As-donor Ligands

Garifyanov, O. I. Knyazeva, G. A. Levshina, and A. D. Troitskaya, Trudy. Kazansk. khim- 

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M(SCH2CH2S)3] with stereochemistry midway between octahedral and trigonal-prismatic, are known for both Nb and Ta. The pentahalides of these two metals act as Lewis acids and form complexes of the type MX5L with O, S, N, P. and As donor ligands. 

Few quantitative data are available on the relative nucleophilicities of L toward various alkyl carbonyls. The rates of the reaction of CpMo(CO)3Me with L in toluene (Table II) decrease as a function of the latter reactant P( -Bu)3 > P( -OBu)j > PPhj > P(OPh)j, but the spread is relatively small (<8). The above order is that customarily observed for 8 2 reactions of low-valent transition metal complexes (J, 214). Interestingly, neither CpMo(CO)3Me nor CpFe(CO)2Me reacts with 1 or N, S, and As donor ligands 28, 79). This is in direct contrast to the insertion reactions of MeMn(CO)5 which manifest much less selectivity toward various L (see Section VI,B,C,D for details). 

Rather limited information is available on how the nature of R affects the rate of CO insertion, all other factors being constant. A generalization that ethylmetal complexes react faster than the corresponding methyl carbonyls derives from investigations on four systems RIr(CO)2(AsPh3)Cl2 (92), RMn(CO)5 (51), CpFe(CO)2R (98), and CpMo(CO)jR (80). When R = Et the reactions with CO or P and As donor ligands proceed at least 6 times faster than when R = Me. 

Complexes with mixed C,P or C,As donor ligands are derived of ortho-metalated phosphines or arsines or of methanide derivatives. The dinuclear complexes [Au2(C6F[3-2-EPh2-6-R)2] (E = P (589), As R = H, Me) are obtained by reaction of 2-EPh2-6-R-C6F[3Li with [AuBr(PEt3)] at —70 °c.2002 2004,20 6 The treatment of the dimer [Au2(C6Fl4PPh2)2] with methyltriflate yields, unexpectedly, [Au5(C6Fl4PPh2)4]+.3134 The mixed dinuclear derivative [Au2(5-Me-C6H3-2-... 

Group 1 Complexes of P- and As-Donor Ligands Keith Izod... 

C6H2 (supermesityl, mes ) into the ligand such substituents sterically occlude vacant metal coordination sites and greatly increase the solubility of the complexes in common organic solvents. The subtle variations possible within P- and As-donor ligand complexes of the alkali metals lead to an almost bewildering array of structural types, many of which are not observed in other areas of alkali metal chemistry, and to wide variations in reactivity between complexes. 

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