Group VB Donors

Ehrl and Vahrenkamp32 34 have produced several examples of arsenido-bridged mixed-metal carbonyls including (CO)4FeAsMe2Co(CO)4, (CO)5CrAsMe2Co(CO)4, and (CO)4FeAsMe2Co(CO)3. 

Two rare examples of unsubstituted Group VB elements bonded to transition metals are Co2(CO)6P2 and Co3(CO)9PS, which are produced from NaCo(CO)4 and PX3 and SPX3, respectively.35 

The reactions of CO with some higher valent cobalt compounds are discussed under the other ligands concerned. 

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B. Chiswell, The chemistry of multidentate ligands containing heavy group Vb donors. 33 pp. (132). 

An active area of metal carbonyl chemistry involves replacement of CO with group VB donor ligands, especially phosphites and phosphines. The direct replacement of CO by the ligand is the simplest means of preparation of the substituted dimers ... 

Dimers that are multiply substituted with group VB donors have been reported. The following sequence of reactions leads to the trimethylphosphite analogue of Co2(CO)s ... 

Polynuclear Carbonyls.—It has been shown that substitution reactions of [Ru3(CO)ia] with Group Vb donors follow the rate law Arobs = Ati + AraiL], where L = PPha, AsPhg, P(OPh)3, P[(OCHa)3CEt], P(OEt)3, or PBu g, and that contrary to earlier reports the k term contributes significantly to the overall rate. A recent, more detailed analysis has now appeared. The nature of the reaction products varies considerably but the kinetic equation above is quite clear. The first-order path corresponds... 

The palladium oxide catalysed reaction between [Re(CO)sX] (X = Cl, Br, I) and L, a group VB donor ligand, proceeds to give cis-[Re(CO)4XL] in high yields (>75%) when L has a cone-angle of less than 150 The amine-oxide assisted decarbonyation of [Re2(CO)10] in the presence of 1,1 -bis(diphenylphosphino)ferrocene (dppf) produces, under different conditions the following products ... 

Vanadium, Niobium, and Tantalum.—Photochemical reactions of CpV(CO)4 with Group Vb donor ligands have given products of the types CpV(CO)3XRs (X = As, Sb, or Bi R = alkyl, Ph, OEt, etc.f and CpV(CO)2L (L = bidentate diphosphine, diarsine, or arsine-phosphine ligand). The dianion [CpV(C0)3] , prepared by reduction of CpV(CO)4 with Na in THF, has been converted into the isolable salt [(Ph3P)2N]+[CpV(CO)3H], which effects hydro-genolysis of various alkyl, aryl, and acyl halides apparently by a radical-chain mechanism. ... 

Di- and Tri-nuclear Carbrniyls.—Substitution reactions of [Ru3(CO)i2] with Group Vb donors follow the rate law kohs = + A 2[L]. For L = AsPhj... 

Ligands that reduce the activity of Hg(II) more than that of Hg(I) lead to disproportionation products when added to a solution containing Hg2 ions. Because the smaller Hg ion is a better electron-pair acceptor acid than the larger Hgj ion, the number of Hg(I) complexes may be limited, but many complexes of Hg(I) are formed by reactions of Hg, with ligands containing donor atoms from groups VB and VIB. Polyethers and polyesters are good solvents for these reactions, ... 

A153. D. M. Adams, Metal-Ligand and Related Vibrations A Critical Survey of the Infrared and Raman Spectra of Metallic and Organometallic Compounds. Arnold, London, 1967. 360 pp. There are tabulated data and references on metal-carbon and related frequencies (especially on Zn, Al, Sn groups) and on metal-ligand frequencies involving heavier group VB and VIB donors. 

The ligand PhCH=CHCOR can also act as a four-electron donor towards iron as in [Fe(CO)s( -PhCH=CHCOR)] (12), where the carbonyl group is also coordinated. Cardaci has studied the kinetics of the reactions between these tricarbonyls (R = H, Me, or Ph) and the Group Vb ligands EPha (E = P, As, or Sb) and a two-step process is described (Scheme 18). The kinetics of the first step where... 

Ligand displacement reactions for [MX]+ and [MX2]+ ions may be used as a measure of ligand strength for a wide variety of donor molecules. The M-O bond in the [MO]+ ion varies from very strong for the groups 3 (IIIB), 4 (IVB), and 5 (VB) metals to weak in the later transition metals. 

The EM acceptor levels are calculated from the VB parameters and, by analogy with the situation for EM donors, we consider first the splitting of the VB under a uniaxial stress. A stress along a <100> or < 111 > direction reduces the point group symmetry of the diamond structure to D4h or Dslinear regime, the strain-induced part H of the VB Hamiltonian corresponding to (8.1) can be written as [57] ... 

Electrons in the CB and holes in the VB can also be introduced by the substitution of acceptor and donor atoms (called dopants) into the semiconductor lattice to produce extrinsic materials. Thus an arsenic atom (a Group V element) behaves as an electron donor when sub-... 

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