4 research outputs found
Rh-POP Pincer Xantphos Complexes for C-S and C-H Activation. Implications for Carbothiolation Catalysis
The neutral RhÂ(I)âXantphos
complex [RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos)ÂCl]<sub><i>n</i></sub>, <b>4</b>, and cationic RhÂ(III) [RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos)Â(H)<sub>2</sub>]Â[BAr<sup>F</sup><sub>4</sub>], <b>2a</b>, and [RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos-3,5-C<sub>6</sub>H<sub>3</sub>(CF<sub>3</sub>)<sub>2</sub>)Â(H)<sub>2</sub>]Â[BAr<sup>F</sup><sub>4</sub>], <b>2b</b>, are described [Ar<sup>F</sup> = 3,5-(CF<sub>3</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>; Xantphos
= 4,5-bisÂ(diphenylphosphino)-9,9-dimethylxanthene; Xantphos-3,5-C<sub>6</sub>H<sub>3</sub>(CF<sub>3</sub>)<sub>2</sub> = 9,9-dimethylxanthene-4,5-bisÂ(bisÂ(3,5-bisÂ(trifluoromethyl)Âphenyl)Âphosphine].
A solid-state structure of <b>2b</b> isolated from C<sub>6</sub>H<sub>5</sub>Cl solution shows a Îș<sup>1</sup>-chlorobenzene
adduct, [RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos-3,5-C<sub>6</sub>H<sub>3</sub>(CF<sub>3</sub>)<sub>2</sub>)Â(H)<sub>2</sub>(Îș<sup>1</sup>-ClC<sub>6</sub>H<sub>5</sub>)]Â[BAr<sup>F</sup><sub>4</sub>], <b>3</b>. Addition of H<sub>2</sub> to <b>4</b> affords,
crystallographically characterized, [RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos)Â(H)<sub>2</sub>Cl], <b>5</b>. Addition of diphenyl
acetylene to <b>2a</b> results in the formation of the CâH
activated metallacyclopentadiene [RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos)Â(ClCH<sub>2</sub>Cl)Â(Ï,Ï-(C<sub>6</sub>H<sub>4</sub>)ÂCÂ(H)î»CPh)]Â[BAr<sup>F</sup><sub>4</sub>], <b>7</b>, a rare example of a crystallographically characterized Rhâdichloromethane
complex, alongside the RhÂ(I) complex <i>mer</i>-[RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos)Â(η<sup>2</sup>-PhCCPh)]Â[BAr<sup>F</sup><sub>4</sub>], <b>6</b>. Halide abstraction from [RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos)ÂCl]<sub><i>n</i></sub> in the presence of diphenylacetylene affords <b>6</b> as the
only product, which in the solid state shows that the alkyne binds
perpendicular to the Îș<sup>3</sup>-POP Xantphos ligand plane.
This complex acts as a latent source of the [RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos)]<sup>+</sup> fragment and facilitates
<i>ortho</i>-directed CâS activation in a number
of 2-arylsulfides to give <i>mer</i>-[RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos)Â(Ï,Îș<sup>1</sup>-Ar)Â(SMe)]Â[BAr<sup>F</sup><sub>4</sub>] (Ar = C<sub>6</sub>H<sub>4</sub>COMe, <b>8</b>; C<sub>6</sub>H<sub>4</sub>(CO)ÂOMe, <b>9</b>; C<sub>6</sub>H<sub>4</sub>NO<sub>2</sub>, <b>10</b>; C<sub>6</sub>H<sub>4</sub>CNCH<sub>2</sub>CH<sub>2</sub>O, <b>11</b>; C<sub>6</sub>H<sub>4</sub>C<sub>5</sub>H<sub>4</sub>N, <b>12</b>).
Similar CâS bond cleavage is observed with allyl sulfide,
to give <i>fac</i>-[RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos)Â(η<sup>3</sup>-C<sub>3</sub>H<sub>5</sub>)Â(SPh)]Â[BAr<sup>F</sup><sub>4</sub>], <b>13</b>. These products of CâS
activation have been crystallographically characterized. For <b>8</b> in situ monitoring of the reaction by NMR spectroscopy reveals
the initial formation of <i>fac</i>-Îș<sup>3</sup>-<b>8</b>, which then proceeds to isomerize to the <i>mer</i>-isomer. With the <i>para</i>-ketone aryl sulfide, 4-SMeC <sub>6</sub>H<sub>4</sub>COMe, CâH activation <i>ortho</i> to the ketone occurs to give <i>mer</i>-[RhÂ(Îș<sup>3</sup>-<sub>P,O,P</sub>-Xantphos)Â(Ï,Îș<sup>1</sup>-4-(COMe)ÂC<sub>6</sub>H<sub>3</sub>SMe)Â(H)]Â[BAr<sup>F</sup><sub>4</sub>], <b>14</b>. The temporal evolution of carbothiolation catalysis using <i>mer</i>-Îș<sup>3</sup>-<b>8</b>, and phenyl acetylene
and 2-(methylthio)Âacetophenone substrates shows initial fast catalysis
and then a considerably slower evolution of the product. We suggest
that the initially formed <i>fac</i>-isomer of the CâS
activation product is considerably more active than the <i>mer</i>-isomer (i.e., <i>mer</i>-<b>8</b>), the latter of
which is formed rapidly by isomerization, and this accounts for the
observed difference in rates. A likely mechanism is proposed based
upon these data
A Generalist approach to social work practice : model and synthesis
The purpose of this research practicum is twofold. First, to present a synthesis of current generalist literature and to formulate a practice model which is both comprehensive and representative of current generalist practice in direct services. To our knowledge there is no single reference or source which in and of itself accomplishes this purpose. Therefore, such a model would make an important contribution to the field. Second, to develop a questionnaire which could be used to conduct a descriptive survey of generalist social work practice in Oregon. It would determine the extent to which practitioners in Oregon are practicing as generalists. We are interested in discovering 1) the relationship between generalist practice and the personal characteristics of practitioners, as well as 2) the relationship between generalist practice and the type of agency in which the practitioner works. It appears to us that certain agencies encourage ineffective, inappropriate, and uni-dimensional practice, while others tend to encourage more effective and holistic practices