is sensitive to both the size and the σ-donor/π-acceptor properties of the PR3 ligand: larger or better donor PR3 ligands cause an increase in the Os–Os bond length. The Os–P distances [range, 2.15(2)–2.478(1) Å] show a similar dependence on the steric and electronic properties of the PR3 ligand.

Synthesis and structure of Ru(CO)4[P(OCH3)3]. The conformation of the trimethyl phosphite ligand in complexes

Abstract Two methods of preparation of Ru(CO)4[P(OCH3)3] from Ru3(CO)12 and P(OCH3)3 are described. The crystal structure of the compound has been determined from three-dimensional X-ray data collected by counter methods. The space group is P21/c with cell dimensions a 13.225(3), b 7.704(3), c 13.278(4) A and β 109.82(2)°. Intensity data for 1879 observed reflections were refined by conventional methods to R  0.044. The structure shows that the phosphite ligand does not have three fold symmetry. From a comparison of the infrared spectrum in the carbonyl region of Ru(CO)4[P(OCH3)3] with that of the corresponding P(OCH2)3CC2H5 derivative it is concluded that the asymmetry of the ligand is maintained on the infrared time scale. The13C and1H NMR spectra however indicate the methyl groups are all equivalent on the NM time scale, even at120°C. The NMR study also indicated there is rapid exchange of the axial and equatorial carbonyl groups in solution.

Evidence for a trigonal twist mechanism involving a phosphite ligand of Os3(CO)7,[P(OMe)3]5

Abstract The fluxional molecule Os3(CO)7[P(OMe)3]5 has been prepared from OS3(CO)12 and P(OMe)3 by a combination of thermal and UV irradiation synthetic methods. An investigation by 31P and 13C NMR spectroscopy indicated that the mechanism of fluxionality in this compound probably involves the P(OMe)3 ligand of the Os(CO)3[P(OMe)3] unit moving from one equatorial site to the other via a trigonal twist mechanism.

Synthesis and structure of [(OC)4Os(PbMe2)]2 and some derivatives of the type Os2(CO)7(SnMe2)2(L)

The complexes [(OC)4Os(PbMe2)]2 (3) and [(OC)4OsSnBu2′]2 (4) have been prepared from be reaction of Na2[Os(CO)4] with Me2PbCl2 and Bu2′SnCl2, respectively, in THF and their X-ray crystal structures determined. The red derivative,3, was light-sensitive in solution. The reactions or [(OC)4 Os(SnMe2)]2 (2), or its decarbonylated derivative [Os3(CO)7(SnMe2)2]2 (7), with olefins or phosphorus donor ligands have also been investigated, and the structures of two derivatives, viz. [Os2(CO)7(SnMe2)2(C2H4)] (5a) and [Os2(CO)7(SnMe2)2(PMe3)] (6a), have been determined; the noncarbonyl ligand occupies an equatorial site in each case. The X-ray crystal structures of all these compounds, like those of [(OC)4Os(EMe2)]2 (E=Ge (1), Sn (2)) which have been reported previously, show leaning of the axial carbonyl ligands toward the metal tetracycle, i.e., an “umbrella” effect. Crystallographic data for compound3: space group, P21/a;a=13.4404(13) Å,b=10.7494(14) A,c=148967(18) A,β=98.204(9)°,R=0.035, 1983 observed reflections. For compound4: space group,P1;a=9.016(1) Å,b=9.370(1),c=11.334(1) A, α=103.67(1)°,β=100.30(1)°, γ=115.03(1)°, R=0.046, 2026 observed reflections. For compound5a: space group,P1;a=9.2933(11)Å,b=9.7181(3),c=12.2508(15) A, α=89.21(1)°,β=87.61(1)°, γ=86.13(1)°,R=0.038, 2770 observed reflections. For compound6a space groupP1:a=8.7244(9)Å,b=10.9318(6),c=13.2560(13) A, α=87.815(6)°,β=83.655(8)°, γ=82.343(6)°, R=0.030, 3497 observed reflections.

Tetranuclear carbonyls of osmium

Osmium forms more neutral binary carbonyls than any other metal; before 1987, nine were known with one to eight osmium atoms. There were, however, no tetranuclear binary carbonyls of osmium known before this data. This review describes the synthesis of Os4(CO)14 (1), Os4(CO)15 (2) and Os4(CO)16 (3) along with various derivatives of these clusters. Addition of Os(CO)5 to Os3(CO)10(C8H14)2 in hexane affords 2 in good yield. The crystal structure of 2 reveals it to have an unusual planar structure with short (2.775 A) and long (2.998 A) peripheral Os—Os bonds (the hinge Os—Os bond length of 2.948 A is more typical of an Os—Os single bond). The unusual metal—metal bond lengths are rationalized in terms of three-center, two-electron metal—metal bonds so that the short bonds have a bond order of 1.5 and the long bonds an order of 0.5. In this way each osmium atom achieves an 18-electron configuration. Several clusters with essentially the same arrangement of metal atoms have also been synthesized (e.g., Os4(CO)14(PMe3) (4), (η5- C5Me5)IrOs3(CO)12). The variable temperature 13C NMR spectra of 2 and 4 indicate that rapid CO-exchange in the equatorial plane occurs in these compounds. Other 62-electron clusters prepared in this study were Os4(μ-H)(CO)14(SnMe3) (8) and Os4(μ-H)2(CO)13(PMe3) (9); whereas 8 has a planar metal skeleton, 9 adopts the more common butterfly arrangement. For these clusters, the planar configuration is adopted when at least one of the metal atoms in the hinge position has four terminal ligands. Refluxing 2 in hexane yields Os4(CO)14 (1), which as expected from polyhedral skeletal electron pair theory has a tetrahedral metal core. Evidence is presented which indicates that in solution the carbonyl ligands in 1 undergo exchange on the infrared time scale. Treatment of 2 in CH2Cl2 at 0 ° C with CO (1 atm) gives Os4(CO)16 (3) in essentially quantitative yield. The crystal structure of 3 reveals it to have a cyclobutane-like Os4 core; the Os—Os bonds are long and range in length from 2.979 to 3.000 A. In solution at room temperature, 3 readily decomposes to give mainly Os3(CO)12. The much greater stability of the trinuclear cluster suggests that the metal—metal bonding in this cluster should be described in terms of a centrally directed molecular orbital plus edge-bridging molecular orbitals, rather than in terms of two-center, two-electron metal—metal bonds. The structures of Os4(CO)15(L) (L = PF3, PMe3, P(OCH2)3CMe, CNBut) have been determined. Only the PF3 derivative has a puckered square arrangement of metal atoms (with long Os—Os bonds) like 3; the other derivatives have a spiked triangular arrangement of metal atoms. The Os—Os bond lengths in the latter clusters range from 2.849 to 2.938 A. From this study it is concluded that it is the electronic properties of L that dictate which structure a cluster of the type Os4(CO)15(L) adopts. The nonrigid properties of 3 and the Os4(CO)15(L) clusters are also briefly discussed. t001. The neutral binary carbonyls of osmium known before 1987 Formula Structure Ref. Os(CO)5 trigonal bipyramidal (D3h) 1 Os2(CO)9 single carbonyl bridge (C2v)a 2 Os3(CO)12 triangular Os3 (D3h) 3 Os5(CO)16 trigonal bipyramidal Os5 4 Os5(CO)19 “bow-tie” Os5 5 Os6(CO)18 capped trigonal bipyramidal Os6 6 Os6(CO)21 planar, “raft-like” Os6b 7 Os7(CO)21 capped octahedral Os7 9 Os8(CO)23 bicapped octahedral Os8 c a Probable structure. b Probable structure based on the structures of Os6(CO)21-x[P(OMe)3]x (x = 1−4) [18,81]. c B.F.G. Johnson, personal communication.

Trichlorosilyl derivatives of the iron triad carbonyls

Abstract The reaction of cis-Ru(CO)4(SiCl3)(H) and cis-M(CO)4(SiCl3)2 (M = Fe, Ru, Os) with PPh3 indicates the SiCl3 group exhibits a large trans effect when bonded to ruthenium. Further substitution in Ru(CO)3L(SiCl3)2 is influenced by the nature of L and the incoming ligand.

Dissociation and isomerization of (OC)5OsRu(CO)3(SiCl3)(Br), a compound with an osmium—ruthenium donor—acceptor bond

In solution the donor—acceptor complex (OC)5OsRu(CO)3(SiCl3)(Br) (Ia) partially dissociates to Os(CO)5 and [Ru(CO)3(SiCl3)(Br)]2. On further standing in solution Ia isomerizes to (Br)(OC)4OsRu(CO)4(SiCl3).

Preparation and crystal structure of (OC)5OsOs(CO)3(GeCl3)(Cl): a compound with an unsupported, donor–acceptor metal–metal bond

The crystal structure of (OC)5OsOs(CO)3(GeCl3)(Cl)[prepared from Os(CO)5 and GeCl4] reveals that the Os(CO)5 unit acts as a donor ligand towards the second osmium atom via an unsupported, donor–acceptor Os–Os bond.