Co-matrix

Two separate publications (125, 126) described the synthesis of a number of carbonyl complexes of vanadium. The mononuclear species V(CO) , n = 1-6, have all been identified by using CO matrix-dilution experiments and mixed CO- CO isotope experiments while main-... 

When Ag vapor is cocondensed with CO at 10-12 K the compound Ag(CO), is formed as separate molecules in a CO matrix. When this is warmed to 30-37 K for about 1 h dimerization takes place ... 

It has been possible to record the IR and UV spectra of several derivatives of the carbene [75] - tetrachlorocyclopentadienylidene [80], indenylidene [81] and fluorenylidene [82] (Bell and Dunkin, 1985). These carbenes were formed by UV photolysis of the corresponding diazo precursors frozen in inert matrices and have a triplet ground state. The carbenes [80]-[82] react with CO in inert matrices at 30 K, but exhibit a lower reactivity than the carbene [75]. Furthermore, they were stabilized in a pure CO matrix at 12 K, whereas the free carbene [75] could not be detected under these conditions. The different reactivity towards CO between [75] and [80]-[82] may be associated with the different steric shielding of the carbene centres and with the different triplet-singlet gap as well. 

The cellular reaction product consisted of alternating plates of C03W lamellae in a solute-depleted Co matrix (eCo). Ffomogenized ingots were cut into slices 1 mm thick and then heat-treated. Spark erosion was used to trepan 3 mm diameter discs which were then jet electropolished to form thin foils for TEM examination in a Philips EM 430 STEM instrument operating at 300 kV in the nanoprobe mode with a probe size of 5 to 10 nm. 

A report by Ozin et al. in 1977 describes the formation of Ti(CO)6 via matrix cocondensation techniques (11). This green complex, while not isolated, was characterized by its infrared and ultraviolet-visible spectra. In a pure CO matrix, a color change from green to reddish-brown was observed on warming from 10 K to about 40-50 K. The infrared spectrum of the reddish-brown material showed no evidence for coordinated CO, thus suggesting the extreme thermal instability of Ti(CO)6. 

In a CO matrix, therefore, the primary product involves an expanded coordination nunber ("ring-slippage") and it is argued that such a species is consistent with the associative mechanism proposed for room temperature substitution reactions of (13 -05115)Co-... 

G.A. Ozin, University of Toronto In our Cr/CO matrix cocondensation experiments (Angew. Chem., Int. Ed. Eng. 1975, 14, 292), we reported evidence for the facile formation of a binuclear chromium carbonyl complex Cr2(CO)i0 or Cr2 (CCOi x which could be described as square pyramidal Cr(CO)5 weakly interacting with either a Cr(CO)5 or Cr(CO)6 moiety in the vacant (sixth) site. As a result, the infrared spectrum of this "weakly-coupled" binuclear species closely resembled that of the mononuclear fragment Cr(CO)5. I would like to ask you, whether or not you have any evidence for the existence of such a binuclear species in your Cr(CO)6 /Xe cryogenic solutions following various photolysis treatments. 

The thermodynamic parameters for COC1 have been evaluated by Jacox and Milligan134, who identified COC1 by its ir spectrum in an argon or CO matrix at 14 °K. 

The simplest case occurs when the a-phase and /3-phase crystals have different compositions but still match almost exactly in all three dimensions. The critical nucleus can then form with a coherent interface and is therefore of relatively low energy.1 Also, any strain energy will be small. This condition is met during the precipitation of Ag-rich precipitates in a A1 + 4 at. % Ag matrix [8] and Co-rich precipitates in a Cu + 1 at. % Co matrix [9] where the precipitates are coherent and essentially spherical in shape. 

The production of buta-1,3-dienes (37) by reaction of 1,2-diarylcyclopropenes with dihalocarbenes is thought to involve electrophilic attack of the carbene to give a dipolar intermediate (38).51 The addition of carbene to CO and H2C=0 has been studied by MNDO calculations.52 Photolysis of diethyl diazomalonate in a CO matrix at low temperature gave rise to ketenes by immediate trapping of the postulated carbene (39).53 The major products of reaction between dichlorocarbene and cyclone were CO and the gem-dichloro species (40).54 The predominance of this pathway over formation of the dichlorooxirane or the cyclopropane is attributed to the aromatic nature of the carbonyl ylide and its twist geometry. 

Y. Mechref andM. V. Novotny, Matrix-assisted laser desorption ionization mass spectrometry of acidic glycoconjugates facilitated by the use of spermine as a co-matrix,. / Am. Soc. Mass Spectrom., 9 (1998) 1293-1302. 

Now it is possible to consider the mechanism of the molecular elimination process (eq. 23) in light of a new isomeric intermediate, hydroxymethylene (hCoH). In the low-temperature matrix photolysis of formaldehyde at 15 K, three sets of photochemical products were found (1) methanol and CO in solid formaldehyde (2) glycoaldehyde in a dilute Ar matrix and (3) hydroxyketene in a CO matrix (227). These observations were... 

Figure 15 Microstructure of a coarse WC-Co hardmetal with gray WC particles embedded in a Co matrix, the size of the largest grains is about 20 xm...

Prepared from the metal vapor in a CO matrix at about 20 K. 

Matrix-isolation techniques permit the isolation of Pd(CO)4 in a CO matrix. This imstable species exhibits a vco of 2066 cm . The analogous Pt(CO)4 gives vco of2044cm and the vco of Ni(CO)4 is 2037 cm. The increase in vco is further indication that d -p r bonding decreases in the order Ni > Pt > Pd. In general, platinum carbonyls have a lower vco value than isostructural palladium complexes. 

Scheme 1 Photochemistry of CpRe(CO)2(H)2 in Nujol. (i) Photolysis processes in Nujol, 12 K (ii) secondary process in N2 matrix (iii) secondary process in CO matrix, (iv) thermal reversal in Nujol, 298 K. Ref. 114...

The Re(CO)s (3) radical, which may also be generated by several other methods, for example, deposition of Re atoms on a CO matrix at 10 K or Pulse Radiolysis of ReBr(CO)s in ethanol, has the theoretically predicted square-pyramidal structure that is maintained in solution at room temperature. Reactions where (3) may play a crucial role after photochemical generation from (1) include halogen abstraction, disproportionation, and electron transfer to an electron acceptor (EA) (Scheme 2). 

Photolysis of Fe(CO)3[(CH=NR)2] (19 R = cyclohexyl) in an Ar or CO matrix is reported to induce the l,4-diazabuta-l,3-diene ligand to change from a,a-N,N - to ir,ir-co-ordination. Steric effects of the N-substituents appear to be important and [19 R=CMej or CH(CHMe2)2], which have more-bulky N-substituents, show only weak i.r. bands due to it,it-co-ordination complexes. This is the first evidence for this type of transformation. ... 

On the calculation of long-range coulombic contributions to the direct space LCAO CO matrix elements of model polymers. They applied the FSGO model for an infinite chain of LiH molecules. 

In this context, it is noteworthy that the IR spectrum of bridge-bonded Rhjj(CO)g [generated from Rh(CO)4 matrix-dimerization reactions and Rh/CO matrix-concentration studies (753)] shows bands in the terminal region at 2060, 2043, and 2038 cm , and in the bridge region at 1852 and 1830 cm , that are very close to the proposed, terminal-bridged, chemisorbed, CO species on clean Rh films and supported Rh clusters (4,34, 50,162) (see Table X). Moreover, the matrix, Vqq frequency observed for RhCO (2013 cm ) (154) falls between the vco values for the proposed terminal and bridge sites of chemisorbed CO on... 

Photolysis of (n -diene)Cr(CO) (diene - butadiene, trans, frans-hexa-2,4-diene, 2,3-dimethylbutadiene) in a matrix leads to loss of CO auid reaction of the resulting complex with to give (Ti -diene)Cr(C0),(N2). In a CO matrix there is stepwise displacement of the diene ligemd to give (n -cliene)Cr(CO) and... 

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