Remarkable aspects of unsaturation in trinuclear metal carbonyl clusters: the triiron species Fe3(CO)n (n = 12, 11, 10, 9)

The trinuclear iron carbonyls Fe(3)(CO)(n) (n = 12, 11, 10, 9) have been studied by density functional theory using the B3LYP and BP86 functionals. The experimentally known C(2)(v) isomer of Fe(3)(CO)(12), namely Fe(3)(CO)(10)(mu-CO)(2), is found to be the global minimum below the unbridged D(3)(h) isomer analogous to the known structures for Ru(3)(CO)(12) and Os(3)(CO)(12). The lowest-energy isomer found for Fe(3)(CO)(11) is Fe(3)(CO)(9)(mu(3)-CO)(2) with iron-iron distances in the Fe(3) triangle, suggesting the one double bond (2.460 A by B3LYP and 2.450 A by BP86) and two single bonds (2.623 A by B3LYP and 2.604 A by BP86) required to give each Fe atom the favored 18-electron configuration. Two different higher-energy dibridged structures Fe(3)(CO)(9)(mu(2)-CO)(2) are also found for Fe(3)(CO)(11). The lowest-energy isomer found for Fe(3)(CO)(10) is Fe(3)(CO)(9)(mu(3)-CO) with equivalent iron-iron distances in the Fe(3) ring (2.47 A by B3LYP or BP86). The lowest-energy isomer found for Fe(3)(CO)(9) is Fe(3)(CO)(6)(mu-CO)(3) with distances in the Fe(3) triangle possibly suggesting one single bond (2.618 A by B3LYP and 2.601 A by BP86), one weak double bond (2.491 A by B3LYP and 2.473 A by BP86), and one weak triple bond (2.368 A by B3LYP and 2.343 A by BP86). A higher-lying isomer of Fe(3)(CO)(9), i.e., Fe(3)(CO)(8)(mu-CO), at approximately 21 kcal/mol above the global minimum, has iron-iron distances strongly suggesting two single bonds (2.6 to 2.7 A) and one quadruple bond (2.068 A by B3LYP and 2.103 A by BP86). Wiberg Bond Indices are also helpful in evaluating the iron-iron bond orders.     

Binuclear homoleptic manganese carbonyls: Mn2(CO)x (x = 10, 9, 8, 7)

The unsaturated homoleptic manganese carbonyls Mn(2)(CO)(n)() (n = 7, 8, 9) are characterized by their equilibrium geometries, thermochemistry, and vibrational frequencies using methods from density functional theory (DFT). The computed metal-metal distances for global minima range from 3.01 A for the unbridged Mn(2)(CO)(10) with a Mn-Mn single bond to 2.14 A for a monobridged Mn(2)(CO)(7) formulated with a metal-metal quadruple bond. The global minimum for Mn(2)(CO)(9) has a four-electron bridging mu-eta(2)-CO group and a 2.96 A Mn-Mn distance suggestive of the single bond required for 18-electron configurations for both metal atoms. This structure is closely related to an experimentally realized structure for the isolated and structurally characterized stable phosphine complex [R(2)PCH(2)PR(2)](2)Mn(2)(CO)(4)(mu-eta(2)-CO). An unbridged (OC)(4)Mn-Mn(CO)(5) structure for Mn(2)(CO)(9) has only slightly (<6 kcal/mol) higher energy with a somewhat shorter metal-metal distance of 2.77 A. For Mn(2)(CO)(8) the lowest energy structure is a D(2)(d)() unbridged structure with a 2.36 A metal-metal distance suggesting the triple bond required for the favored 18-electron configuration for both metal atoms. However, the unbridged unsymmetrical (CO)(3)Mn-Mn(CO)(5) structure with a metal-metal bond distance of 2.40 A lies only 1 to 3 kcal/mol above this global minimum. The lowest energy structure of Mn(2)(CO)(7) is an unbridged C(s)() structure with a short metal-metal distance of 2.26 A. This is followed energetically by another C(s)() unbridged Mn(2)(CO)(7) structure with a somewhat longer metal-metal distance of 2.38 A.     

单、双核钌羰基化合物Ru（CO）n（n=5，4，3）和Ru2（CO）n（n=9，8）的理论研究

采用两种密度泛函方法对中性单核Ru（CO）n（n=5,4,3）和双核Ru2（CO）n（n=9,8）化合物进行理论计算,优化出16个稳定异构体．研究发现,和Os（CO）5类似,Ru（CO）5存在两个能量接近的最低异构体．Ru（CO）4的能量最低异构体为C2v对称性的单态构型．Ru（CO）3能量最低异构体为G对称性的单态构型．Ru2（c0）。的两个能量接近的最低异构体分别含有单个桥羰基和3个桥羰基．双核不饱和Ru2（CO）8的能量最低异构体为含有两个桥羰基的单态Q构型．通过比较M2（CO）n（M=Fe,Ru,Os;n=9,8）的能量最低构型,发现Fe和Ru倾向于形成含有多个桥配位羰基的构型,而Os则更倾向于形成不含桥配位羰基的构型．对离解能的研究表明,和失去一个羰基生成Ru2（CO）8相比,Ru2（CO）9更容易离解为Ru（CO）5和Ru（CO）4．     

Activation of two C-H bonds of NHC N-methyl groups on triosmium and triruthenium carbonyl clusters

The thermolysis of the NHC triosmium cluster [Os3(Me2Im)(CO)11] (1a; Me2Im = 1,3-dimethylimidazol-2-ylidene) in toluene at reflux temperature sequentially affords the edge-bridged cluster [Os3(micro-H)(micro-kappa2-MeImCH2)(CO)10] () and the face-capped derivative [Os3(micro-H)2(micro3-kappa2-MeImCH)(CO)9] (3a). These products result from the sequential oxidative addition of one (2a) and two (3a) N-methyl C-H bonds of the original NHC ligand. The related face-capped triruthenium cluster [Ru3(micro-H)2(micro3-kappa2-MeImCH)(CO)9] (3b) has been prepared by heating the NHC triruthenium cluster [Ru3(Me2Im)(CO)11] (1b) in THF at reflux temperature. In this case, the pentanuclear derivatives [Ru5(Me2Im)(micro4-kappa2-CO)(CO)14] (4b) and [Ru5(Me2Im)2(micro4-kappa2-CO)(CO)13] (5b) are minor reaction products, but a ruthenium cluster analogous to has not been obtained. The face-capped oxazole-derived NHC triruthenium cluster [Ru3(micro-H)2(micro3-kappa2-OxCH)(CO)9] (3c; MeOx = N-methyloxazol-2-ylidene) is the only isolated product of the thermolysis of [Ru3(MeOx)(CO)11] (1c) in THF at reflux temperature.     

Manganese carbonyl nitrosyls: comparison with isoelectronic iron carbonyl derivatives

The manganese carbonyl nitrosyls Mn(NO)(CO)4, Mn2(NO)2(CO)n (n = 7, 6, 5, 4), and Mn3(NO)3(CO)9 have been studied by density functional theory (DFT) using the B3LYP and BP86 methods for comparison of their predicted structures with those of isoelectronic iron carbonyl derivatives. DFT predicts a trigonal bipyramidal structure for Mn(NO)(CO)4 with an equatorial NO group very close to the experimental structure. The predicted lowest energy structure for Mn2(NO)2(CO)7 has two bridging NO groups in contrast to the known structure of the isoelectronic Fe2(CO)9, which has three bridging CO groups. The structures for the unsaturated binuclear Mn2(NO)2(CO)n (n = 6, 5, 4) derivatives are similar to those of the corresponding binuclear iron carbonyls Fe2(CO)n+2 derivatives but always with a preference of bridging NO groups over bridging CO groups. The trinuclear Mn3(NO)3(CO)9 is predicted to have a structure analogous to the known structure for Fe3(CO)12 but with two bridging NO groups rather than two bridging CO groups across one of the metal-metal edges of the M3 triangle. The dark red solid photolysis product of Mn(NO)(CO)4 characterized by its nu(CO) and nu(NO) frequencies approximately 45 years ago is suggested by these DFT studies not to be the originally assumed Mn2(NO)2(CO)7 analogous to Fe2(CO)9. Instead, this photolysis product appears to be Mn2(NO)2(CO)5 with a Mn(triple bond)Mn formal triple bond analogous to (eta5-C5H5)2V2(CO)5 obtained from the photolysis of (eta5-C5H5)V(CO)4.     

Multiple additions of phenylgermanium ligands to tetraruthenium and tetraosmium carbonyl cluster complexes

Three new compounds, Ru4(mu4-GePh)2(mu-GePh2)2(mu-CO)2(CO)8 (11), Ru4(mu4-GePh)2(mu-GePh2)3(mu-CO)(CO)8 (12), and Ru4(mu4-GePh)2(mu-GePh2)4(CO)8 (13), were obtained from the reaction of H(4)Ru(4)(CO)12 with excess Ph(3)GeH in octane (11 and 12) or decane (13) reflux. Compound 11 was converted to compound 13 by reaction with Ph(3)GeH by heating solutions in nonane solvent to reflux. Compounds 11-13 each contain a square-type arrangement of four Ru atoms capped on each side by a quadruply bridging GePh ligand to form an octahedral geometry for the Ru(4)Ge(2) group. Compound 11 also contains two edge-bridging GePh(2) groups on opposite sides of the cluster and two bridging carbonyl ligands. Compound 12 contains three edge-bridging GePh(2) groups and one bridging carbonyl ligand. Compound 13 contains four bridging GePh(2) groups, one on each edge of the Ru4 square. The reaction of H(4)Os(4)(CO)12 with excess Ph(3)GeH in decane at reflux yielded two new tetraosmium cluster complexes, Os4(mu4-GePh)2(mu-GePh2)3(mu-CO)(CO)8 (14) and Os4(mu4-GePh)2(mu-GePh(2))4(CO)8 (15). These compounds are structurally similar to compounds 12 and 13, respectively.     

Unsaturation and variable hapticity in binuclear azulene manganese carbonyl complexes

Azulene is reported to react with Mn(2)(CO)(10) to give trans-C(10)H(8)Mn(2)(CO)(6), which has been shown by X-ray crystallography to have a bis(pentahapto) structure with no metal-metal bond. This structure is found by density functional theory to be the lowest energy C(10)H(8)Mn(2)(CO)(6) structure. However, a corresponding bis(pentahapto) cis-C(10)H(8)Mn(2)(CO)(6) structure, also without an Mn···Mn bond, lies within ~1 kcal mol(-1) of this global minimum. The lowest energy C(10)H(8)Mn(2)(CO)(5) structure is singlet cis-η(5),η(5)-C(10)H(8)Mn(2)(CO)(5) with an Mn→Mn dative bond from the Mn(CO)(3) group to the Mn(CO)(2) group. However, a singlet cis-η(6),η(4)-C(10)H(8)Mn(2)(CO)(5) structure with a normal Mn-Mn single bond lies within ~6 kcal mol(-1) of this global minimum. The lowest energy structures of the more highly unsaturated C(10)H(8)Mn(2)(CO)(n) (n = 4, 3, 2) systems all have cis geometries and manganese-manganese bonds of various orders. The corresponding global minima are triplet cis-η(5),η(3)-C(10)H(8)Mn(2)(CO)(3)(η(2)-μ-CO) for the tetracarbonyl with a four-electron donor bridging carbonyl group, singlet cis-η(5),η(5)-C(10)H(8)Mn(2)(CO)(3) for the tricarbonyl, and triplet cis-η(6),η(4)-C(10)H(8)Mn(2)(CO)(η(2)-μ-CO) for the dicarbonyl.     

Boronyl ligand as a member of the isoelectronic series BO(-) → CO → NO(+): viable cobalt carbonyl boronyl derivatives?

Recently the first boronyl (oxoboryl) complex [(c-C(6)H(11))(3)P](2)Pt(BO)Br was synthesized. The boronyl ligand in this complex is a member of the isoelectronic series BO(-) → CO → NO(+). The cobalt carbonyl boronyls Co(BO)(CO)(4) and Co(2)(BO)(2)(CO)(7), with cobalt in the formal d(8) +1 oxidation state, are thus isoelectronic with the familiar homoleptic iron carbonyls Fe(CO)(5) and Fe(2)(CO)(9). Density functional theory predicts Co(BO)(CO)(4) to have a trigonal bipyramidal structure with the BO group in an axial position. The tricarbonyl Co(BO)(CO)(3) is predicted to have a distorted square planar structure, similar to those of other 16-electron complexes of d(8) transition metals. Higher energy Co(BO)(CO)(n) (n = 3, 2) structures may be derived by removal of one (for n = 3) or two (for n = 2) CO groups from a trigonal bipyramidal Co(BO)(CO)(4) structure. Structures with a CO group bridging 17-electron Co(CO)(4) and Co(BO)(2)(CO)(3) units and no Co-Co bond are found for Co(2)(BO)(2)(CO)(8). However, Co(2)(BO)(2)(CO)(8) is not viable because of the predicted exothermic loss of CO to give Co(2)(BO)(2)(CO)(7). The lowest lying Co(2)(BO)(2)(CO)(7) structure is a triply bridged (2BO + CO) structure closely related to the experimental Fe(2)(CO)(9) structure. However, other relatively low energy Co(2)(BO)(2)(CO)(7) structures are found, either with a single CO bridge, similar to the experimental Os(2)(CO)(8)(μ-CO) structure; or with 17-electron Co(CO)(4) and Co(BO)(2)(CO)(3) units joined by a single Co-Co bond with or without semibridging carbonyl groups. Both triplet and singlet Co(2)(BO)(2)(CO)(6) structures are found. The lowest lying triplet Co(2)(BO)(2)(CO)(6) structures have a Co(CO)(3)(BO)(2) unit coordinated to a Co(CO)(3) unit through the oxygen atoms of the boronyl groups with a non-bonding ～4.3 ? Co···Co distance. The lowest lying singlet Co(2)(BO)(2)(CO)(6) structures have either two three-electron donor bridging η(2)-μ-BO groups and no Co···Co bond or one such three-electron donor BO group and a formal Co-Co single bond.     

Novel rhodium and ruthenium carbonyl cluster complexes with face- and edge-bridging GaCp* ligands. Synthesis and structural characterization of the Rh6(CO)12(mu3-GaCp*)4 and Ru6(eta6-C)(mu2-CO)(CO)13(mu3-GaCp*)2(mu2-GaCp*) clusters

Reactions of hexanuclear carbonyl clusters of rhodium Rh(6)(CO)(16) and ruthenium Ru(6)(eta(6)-C)(micro(2)-CO)(CO)(16) with GaCp*(Cp*= C(5)Me(5)) in the mild conditions result in substitution of CO ligands and formation of the Rh(6)(CO)(12)(micro(3)-GaCp*)(4) and the Ru(6)(eta(6)-C)(micro(2)-CO)(CO)(13)(micro(3)-GaCp*)(2)(micro(2)-GaCp*) cluster derivatives.     

Chromium carbonyl nitrosyls: comparison with isoelectronic manganese carbonyl derivatives

Density functional methods indicate that the global minimum for Cr2(NO)2(CO)8 is a staggered D4d structure in accord with experiment and analogous to the isoelectronic Mn2(CO)10. For the unsaturated Cr2(NO)2(CO)n derivatives the lowest energy structures are very different from the lowest energy structures for the isoelectronic Mn2(CO)n+2 derivatives. Thus the global minimum for Cr2(NO)2(CO)7 is an unbridged structure with a Cr(NO)(CO)4 fragment linked to a Cr(NO)(CO)3 fragment through a Cr=Cr double bond. For Cr2(NO)2(CO)6 the global minimum is a structure with two bridging CO groups, whereas the global minimum for Mn2(CO)8 is an unbridged structure. For Cr2(NO)2(CO)5 both NO groups are bridging NO groups with one of them having a short enough Cr-O distance to be considered a formal five-electron donor eta2-mu-NO group. Thus the isoelectronic substitution of NO for CO with a necessary adjustment in the central metal atom can lead to significant shifts in the relative energies of various structural types of metal carbonyl nitrosyls, particularly for unsaturated molecules. For the mononuclear Cr(NO)2(CO)3 the theoretical structure differs from that deduced from matrix isolation experiments. Moreover, the nu(CO) and nu(NO) vibrational frequencies predicted here for Cr(NO)2(CO)3 correspond more closely with the unassigned species labeled "Cr(NO)(CO)x" in the experiments rather than the species claimed to be Cr(NO)2(CO)3.     

Platinum-rhodium carbonyl clusters: new structures and new types of dynamical activity

The reaction of Rh(4)(CO)(12) with Pt(PBu(t)(3))(2) in CH(2)Cl(2) at room temperature yielded three new complexes: Rh(4)(CO)(4)-(mu-CO)(4)(mu(4)-CO)(PBu(t)(3))(2)[Pt(PBu(t)(3))], 10, Rh(2)(CO)(8)[Pt(PBu(t)(3))](2)[Pt(CO)], 11, and Rh(2)(CO)(8)[Pt(PBu(t)(3))](3), 12. The reaction of Rh(4)(CO)(12) with an excess of Pt(PBu(t)(3))(2) in hexane at 68 degrees C yielded the new hexarhodium-tetraplatinum compound, Rh(6)(CO)(16)[Pt(PBu(t)(3))](4), 13, in a low yield. All four compounds were characterized by (31)P NMR and single-crystal X-ray diffraction analyses. Compound 10 contains an unsymmetrical quadruply bridging carbonyl ligand in the fold of a butterfly tetrahedral cluster of four rhodium atoms with a Pt(PBu(t)(3)) group bridging the hinge of the butterfly tetrahedron. Compound 11 contains an unsaturated trigonal bipyramidal Rh(2)Pt(3) cluster. Compound 12 is similar to 11 except the trigonal bipyramidal Rh(2)Pt(3) cluster opened by cleavage of one Pt-Rh bond due to steric interactions produced by the replacement of one of the carbonyl ligands in 11 with a tri-tert-butylphosphine ligand. Compound 12 undergoes facile dynamical rearrangements of the metal atoms in the cluster which average the three inequivalent phosphine ligands on the platinum atoms. Compound 13 contains an octahedral cluster of six rhodium atoms with four Pt(PBu(t)(3)) groups bridging edges of that octahedron.     

Homoleptic tetranuclear osmium carbonyls: from the rhombus via the butterfly to the tetrahedron

The structures of the tetranuclear osmium carbonyl derivatives Os4(CO)n (n = 16, 15, 14, 13, 12) have been investigated using the density functional theory method MPW1PW91 with the SDD effective core potential basis set, found to be effective in previous work for the study of Os3(CO)12. The Os4 clusters in the lowest energy structures for Os4(CO)16, Os4(CO)15, and Os4(CO)14 are found to be rhombi, butterflies, and tetrahedra with four, five, and six Os-Os bonds, respectively, in accord with structures determined by X-ray diffraction as well as the 18-electron rule. The fluxionality of tetrahedral Os4(CO)14, suggested by experimental work of Johnston, Einstein, and Pomeroy, is confirmed by our DFT studies, which find four Os4(CO)14 structures within 1.5 kcal mol-1 of each other with similar tetrahedral Os4 frameworks but with different arrangements of bridging and semibridging carbonyl groups. The lowest energy structures for the more unsaturated Os4(CO)13 and Os4(CO)12 are also based on Os4 tetrahedra but with shorter Os-Os edge lengths than in Os4(CO)14 suggesting delocalized multiple bonding in the more highly unsaturated systems. Thus the global minimum for Os4(CO)12 is predicted to have tetrahedral symmetry, with all terminal carbonyl groups analogous to the experimentally known structure of (mu3-H)4Re3(CO)12, but without the face-bridging hydrogen atoms.     

Binuclear iron carbonyl nitrosyls: bridging nitrosyls versus bridging carbonyls

The iron carbonyl nitrosyls Fe 2(NO) 2(CO) n ( n = 7, 6, 5, 4, 3) have been studied by density functional theory (DFT) using the B3LYP and BP86 methods, for comparison of their predicted structures with those of isoelectronic cobalt carbonyl derivatives. The lowest energy structures for Fe 2(NO) 2(CO) 7 and Fe 2(NO) 2(CO) 6 have two NO bridges, and the lowest energy structure for Fe 2(NO) 2(CO) 5 has a single NO bridge with metal-metal distances (BP86) of 3.161, 2.598, and 2.426 A, respectively, corresponding to the formal metal-metal bond orders of zero, one, and two, respectively, required for the favored 18-electron configuration for the iron atoms. The heptacarbonyl Fe 2(NO) 2(CO) 7 is thermodynamically unstable with respect to CO loss to give Fe 2(NO) 2(CO) 6. The favored structures for the more highly unsaturated Fe 2(NO) 2(CO) 4 and Fe 2(NO) 2(CO) 3 also have bridging NO groups but avoid iron-iron bond orders higher than two by formal donation of five electrons from bridging NO groups with relatively short Fe-O distances. The lowest energy structures of the unsaturated Fe 2(NO) 2(CO) n derivatives ( n = 5, 4, 3) are significantly different from the isoelectronic cobalt carbonyls Co 2(CO) n +2 owing to the tendency for Fe 2(NO) 2(CO) n to form structures with bridging NO groups and metal-metal formal bond orders no higher than two.     

Bonding and redox properties of [Os(3)(CO)(9)(tmbp)(L)] (tmbp=4,4',5,5'-tetramethyl-2,2'-biphosphinine; L=CO, PPh(3)) clusters with an unprecedented electron-deficient metallic core and doubly bridging biphosphinine dianion

Herein we describe in detail the bonding properties and electrochemical behavior of the first known triosmium carbonyl clusters with a coordinated redox-active ligand 4,4',5,5'-tetramethyl-2,2'-biphosphinine (tmbp), the phosphorus derivative of 2,2'-bipyridine. The clusters investigated were [Os(3)(CO)(10)(tmbp)] (1) and its derivative [Os(3)(CO)(9)(PPh(3))(tmbp)] (2). The crystal structures of both clusters are compared with those of relevant compounds; they served as the basis for density functional theory (DFT and time-dependent DFT) calculations. The experimental and theoretical data reveal an unexpected and unprecedented bridging coordination mode of tmbp, with each P atom bridging two metal atoms. The tmbp ligand is formally reduced by transfer of two electrons from the triangular cluster core that consequently lacks one of the metal-metal bonds. Both 1 and 2 therefore represent 50e(-) clusters with a coordinated 8e(-) donor, [tmbp](2-). The HOMO and LUMO of 1 and 2 possess a predominant contribution from different pi*(tmbp) orbitals, implying that the lowest energy excited state possesses a significant intraligand character. This is in agreement with the photostability of these clusters. DFT calculations also predict the experimentally observed structure of 1 to be the most stable one in a series of several plausible structural isomers. Stepwise two-electron electrochemical reduction of 1 and 2 results in dissociation of CO and PPh(3), respectively, and formation of the [Os(3)(CO)(9)(tmbp)](2-) ion. The initially produced radical anions of the parent clusters, in which the odd electron is predominantly localized on the tmbp ligand, are sufficiently stable at low temperatures and can be observed with IR spectroelectrochemistry. The electron-deficiency of the cluster core in 1 permits facile electrocatalytic substitution of a CO ligand by tertiary phosphane and phosphite donors.     

Rhodium cluster complexes containing bridging phenylgermanium ligands

The reaction of Rh(4)(CO)(12) with Ph(3)GeH at 97 degrees C has yielded the first rhodium cluster complexes containing bridging germylene and germylyne ligands: Rh(8)(CO)(12)(mu(4)-GePh)(6), 9, and Rh(3)(CO)(5)(GePh(3))(mu-GePh(2))(3)(mu(3)-GePh)(mu-H), 10. When the reaction is performed under hydrogen, the yield of 9 is increased to 42% and no 10 is formed. Compound 9 contains a cluster of eight rhodium atoms arranged in the form of a distorted cube. There are six mu(4)-GePh groups bridging each face of this distorted cube. Four of the rhodium atoms have two terminal carbonyl ligands, while the remaining four rhodium atoms have only one carbonyl ligand. Compound 10 contains a triangular cluster of three rhodium atoms with one terminal GePh(3) ligand, three bridging GePh(2) ligands, and one triply bridging GePh ligand. There is also one hydrido ligand that is believed to bridge one of the Rh-Ge bonds. Compound 9 reacted with PPhMe(2) at 25 degrees C to give the tetraphosphine derivative Rh(8)(CO)(8)(PPhMe(2))(4)(mu(4)-GePh)(6), 11. The structure of 11 is similar to 9 except that a PPhMe(2) ligand has replaced a carbonyl ligand on each the four Rh(CO)(2) groups. Compound 10 reacted with CO at 68 degrees C to give the complex Rh(3)(CO)(6)(mu-GePh(2))(3)(mu(3)-GePh), 12. Compound 12 is formed by the loss of the hydrido ligand and the terminal GePh(3) ligand from 10 and the addition of one carbonyl ligand. All compounds were fully characterized by IR, NMR, elemental, and single-crystal X-ray diffraction analyses.     

Structures and Mössbauer spectra of phosphido-bridged heterobimetallic complexes CpFe(CO)2(μ-PPh2)W(CO)5 and CpFe(CO)(μ-CO)(μ-PPh2)W(CO)4

Structures of non metal-metal bonded phosphido-bridged heterobimetallic complexes, including CpFe(CO)₂(μ-PPh₂)W(CO)₅ (1-W) and metal-metal bonded CpFe(CO)(μ-CO)(μ-PPh₂)W(CO)₄ (2), were determined by a single crystal X-ray diffraction study. In 1-W, the long distance between Fe and W indicates no metal-metal bond to exist. In 2, a Fe---W bond with bond length 2.851 Å and a semibridging carbonyl with W---C---O angle 153° were observed. Mössbauer spectra of 1-W and 2 were taken at 77 K. Isomer shifts of 1-W and 2 were − 0.0203 mm s⁻¹ and 0. 1917 mm s⁻¹ respectively.     

Theoretical study on homoleptic mononuclear and binuclear ruthenium carbonyls Ru(CO)n (n= 3–5) and Ru2(CO)n (n = 8, 9)

Homoleptic mononuclear and binuclear ruthenium carbonyls Ru(CO) _n (n = 3–5) and Ru₂(CO) _n (n = 8,9) have been investigated using density functional theory. Sixteen isomers are obtained. For Ru(CO)₅, the lowest-energy structure is the singlet D _3h trigonal bipyramid. Similar to Os(CO)₅, the distorted square pyramid isomer with C _2v symmetry lies ∼7 kJ·mol⁻¹ higher in energy. For the unsaturated mononuclear ruthenium carbonyls Ru(CO)₄ and Ru(CO)₃, a singlet structure with C _2v symmetry and a C _s bent T-shaped structure are the lowest-energy structures, respectively. The global minimum for the Ru₂(CO)₉ is a singly bridged (CO)₄Ru(μ-CO)Ru(CO)₄ structure. A triply bridged Ru₂(CO)₆(μ-CO)₃ structure analogous to the known Fe₂(CO)₉ structure is predicted to lie very close in energy to the global minimum. For Ru₂(CO)₈, the doubly bridged C ₂ structure is predicted to be the global minimum. For the lowest-energy structures of M₂(CO) _n (M = Fe, Ru, Os, n = 9,8), it is found that both iron and ruthenium are favored to form structures containing more bridging carbonyl groups, while osmium prefers to have structures with less bridging carbonyl groups. The study of dissociation energy shows that the dissociation of Ru₂(CO)₉ into the mononuclear fragments Ru(CO)₅ + Ru(CO)₄ is a less energetically demanding process than the dissociation of one carbonyl group from Ru₂(CO)₉ to give Ru₂(CO)₈.     

Platinum-osmium cluster complexes from the addition of Pt(PBut3) groups to Os3(CO)12

Three new compounds, PtOs(3)(CO)(12)(PBu(t)(3)) (10), Pt(2)Os(3)(CO)(12)(PBu(t)(3))(2) (11), and Pt(3)Os(3)(CO)(12)(PBu(t)(3))(3) (12), have been obtained from the reaction of Pt(PBu(t)(3))(2) with Os(3)(CO)(12) (9). The products were formed by the sequential addition of 1-3 Pt(PBu(t)(3)) groups to the three Os-Os bonds of the metal cluster of Os(3)(CO)(12). In solution, compounds 10-12 interconvert among themselves by intermolecular exchange of the Pt(PBu(t)(3)) groups. When 11 is treated with PPh(3), the mono- and bis(PPh(3)) derivatives of 9, Os(3)(CO)(11)(PPh(3)) and Os(3)(CO)(10)(PPh(3))(2), were obtained by elimination of the Pt(PBu(t)(3)) groups together with one and two CO ligands, respectively. When heated, compound 11 was transformed into the new compound Pt(2)Os(3)(CO)(10)(PBu(t)(3))(PBu(t)(2)CMe(2)CH(2))(mu-H) (13) by the loss of two CO ligands and a metalation of one of the methyl groups of one of the PBu(t)(3) ligands. Compounds 10-13 have been characterized by single-crystal X-ray diffraction analyses.     

Binuclear manganese and rhenium carbonyls M2(CO)n (n = 10, 9, 8, 7): comparison of first row and third row transition metal carbonyl structures

The equilibrium geometries, thermochemistry, and vibrational frequencies of the homoleptic binuclear rhenium carbonyls Re2(CO)n (n = 10, 9, 8, 7) were determined using the MPW1PW91 and BP86 methods from density functional theory (DFT) with the effective core potential basis sets LANL2DZ and SDD. In all cases triplet structures for Re2(CO)n were found to be unfavorable energetically relative to singlet structures, in contrast to corresponding Mn2(CO)n derivatives, apparently owing to the larger ligand field splitting of rhenium. For M2(CO)10 (M = Mn, Re) the unbridged structures (OC)5M-M(CO)5 are preferred energetically over structures with bridging CO groups. For M2(CO)9 (M = Mn, Re) the two low energy structures are (OC)4M(micro-CO)M(CO)4 with an M-M single bond and a four-electron donor bridging CO group and (OC)4M[double bond, length as m-dash]M(CO)5 with no bridging CO groups and an M[double bond, length as m-dash]M distance suggesting a double bond. The lowest energy structures for Re2(CO)8 have Re[triple bond, length as m-dash]Re distances in the range 2.6-2.7 A suggesting the triple bonds required to give the Re atoms the favored 18-electron configuration. Low energy structures for Re2(CO)7 are either of the type (OC)(4)M[triple bond, length as m-dash]M(CO)3 with short metal-metal distances suggesting triple bonds or have a single four-electron donor bridging CO group and longer M-M distances consistent with single or double bonds. The 18-electron rule thus appears to be violated in these highly unsaturated Re2(CO)7 structures.     

Versatile behavior of the fluorophosphinidene ligand in iron carbonyl chemistry

Fluorophosphinidene (PF) is a versatile ligand found experimentally in the transient species M(CO)(5)(PF) (M = Cr, Mo) as well as the stable cluster Ru(5)(CO)(15)(μ(4)-PF). The PF ligand can function as either a bent two-electron donor or a linear four-electron donor with the former being more common. The mononuclear tetracarbonyl Fe(PF)(CO)(4) is predicted to have a trigonal bipyramidal structure analogous to Fe(CO)(5) but with a bent PF ligand replacing one of the equatorial CO groups. The tricarbonyl Fe(PF)(CO)(3) is predicted to have two low-energy singlet structures, namely, one with a bent PF ligand and a 16-electron iron configuration and the other with a linear PF ligand and the favored 18-electron iron configuration. Low-energy structures of the dicarbonyl Fe(PF)(CO)(2) have bent PF ligands and triplet spin multiplicities. The lowest energy structures of the binuclear Fe(2)(PF)(CO)(8) and Fe(2)(PF)(2)(CO)(7) derivatives are triply bridged structures analogous to the experimental structure of the analogous Fe(2)(CO)(9). The three bridges in each Fe(2)(PF)(CO)(8) and Fe(2)(PF)(2)(CO)(7) structure include all of the PF ligands. Other types of low-energy Fe(2)(PF)(2)(CO)(7) structures include the phosphorus-bridging carbonyl structure (FP)(2)COFe(2)(CO)(6), lying only ~2 kcal/mol above the global minimum, as well as an Fe(2)(CO)(7)(μ-P(2)F(2)) structure in which the two PF groups have coupled to form a difluorodiphosphene ligand unsymmetrically bridging the central Fe(2) unit.