Niobium complexes carbonyls

A related reaction is shown for the molybdenum-niobium complex (equation 9). As described in a review by Horowitz and Shriver on bridging carbonyl ligands, this complex is a rare example of a structure containing terminal, bridging, and r-bridging CO ligands. All such complexes, of necessity, include metal-metal bonding. 

Many carbonyl and carbonyl metallate complexes of the second and third row, in low oxidation states, are basic in nature and, for this reason, adequate intermediates for the formation of metal— metal bonds of a donor-acceptor nature. Furthermore, the structural similarity and isolobal relationship between the proton and group 11 cations has lead to the synthesis of a high number of cluster complexes with silver—metal bonds.1534"1535 Thus, silver(I) binds to ruthenium,15 1556 osmium,1557-1560 rhodium,1561,1562 iron,1563-1572 cobalt,1573 chromium, molybdenum, or tungsten,1574-1576 rhe-nium, niobium or tantalum, or nickel. Some examples are shown in Figure 17. 

The monomeric carbonyl complexes of d M1 isolated so far are mainly the seven-coordinated [MX(CO)2(dmpe)2] compounds (M = Nb, X = Cl, Br, N3 697 M = Ta, X = H, Cl, Br, CN, Me, Et, Pr ) (53) has been obtained by reduction of [TaCl2(dmpe)2] with one equivalent of sodium naphthalenide under CO the other tantalum derivatives were generally prepared by oxidative additions to [Ta(CO)2(dmpe)2] formed in situ by reduction of (53 Scheme 10). The niobium analogs were formed by reductive carbonylation of [NbCU(dmpe)2].698... 

Aza[3]ferrocenophanes, synthesis, 6, 187 Azaheterocycles, alkynylation with Ir catalysts, 7, 340 7-Azaindole, in trinuclear Ru and Os clusters, 6, 725 Azametallacyclobutane, tantalum complexes, 5, 168 Azametallacyclopropane, with niobium, 5, 87 Aza-oxo ligands, chromium complexes, 5, 353 Azaphosphirenes, with tungsten carbonyls, 5, 623 2H-Azaphosphirenes, with tungsten carbonyls, 5, 679 Aza-titanacyclopentenes, synthesis, 4, 407-408 Azavinylidenes... 

Cyclopentadienones, in molybdenum carbonyls, 5, 451 Cyclopentadienyl alkenes, with niobium, 5, 76 Cyclopentadienyl-alkoxo complexes, with Ti(IV), 4, 495 Cyclopentadienyl alkyl complexes, with niobium, 5, 66 Cyclopentadienyl-amido complexes, with Ti(IV), via dehalosilylation, 4, 448... 

Cyclopentadienyl carbonyl complexes, with niobium, 5, 64 Cyclopentadienyl chromium bis(Ti-allyl) complexes, with chromium, 5, 305-306 Cyclopentadienyl chromium carbonyls... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

No cationic carbonyl complexes of niobium and tantalum have been reported. 

R. R.Schrock, The Reaction of Niobium and Tantalum Neopentylidene Complexes with the Carbonyl Function, J. Am. Chem. Soc. 98, 5399-5400 (1976). 

No derivative in which niobium or tantalum displays an oxidation state of —II has been reported so far, while carbonyl complexes derived from [M(CO)s] represent the only coordination compounds for these metals in oxidation state —III. 

A recent review gives a chronological survey of the syntheses and characterizations of homoleptic mononuclear metal-carbonyl (see Carbonyl Complexes of the Transition Metals) anions. [M(CO)6] is a key precursor to niobium and tantalum carbonyls. More reliable synthesis of [Ta(CO)6] ... 

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