R. Angharad Baber

Synthesis and transition metal chemistry of ‘phosphomide’ ligands: a comparison of the reactivity and electronic properties of diphenyl-P-perfluoro-octanoyl-phosphine, P-acetyl-diphenylphosphine and P-anisoyl-diphenylphosphine. X-ray crystal structure of [RhCp*(Ph2PC(O)CH3)Cl2]

Abstract A convenient synthesis of several ‘phosphomide’ ligands (P adjacent to carbonyl group) from secondary phosphines is reported. The new anisoyl substituted phosphines are considerable more stable to hydrolysis, and are stronger σ-donor ligands than P -acetyl-diphenylphosphine as determined by the measurement of ν (CO) for the corresponding rhodium carbonyl complexes trans -[RhL 2 (CO)Cl]. In contrast, a new phosphomide derived from perfluoro-octanoyl chloride was found to be a highly unstable, electron poor π-acceptor ligand. The crystal structure of [RhCp*Cl 2 {Ph 2 PC(O)CH 3 }] showed a normal pseudo -octahedral piano-stool molecular geometry with a RhP bond length of 2.3186(5) A. The extra stability observed for the P -anisoyl phosphomides has led us to apply this class of ligand in rhodium catalysed hydroformylation for the first time.

The solid-state structure of diboronic acid, B2(OH)4

The crystal structure of diboronic acid contains molecules of B2(OH)4 hydrogen-bonded into two-dimensional sheets linked by B⋯O interactions.

Primary amido substituted diborane(4) compounds and imidodiborate(4) anions

Treatment of the diborane(4) compound B(2)(NMe(2))(4) with aniline or 2,6-dimethylaniline results in the primary amido compounds B(2)(NHR)(4)(R = Ph, 2,6-Me(2)C(6)H(3)); subsequent treatment with n-BuLi in toluene in each case affords the first examples of anionic imidodiborates namely Li(4)(thf)(6)B(2)(NPh)(4) and Li(4)(thf)(4)B(2)(N-2,6-Me(2)C(6)H(3))(4); all complexes have been characterised crystallographically.

Iodination of triazenide-bridged rhodium and iridium complexes: oxidative addition vs. one-electron oxidation

The triazenide-bridged tetracarbonyls [(OC)(2)Rh(mu-p-MeC(6)H(4)NNNC(6)H(4)Me-p)(2)M(CO)(2)] (M = Rh or Ir) undergo oxidative addition of iodine across the dimetal centre, giving the [RhM](4+) complexes [I(OC)(2)Rh(mu-p-MeC(6)H(4)NNNC(6)H(4)Me-p)(2)M(CO)(2)I], structurally characterised for M = Ir. The anionic tricarbonyl iodide [I(OC)Rh(mu-p-MeC(6)H(4)NNNC(6)H(4)Me-p)(2)Rh(CO)(2)](-) forms [I(2)(OC)Rh(mu-p-MeC(6)H(4)NNNC(6)H(4)Me-p)(2)Rh(CO)I](-) by initial one-electron transfer whereas the analogous tricarbonyl phosphine complexes [(OC)(Ph(3)P)Rh(mu-p-MeC(6)H(4)NNNC(6)H(4)Me-p)(2)M(CO)(2)] (M = Rh or Ir) undergo bridge cleavage, giving mononuclear [Rh(p-MeC(6)H(4)NNNC(6)H(4)Me-p)I(2)(CO)(PPh(3))] and dimeric [I(OC){RNNN(R)C(O)}M(mu-I)(2)M{C(O)N(R)NNR}(CO)I] (M = Rh or Ir, R = C(6)H(4)Me-p) in which CO has been inserted into a metal-nitrogen bond.

M⋯HNR interactions in imino-bound diaryltriazene complexes: structure and fluxionality

The nominally square-planar coordination of the d(8) complexes [MClL(1)L(2)(p-XC(6)H(4)NNNHC(6)H(4)X-p)](M = Rh, L(1)= L(2)= CO, X = H, Me, Et or F; M = Ir, L(1)= L(2)= CO, X = Me; M = Pd or Pt, L(1)= Cl, L(2)= PPh(3), X = Me; M = Pd, L(1)L(2)=eta(3)-C(3)H(5), X = Me), with the triazene N-bonded via the imine group, is supplemented by an axial M...H-N interaction involving the terminal amino group.