Carbonyl Complexes of Cr, Mo and

Monosubstituted complexes (M(CO)gLj with L = Ph3P CH(CN) radical anions of 2,1,3-benzoxadiazole, 2,1,3-benzothiadiazole, or 2,1,3-benzoselenadiazole, (P(CN)2) , Ph2PCH2CHp(CH2)3/ 

Among the disubstituted complexes [M(C0) L2l studied have been those with chelate ligands L 4,4 - or 5,5 -disubstituted- 

2 -bipyridyls, chiral diazadienes, Schiff bases derived 

RN=CHCH=NR (R = aryl)have been examined. The [Mo(CO).(chelate)3 

or W) have been studied. Oxidation of the arylamine ligands of [Cr(CO)g(NH2R)3 using lead(IV) acetate produces 

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The mono- and dinuclear carbonyl metalates of Cr, Mo, and W, first prepared by us using liquid NHS, have also been of great importance for the synthesis of numerous neutral complexes not accessible by other routes. Special attention is drawn to the deeply colored and very unstable mono- and dinuclear paramagnetic complexes Cr(CO)sI, Cr (CO),oI, Cr(CO)5CN, Cr(CO)sNCS, Cr COl.oNCS, and Cr(CO)sSH. 

The reactivity of carbonyls of Cr, Mo, and W with alkyl lithium is somewhat lower than that of nickel and iron carbonyls. The most interesting reaction of these metal carbonyls, found and studied extensively by Fischer and his coworkers, is the formation of carbene complexes 98-"). Phenyl or methyl lithium adds readily to W(CO)6 at room temperature to form carbonylate complexes. The tetramethyl ammonium salt of the complex is treated with acid and then with diazomethane to give a neutral complex whose structure was found to be that of a carbene complex. In this way a series of carbene complexes of Cr, Mo, and Mn were synthesized. 

Synthesis of metal carbonyl complexes of Cr, Mo, W, and Fe highly enriched in CO. 

Carbonyl Substitution. Replacement of one CO by an NHC ligand such as IDM is a common reaction, which has been applied to carbonyl complexes of Cr(0), Mo(0), W(0), Fe(0), Ni(0), and so on. The corresponding IDM-carbonyl complexes (44)-(46) were easily isolated in good yield as depicted in Scheme T. ... 

Besides the organometallic and carbonyl complexes, which are dealt with in subsequent sections, the photosubstitution chemistry of these elements has been concerned principally with the hexacoordinated complexes of Cr(lII) and the octacyano complexes of Mo(IV) and W(IV). 

The relationship between metal carbonyl hydrides and dihydrogen complexes of metal carbonyl derivatives has been further explored.The interactions of d ML5 fragments with H2 have been studied by EHMO methods,and the structures and some reactions of n -H2 complexes of Cr, Mo, W, Fe and Co carbonyl derivatives examined.Intramolecular ligand rearrangements in [M(C0)5H] anions (M = Cr or Mo) have been investigated using variable temperature n.m.r. A twist mechanism that provides a pathway for intramolecular axial-equatorial CO exchange is favoured.The catalytic role of these... 

Considering the isolobal relations between W(CO)5 or RSb, the complexes of type 29 and 30 may be considered as analogs of cvc/o-R3Sb3 or of complexes with a cyc/o-R3Sb3 ligand, which are still unknown. Closely related are the complexes [MeC(CH2Sb)3M(CO)5] (M = Cr, Mo, W)124 where a polycyclic tristibine is coordinated to metal carbonyl units. 

Carbonylation reactions with microwave irradiation have been investigated in connection with solid-state combinatorial chemistry.Since reactions requiring gaseous reagents cannot use microwave irradiation, metal carbonyl complexes, such as Mo(CO)6, Cr(CO)6, W(CO)6, and Co2(CO)8 have been employed as source of carbon monoxide. " Examples of aminocarbonylation performed with microwave irradiation are presented in Section 11.15.4.3 (vide supra). 

Metal carbonyl complexes of the type M(CO)4L, where M = Cr, Mo, or W and L is the bidentate 2,7-dimethyl-l,8-naphthyridine, have recently been prepared by Hendricker and Reed.157... 

These carbene (or alkylidene) complexes are used as either stoichiometric reagents or catalysts for various transformations which are different from those of free carbenes. Reactions involving the carbene complexes of W, Mo, Cr, Re, Ru, Rh, Pd, Ti and Zr are known. Carbene complexes undergo the following transformations (i) alkene metathesis (ii) alkene cyclopropanation (iii) carbonyl alkenation (iv) insertion to C—H, N—H and O—H bonds (v) ylide formation and (vi) dimerization. Their chemoselectivity depends mainly on the metal species and ligands, as discussed in the following sections. 

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