Photolysis carbonyl complexes

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. 

Donor-substituted alkynes can insert into the C-M double bond of alkoxycarbene complexes, yielding donor-substituted vinylcarbene complexes [191,192]. In addition to this, photolysis or thermolysis of a-alkoxycyclopropyl carbonyl complexes or a-alkoxycyclobutanoyl complexes can lead to rearrangement to metallacyclic carbene complexes (Table 2.11). This methodology has not been used as extensively for the preparation of carbene complexes as the other methods described above. 

The facility of 1H-azepines to form transition metal carbonyl complexes was realized soon after they were first synthesized. Variable temperature HNMR studies on the tricarbonyliron complex formed either by photolysis of 1-ethoxycarbonyl-l//-azepine with tricarbonyliron in THF, or by heating the azepine with nonacarbonyldiiron in hexane, demonstrated that it undergoes rapid reversible valence tautomerism and that there is considerable restricted rotation about the N—CO bond (B-69MI51600). The molecular geometry of the complex has been determined by X-ray analysis (see Section 5.16.2.2). 

Base-free alkyl-substituted germyl(germylene)tungsten carbonyl complexes 37 and 38 were synthesized by the photolysis of digermyl complexes of tungsten 39 and 40 in benzene (equation 38). These complexes are formed by the 1,2-germyl migrations after the initial photodissociation of CO from 39 and 40146. 

Photolysis of mononuclear chlorogermyl metal carbonyl complexes yields binuclear bis(/r-germylene) metal carbonyl compounds (equation 53). The dimerization is believed to occur through a radical process8. 

A binuclear bis(/z-germylene) osmium carbonyl complex [(OC)4Os(GeMe2)]2 on photolysis or thermolysis yields a mixture of an interesting series of (/z-germylene) osmium clusters36. Bis(metalcarbonyl)germacyclopentene complexes on photolysis or thermolysis... 

To stabilize the antiaromatic 4ir-electron selenirenes (115), considered as possible intermediates in the thermolysis and photolysis of 1,2,3-selenadizoIes, Rees and coworkers <77CC418,72JCS(Pl)2l65) studied the iron carbonyl complex formation of 1,2,3-selenadiazoles. 

Fig. 11 (a) Trinuclear rhenium carbonyl complexes 7 and 8 and (b) UV-Vis difference spectra (Aabs = At - At = 0) of compound 7 in CH3CN at 293 K after irradiation at 366 nm for 0, 1,2, 3, 4, 6 h, and inset shows the emission spectral changes before and after photolysis (reproduced with permission from [39])... 

The hypothetical titanium heptacarbonyl Ti(CO)7 is as yet unknown. However, Ti(CO)6 has been prepared and characterized by matrix isolation techniques. Ti(CO)6, thus prepared, is found to be unstable above —200 °C Titanium carbonyls Ti(CO)x (x = 1 6) are formed during deposition of laser-ablated titanium atoms with CO during condensation in excess Ne, or on annealing and photolysis of the matrix. Titanium carbonyl complexes see Carbonyl Complexes of the Transition Metals) have also been observed spectroscopically (by IR) as intermediates in the low-temperature reaction of Ti(CH2Ph)4 and its dicyclohexylamine adduct with CO. ... 

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