Ligand lability studies in bridging hydride complexes of Group 6B metal carbonylates

Anionic Group 6B metal carbonyls as homogeneous catalysts for carbon dioxide/hydrogen activation. The production of alkyl formates

“…to 2.4), with formation of bis phosphine derivatives of tungsten being observed. 30 When reaction 3 was carried out with use of ethanol as solvent the results obtained were totally consistent with those observed in methanol; however, the catalytic activity for ethyl formate production was significantly diminished over that for methyl formate production (Table II). This reduction in catalytic activity is likely due to the better coordinating ability of ethanol which would be expected to inhibit addition of dihydrogen to the unsaturated metal species.…”

Structural and chemical characterization of a phosphine bound M-H-M bridged carbonylate: Et4N+(.mu.-H)[Mo2(CO)9PPh3]-

“…There is no intermolecular separation involving the bridging hydride that is less than 3.75 A. The seven closest contacts of anion and cation are defined by the ethyl carbon-carbonyl oxygen distances and are as follows: C(29)---0(3), 3.377 (9); C(29)---0(4), 3.394 (10); C(29)---0(7), 3.530 (9); C(31)---0(2'), 3.354 (11); C(31)---0(4), 3.644 (12); C(33)---0(5"), 3.494 (10); C(35)---0(1"), 3.642 (11) A. 27 A combination of features, the asymmetric hydride and the substituent basic PPh3 ligand, leads to an interesting structural effect.…”

“…Refinement of the positional and thermal parameters of the C(7)-Mo(2)-H( 16) 104 (1) C( 16)-P-Mo(2) 118. 3 (2) C(8)-Mo(2)-H( 16) 168 (1) C( 22)-P-Mo (2) 114.5 (2) C(9)-Mo(2)-H( 16)…”

“…For the reaction of Et4N+-(µ-) [Mo(CO)5]2~w ith PPh3 in THF, an intermediate, Et4N+^-H)[Mo2(CO)9PPh3]-(1), was isolated prior to 0002-7863/79/1501 -2631 $01.00/0 dimer disruption and was tentatively identified as an equatorially substituted Mo dimer. 3 Subsequent work has intimated that the effects of M-M interaction in these bridged hydride-dinuclear carbonylates make tenuous the local symmetry approximation used in the KCO) infrared-based structure assignment.4 An X-ray crystal structure determination was initiated to ascertain the geometry of the substituted anion as well as the details of structural modification on substitution of CO by the relatively enormous PPh3 ligand. The refined structure of 1 (including the hydride position), the kinetic determination of the Mo-P bond strength in 1, and the use of 1 as a precursor to other substituted dinuclear hydrides are reported here.…”

Influence of Sulfur Metalation on the Accessibility of the NiII/I Couple in [N,N‘-Bis(2-mercaptoethyl)-1,5-diazacyclooctanato]nickel(II): Insight into the Redox Properties of [NiFe]-Hydrogenase

“…Thus a question arises in references to the likelihood and the source of a hydride in the oxidized form of the enzyme. Certainly there are examples of air-stable hydrides, especially when stabilized in a bridging environment . Hence, the prospects of a Ni III −H−Fe state, derived by protonation of a bimetallic Ni−C (Ni I ) as expressed above, or by heterolytic cleavage of H 2 from a Ni III ···η 2 H 2 ·Fe interaction are also worthy modeling problems.…”